Clinical microbiology laboratories do not always detect resistance of Haemophilus influenzae with disk or tablet diffusion methods. Finnish Study Group for Antimicrobial Resistance (FiRe).

PubMed

Manninen, R; Huovinen, P; Nissinen, A

1998-04-01

The performance of disk diffusion testing of Haemophilus influenzae was evaluated in 20 laboratories. Thirteen disk-medium-breakpoint-inoculum modifications were used in Finnish clinical microbiology laboratories. The performance of various methods was evaluated by testing a susceptible control strain and one with non-beta-lactamase-mediated ampicillin resistance 10 times in 16 laboratories. Gaps in millimeters were measured between these two groups of results. The strains were separated by a gap of at least 5 mm in 8/16 laboratories testing ampicillin, in 7/15 laboratories testing cefaclor, in 5/ 16 laboratories testing cefuroxime, and in 15/16 laboratories testing trimethoprim-sulfa. Detection of ampicillin resistance was better with 2.5 microg tablets than with 10 microg disks or 33 microg tablets. For MIC-determinations, 785 isolates and their disk diffusion results were collected. None of the 12 clinical isolates with non-beta-lactamase-mediated ampicillin resistance was detected as resistant in the participating laboratories. The ampicillin and cefaclor results of the isolates were no better even when a laboratory was able to separate the control strains. Cefaclor results were unreliable because of poor disk diffusion-MIC correspondence and incoherent breakpoint references. Interlaboratory variation of the zone diameters caused false intermediate results of cefuroxime-susceptible strains. When ampicillin, cefaclor and cefuroxime were tested, the discrimination of laboratories using disks and tablets was equal, whereas the laboratories using paper disks were better able to detect trimethoprim-sulfa resistance.

Evaluation of an Automated System for Reading and Interpreting Disk Diffusion Antimicrobial Susceptibility Testing of Fastidious Bacteria.

PubMed

Idelevich, Evgeny A; Becker, Karsten; Schmitz, Janne; Knaack, Dennis; Peters, Georg; Köck, Robin

2016-01-01

Results of disk diffusion antimicrobial susceptibility testing depend on individual visual reading of inhibition zone diameters. Therefore, automated reading using camera systems might represent a useful tool for standardization. In this study, the ADAGIO automated system (Bio-Rad) was evaluated for reading disk diffusion tests of fastidious bacteria. 144 clinical isolates (68 β-haemolytic streptococci, 28 Streptococcus pneumoniae, 18 viridans group streptococci, 13 Haemophilus influenzae, 7 Moraxella catarrhalis, and 10 Campylobacter jejuni) were tested on Mueller-Hinton agar supplemented with 5% defibrinated horse blood and 20 mg/L β-NAD (MH-F, Oxoid) according to EUCAST. Plates were read manually with a ruler and automatically using the ADAGIO system. Inhibition zone diameters, indicated by the automated system, were visually controlled and adjusted, if necessary. Among 1548 isolate-antibiotic combinations, comparison of automated vs. manual reading yielded categorical agreement (CA) without visual adjustment of the automatically determined zone diameters in 81.4%. In 20% (309 of 1548) of tests it was deemed necessary to adjust the automatically determined zone diameter after visual control. After adjustment, CA was 94.8%; very major errors (false susceptible interpretation), major errors (false resistant interpretation) and minor errors (false categorization involving intermediate result), calculated according to the ISO 20776-2 guideline, accounted to 13.7% (13 of 95 resistant results), 3.3% (47 of 1424 susceptible results) and 1.4% (21 of 1548 total results), respectively, compared to manual reading. The ADAGIO system allowed for automated reading of disk diffusion testing in fastidious bacteria and, after visual validation of the automated results, yielded good categorical agreement with manual reading.

Application of Artificial Intelligence to the Prediction of the Antimicrobial Activity of Essential Oils.

PubMed

Daynac, Mathieu; Cortes-Cabrera, Alvaro; Prieto, Jose M

2015-01-01

Essential oils (EOs) are vastly used as natural antibiotics in Complementary and Alternative Medicine (CAM). Their intrinsic chemical variability and synergisms/antagonisms between its components make difficult to ensure consistent effects through different batches. Our aim is to evaluate the use of artificial neural networks (ANNs) for the prediction of their antimicrobial activity. Methods. The chemical composition and antimicrobial activity of 49 EOs, extracts, and/or fractions was extracted from NCCLS compliant works. The fast artificial neural networks (FANN) software was used and the output data reflected the antimicrobial activity of these EOs against four common pathogens: Staphylococcus aureus, Escherichia coli, Candida albicans, and Clostridium perfringens as measured by standardised disk diffusion assays. Results. ANNs were able to predict >70% of the antimicrobial activities within a 10 mm maximum error range. Similarly, ANNs were able to predict 2 or 3 different bioactivities at the same time. The accuracy of the prediction was only limited by the inherent errors of the popular antimicrobial disk susceptibility test and the nature of the pathogens. Conclusions. ANNs can be reliable, fast, and cheap tools for the prediction of the antimicrobial activity of EOs thus improving their use in CAM.

Application of Artificial Intelligence to the Prediction of the Antimicrobial Activity of Essential Oils

PubMed Central

Daynac, Mathieu; Cortes-Cabrera, Alvaro; Prieto, Jose M.

2015-01-01

Essential oils (EOs) are vastly used as natural antibiotics in Complementary and Alternative Medicine (CAM). Their intrinsic chemical variability and synergisms/antagonisms between its components make difficult to ensure consistent effects through different batches. Our aim is to evaluate the use of artificial neural networks (ANNs) for the prediction of their antimicrobial activity. Methods. The chemical composition and antimicrobial activity of 49 EOs, extracts, and/or fractions was extracted from NCCLS compliant works. The fast artificial neural networks (FANN) software was used and the output data reflected the antimicrobial activity of these EOs against four common pathogens: Staphylococcus aureus, Escherichia coli, Candida albicans, and Clostridium perfringens as measured by standardised disk diffusion assays. Results. ANNs were able to predict >70% of the antimicrobial activities within a 10 mm maximum error range. Similarly, ANNs were able to predict 2 or 3 different bioactivities at the same time. The accuracy of the prediction was only limited by the inherent errors of the popular antimicrobial disk susceptibility test and the nature of the pathogens. Conclusions. ANNs can be reliable, fast, and cheap tools for the prediction of the antimicrobial activity of EOs thus improving their use in CAM. PMID:26457111

IN VITRO ANTIMICROBIAL SCREENING OF AQUILARIA AGALLOCHA ROOTS.

PubMed

Canlı, Kerem; Yetgin, Ali; Akata, Ilgaz; Altuner, Ergin Murat

2016-01-01

It was previously shown that some parts of Aquilaria agallocha , which is commonly known as oud or oodh, such as roots have been used as a traditional medical herbal in different countries. In Turkey A. agallocha is one of the ingredients while preparing famous Mesir paste, which was invented as a medicinal paste and used from the Ottoman period to now at least for 500 years. The identification the in vitro antimicrobial activity of ethanol extract of A. agallocha roots is main purpose of this analysis. By using 17 bacteria and 1 fungi, which include Bacillus, Candida, Enterobacter, Enterococcus, Escherichia, Klebsiella, Listeria, Pseudomonas, Salmonella and Staphylococcus genera, the activity of A. agallocha root extracts were analysed by the help of the disk diffusion method, that is one of the methods commonly used to determine antimicrobial activities. As a result of the study it was observed that ethanol extracts of A. agallocha roots have a clear antimicrobial activity against nearly all microorganism used in the study, but only two bacteria namely E. coli ATCC 25922 and S. typhimurium SL 1344. According to the disk diffusion test results it may be possible to propose that A. agallocha roots should have a medicinal uses especially against E. faecium , L. monocytogenes ATCC 7644, B. subtilis DSMZ 1971, C. albicans DSMZ 1386, S. epidermidis DSMZ 20044 and S. aureus ATCC 25923.

COMPARISON BETWEEN AUTOMATED SYSTEM AND PCR-BASED METHOD FOR IDENTIFICATION AND ANTIMICROBIAL SUSCEPTIBILITY PROFILE OF CLINICAL Enterococcus spp

PubMed Central

Furlaneto-Maia, Luciana; Rocha, Kátia Real; Siqueira, Vera Lúcia Dias; Furlaneto, Márcia Cristina

2014-01-01

Enterococci are increasingly responsible for nosocomial infections worldwide. This study was undertaken to compare the identification and susceptibility profile using an automated MicrosScan system, PCR-based assay and disk diffusion assay of Enterococcus spp. We evaluated 30 clinical isolates of Enterococcus spp. Isolates were identified by MicrosScan system and PCR-based assay. The detection of antibiotic resistance genes (vancomycin, gentamicin, tetracycline and erythromycin) was also determined by PCR. Antimicrobial susceptibilities to vancomycin (30 µg), gentamicin (120 µg), tetracycline (30 µg) and erythromycin (15 µg) were tested by the automated system and disk diffusion method, and were interpreted according to the criteria recommended in CLSI guidelines. Concerning Enterococcus identification the general agreement between data obtained by the PCR method and by the automatic system was 90.0% (27/30). For all isolates of E. faecium and E. faecalis we observed 100% agreement. Resistance frequencies were higher in E. faecium than E. faecalis. The resistance rates obtained were higher for erythromycin (86.7%), vancomycin (80.0%), tetracycline (43.35) and gentamicin (33.3%). The correlation between disk diffusion and automation revealed an agreement for the majority of the antibiotics with category agreement rates of > 80%. The PCR-based assay, the van(A) gene was detected in 100% of vancomycin resistant enterococci. This assay is simple to conduct and reliable in the identification of clinically relevant enterococci. The data obtained reinforced the need for an improvement of the automated system to identify some enterococci. PMID:24626409

The effect of lactic acid bacteria isolates on the urinary tract pathogens to infants in vitro.

PubMed

Lim, In Seok; Lee, Ho Seok; Kim, Won Yong

2009-01-01

Urinary tract infections are common clinical problems in children, even though lots of treatment strategies have been tried. Many studies of the application of probiotics for urinary tract infection in female adults exist, but there is a lack of studies in children. The aims of this study were to screen probiotic strains for inhibiting the uropathogens in vitro, to find candidates for in vivo study. Nine strains of E. coli were isolated from children with urinary tract infection and six uropathogens were obtained from Korean Collection for Type Cultures and American Type Culture Collection. Also 135 lactic acid bacteria (LAB) strains were isolated from healthy children, and were identified through physiologic, biochemical methods, 16S rDNA PCR, and data analysis. And with agar disk diffusion assay technique the antimicrobial activities of these LAB strains against those uropathogens were examined. Three strains of separated LAB strains demonstrated major antimicrobial activity against all the uropathogens. In the agar disk diffusion assay technique, antimicrobial activities increased most in the 4th day culture broth with separated Lactobacillus. In summary, some LAB can be used as candidates to develop the probiotic microorganisms that inhibit uropathogens in children, and are expected to be applied to treatment and prevention of pediatric urinary tract infection.

In vitro comparison of antimicrobial activity of aqueous decoction of Coriandrum sativum, and Dentol Drop with chlorhexidine on Streptococcus mutans.

PubMed

Moradian, Hamid; Bazargani, Abdollah; Rafiee, Azade; Nazarialam, Ali

2013-09-01

Dental caries is still remained as a major health problem. This problem has created a new interest to search for new antimicrobial agents from various sources including medicinal plants. Since limited data is available so far regarding the antibacterial effect of Coriandrum sativum seed and Dentol Drop against Streptococcus mutans, this study aims to assess this activity. This experimental study was conducted in Shiraz University of Medical Sciences. In vitro comparison of antimicrobial activity of aqueous decoction of Coriandrum sativum seed and Dentol drop with chlorhexidine against Streptococcus mutans was evaluated using disk diffusion and broth microdilution assays. Positive and negative controls were considered. The data was statistically analyzed by applying Kruskal-Wallis and Tukey post-hoc test to compare the groups using SPSS software (version 17). Dentol drop showed a remarkable antibacterial activity, in comparison with chlorhexidine, against S. mutans in the disk diffusion (p value = 0.005), and broth microdilution assays (p value = 0.0001). Based on the results of this study, Coriandrum sativum seed did not posses any antibacterial property. Coriandrum sativum seed showed no anti-Streptococcus mutans activity. Dentol drop exhibited a remarkable antibacterial activity against S. mutans when tested in vitro. Dentol drop can be further studied as a preventive measure for dental caries.

Minimum inhibitory concentration breakpoints and disk diffusion inhibitory zone interpretive criteria for tilmicosin susceptibility testing against Pasteurella multocida and Actinobacillus pleuropneumoniae associated with porcine respiratory disease.

PubMed

Shryock, Thomas R; Staples, J Mitchell; DeRosa, David C

2002-09-01

Tilmicosin is a novel macrolide antibiotic developed for exclusive use in veterinary medicine. Tilmicosin has been approved as a feed premix to control porcine respiratory disease associated with Pasteurella multocida and Actinobacillus pleuropneumoniae. The development of antimicrobial susceptibility testing guidelines for tilmicosin was predicated on the relationship of clinical efficacy studies that demonstrated a favorable therapeutic outcome, on pharmacokinetic data, and on in vitro test data, as recommended by the National Committee for Clinical Laboratory Standards (NCCLS). The approved breakpoints for the minimum inhibitory concentration dilution testing for both species are resistant, > or = 32 microg/ml, and susceptible, < or = 16 microg/ml. The zone of inhibition interpretive criteria for disk diffusion testing with a 15-microg tilmicosin disk are resistant, < or = 10 mm, and susceptible, > or = 11 mm.

Chlorhexidine Uptake and Release From Modified Titanium Surfaces and Its Antimicrobial Activity.

PubMed

Ryu, Hyo-Sook; Kim, Yoon-Il; Lim, Bum-Soon; Lim, Young-Jun; Ahn, Sug-Joon

2015-11-01

Decontamination by adjunctive antiseptic agents such as chlorhexidine (CHX) is often recommended for the treatment of peri-implant infections. However, its action on the titanium implant surface needs further research. This study is designed to evaluate the ability of modified titanium surfaces to release chlorhexidine after periodic CHX exposure. Four titanium surfaces were prepared: 1) no surface treatment control (machined surface [MA]); 2) an acid mix of 10% HNO3 and 5% HF (HNF); 3) resorbable blast media (RBM); and 4) sandblasting and acid etching (SLA). Each surface was analyzed using a confocal laser scanning microscope and a scanning electron microscope. Each sample was incubated with whole saliva or phosphate-buffered saline for 2 hours. Measurements of CHX release were performed using spectrometry on days 1, 2, and 5 after 1-minute exposure to 0.5% chlorhexidine digluconate solution during a 5-day cycle. CHX-releasing experiments were repeated three consecutive times for 15 days. The antimicrobial activity of CHX-adsorbed disks was determined by a disk diffusion test using Streptococcus gordonii. The CHX-adsorbed titanium surfaces exhibited a short-term release of CHX, and CHX levels dropped rapidly within 3 days. SLA and RBM with smaller and narrower depressions released more CHX than HNF and MA, specifically in the saliva-coated group. The disk diffusion test revealed that after CHX uptake, saliva-coated SLA and RBM showed the highest antimicrobial activity. This study suggests that CHX release is significantly influenced by titanium surface modifications and that SLA and RBM might provide effective CHX uptake capacity in the saliva-filled oral cavity.

Comparative evaluation of antibacterial activity of caffeic acid phenethyl ester and PLGA nanoparticle formulation by different methods

NASA Astrophysics Data System (ADS)

Arasoglu, Tülin; Derman, Serap; Mansuroglu, Banu

2016-01-01

The aim of the present study was to evaluate the antimicrobial activity of nanoparticle and free formulations of the CAPE compound using different methods and comparing the results in the literature for the first time. In parallel with this purpose, encapsulation of CAPE with the PLGA nanoparticle system (CAPE-PLGA-NPs) and characterization of nanoparticles were carried out. Afterwards, antimicrobial activity of free CAPE and CAPE-PLGA-NPs was determined using agar well diffusion, disk diffusion, broth microdilution and reduction percentage methods. P. aeroginosa, E. coli, S. aureus and methicillin-resistant S. aureus (MRSA) were chosen as model bacteria since they have different cell wall structures. CAPE-PLGA-NPs within the range of 214.0 ± 8.80 nm particle size and with an encapsulation efficiency of 91.59 ± 4.97% were prepared using the oil-in-water (o-w) single-emulsion solvent evaporation method. The microbiological results indicated that free CAPE did not have any antimicrobial activity in any of the applied methods whereas CAPE-PLGA-NPs had significant antimicrobial activity in both broth dilution and reduction percentage methods. CAPE-PLGA-NPs showed moderate antimicrobial activity against S. aureus and MRSA strains particularly in hourly measurements at 30.63 and 61.25 μg ml-1 concentrations (both p < 0.05), whereas they failed to show antimicrobial activity against Gram-negative bacteria (P. aeroginosa and E. coli, p > 0.05). In the reduction percentage method, in which the highest results of antimicrobial activity were obtained, it was observed that the antimicrobial effect on S. aureus was more long-standing (3 days) and higher in reduction percentage (over 90%). The appearance of antibacterial activity of CAPE-PLGA-NPs may be related to higher penetration into cells due to low solubility of free CAPE in the aqueous medium. Additionally, the biocompatible and biodegradable PLGA nanoparticles could be an alternative to solvents such as ethanol, methanol or DMSO. Consequently, obtained results show that the method of selection is extremely important and will influence the results. Thus, broth microdilution and reduction percentage methods can be recommended as reliable and useful screening methods for determination of antimicrobial activity of PLGA nanoparticle formulations used particularly in drug delivery systems compared to both agar well and disk diffusion methods.

Synergy between antibiotics and natural agents results in increased antimicrobial activity against Staphylococcus epidermidis.

PubMed

Abidi, Syed Hani; Ahmed, Khalid; Sherwani, Sikander Khan; Kazmi, Shahana Urooj

2015-09-27

Staphylococcus epidermidis is one of the most frequent causes of biofilm-associated infections on indwelling medical devices. With the emergence of methicillin-resistant S. epidermidis (MRSE), there is an urgent need to discover novel active agents against a range of Gram-positive pathogens. We screened the clinical isolates of S. epidermidis for susceptibility/resistance against commonly prescribed antibiotics. Furthermore, we tested some natural agents alone and in combination with antibiotics to find possible synergistic antimicrobial effects. S. epidermidis clinical isolates were screened for susceptibility/resistance against vancomycin, erythromycin, tetracycline, chloramphenicol, ampicillin, ofloxacin, cephalexin, and gentamicin using the Kirby-Bauer disk diffusion method. The antimicrobial potential of Camellia sinensis, Juglans regia, and Hippophae rhamnoides alone and in combination with antibiotics were examined using the disk diffusion method, where the antimicrobial potential activity was measured in terms of formation of zones of inhibition. Most S. epidermidis isolates were found to be resistant to one or more antibiotics. Gentamycin and ofloxacin were found to be the most effective antibiotics against S. epidermidis isolates. Extracts of Hippophae rhamnoides, Juglans regia, and Camellia sinensis were found to be equally effective against S. epidermidis isolates. In combination with antibiotics, these extracts exhibited appreciable synergistic activity; the highest synergistic activity was observed with erythromycin and cephalexin. In the case of cephalexin, a reversion in resistance was observed. The plant extracts used in the study exhibited additive and synergistic antibacterial activity against S. epidermidis, hence providing an effective alternative to deal with the problem of multidrug resistance.

Prevalence and Antimicrobial Resistance of Campylobacter Isolated from Dressed Beef Carcasses and Raw Milk in Tanzania

PubMed Central

Kashoma, Isaac P.; Kassem, Issmat I.; John, Julius; Kessy, Beda M.; Gebreyes, Wondwossen; Kazwala, Rudovick R.

2016-01-01

Campylobacter species are commonly transmitted to humans through consumption of contaminated foods such as milk and meat. The aim of this study was to investigate the prevalence, antimicrobial resistance, and genetic determinants of resistance of Campylobacter isolated from raw milk and beef carcasses in Tanzania. The antimicrobial resistance genes tested included blaOXA-61 (ampicillin), aph-3-1 (aminoglycoside), tet(O) (tetracycline), and cmeB (multi-drug efflux pump). The prevalence of Campylobacter was 9.5% in beef carcasses and 13.4% in raw milk, respectively. Using multiplex-polymerase chain reaction (PCR), we identified 58.1% of the isolates as Campylobacter jejuni, 30.7% as Campylobacter coli, and 9.7% as other Campylobacter spp. One isolate (1.6%) was positive for both C. jejuni and C. coli specific PCR. Antimicrobial susceptibility testing using the disk diffusion assay and the broth microdilution method showed resistance to: ampicillin (63% and 94.1%), ciprofloxacin (9.3% and 11.8%), erythromycin (53.7% and 70.6%), gentamicin (0% and 15.7%), streptomycin (35.2% and 84.3%), and tetracycline (18.5% and 17.7%), respectively. Resistance to azithromycin (42.6%), nalidixic acid (64.8%), and chloramphenicol (13%) was determined using the disk diffusion assay only, while resistance to tylosin (90.2%) was quantified using the broth microdilution method. The blaOXA-61 (52.6% and 28.1%), cmeB (26.3% and 31.3%), tet(O) (26.3% and 31.3%), and aph-3-1 (5.3% and 3.0%) were detected in C. coli and C. jejuni. These findings highlight the extent of antimicrobial resistance in Campylobacter occurring in important foods in Tanzania. The potential risks to consumers emphasize the need for adequate control approaches, including the prudent use of antimicrobials to minimize the spread of antimicrobial-resistant Campylobacter. PMID:26153978

Prevalence and Antimicrobial Resistance of Campylobacter Isolated from Dressed Beef Carcasses and Raw Milk in Tanzania.

PubMed

Kashoma, Isaac P; Kassem, Issmat I; John, Julius; Kessy, Beda M; Gebreyes, Wondwossen; Kazwala, Rudovick R; Rajashekara, Gireesh

2016-01-01

Campylobacter species are commonly transmitted to humans through consumption of contaminated foods such as milk and meat. The aim of this study was to investigate the prevalence, antimicrobial resistance, and genetic determinants of resistance of Campylobacter isolated from raw milk and beef carcasses in Tanzania. The antimicrobial resistance genes tested included blaOXA-61 (ampicillin), aph-3-1 (aminoglycoside), tet(O) (tetracycline), and cmeB (multi-drug efflux pump). The prevalence of Campylobacter was 9.5% in beef carcasses and 13.4% in raw milk, respectively. Using multiplex-polymerase chain reaction (PCR), we identified 58.1% of the isolates as Campylobacter jejuni, 30.7% as Campylobacter coli, and 9.7% as other Campylobacter spp. One isolate (1.6%) was positive for both C. jejuni and C. coli specific PCR. Antimicrobial susceptibility testing using the disk diffusion assay and the broth microdilution method showed resistance to: ampicillin (63% and 94.1%), ciprofloxacin (9.3% and 11.8%), erythromycin (53.7% and 70.6%), gentamicin (0% and 15.7%), streptomycin (35.2% and 84.3%), and tetracycline (18.5% and 17.7%), respectively. Resistance to azithromycin (42.6%), nalidixic acid (64.8%), and chloramphenicol (13%) was determined using the disk diffusion assay only, while resistance to tylosin (90.2%) was quantified using the broth microdilution method. The blaOXA-61 (52.6% and 28.1%), cmeB (26.3% and 31.3%), tet(O) (26.3% and 31.3%), and aph-3-1 (5.3% and 3.0%) were detected in C. coli and C. jejuni. These findings highlight the extent of antimicrobial resistance in Campylobacter occurring in important foods in Tanzania. The potential risks to consumers emphasize the need for adequate control approaches, including the prudent use of antimicrobials to minimize the spread of antimicrobial-resistant Campylobacter.

Diagnostic Accuracy Assessment of Sensititre and Agar Disk Diffusion for Determining Antimicrobial Resistance Profiles of Bovine Clinical Mastitis Pathogens▿

PubMed Central

Saini, V.; Riekerink, R. G. M. Olde; McClure, J. T.; Barkema, H. W.

2011-01-01

Determining the accuracy and precision of a measuring instrument is pertinent in antimicrobial susceptibility testing. This study was conducted to predict the diagnostic accuracy of the Sensititre MIC mastitis panel (Sensititre) and agar disk diffusion (ADD) method with reference to the manual broth microdilution test method for antimicrobial resistance profiling of Escherichia coli (n = 156), Staphylococcus aureus (n = 154), streptococcal (n = 116), and enterococcal (n = 31) bovine clinical mastitis isolates. The activities of ampicillin, ceftiofur, cephalothin, erythromycin, oxacillin, penicillin, the penicillin-novobiocin combination, pirlimycin, and tetracycline were tested against the isolates. Diagnostic accuracy was determined by estimating the area under the receiver operating characteristic curve; intertest essential and categorical agreements were determined as well. Sensititre and the ADD method demonstrated moderate to highly accurate (71 to 99%) and moderate to perfect (71 to 100%) predictive accuracies for 74 and 76% of the isolate-antimicrobial MIC combinations, respectively. However, the diagnostic accuracy was low for S. aureus-ceftiofur/oxacillin combinations and other streptococcus-ampicillin combinations by either testing method. Essential agreement between Sensititre automatic MIC readings and MIC readings obtained by the broth microdilution test method was 87%. Essential agreement between Sensititre automatic and manual MIC reading methods was 97%. Furthermore, the ADD test method and Sensititre MIC method exhibited 92 and 91% categorical agreement (sensitive, intermediate, resistant) of results, respectively, compared with the reference method. However, both methods demonstrated lower agreement for E. coli-ampicillin/cephalothin combinations than for Gram-positive isolates. In conclusion, the Sensititre and ADD methods had moderate to high diagnostic accuracy and very good essential and categorical agreement for most udder pathogen-antimicrobial combinations and can be readily employed in veterinary diagnostic laboratories. PMID:21270215

Changes of Antimicrobial Resistance among Staphylococcus Aureus Isolated in 8 Consecutive Years in the First Bethune Hospital

NASA Astrophysics Data System (ADS)

Xu, Wei; Zhou, Qi; Yang, Chunguang; Yao, Hanxin; Xu, Jiancheng

This study was to investigate the antimicrobial resistance of Staphylococcus aureus isolated in 8 consecutive years in the First Bethune Hospital. Disk diffusion test was used to study the antimicrobial resistance. The data were analyzed by WHONET 5 software according to Clinical and Laboratory Standards Institute (CLSI). Most of 1469 strains of Staphylococcus aureus were collected from sputum 705 (18.0%), secretions 206 (14.0%), pus 177 (12.0%) during the past 8 years. The rates of methicillin-resistant Staphylococcus aureus (MRSA) were between 50.8% and 83.3% during the past 8 years, respectively. In recent 8 years, the antimicrobial resistance of Staphylococcus aureus had increased. Monitoring the antimicrobial resistance to Staphylococcus aureus should be strengthened. The change of the antimicrobial resistance should be investigated in order to direct rational drug usage in the clinic and prevent bacterial strain of drug resistance from being transmitted.

Eight-Year Surveillance of Antimicrobial Resistance among Enterobacter Cloacae Isolated in the First Bethune Hospital

NASA Astrophysics Data System (ADS)

Zhou, Qi; Zhang, Man; Wang, Ailin; Xu, Jiancheng; Yuan, Ye

This study was to investigate the antimicrobial resistance of Enterobacter cloacae isolated in 8 consecutive years in the First Bethune Hospital. Disk diffusion test was used to study the antimicrobial resistance. The data were analyzed by WHONET 5 software according to Clinical and Laboratory Standards Institute (CLSI). Most of 683 strains of Enterobacter cloacae were collected from sputum 410 (60.0%), secretions and pus 105 (15.4%), urine 69 (10.1%) during the past 8 years. No Enterobacter cloacae was resistant to imipenem and meropenem in the First Bethune Hospital. The antimicrobial resistance of Enterobacter cloacae had increased in recent 8 years. The change of the antimicrobial resistance should be investigated in order to direct rational drug usage in the clinic and prevent bacterial strain of drug resistance from b eing transmitted.

In vitro comparison of antimicrobial activity of aqueous decoction of Coriandrum sativum, and Dentol Drop with chlorhexidine on Streptococcus mutans

PubMed Central

Moradian, Hamid; Bazargani, Abdollah; Rafiee, Azade; Nazarialam, Ali

2013-01-01

Background and objectives Dental caries is still remained as a major health problem. This problem has created a new interest to search for new antimicrobial agents from various sources including medicinal plants. Since limited data is available so far regarding the antibacterial effect of Coriandrum sativum seed and Dentol Drop against Streptococcus mutans, this study aims to assess this activity. Materials and Methods This experimental study was conducted in Shiraz University of Medical Sciences. In vitro comparison of antimicrobial activity of aqueous decoction of Coriandrum sativum seed and Dentol drop with chlorhexidine against Streptococcus mutans was evaluated using disk diffusion and broth microdilution assays. Positive and negative controls were considered. The data was statistically analyzed by applying Kruskal-Wallis and Tukey post-hoc test to compare the groups using SPSS software (version 17). Results Dentol drop showed a remarkable antibacterial activity, in comparison with chlorhexidine, against S. mutans in the disk diffusion (p value = 0.005), and broth microdilution assays (p value = 0.0001). Based on the results of this study, Coriandrum sativum seed did not posses any antibacterial property. Conclusion Coriandrum sativum seed showed no anti-Streptococcus mutans activity. Dentol drop exhibited a remarkable antibacterial activity against S. mutans when tested in vitro. Dentol drop can be further studied as a preventive measure for dental caries. PMID:24475330

Antimicrobial Activity of Lippia Species from the Brazilian Semiarid Region Traditionally Used as Antiseptic and Anti-Infective Agents

PubMed Central

Pinto, Cristiana da Purificação; Rodrigues, Velize Dias; Pinto, Fernanda da Purificação; Pinto, Renata da Purificação; Uetanabaro, Ana Paula Trovatti; Pinheiro, Carla Santos Ribeiro; Gadea, Suzana Ferreira Magalhães; Silva, Tânia Regina dos Santos; Lucchese, Angélica Maria

2013-01-01

Lippia origanoides Kunth, Lippia alnifolia Schauer, and Lippia thymoides Martius and Schauer are shrubs used in the traditional Brazilian medicine as antiseptics, as well as in the treatment of infectious diseases. This study was designed to investigate the antibacterial and antifungal activities of the methanolic extracts of these species, as new potential sources of antimicrobial drugs. The antimicrobial activity of methanolic extracts was investigated against resistant yeasts and bacteria by agar disk diffusion. Then, the MIC determination of the most active species and its fractions in hexane, dichloromethane, ethyl acetate, and water was performed. By the agar diffusion assay, all species were active against at least two microorganisms, giving evidence to support their use in the popular medicine. L. origanoides leaves exhibited the widest antimicrobial action, inhibiting the growth of two Gram-positive bacteria and two yeasts; this activity was also confirmed by the MIC evaluation. The fractionation of L. origanoides crude extracts improved the activity in spectrum and intensity. The results obtained in this study indicate that L. origanoides may be a promising alternative in the treatment of bacterial and fungal infections and in the seeking of new antimicrobial drugs. PMID:24109492

Incidence and Characteristics of Scarlet Fever, South Korea, 2008-2015.

PubMed

Park, Duck Woong; Kim, Sun-Hee; Park, Jung Wook; Kim, Min-Ji; Cho, Sun Ju; Park, Hye Jung; Jung, So Hyang; Seo, Mi Hee; Lee, Yong Seok; Kim, Byung Hee; Min, Hyeran; Lee, Su Ya; Ha, Dong Ryong; Kim, Eun Sun; Hong, Yeongjin; Chung, Jae Keun

2017-04-01

The incidence rate for scarlet fever in South Korea is rising. During 2008-2015, we collected group A Streptococcus isolates and performed emm and exotoxin genotyping and disk-diffusion antimicrobial tests. Scarlet fever in South Korea was most closely associated with emm types emm4, emm28, emm1, and emm3. In 2015, tetracycline resistance started increasing.

Short communication: No antimicrobial effects from one source of commercial dried distillers grains with solubles.

PubMed

Sankarlal, V Manimanna; Testroet, E D; Beitz, D C; Clark, S

2015-12-01

Because residual antibiotics in dried distillers grains with solubles (DDGS) could lead to inadvertent feeding of antibiotics to animals, the objective of our study was to determine if a commercial DDGS contained antibiotics. The DDGS used in a feeding study, and milk from cows fed the DDGS, were below the detection limits for at least 17 antibiotics. Additionally, we evaluated if DDGS had any antimicrobial effect against Salmonella Typhimurium, Listeria innocua, Escherichia coli ATCC 25922, Staphylococcus aureus, Pediococcus acidilactici, Lactobacillus casei, Lactobacillus acidophilus, Bacillus licheniformis, Paenibacillus odorifer, Pseudomonas fluorescens, and Paenibacillus amylolyticus using the disk diffusion seeded agar overlay method. Neither the buffered nor nonbuffered water-soluble fractions of DDGS yielded clear zones around disks, indicating that the water-soluble DDGS fraction had no antimicrobial properties against any of the microorganisms tested. The absence of antibiotic residues in DDGS and milk samples in this study confirmed that this source of DDGS can be used as livestock feed without fear of inadvertent feeding of antibiotics. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Antimicrobial susceptibility pattern of Klebsiella species from Ebonyi State University Teaching Hospital Abakaliki, Nigeria.

PubMed

Akujobi, C N

2005-12-01

Klesiella specie isolated from clinical specimens from Ebonyi State University Teaching Hospital (EBSUTH). Abakakliki were studied to determine the antimicrobial susceptibility pattern. Between January, 2003 and September 2004 a total of 3.600 specimens processed in the routine Medical Microbiology laboratory of EBSUTH, of which 245(6.8%) yielded Klebsiella species, with 84 from out - patients and 161 from in - patients. The number of isolates from various samples were: Urine 126, Sputum 37 Endocervical swab 13, Aspirates 8, High Vaginal Swab 7, Blood 3, Eye Swab, Ear Swab and Cerebrospinal fluid were 2 samples each. Organisms were identified by conventional methods. Antimicrobial susceptibility was done by the disk diffusion methods. The antimicrobial disk used include: Ceftazidime, Cefuroxime, Cefotaxine, Augmentin, Pefloxacin (30ug), Doxycyline (25ug) Genticin (10 ug) Ciprofloacin and Ofloxacin (5ug) each and Erythromycin (15ug). All were Oxoid products. Results were interpreted according to NCCLS criteria. Klebsilla species were isolated mostly from urine specimens (51.4%) followed by wound swabs (18.4%). Antimicrobial susceptibility to various groups drugs used was generally poor. The most sensitive antimicrobial was Ciprofloxacin with 121(49.4%) isolates susceptible to it, followed by Gentamicin with 95 (38.8%) and Ceftazidime with 90(36.7%). Seventeen isolates were multiresistant to all the antimicrobial agents used. The result of this study will help in the empiric therapy of infection caused by Klebsiella species in Ebonyi State University Teaching Hospital, Abakaliki, Nigeria but continuous surverillance of antimicrobial resistance of the organnisn is very necessary in the formulation of a sound antibiotic policy in the hospital.

Analysis of antimicrobial, antifungal and antioxidant activities of Juniperus excelsa M. B subsp. Polycarpos (K. Koch) Takhtajan essential oil

PubMed Central

Moein, M. R.; Ghasemi, Y.; Moein, S.; Nejati, M.

2010-01-01

Juniperus excelsa M.B subsp. Polycarpos (K.Koch), collected from south of Iran, was subjected to hydrodistillation using clevenger apparatus to obtain essential oil. The essential was analyzed by gas chromatography/mass spectrometry (GC/MS) and studied for antimicrobial, antifungal and antioxidant activities. The results indicated α-pinene (67.71%) as the major compound and α-cedral (11.5%), δ3-carene (5.19%) and limonene (4.41%) in moderate amounts. Antimicrobial tests were carried out using disk diffusion method, followed by the measurement of minimum inhibitory concentration (MIC). All the Gram positive and Gram negative bacteria were susceptible to essential oil. The oil showed radical scavenging and antioxidant effects. PMID:21808554

Antimicrobial susceptibility and distribution of inhibition zone diameters of bovine mastitis pathogens in Flanders, Belgium.

PubMed

Supré, K; Lommelen, K; De Meulemeester, L

2014-07-16

In dairy farms, antimicrobial drugs are frequently used for treatment of (sub)clinical mastitis. Determining the antimicrobial susceptibility of mastitis pathogens is needed to come to a correct use of antimicrobials. Strains of Staphylococcus aureus (n=768), Streptococcus uberis (n=939), Streptococcus dysgalactiae (n=444), Escherichia coli (n=563), and Klebsiella species (n=59) originating from routine milk samples from (sub)clinical mastitis were subjected to the disk diffusion method. Disks contained representatives of frequently used antibiotics in dairy. A limited number of clinical breakpoints were available through CLSI, and showed that susceptibility of Staph. aureus, E. coli, and Klebsiella was moderate to high. For streptococcal species however, a large variation between the tested species and the different antimicrobials was observed. In a next step, wild type populations were described based on epidemiological cut off values (EUCAST). Because of the limited number of official cut off values, the data were observed as a mastitis subpopulation and self-generated cut off values were created and a putative wild type population was suggested. The need for accurate clinical breakpoints for veterinary pathogens is high. Despite the lack of these breakpoints, however, a population study can be performed based on the distribution of inhibition zone diameters on the condition that a large number of strains is tested. Copyright © 2014 Elsevier B.V. All rights reserved.

Incidence and Characteristics of Scarlet Fever, South Korea, 2008–2015

PubMed Central

Park, Duck Woong; Kim, Sun-Hee; Park, Jung Wook; Kim, Min-Ji; Cho, Sun Ju; Park, Hye Jung; Jung, So Hyang; Seo, Mi Hee; Lee, Yong Seok; Kim, Byung Hee; Min, Hyeran; Lee, Su Ya; Ha, Dong Ryong; Kim, Eun Sun

2017-01-01

The incidence rate for scarlet fever in South Korea is rising. During 2008–2015, we collected group A Streptococcus isolates and performed emm and exotoxin genotyping and disk-diffusion antimicrobial tests. Scarlet fever in South Korea was most closely associated with emm types emm4, emm28, emm1, and emm3. In 2015, tetracycline resistance started increasing. PMID:28322696

Antimicrobial Susceptibilities and Plasmid Contents of Neisseria gonorrhoeae Isolates from Commercial Sex Workers in Dhaka, Bangladesh: Emergence of High-Level Resistance to Ciprofloxacin

PubMed Central

Bhuiyan, Bahar Uddin; Rahman, Motiur; Miah, Mohammed Ruhul Amin; Nahar, Shamsun; Islam, Nazrul; Ahmed, Monira; Rahman, Kazi Masihur; Albert, M. John

1999-01-01

Commercial sex workers (CSWs) serve as the most important reservoir of sexually transmitted diseases (STD), including gonorrhea. Periodic monitoring of the antimicrobial susceptibility profile of Neisseria gonorrhoeae in a high-risk population provides essential clues regarding the rapidly changing pattern of antimicrobial susceptibilities. A study concerning the prevalence of gonococcal infection among CSWs was conducted in Bangladesh. The isolates were examined with regards to their antimicrobial susceptibility to, and the MICs of, penicillin, tetracycline, ciprofloxacin, cefuroxime, ceftriaxone, and spectinomycin by disk diffusion and agar dilution methods. The total plasmid profile of the isolates was also analyzed. Of the 224 CSWs, 94 (42%) were culture positive for N. gonorrhoeae. There was a good correlation between the results of the disk diffusion and agar dilution methods. Some 66% of the isolates were resistant to penicillin, and 34% were moderately susceptible to penicillin. Among the resistant isolates, 23.4% were penicillinase-producing N. gonorrhoeae (PPNG). 60.6% of the isolates were resistant and 38.3% were moderately susceptible to tetracycline, 17.5% were tetracycline-resistant N. gonorrhoeae, 11.7% were resistant and 26.6% had reduced susceptibility to ciprofloxacin, 2.1% were resistant and 11.7% had reduced susceptibility to cefuroxime, and 1% were resistant to ceftriaxone. All PPNG isolates contained a 3.2-MDa African type of plasmid, and a 24.2-MDa conjugative plasmid was present in 34.1% of the isolates. Since quinolones such as ciprofloxacin are recommended as the first line of therapy for gonorrhea, the emergence of significant resistance to ciprofloxacin will limit the usefulness of this drug for treatment of gonorrhea in Bangladesh. PMID:10074537

Susceptibility to antimicrobials of mastitis-causing Staphylococcus aureus, Streptococcus uberis and Str. dysgalactiae from New Zealand and the USA as assessed by the disk diffusion test.

PubMed

Petrovski, K R; Grinberg, A; Williamson, N B; Abdalla, M E; Lopez-Villalobos, N; Parkinson, T J; Tucker, I G; Rapnicki, P

2015-07-01

To compare the antimicrobial susceptibility patterns of three common mastitis pathogens (Staphylococcus aureus, Streptococcus uberis and Str. dysgalactiae) isolated from milk samples from New Zealand and the USA. A total of 182 S. aureus, 126 Str. uberis and 89 Str. dysgalactiae isolates from New Zealand (107, 106 and 41, respectively) and the USA (75, 20 and 48, respectively) were assessed using the disk diffusion test. Susceptibility varied among the bacterial species. All isolates were susceptible to the amoxicillin-clavulanic acid combination. Resistance to lincomycin was most frequent (susceptibility of 8.6%) across all species. Non-susceptible (i.e. resistant or intermediate) isolates of S. aureus were identified for the three non-isoxazolyl penicillins (amoxicillin, ampicillin and penicillin: 20.6% and 36.0%) and lincomycin (99.9% and 94.6%) for NZ and the USA, respectively. Resistance to erythromycin (5.3%) and tetracyclines (6.7%) was detected only in isolates from the USA. There were differences in susceptibility between Str. uberis and Str. dysgalactiae; all streptococcal isolates demonstrated resistance to aminoglycosides (neomycin 52.4% and streptomycin 27.9%) and enrofloxacin (28%). Resistance of Str. dysgalactiae to tetracycline was almost 100.0% and to oxytetracycline 89.9%. Most of the isolates tested were susceptible to most of the antimicrobials commonly used for treatment of bovine mastitis, with the exception of the lincosamides. Susceptibility to a selected class-representative antimicrobial and at the genus level should be interpreted with caution. Differences between NZ and the USA confirm the value of national surveys to determine the susceptibility patterns of mastitis pathogens. © 2015 Australian Veterinary Association.

[Antimicrobial susceptibility testing in clinically relevant non-fermenting gram-negative bacilli: recommendations from the Antimicrobial Agents Subcommittee of the Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas, Asociación Argentina de Microbiología].

PubMed

Radice, Marcela; Marín, Marcelo; Giovanakis, Marta; Vay, Carlos; Almuzara, Marisa; Limansky, Adriana; Casellas, José M; Famiglietti, Angela; Quinteros, Mirta; Bantar, Carlos; Galas, Marcelo; Kovensky Pupko, Jaime; Nicola, Federico; Pasterán, Fernando; Soloaga, Rolando; Gutkind, Gabriel

2011-01-01

This document contains the recommendations for antimicrobial susceptibility testing of the clinically relevant non-fermenting gram-negative bacilli (NFGNB), adopted after conforming those from international committees to the experience of the Antimicrobial Agents Subcommittee members and invited experts. This document includes an update on NFGNB classification and description, as well as some specific descriptions regarding natural or frequent antimicrobial resistance and a brief account of associated resistance mechanisms. These recommendations not only suggest the antimicrobial drugs to be evaluated in each case, but also provide an optimization of the disk diffusion layout and a selection of results to be reported. Finally, this document also includes a summary of the different methodological approaches that may be used for detection and confirmation of emerging b-lactamases, such as class A and B carbapenemases.

The antimicrobial activity of probiotic bacteria Escherichia coli isolated from different natural sources against hemorrhagic E. coli O157:H7.

PubMed

Karimi, Sahar; Azizi, Fatemeh; Nayeb-Aghaee, Mohammad; Mahmoodnia, Leila

2018-03-01

Diarrheal diseases have been seen in all geographical areas throughout the world. Therefore, considering treatment, could be deemed a necessary action. The aim of this study was to determine the antimicrobial effect of probiotic bacterial strains isolated from different natural sources against 2 pathotypes of pathogenic E. coli. This cross-sectional study of Martyr Chamran University of Ahvaz was carried out from December 2013 to July 2014. A total of 13 probiotic colonies isolated from 20 samples of traditional dairy products including (yogurt, cheese, milk) and 20 samples of vegetables including carrots and cabbages (red and white) of which 5 isolates were selected to evaluate the antimicrobial effect against 2 Escherichia coli pathotypes, randomly. Antimicrobial effect was evaluated using two methods: disk diffusion and well diffusion tests and measuring growth inhibition zones of probiotics against 2 pathotypes of pathogenic E. coli. Obtained results showed growth inhibition effects of all 5 probiotic strains against Escherichia coli pathotypes in both used methods. All selected strains showed considerable antimicrobial effect on Escherichia coli O157:H7 strain, but had no inhibitory effect against Enterohemorrhagic Escherichia coli. This study demonstrated considerable antimicrobial effect against E. coli O157:H7 strain. Due to this, characteristic and similar antimicrobial effects of probiotics bacteria, increasing use of the probiotics as a natural and modern method for prevention of different diseases is recommended.

Screening of antimicrobial activity of macroalgae extracts from the Moroccan Atlantic coast.

PubMed

El Wahidi, M; El Amraoui, B; El Amraoui, M; Bamhaoud, T

2015-05-01

The aim of this work is the screening of the antimicrobial activity of seaweed extracts against pathogenic bacteria and yeasts. The antimicrobial activity of the dichloromethane and ethanol extracts of ten marine macroalgae collected from the Moroccan's Atlantic coast (El-Jadida) was tested against two Gram+ (Bacillus subtilis and Staphylococcus aureus) and two Gram- (Escherichia coli and Pseudomonas aeruginosa) human pathogenic bacteria, and against two pathogenic yeasts (Candida albicans and Cryptococcus neoformans) using the agar disk-diffusion method. Seven algae (70%) of ten seaweeds are active against at least one pathogenic microorganisms studied. Five (50%) are active against the two studied yeast with an inhibition diameter greater than 15 mm for Cystoseira brachycarpa. Six (60%) seaweeds are active against at least one studied bacteria with five (50%) algae exhibiting antibacterial inhibition diameter greater than 15 mm. Cystoseira brachycarpa, Cystoseira compressa, Fucus vesiculosus, and Gelidium sesquipedale have a better antimicrobial activity with a broad spectrum antimicrobial and are a potential source of antimicrobial compounds and can be subject of isolation of the natural antimicrobials. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Antimicrobial activity and cytotoxic effects of Magnolia dealbata and its active compounds.

PubMed

Jacobo-Salcedo, Maria del Rosario; Gonzalez-Espindola, Luis Angel; Alonso-Castro, Angel Josabad; Gonzalez-Martinez, Marisela del Rocio; Domínguez, Fabiola; Garcia-Carranca, Alejandro

2011-08-01

Multi-drug resistance is of great concern for public health worldwide and necessitates the search for new antimicrobials from sources such as plants. Several Magnolia (Magnoliaceae) species have been reported to exert antimicrobial effects on sensitive and multidrug-resistant microorganisms. However, the antimicrobial properties of Magnolia dealbata have not been experimentally evaluated. The antimicrobial effects of an ethanol extract of Magnolia dealbata seeds (MDE) and its active compounds honokiol (HK) and magnolol (MG) were tested against the phytopathogen Clavibacter michiganensis subsp. michiganensis and several human multi-drug resistant pathogens using the disk-diffusion assay. The effects of MDE and its active compounds on the viability of human peripheral blood mononuclear cells (PBMC) were evaluated using MTT assay. MDE and its active compounds had antimicrobial activity (inhibition zone > 10 mm) against C. michiganensis, Pseudomonas aeruginosa, Acinetobacter baumannii, Acinetobacter lwoffii, Candida albicans, Candida tropicalis and Trichosporon belgeii. The results suggest that M. dealbata and its active compounds have selective antimicrobial effects against drug-resistant fungal and Gram (-) bacteria and exert minimal toxic effects on human PMBC.

Eight-year Surveillance of Antimicrobial Resistance among Enterococcus Spp. Isolated in the First Bethune Hospital

NASA Astrophysics Data System (ADS)

Xu, Jiancheng; Wang, Liqiang; Wang, Kai; Zhou, Qi

This study was to investigate the antimicrobial resistance of Enterococcus spp. isolated in 8 consecutive years in the First Bethune Hospital. Disk diffusion test was used to study the antimicrobial resistance. The data were analyzed by WHONET 5 software according to Clinical and Laboratory Standards Institute (CLSI). Most of 1446 strains of Enterococcus spp. were collected from urine 640 (44.3%), sputum 315 (21.8%), secretions and pus 265 (18.3%) during the past 8 years. The rates of high-level aminoglycoside resistance in Enterococcus faecalis and Enterococcus faecium were 57.4%∼75.9% and 69.0%∼93.8% during the past 8 years, respectively. No Enterococcus spp. was resistant to vancomycin. The antimicrobial resistance of Enterococcus spp. had increased in recent 8 years. The change of the antimicrobial resistance should be investigated in order to direct rational drug usage in the clinic and prevent bacterial strain of drug resistance from being transmitted.

GC-MS analysis and antimicrobial activity determination of Citrus medica L. var proper leaf essential oil from South Sulawesi against skin pathogen microorganism

NASA Astrophysics Data System (ADS)

Aliyah; Himawan, A.; Rante, H.; Mufidah; Ningsih, D. R.

2017-11-01

A research about Citrus medica L. var sarcodactylis had been conducted and it showed a significant antimicrobial activity, thus drive our curiosity to investigate the other variety from the same species, Citrus medica L. var proper. This research focuses in chemical compound study and antimicrobial activity screening against Staphylococcus aureus, Propionibacterium acne, and Candida albicans of Citrus medica L. var Proper leaves’ essential oil. The essential oil is distillated from fresh leaves by hydrodestillation. The chemical compound was analysed using GC-MS instrument while the antimicrobial activity was tested using disk diffusion method. The results showed that the major component of the essential oil was Z-citral, citral and limonene compounds. The antimicrobial activity test results against the test microorganism are 9.15±0.15 mm, 11.15±1.3 mm and 8.02±0.48 mm, consecutively, for Staphylococcus aureus, Propionibacterium acne and Candida albicans.

Choosing the correct empirical antibiotic for urinary tract infection in pediatric: Surveillance of antimicrobial susceptibility pattern of Escherichia coli by E-Test method.

PubMed

Sedighi, Iraj; Solgi, Abbas; Amanati, Ali; Alikhani, Mohammad Yousef

2014-12-01

Urinary Tract Infections (UTIs) are of the most common bacterial diseases worldwide. We investigate the antibiotic susceptibility patterns of Escherichia coli (E. coli) strains isolated from pediatric patients with community acquired urinary tract infection (UTI) to find a clinical guidance for choosing a right empirical antibiotic in these patients. In this cross sectional study, 100 urine specimens which were positive for E. coli had been investigated for antibiotics susceptibility pattern. The susceptibility to Co-trimoxazol (25μg), Amikacin (30μg), Ceftriaxone (30μg), Nalidixic Acid (30μg), Cefixime (5μg), and Nitrofurantoin (300μg) tested with Disk diffusion agar and MIC determined with the E-test. Mean age of patients was 38 Months. Girls had greater proportion than boys (74 versus 26%). In Disk diffusion method, 26% of the isolates were susceptible to cotrimoxazole. Susceptibility to amikacin, ceftriaxone, nitrofurantoin, nalidixic acid and cefixime was 94%, 66%, 97%, 62% and 52%, respectively. By E-Test method and according to CLSI criteria susceptibility for co-trimoxazol, amikacin, ceftriaxone and nalidixic acid was 37%, 97%, 67% and 50%, respectively. The highest percentage of agreement between Disk diffusion and E-Test method was found for amikacin (96%) and the lowest percentage for co-trimoxazole (89%). Treatment failure, prolonged or repeated hospitalization, increased costs of care, and increased mortality are some consequence of bacterial resistance in UTIs. Misuse of antibiotics in each geographic location directly affects antibiotic resistance pattern. In the treatment of UTI, proper selection of antimicrobial agents should be relevant to the bacterial susceptibility testing surveillance. According to our results, amikacin as an injectable drug and nitrofurantoin as an oral agent could be used as a drug of choice in our region for children with UTIs.

Bioactive capacity of some Romanian wild edible mushrooms consumed mainly by local communities.

PubMed

Vamanu, Emanuel

2018-02-01

Wild edible mushrooms are considered as a cheap food source, but rich in bioactive compounds, especially in phenolic compounds. The purpose of the study was to determine the antioxidant and antimicrobial activity and the content of polyphenolcarboxylic acids in 10 species of mushrooms commonly used (consumed) in Romania and two controls. The effect against free radicals, lipid peroxidation and reducing power were determined. The antimicrobial effect was revealed on some strains with pathogenic effect by disk diffusion assay. The antioxidant capacity expressed in vitro was correlated both with the presence of the main polyphenolcarboxylic acids, and also with the presence of other bioactive molecules (flavonoids, carotenoid compounds, etc.).

Prevalence of Methicillin-Resistant and Methicillin-Susceptible S. Aureusin the Saliva of Health Professionals

PubMed Central

de Carvalho, Milton Jorge; Pimenta, Fabiana Cristina; Hayashida, Miyeko; Gir, Elucir; da Silva, Adriana Maria; Barbosa, Caio Parente; da Silva Canini, Silvia Rita Marin; Santiago, Silvana

2009-01-01

INTRODUCTION: S. aureus is one of the main agents of nosocomial infection and is sometimes difficult to treat with currently available active antimicrobials. PURPOSE: To analyze the prevalence of methicillin-susceptible S.aureus (MSSA) and methicillin-resistant S. aureus (MRSA) as well as the MRSA antimicrobial susceptibility profile isolated in the saliva of health professionals at a large public education hospital. MATERIALS AND METHODS: The project was approved by the research and ethics committee of the institution under study. Three samples of saliva from 340 health professionals were collected. The saliva analysis used to identify S. aureus was based on mannitol fermentation tests, catalase production, coagulase, DNAse, and lecithinase. In order to detect MRSA, samples were submitted to the disk diffusion test and the oxacillin agar screening test. In order to identify the minimum inhibitory concentration, the Etest® technique was used. RESULTS: The prevalence of MSSA was 43.5% (148/340), and MRSA was 4.1% (14/340). MRSA detected by the diffusion disk test, was 100% resistant to penicillin and oxacillin, 92.9% resistant to erythromycin, 57.1% resistant to clindamycin, 42.9% resistant to ciprofloxacin and 57.1% resistant to cefoxetin. CONCLUSION: This subject is important for both the education of health professionals and for preventative measures. Standard and contact-precautions should be employed in professional practice. PMID:19488585

GC-MS profile of antimicrobial and antioxidant fractions from Cordia rothii roots.

PubMed

Khan, Kehkashan; Firdous, Sadiqa; Ahmad, Aqeel; Fayyaz, Nida; Nadir, Muhammad; Rasheed, Munawwer; Faizi, Shaheen

2016-11-01

An ethnobotanical survey of Cordia rothii Roem. & Schult. (Boraginaceae) reveals it as a medicinal plant. Antimicrobial and antioxidant potential evaluation and identification of chemical constituents via GC-MS of C. rothii roots fractions. To the best of our knowledge, this is the first systematic investigation of the roots exploiting GC-MS. Extraction and fractionation of C. rothii roots furnished various fractions using solvents of varying polarity, i.e., n-hexane, chloroform, ethyl acetate, acetone and methanol. In vitro antimicrobial and antioxidant screening was performed using disk diffusion and DPPH methods, respectively. MIC of active fractions was also determined using disk diffusion method. GC-MS was used to identify constituents which may be responsible for these activities. Among various fractions from C. rothii roots, fraction KA-C showed strong antibacterial activity against 17 microorganisms tested, with MIC ranging from 250-31.25 μg/mL. Fractions KA-A, KM and KM-A exhibited significant antioxidant potential with EC 50 46.875 μg/mL, while fractions KEA-PE, KM-PE and KM-M were good with EC 50 93.750 μg/mL. Forty-five phytochemicals were identified in GC-MS studies including eight hydrocarbons, six free fatty acids, 11 fatty acids esters, two phenylpropanoids, four aromatics, four terpenoid quinones/hydroquinones, three triterpenes, four phytosterols, two hexose metabolites and a DNA base. Of these, 32 constituents have been reported for the first time from C. rothii, 24 from genus Cordia and 15 from Boraginaceae. Strong antibacterial and antioxidant potential of C. rothii roots may be due to the contribution of phytoconstituents identified through GC-MS studies.

Antimicrobial and cytotoxic effects of Mexican medicinal plants.

PubMed

Jacobo-Salcedo, Maria del Rosario; Alonso-Castro, Angel Josabad; Salazar-Olivo, Luis A; Carranza-Alvarez, Candy; González-Espíndola, Luis Angel; Domínguez, Fabiola; Maciel-Torres, Sandra Patricia; García-Lujan, Concepción; González-Martínez, Marisela del Rocio; Gómez-Sánchez, Maricela; Estrada-Castillón, Eduardo; Zapata-Bustos, Rocio; Medellin-Milán, Pedro; García-Carrancá, Alejandro

2011-12-01

The antimicrobial effects of the Mexican medicinal plants Guazuma ulmifolia, Justicia spicigera, Opuntia joconostle, O. leucotricha, Parkinsonia aculeata, Phoradendron longifolium, P. serotinum, Psittacanthus calyculatus, Tecoma stans and Teucrium cubense were tested against several human multi-drug resistant pathogens, including three Gram (+) and five Gram (-) bacterial species and three fungal species using the disk-diffusion assay. The cytotoxicity of plant extracts on human cancer cell lines and human normal non-cancerous cells was also evaluated using the MTT assay. Phoradendron longifolium, Teucrium cubense, Opuntia joconostle, Tecoma stans and Guazuma ulmifolia showed potent antimicrobial effects against at least one multidrug-resistant microorganism (inhibition zone > 15 mm). Only Justicia spicigera and Phoradendron serotinum extracts exerted active cytotoxic effects on human breast cancer cells (IC50 < or = 30 microg/mL). The results showed that Guazuma ulmifolia produced potent antimicrobial effects against Candida albicans and Acinetobacter lwoffii, whereas Justicia spicigera and Phoradendron serotinum exerted the highest toxic effects on MCF-7 and HeLa, respectively, which are human cancer cell lines. These three plant species may be important sources of antimicrobial and cytotoxic agents.

Antimicrobial-resistant Klebsiella species isolated from free-range chicken samples in an informal settlement.

PubMed

Fielding, Burtram C; Mnabisa, Amanda; Gouws, Pieter A; Morris, Thureyah

2012-02-29

Sub-therapeutic doses of antimicrobial agents are administered routinely to poultry to aid growth and to prevent disease, with prolonged exposure often resulting in bacterial resistance. Crossover of antibiotic resistant bacteria from poultry to humans poses a risk to human health. In this study, 17 chicken samples collected from a vendor operating in an informal settlement in the Cape Town Metropolitan area, South Africa were screened for antimicrobial-resistant Gram-negative bacilli using the Kirby Bauer disk diffusion assay. IN TOTAL, SIX ANTIBIOTICS WERE SCREENED: ampicillin, ciprofloxacin, gentamicin, nalidixic acid, tetracycline and trimethoprim. Surprisingly, Klebsiella ozaenae was identified in 96 and K. rhinoscleromatis in 6 (n=102) of the samples tested. Interestingly, ∼40% of the isolated Klebsiella spp. showed multiple resistance to at least three of the six antibiotics tested. Klebsiella ozaenae and K. rhinoscleromatis cause clinical chronic rhinitis and are almost exclusively associated with people living in areas of poor hygiene.

Comparison of antimicrobial susceptibilities of Corynebacterium species by broth microdilution and disk diffusion methods.

PubMed Central

Weiss, K; Laverdière, M; Rivest, R

1996-01-01

Corynebacterium species are increasingly being implicated in foreign-body infections and in immunocompromised-host infections. However, there are no specific recommendations on the method or the criteria to use in order to determine the in vitro activities of the antibiotics commonly used to treat Corynebacterium infections. The first aim of our study was to compare the susceptibilities of various species of Corynebacterium to vancomycin, erythromycin, and penicillin by using a broth microdilution method and a disk diffusion method. Second, the activity of penicillin against our isolates was assessed by using the interpretative criteria recommended by the National Committee for Clinical Laboratory Standards for the determination of the susceptibility of streptococci and Listeria monocytogenes to penicillin. Overall, 100% of the isolates were susceptible to vancomycin, while considerable variations in the activities of erythromycin and penicillin were noted for the different species tested, including the non-Corynebacterium jeikeium species. A good correlation in the susceptibilities of vancomycin and erythromycin between the disk diffusion and the microdilution methods was observed. However, a 5% rate of major or very major errors was detected with the Listeria criteria, while a high rate of minor errors (18%) was noted when the streptococcus criteria were used. Our findings indicate considerable variations in the activities of erythromycin and penicillin against the various species of Corynebacterium. Because of the absence of definite recommendations, important discrepancies were observed between the methods and the interpretations of the penicillin activity. PMID:8849254

The Prevalence of Extended-Spectrum Beta-Lactamase-Producing Multidrug-Resistant Escherichia Coli in Poultry Chickens and Variation According to Farming Practices in Punjab, India

PubMed Central

Mandal, Siddhartha; Hayer, Shivdeep; Sran, Mandeep; Zehra, Asima; Patel, Sunny J.; Kaur, Ravneet; Chatterjee, Leena; Mishra, Savita; Das, B.R.; Singh, Parminder; Singh, Randhir; Gill, J.P.S.

2017-01-01

Background: Agricultural use of antimicrobials in subtherapeutic concentrations is increasing in response to the rising demand for food animal products worldwide. In India, the use of antimicrobials in food animal production is unregulated. Research suggests that many clinically important antimicrobials are used indiscriminately. This is the largest study to date in India that surveys poultry production to test for antimicrobial resistance and the occurrence of extended-spectrum β-lactamases (ESBLs) modulated by farming and managerial practices. Objectives: Our goal was to survey poultry production for resistance to eleven clinically relevant antimicrobials and phenotypic occurrence of ESBLs as modulated by farming and managerial practices. Methods: Eighteen poultry farms from Punjab were surveyed, and 1,556 Escherichia coli isolates from 530 birds were tested for susceptibility to 11 antimicrobials using the disk diffusion method and validated using VITEK 2 (bioMérieux, Marcy-L’Étoile, France). Samples from 510 of these birds were phenotypically tested for ESBL production using the combination disk method and confirmed using VITEK 2. Generalized linear mixed models were used to infer differences in resistance profiles associated with different farming practices and facility types. Results: Resistance profiles were significantly different between broiler and layer farms. Broiler farms were 2.2 [ampicillin (AMP), p=0.017] to 23 [nalidixic acid (NX), p<0.001] times more likely to harbor resistant E. coli strains than layer farms. Adjusting for farm type (broiler vs. layer), the odds of resistance (although not statistically significant) to all antimicrobials except nitrofurantoin (NIT) were higher in independent facilities (IUs) as compared to contracted facilities (CFs). Increased prevalence of multidrug resistance (MDR; 94% compared to 60% in layers), including prevalence of ESBL-producing strains (87% compared to 42% in layers), was observed in broiler farms. Conclusions: Our findings suggest that unregulated use of clinically relevant antimicrobials in Indian broiler and layer farms may contribute to the emergence of resistance and support the need to curb the nontherapeutic use of medically important antimicrobials in food animal production. https://doi.org/10.1289/EHP292 PMID:28749780

Evaluation of the effectiveness of different brands' disks in antimicrobial disk susceptibility tests.

PubMed

Lam, C P; Tsai, W C

1989-08-01

A total of 813 routine isolates of aerobic and facultatively anaerobic bacteria were employed to determine the efficacy of different branded (Oxoid, Difco, BBL) antimicrobial disks, using disk antimicrobial susceptibility tests, for a total of 22 kinds of antimicrobial disks and 10,740 antibiotic-organism comparisons. Major positive and major negative discrepancies in results were defined as a change from "susceptible" to "both resistant", and a change from "resistant" to "both susceptible" according to the National Committee for Clinical Laboratory Standards' interpretive standards for zone diameters. Minor positive and minor negative discrepancies were defined as a change from "susceptible" to "both intermediate", or "intermediate" to "both resistant"; and a change from "resistant" to "both intermediate", or "intermediate" to "both susceptible". The overall agreements of Oxoid, Difco, and BBL systems were 98%, 98.7%, and 98.4% respectively, and their differences are not statistically significant. Different kinds of antimicrobial disks' representative patterns of these three brands are further analyzed: (A) In the Oxoid series, there were 220 discrepancies. Minor negative discrepancy is predominant, most frequently related to carbenicillin (25), gentamicin (13) and cephalothin (10). Besides minor negative discrepancy, carbenicillin also had six minor positive discrepancies. Tetracyclin had ten minor positive discrepancies. (B) In the Difco series, there were 137 discrepancies. The majority of them are minor positive discrepancies. Moxalactam (11) and cefotaxime (10) are the most common antibiotics involved. (C) In the BBL series, there were 170 discrepancies. Minor positive discrepancy was the predominant one, which mostly related to carbenicillin (24), amikacin (13), and ceftizoxime (12). In addition, tetracyclin had 24 times minor negative discrepancies. Laboratory workers must pay attention to these different patterns of representation. In order to evaluate the quality of 11 pairs of the give-away and the purchased BBL disks, we also compared the results for these 813 routine isolates (a total of 5,482 antibiotic-organism comparisons). The giveaway disks demonstrated 99.1% overall agreement with the purchased disks. There were 48 minor discrepancies [26 (0.47%) minor positive discrepancies and 22 (0.4%) minor negative discrepancies]. These results allow this study to emphasize the followings in order to raise the awareness of the laboratory workers: (i) alteration of disk efficacy during transportation and storage; (ii) major considerations in choosing different brands' antimicrobial disks, and (iii) the important roles played by salespersons and pharmaceutical companies in achieving sound results.

Antimicrobial activity of honey of stingless bees, tiúba (Melipona fasciculata) and jandaira (Melipona subnitida) compared to the strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa

NASA Astrophysics Data System (ADS)

Tenório, Eleuza Gomes; de Jesus, Natália Rocha; Nascimento, Adenilde Ribeiro; Teles, Amanda Mara

2015-12-01

This study aimed to investigate the antimicrobial activity of honeys of stingless bees produced in Maranhão, tiúba (Melipona fasciculata) and jandaira (Melipona subnitida), opposite the strains of pathogenic bacteria, namely, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. The honey samples were collected from different regions of Maranhão. Of the 17 samples collected, twelve samples were honey M. fasciculata and five were honey M. subnitida. We used the Kirby-Bauer method, and the technique of agar disk diffusion through the extent of inhibition in milimetros. Results were negative for all samples from M. fasciculata. However, the tests for M. subnitida demonstrated bacteriostatic halos ranging from 12 to 32,6mm.

Essential oil of the leaves of Ricinus communis L.: in vitro cytotoxicity and antimicrobial properties.

PubMed

Zarai, Zied; Ben Chobba, Ines; Ben Mansour, Riadh; Békir, Ahmed; Gharsallah, Néji; Kadri, Adel

2012-08-13

The aim of the present study was to appraise the antimicrobial activity of Ricinus communis L. essential oil against different pathogenic microorganisms and the cytotoxic activity against HeLa cell lines. The agar disk diffusion method was used to study the antibacterial activity of Ricinus communis L. essential oil against 12 bacterial and 4 fungi strains. The disc diameters of zone of inhibition (DD), the minimum inhibitory concentrations (MIC) and the concentration inhibiting 50% (IC50) were investigated to characterize the antimicrobial activities of this essential oil. The in vitro cytotoxicity of Ricinus communis L. essential oil was examined using a modified MTT assay; the viability and the IC50 were used to evaluate this test. The essential oil from the leaves of Ricinus communis L. was analyzed by GC-MS and bioassays were carried out. Five constituents of the oil were identified by GC-MS. The antimicrobial activity of the oil was investigated in order to evaluate its efficacy against twelve bacteria and four fungi species, using disc diffusion and minimum inhibitory concentration methods. The essential oil showed strong antimicrobial activity against all microorganisms tested with higher sensitivity for Bacillus subtilis, Staphylococcus aureus and Enterobacter cloacae. The cytotoxic and apoptotic effects of the essential oil on HeLa cell lines were examined by MTT assay. The cytotoxicity of the oil was quite strong with IC50 values less than 2.63 mg/ml for both cell lines. The present study showed the potential antimicrobial and anticarcinogenic properties of the essential oil of Ricinus communis L., indicating the possibilities of its potential use in the formula of natural remedies for the topical treatment of infections.

Antimicrobial activity and mechanism of the human milk-sourced peptide Casein201

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Fan; Department of Endocrinology, Children's Hospital of Nanjing Medical University, Nanjing; Cui, Xianwei

Introduction: Casein201 is one of the human milk sourced peptides that differed significantly in preterm and full-term mothers. This study is designed to demonstrate the biological characteristics, antibacterial activity and mechanisms of Casein201 against common pathogens in neonatal infection. Methodology: The analysis of biological characteristics was done by bioinformatics. Disk diffusion method and flow cytometry were used to detect the antimicrobial activity of Casein201. Killing kinetics of Casein201 was measured using microplate reader. The antimicrobial mechanism of Casein201 was studied by electron microscopy and electrophoresis. Results: Bioinformatics analysis indicates that Casein201 derived from β-casein and showed significant sequence overlap. Antibacterialmore » assays showed Casein201 inhibited the growth of S taphylococcus aureus and Y ersinia enterocolitica. Ultrastructural analyses revealed that the antibacterial activity of Casein201 is through cytoplasmic structures disintegration and bacterial cell envelope alterations but not combination with DNA. Conclusion: We conclude the antimicrobial activity and mechanism of Casein201. Our data demonstrate that Casein201 has potential therapeutic value for the prevention and treatment of pathogens in neonatal infection.« less

Antimicrobial activity and mechanism of the human milk-sourced peptide Casein201.

PubMed

Zhang, Fan; Cui, Xianwei; Fu, Yanrong; Zhang, Jun; Zhou, Yahui; Sun, Yazhou; Wang, Xing; Li, Yun; Liu, Qianqi; Chen, Ting

2017-04-08

Casein201 is one of the human milk sourced peptides that differed significantly in preterm and full-term mothers. This study is designed to demonstrate the biological characteristics, antibacterial activity and mechanisms of Casein201 against common pathogens in neonatal infection. The analysis of biological characteristics was done by bioinformatics. Disk diffusion method and flow cytometry were used to detect the antimicrobial activity of Casein201. Killing kinetics of Casein201 was measured using microplate reader. The antimicrobial mechanism of Casein201 was studied by electron microscopy and electrophoresis. Bioinformatics analysis indicates that Casein201 derived from β-casein and showed significant sequence overlap. Antibacterial assays showed Casein201 inhibited the growth of S taphylococcus aureus and Y ersinia enterocolitica. Ultrastructural analyses revealed that the antibacterial activity of Casein201 is through cytoplasmic structures disintegration and bacterial cell envelope alterations but not combination with DNA. We conclude the antimicrobial activity and mechanism of Casein201. Our data demonstrate that Casein201 has potential therapeutic value for the prevention and treatment of pathogens in neonatal infection. Copyright © 2017 Elsevier Inc. All rights reserved.

Short communication: Lactic acid bacteria from the honeybee inhibit the in vitro growth of mastitis pathogens.

PubMed

Piccart, K; Vásquez, A; Piepers, S; De Vliegher, S; Olofsson, T C

2016-04-01

Despite the increasing knowledge of prevention and control strategies, bovine mastitis remains one of the most challenging diseases in the dairy industry. This study investigated the antimicrobial activity of 13 species of lactic acid bacteria (LAB), previously isolated from the honey crop of the honeybee, on several mastitis pathogens. The viable LAB were first reintroduced into a sterilized heather honey matrix. More than 20 different bovine mastitis isolates were tested against the mixture of the 13 LAB species in the honey medium using a dual-culture overlay assay. The mastitis isolates were identified through bacteriological culturing, followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Additionally, the mastitis isolates were subjected to antimicrobial susceptibility testing through disk diffusion. Growth of all tested mastitis pathogens, including the ones displaying antimicrobial resistance to one or more antimicrobial compounds, were inhibited to some extent by the honey and LAB combination. The antibacterial effect of these LAB opens up new perspectives on alternative treatment and prevention of bovine mastitis. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Pathogenic Vibrio species isolated from estuarine environments (Ceará, Brazil) - antimicrobial resistance and virulence potential profiles.

PubMed

Menezes, Francisca G R DE; Rodriguez, Marina T T; Carvalho, Fátima C T DE; Rebouças, Rosa H; Costa, Renata A; Sousa, Oscarina V DE; Hofer, Ernesto; Vieira, Regine H S F

2017-01-01

Detection of virulent strains associated with aquatic environment is a current concern for the management and control of human and animal health. Thus, Vibrio diversity was investigated in four estuaries from state of Ceará (Pacoti, Choró, Pirangi and Jaguaribe) followed by antimicrobial susceptibility to different antimicrobials used in aquaculture and detection of main virulence factors to human health. Isolation and identification were performed on TCBS agar (selective medium) and dichotomous key based on biochemical characteristics, respectively. Nineteen strains of genus Vibrio were catalogued. Vibrio parahaemolyticus (Choró River) and V. alginolyticus (Pacoti River) were the most abundant species in the four estuaries. All strains were submitted to disk diffusion technique (15 antimicrobials were tested). Resistance was found to: penicillin (82%), ampicillin (54%), cephalotin (7%), aztreonan (1%), gentamicin, cefotaxime and ceftriaxone (0.5%). Five pathogenic strains were chosen to verification of virulence factors. Four estuaries showed a high abundance of species. High number of tested positive strains for virulence is concerning, since some of those strains are associated to human diseases, while others are known pathogens of aquatic organisms.

Antimicrobial activity of biopolymeric thin films containing flavonoid natural compounds and silver nanoparticles fabricated by MAPLE: A comparative study

NASA Astrophysics Data System (ADS)

Cristescu, R.; Visan, A.; Socol, G.; Surdu, A. V.; Oprea, A. E.; Grumezescu, A. M.; Chifiriuc, M. C.; Boehm, R. D.; Yamaleyeva, D.; Taylor, M.; Narayan, R. J.; Chrisey, D. B.

2016-06-01

The purpose of this study was to investigate the interactions between microorganisms, including the planktonic and adherent organisms, and biopolymer (polyvinylpyrrolidone), flavonoid (quercetin dihydrate and resveratrol)-biopolymer, and silver nanoparticles-biopolymer composite thin films that were deposited using matrix assisted pulsed laser evaporation (MAPLE). A pulsed KrF* excimer laser source was used to deposit the aforementioned composite thin films, which were characterized using Fourier transform infrared spectroscopy (FT-IR), infrared microscopy (IRM), scanning electron microscopy (SEM), Grazing incidence X-ray diffraction (GIXRD) and atomic force microscopy (AFM). The antimicrobial activity of thin films was quantified using an adapted disk diffusion assay against Gram-positive and Gram-negative bacteria strains. FT-IR, AFM and SEM studies confirmed that MAPLE may be used to fabricate thin films with chemical properties corresponding to the input materials as well as surface properties that are appropriate for medical use. The silver nanoparticles and flavonoid-containing films exhibited an antimicrobial activity both against Gram-positive and Gram-negative bacterial strains demonstrating the potential use of these hybrid systems for the development of novel antimicrobial strategies.

An eight-year study of Shigella species in Beijing, China: serodiversity, virulence genes, and antimicrobial resistance.

PubMed

Qu, Mei; Zhang, Xin; Liu, Guirong; Huang, Ying; Jia, Lei; Liang, Weili; Li, Xitai; Wu, Xiaona; Li, Jie; Yan, Hanqiu; Kan, Biao; Wang, Quanyi

2014-07-14

This study was conducted to determine the prevalence of serotypes, virulence factors, and antimicrobial resistance patterns of Shigella spp. in Beijing, China, from 2004 to 2011. Real-time PCR assays were used to detect virulent genes, and the Kirby-Bauer disk diffusion method was used to evaluate antimicrobial resistance. Among the total of 1,652 Shigella isolates, S. sonnei (57.1%) was the predominant species, followed by S. flexneri (42.3%), S. dysenteriae (0.4%), and S. boydii (0.2%). Nineteen serotypes were discovered among S. flexneri strains. The virulence gene ipaH was the most frequent, followed by sen and set. The presence of set showed significant difference in two dominant serogroups, S. flexneri and S. sonnei. Over 90% of Shigella isolates showed resistance to at least three drugs with widened spectrum. High-level antimicrobial resistance to single and multiple antibiotics was more common among S. sonnei than S. flexneri. There was an obvious serotype change and a dramatic increase of antibiotic resistance in Shigella prevalence in Beijing.

Antimicrobial activity and mechanism of PDC213, an endogenous peptide from human milk.

PubMed

Sun, Yazhou; Zhou, Yahui; Liu, Xiao; Zhang, Fan; Yan, Linping; Chen, Ling; Wang, Xing; Ruan, Hongjie; Ji, Chenbo; Cui, Xianwei; Wang, Jiaqin

2017-02-26

Human milk has always been considered an ideal source of elemental nutrients to both preterm and full term infants in order to optimally develop the infant's tissues and organs. Recently, hundreds of endogenous milk peptides were identified in human milk. These peptides exhibited angiotensin-converting enzyme inhibition, immunomodulation, or antimicrobial activity. Here, we report the antimicrobial activity and mechanism of a novel type of human antimicrobial peptide (AMP), termed PDC213 (peptide derived from β-Casein 213-226 aa). PDC213 is an endogenous peptide and is present at higher levels in preterm milk than in full term milk. The inhibitory concentration curve and disk diffusion tests showed that PDC213 had obvious antimicrobial against S. aureus and Y. enterocolitica, the common nosocomial pathogens in neonatal intensive care units (NICUs). Fluorescent dye methods, electron microscopy experiments and DNA-binding activity assays further indicated that PDC213 can permeabilize bacterial membranes and cell walls rather than bind intracellular DNA to kill bacteria. Together, our results suggest that PDC213 is a novel type of AMP that warrants further investigation. Copyright © 2017 Elsevier Inc. All rights reserved.

Photochemically synthesized heparin-based silver nanoparticles: an antimicrobial activity study

NASA Astrophysics Data System (ADS)

Rodriguez-Torres, Maria del Pilar; Acosta-Torres, Laura Susana; Díaz-Torres, Luis Armando

2017-08-01

The antimicrobial activity of silver nanoparticles has been extensively studied in the last years. Such nanoparticles constitute a potential and promising approach for the development of new antimicrobial systems especially due to the fact that several microorganisms are developing resistance to some already existing antimicrobial agents, therefore making antibacterial and antimicrobial studies on alternative materials necessary to overcome this issue. Silver nanoparticle concentration and size are determining factors on the antimicrobial activity of these nano systems. Heparin is a polysaccharide that belongs to the glycosaminoglycans (GAGs) family, molecules formed by a base disaccharide whose components are joined by a glycosidic linkage that is a repeating unit along their structure. It is highly sulfated making it a negatively charged material that is also widely used as an anticoagulant in Medicine because its biocompatibility besides it is also produced within the human body, specifically in the mast cells. Heparin alone possesses antimicrobial activity although it has not been studied very much in detail, it only has been demonstrated that it inhibits E. coli, P. aeruginosa, S. aureus and S. epidermidis, so taking this into account, this study is dedicated to assess UV photochemically-synthesized (λ=254 nm) heparin-based silver nanoparticles antimicrobial activity using the agar disk diffusion method complemented by the broth microdilution method to estimate de minimum inhibitory concentration (MIC), that is the lowest concentration at which an antimicrobial will inhibit visible growth of a microorganism. The strains used were the ones aforementioned to assess the antimicrobial activity degree these heparinbased nanoparticles exhibit.

Imipenem resistance in clinical Escherichia coli from Qom, Iran.

PubMed

Shams, Saeed; Hashemi, Ali; Esmkhani, Mohammad; Kermani, Somaye; Shams, Elham; Piccirillo, Alessandra

2018-05-18

The emergence of metallo-β-lactamase-producing Enterobacteriaceae is a worldwide health concern. In this study, the first evaluation of MBL genes, bla IMP and bla VIM , in Escherichia coli resistant to imipenem isolated from urine and blood specimens in Qom, Iran is described. Three hundred urine and blood specimens were analysed to detect the presence of E. coli. Resistance to imipenem and other antimicrobials was determined by disk diffusion and MIC. MBL production was screened using CDDT. PCR was also carried out to determine the presence of bla IMP and bla VIM genes in imipenem-resistant isolates. In total, 160 E. coli isolates were collected from March to May 2016. According to disk diffusion, high-level of resistance (20%) to cefotaxime was observed, whereas the lowest (1%) was detected for tetracycline. In addition, five isolates showed resistance to imipenem with a MIC ≥ 4 µg/mL. CDDT test confirmed that five isolates were MBL-producing strains, but no bla IMP and bla VIM genes were detected. Results of this study show a very low level of resistance to imipenem in our geographical area.

[Clinical characteristics of whooping cough in neonates and antimicrobial resistance of the pathogenic bacteria].

PubMed

Luo, Jie; Wang, Hui-Xin; Yuan, Lin; Gu, Song; Jiang, Min; Ding, Yi-Jun; Guo, Dan; Yao, Kai-Hu; Wang, Ya-Juan

2014-10-01

To study the clinical characteristics of whooping cough in neonates and the antimicrobial resistance of the bacterial isolates. Clinical information of 7 neonates with whooping cough confirmed by bacterial culture was collected. The antimirobial resistance of the isolates was tested using E-test and disk diffusion methods. The children′s mothers or other family members had cough for more than 10 days in 6 neonates, in which four neonates contacted with 3 or more family members with cough. All the neonates had rhinobyon and slight cough at the beginning of the disease. Five cases presented typical spasmodic cough after 4-7 days of the onset. Five cases displayed cyanosis, four cases occurred apnea, three cases suffered breath holding, and only two cases had fever. Nares flaring and three depression signs were found in the physical examination. No bacteriostatic ring around the erythromycin disks were found for five bacterial isolates. The minimal inhibitory concentration (MIC) for erythromycin, azithromycin, clarithromycin and clindamycin were all >256 mg/L against the five isolates. Whooping cough should be considered for neonates with respiratory symptoms and a history of close contact with respiratory infection patients. Macrolide-resistant Bordetella pertussis is common in children with whooping cough.

[Oxacillin-resistant coagulase-negative Staphylococci bacteremia at a teaching hospital in Santa Maria, State of Rio Grande do Sul, Brazil].

PubMed

Rigatti, Fabiane; Tizotti, Maísa Kraulich; Hörner, Rosmari; Domingues, Vanessa Oliveira; Martini, Rosiéli; Mayer, Letícia Eichstaedt; Khun, Fábio Teixeira; de França, Chirles Araújo; da Costa, Mateus Matiuzzi

2010-01-01

This study aimed to characterize the prevalence and susceptibility profile to oxacillin-resistant Coagulase-negative Staphylococci strains isolated from blood cultures in a teaching hospital, located in Santa Maria, RS. In addition, different methodologies for phenotypic characterization of mecA-mediated oxacillin resistance were compared with genotypic reference testing. After identification (MicroScan - Siemens), the isolates were tested for antimicrobial sensitivity using disk diffusion and automation (MicroScan - Siemens). The presence of mecA gene was identified by the polymerase chain reaction molecular technique. The most common species was Staphylococcus epidermidis (n=40, 67%). The mecA gene was detected in 54 (90%) strains, while analysis of the sensitivity profiles revealed a high rate of resistance to multiple classes of antimicrobial drugs. However, all isolates were uniformly sensitive to vancomycin and tigecycline. The cefoxitin disk was the phenotypic method that best correlated with the gold standard. Analysis of the clinical significance of CoNS isolated from hemocultures and the precise detection of oxacillin resistance represent decisive factors for the correct choice of antibiotic therapy. Although vancomycin constitutes the normal treatment in most Brazilian hospitals, reduction in its use is recommended.

NORMAL VAGINAL BACTERIAL FLORA OF GIANT PANDAS (AILUROPODA MELANOLEUCA) AND THE ANTIMICROBIAL SUSCEPTIBILITY PATTERNS OF THE ISOLATES.

PubMed

Yang, Xin; Yang, Jiang; Wang, Hongning; Li, Caiwu; He, Yongguo; Jin, SenYan; Zhang, Hemin; Li, Desheng; Wang, Pengyan; Xu, Yuesong; Xu, Changwen; Fan, Chengyun; Xu, Lulai; Huang, Shan; Qu, Chunmao; Li, Guo

2016-03-01

In order to study the typical vaginal bacterial flora of giant pandas (Ailuropoda melanoleuca), we took vaginal swabs for the sake of bacterial isolation, from 24 healthy female giant pandas. A total of 203 isolates were identified, representing a total of 17 bacterial species. The most common bacteria isolated were Lactobacillus spp. (54.2%, 13 of 24), followed by Staphylococcus epidermidis (41.7%, 10 of 24) and Escherichia coli (33.3%, 8 of 24). Some opportunistic pathogenic bacteria, such as Peptostreptococcus spp., Klebsiella pneumoniae, and Proteus mirabilis, were also isolated but showed no pathology. Antimicrobial susceptibility testing of aerobic bacterial isolates was performed with disk diffusion method. Of the 152 isolates, resistance was most frequently observed with chloramphenicol (17.8%), followed by tetracycline (14.5%), ciprofloxacin (12.5%), streptomycin (11.8%), and florfenicol (11.8%), while 7.2% were multidrug resistant. This is the first report of the normal vaginal culturable bacterial flora of giant pandas, followed by the antimicrobial susceptibility patterns of the isolates.

NORMAL VAGINAL BACTERIAL FLORA OF GIANT PANDAS (AILUROPODA MELANOLEUCA) AND THE ANTIMICROBIAL SUSCEPTIBILITY PATTERNS OF THE ISOLATES.

PubMed

Yang, Xin; Yang, Jiang; Wang, Hongning; Li, Caiwu; He, Yongguo; Jin, SenYan; Zhang, Hemin; Li, Desheng; Wang, Pengyan; Xu, Yuesong; Xu, Changwen; Fan, Chengyun; Xu, Lulai; Huang, Shan; Qu, Chunmao; Li, Guo

2016-06-01

To study the typical vaginal bacterial flora of giant pandas (Ailuropoda melanoleuca), we took vaginal swabs for the sake of bacterial isolation, from 24 healthy female giant pandas. A total of 203 isolates were identified, representing a total of 17 bacterial species. The most common bacteria isolated were Lactobacillus spp. (54.2%, 13/24), followed by Staphylococcus epidermidis (41.7%, 10/24) and Escherichia coli (33.3%, 8/24). Some opportunistic pathogenic bacteria, such as Peptostreptococcus spp., Klebsiella pneumoniae , and Proteus mirabilis , were also isolated but showed no pathology. Antimicrobial susceptibility testing of aerobic bacterial isolates was performed with the disk diffusion method. Of the 152 isolates, resistance was most frequently observed with chloramphenicol (17.8%), followed by tetracycline (14.5%), ciprofloxacin (12.5%), streptomycin (11.8%), and florfenicol (11.8%), whereas 7.2% were multidrug resistant. This is the first report of the normal culturable vaginal bacterial flora of giant pandas and the antimicrobial susceptibility patterns of the isolates.

Ultrafiltration and thermal processing effects on Maillard reaction products and biological properties of date palm sap syrups (Phoenix dactylifera L.).

PubMed

Makhlouf-Gafsi, Ines; Krichen, Fatma; Mansour, Riadh Ben; Mokni, Abir; Sila, Assad; Bougatef, Ali; Blecker, Christophe; Attia, Hamadi; Besbes, Souhail

2018-08-01

The effect of ultrafiltration process and temperature concentration on MRPs content and antioxidant, antimicrobial and cytotoxic properties of date palm sap syrups were investigated. MRPs were analyzed by HPLC. Antioxidant activity was evaluated by reducing power and DPPH free radical and H 2 O 2 scavenging activities. Antimicrobial activity was evaluated by the agar disk diffusion method. In vitro cytotoxic activity was examined by cell proliferation assay. Date sap syrups displayed strong antioxidant activities which are correlated 5HMF and 2F contents. In addition, concentration at 100 °C, unlike ultrafiltration process, enhanced significantly the antioxidant activities sap syrups and total phenolic contents. The antimicrobial activities showed marked activity against S. enterica, P. aeruginosa, S. aureus, L. monocytogenes with an inhibition zone of 21, 34, 27 and 34 mm respectively. Cytotoxicity assays showed that sap syrups can inhibit the proliferation of HeLa cell lines at high concentration. Published by Elsevier Ltd.

Prevalence, antimicrobial susceptibility and multiplex PCR-serotyping of Listeria monocytogenes isolated from humans, foods and livestock in Iran.

PubMed

Lotfollahi, Lida; Chaharbalesh, Ardalan; Ahangarzadeh Rezaee, Mohammad; Hasani, Alka

2017-06-01

Listeria monocytogenes is a foodborne pathogen causing listeriosis, which potentially affects all individuals, especially pregnant women and immunocompromised persons. The present study investigated the prevalence, antimicrobial susceptibility and serotypes distribution of the isolated L. monocytogenes from Iran. Twenty two (4.97%) of 442 human, food and livestock samples were found to be positive for L. monocytogenes. L. monocytogenes was identified in 8.8% of 125 human samples, 2.99% of 267 food and 6% of 50 livestock samples. The standard disk diffusion method and minimum inhibitory concentration (MIC) assay were used for antimicrobial susceptibility testing and multiplex PCR for serotyping. Among the 22 isolates tested, 6 (27.2%) displayed resistance to penicillin G, with all of the isolates and 2 (9%) of them showing intermediate susceptibility to clindamycin and rifampicin, respectively. According to the MIC assay, the rate of resistance to penicillin G was the same as that of disk diffusion method, but 16 (72.7%) of isolates showed intermediate susceptibility to clindamycin using E-test. In the multiplex PCR, 19 (86.4%) of isolates belonged to serotype 1/2c or 3c and the remaining 3 isolates were identified as (4b, 4d or 4e) and (1/2a or 3a), respectively. The occurrence of resistance to penicillin G, which can be used in the treatment of listeriosis, is very alarming and more prevalence of 1/2c serotype, in comparison to 3 other important ones (1/2a, 1/2b and 4b), in Iran has been reported for the first time. To the best of our knowledge, this is the first study showing the distribution of various serogroups of L. monocytogenes from human and livestock in Iran. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Evaluation of methods for studying susceptibility to oxacillin and penicillin in 60 Staphylococcus lugdunensis isolates].

PubMed

Batista, Nínive; Fernández, M Paula; Lara, Magdalena; Laich, Federico; Méndez, Sebastián

2009-03-01

Staphylococcus lugdunensis is a coagulase-negative staphylococcus associated with a variety of clinical infections. In this paper we present the results of a comparative study using 4 methods to determine antimicrobial susceptibility to oxacillin and penicillin in 60 S. lugdunensis isolates. We studied 60 S. lugdunensis isolates obtained from clinical specimens sent to our laboratory over an 8-year period. All isolates were free coagulase-negative and DNase-negative, and biochemically identified by API ID 32 STAPH (bioMérieux). Presence of mecA and ss-lactamase production were studied in all cases. Antimicrobial susceptibility was determined by the Vitek 2 System (bioMérieux) and broth microdilution (Wider) (Soria Melguizo) for penicillin and oxacillin, and the E-test (AB Biodisk) and cefoxitin disk diffusion test (BD BBLTM) for oxacillin. All isolates lacked the mecA gene and were susceptible to oxacillin by broth microdilution, E-test, and cefoxitin disk diffusion test. Only two isolates were oxacillin-resistant by the Vitek 2 System. Twenty-four isolates (40%) were ss-lactamase-positive, 4 after induction. Susceptibility testing to penicillin determined that 48 isolates showed concordance between the results obtained by broth microdilution and Vitek 2, but 12 isolates (20%), showed divergent results. We detected no resistance to oxacillin in S. lugdunensis. All the methods evaluated were adequate for determining oxacillin resistance. The Vitek 2 System is useful for detecting penicillin resistance, but the ss-lactamase test should be applied to isolates with a MIC=0.25microg/ml to avoid the interpretation of false resistance to this antibiotic.

Synthesis, Antimicrobial, and Antioxidant Activities of Chalcogen-Containing Nitrone Derivatives from (R)-citronellal

PubMed Central

Ferraz, Mariana C.; Mano, Renata A.; Oliveira, Daniela H.; Maia, Darla S. V.; Silva, Wladimir P.; Savegnago, Lucielli; Lenardão, Eder J.; Jacob, Raquel G.

2017-01-01

Background: The main constituents of Cymbopogonnardus (L) Rendle and C. citratus (DC) Stapfessential oils are (R)-citronellal and citral, respectively. Organochalcogen compounds can boost the biological activities of natural products. Methods: Several chalcogen-containing nitrones derived from (R)-citronellal and citral were prepared and evaluated for their antimicrobial and antioxidant activities. The antimicrobial activity was evaluated by the disc diffusion test and the antioxidant properties were evaluated in vitro by DPPH (1,1-diphenyl-2-picryl-hydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), and FRAP (ferric ion reducing antioxidant power) assays. Results: In the antimicrobial assay, (E)-N,3,7-trimethyl-3-(phenylthio)oct-6-en-1-imine oxide 5c exhibited halos between 21.5 mm (Escherichia coli O157:H7) and 26.0 mm (Listeria monocytogenes), while (E)-N,3,7-trimethyloct-6-en-1-imine oxide 5d presented halos between 22.5 mm (E. coli O157:H7) and 31.0 mm (L. monocytogenes). (E)-N,3,7-Trimethyl-2-(phenylthio)oct-6-en-1-imine oxide 5a showed the lowest minimal inhibitory concentration (MIC) value against Bacillus cereus (0.48 mM), and 5c was the most potent bactericide, with a minimal bactericidal concentration (MBC) of 0.52 mM for E. coli O157:H7. In the antioxidant assays, 5c, 5d, and 10 ((E)-3,7-dimethyl-2-(phenylselanyl)oct-6-enal oxime) were the most actives in the DPPH, ABTS, and FRAP assays, respectively. Conclusions: The presence of a phenylthio group in the nitrone increases its antimicrobial activity against Gram-positive and Gram-negative foodborne pathogens in the disk diffusion test and the antioxidant activity in vitro. PMID:28930254

Antimicrobial activity of jasmine oil against oral microorganisms

NASA Astrophysics Data System (ADS)

Thaweboon, S.; Thaweboon, B.; Kaypetch, R.

2018-02-01

Jasmine sambac is a species of jasmine indigenous to the tropical and warm temperature regions in particular West and Southeast Asia. Essential oil extracted from the flowers of J. sambac has been shown to have anti-oxidant activity. However, very little information regarding antimicrobial activity especially oral microorganisms exists. Objective: To investigate antimicrobial effect of essential oil extracted from flowers of J. sambac against various oral microorganisms. Materials and Methods: Oral microbial strains used in the study were Streptococcus mutans KPSK2, Staphylococcus aureus ATCC 5638, Lactobacillus casei ATCC 6363, Klebsiella pneumoniae (clinical isolate), Escherichia coli ATCC 25922, Candida albicans ATCC 10231, Candida krusei ATCC 6258, Candida parapsilosis ATCC 22019, Candida tropicalis (clinical isolate), Candida glabrata ATCC 90030, Candida pseudotropicalis (clinical isolate) and Candida stellatoidia (clinical isolate). The potential of microbial growth inhibition of the oil was firstly screened by Kirby-Bauer disk diffusion method and then the minimum inhibitory concentration (MIC) was determined by agar dilution method. Results: Jasmine oil showed antimicrobial activities against S. mutans, L. casei, E. coli and all strains of Candida species with the zones of inhibition ranging from 9 to 26 mm and MIC values of 0.19-1.56 %v/v. Conclusion: Results from the present study are scientific evidence to demonstrate that jasmine oil could be employed as a natural antimicrobial agent against oral microorganisms.

Antimicrobial activity of essential oil and aqueous and ethanol extracts of Teucrium polium L. subsp. gabesianum (L.H.) from Tunisia.

PubMed

Ben Othman, Mahmoud; Bel Hadj Salah-Fatnassi, Karima; Ncibi, Saida; Elaissi, Amer; Zourgui, Lazhar

2017-07-01

The antimicrobial effects of essential oil, ethanol and aqueous extracts of Teucrium polium L. were investigated against 13 microorganisms. Extracts and essential oil were obtained from maceration, decoction and hydrodistillation respectively. Samples were tested for their antimicrobial activity using the disk diffusion, the agar dilution and the agar incorporation method. Essential oil was analysed using GC/MS, results showed that β-pinene (35.97%) and α-pinene (13.32%) were the main components. Furthermore, essential oil exhibited the highest antimicrobial activity, it was most effective against Proteus mirabilis, Staphylococcus aureus and Citrobacter freundei where inhibition zone ranged between 15 and 25 mm, and with the microbial inhibitory concentration (MIC) values of 0.078-0.156 mg/ml. The oil and ethanol extract showed the best antifungal activity against Microsporum canis , Scopulariopsis brevicaulis , and Trichophyton rubrum with the inhibition percentage (I%) ranging from 18.94 to 100%. However, none of the samples exhibited antifungal activity against Aspergillus fumigatus . In this study, the obtained results showed significant effects of essential oils and ethanol extracts of T. polium which may used as a substitute to the synthetic drugs against certain microbial diseases.

Analysis of antimicrobial resistance genes in Aeromonas spp. isolated from cultured freshwater animals in China.

PubMed

Deng, Yu-Ting; Wu, Ya-Li; Tan, Al-Ping; Huang, Yu-Ping; Jiang, Lan; Xue, Hui-Juan; Wang, Wei-Li; Luo, Li; Zhao, Fei

2014-08-01

The development of resistance to antimicrobials used in aquatic animals is an increasing concern for aquaculture and public health. To monitor the occurrence of antimicrobial resistance and resistance genes in Aeromonas, a total of 106 isolates were collected from cultured freshwater animals in China from 1995 to 2012. Antimicrobial susceptibilities were determined by the disk diffusion method. The highest resistance percentage occurred with ampicillin, rifampin, streptomycin, and nalidixic acid. Most strains were sensitive to fluoroquinolones, doxycycline, cefotaxime, chloramphenicol, and amikacin. The isolates from turtle samples had the highest levels of resistance to 11 of the 12 tested antimicrobials when compared with those from fish or shrimp. Polymerase chain reaction and DNA sequence results showed that all trimethoprim/sulfamethoxazole-resistant strains contained sul1, and 37.0% were positive for tetA in tetracycline-resistant strains. ant(3″)-Ia was identified in 13 (24.5%) streptomycin-resistant strains. Plasmid-borne quinolone resistance genes were detected in five Aeromonas hydrophila (4.7%), two of which carried qnrS2, while the other three strains harbored aac(6')-Ib-cr. Two cefotaxime-resistant A. hydrophila were positive for bla(TEM-1) and bla(CTX-M-3). To our knowledge, this is the first report characterizing antimicrobial resistance in Aeromonas isolated from cultured freshwater animals in China, and providing resistance information of pathogen in Chinese aquaculture.

Antimicrobial resistance in Gram-positive bacteria from Timorese River Buffalo (Bubalus bubalis) skin microbiota.

PubMed

Oliveira, Manuela; Monteiro, José L; Rana, Sílvia; Vilela, Cristina L

2010-06-01

The Timorese River Buffalo (Bubalus bubalis) plays a major role in the East Timor economy, as it is an important source of animal protein in human nutrition. They are widely spread throughout the country and are in direct contact with the populations. In spite of this proximity, information on their microbiota is scarce. This work aimed at characterizing the skin microbiota of the East Timorese River Buffalo and its antimicrobial resistance profile. Skin swab samples were taken from 46 animals in surveys conducted in three farms located in "Suco de Nairete", Lospalos district, during July and August 2006. Bacteria were isolated and identified according to conventional microbiological procedures. A total of 456 isolates were obtained, including Gram-positive (n = 243) and Gram-negative (n = 213) bacteria. Due to their importance as potential pathogens and as vehicles for antimicrobial resistance transmission, Gram-positive cocci (n = 27) and bacilli (n = 77) isolates were further characterized, and their antimicrobial resistance profile determined by the disk diffusion method according to the Clinical and Laboratory Standards Institute guidelines. This study shows the high bacterial diversity of B. bubalis skin microbiota, representing an important first step towards understanding its importance and epidemiologic role in animal health. It also points out the potential role of these animals as vectors of antimicrobial resistant bacteria dissemination and the importance of antimicrobial resistance monitoring in developing countries.

Comparison of results of fluconazole disk diffusion testing for Candida species with results from a central reference laboratory in the ARTEMIS global antifungal surveillance program.

PubMed

Pfaller, M A; Hazen, K C; Messer, S A; Boyken, L; Tendolkar, S; Hollis, R J; Diekema, D J

2004-08-01

The accuracy of antifungal susceptibility tests is important for accurate resistance surveillance and for the clinical management of patients with serious infections. Our main objective was to compare the results of fluconazole disk diffusion testing of Candida spp. performed by ARTEMIS participating centers with disk diffusion and MIC results obtained by the central reference laboratory. A total of 2,949 isolates of Candida spp. were tested by NCCLS disk diffusion and reference broth microdilution methods in the central reference laboratory. These results were compared to the results of disk diffusion testing performed in the 54 participating centers. All tests were performed and interpreted following NCCLS recommendations. Overall categorical agreement between participant disk diffusion test results and reference laboratory MIC results was 87.4%, with 0.2% very major errors (VME) and 3.3% major errors (ME). The categorical agreement between the disk diffusion test results obtained in the reference laboratory with the MIC test results was similar: 92.8%. Likewise, good agreement was observed between participant disk diffusion test results and reference laboratory disk diffusion test results: 90.4%, 0.4% VME, and 3.4% ME. The disk diffusion test was especially reliable in detecting those isolates of Candida spp. that were characterized as resistant by reference MIC testing. External quality assurance data obtained by surveillance programs such as the ARTEMIS Global Antifungal Surveillance Program ensure the generation of useful surveillance data and result in the continued improvement of antifungal susceptibility testing practices.

Evaluation of the antibacterial activity of a conventional orthodontic composite containing silver/hydroxyapatite nanoparticles.

PubMed

Sodagar, Ahmad; Akhavan, Azam; Hashemi, Ehsan; Arab, Sepideh; Pourhajibagher, Maryam; Sodagar, Kosar; Kharrazifard, Mohammad Javad; Bahador, Abbas

2016-12-01

One of the most important complications of fixed orthodontic treatment is the formation of white spots which are initial carious lesions. Addition of antimicrobial agents into orthodontic adhesives might be a wise solution for prevention of white spot formation. The aim of this study was to evaluate the antibacterial properties of a conventional orthodontic adhesive containing three different concentrations of silver/hydroxyapatite nanoparticles. One hundred and sixty-two Transbond XT composite discs containing 0, 1, 5, and 10 % silver/hydroxyapatite nanoparticles were prepared and sterilized. Antibacterial properties of these composite groups against Streptococcus mutans, Lactobacillus acidophilus, and Streptococcus sanguinis were investigated using three different antimicrobial tests. Disk agar diffusion test was performed to assess the diffusion of antibacterial agent on brain heart infusion agar plate by measuring bacterial growth inhibition zones. Biofilm inhibition test showed the antibacterial capacity of composite discs against resistant bacterial biofilms. Antimicrobial activity of eluted components from composite discs was investigated by comparing the viable counts of bacteria after 3, 15, and 30 days. Composite discs containing 5 and 10 % silver/hydroxyapatite nanoparticles were capable of producing growth inhibition zones for all bacterial types. Results of biofilm inhibition test showed that all of the study groups reduced viable bacterial count in comparison to the control group. Antimicrobial activity of eluted components from composite discs was immensely diverse based on the bacterial type and the concentration of nanoparticles. Transbond XT composite discs containing 5 and 10 % silver/hydroxyapatite nanoparticles produce bacterial growth inhibition zones and show antibacterial properties against biofilms.

Complex Analysis of Diffusion Transport and Microstructure of an Intervertebral Disk.

PubMed

Byvaltsev, V A; Kolesnikov, S I; Belykh, E G; Stepanov, I A; Kalinin, A A; Bardonova, L A; Sudakov, N P; Klimenkov, I V; Nikiforov, S B; Semenov, A V; Perfil'ev, D V; Bespyatykh, I V; Antipina, S L; Giers, M; Prul, M

2017-12-01

We studied the relationship between diffusion transport and morphological and microstructural organization of extracellular matrix of human intervertebral disk. Specimens of the lumbar intervertebral disks without abnormalities were studied ex vivo by diffusion-weighed magnetic resonance imaging, histological and immunohistochemical methods, and electron microscopy. Distribution of the diffusion coefficient in various compartments of the intervertebral disk was studied. Significant correlations between diffusion coefficient and cell density in the nucleus pulposus, posterior aspects of annulus fibrosus, and endplate at the level of the posterior annulus fibrosus were detected for each disk. In disks with nucleus pulposus diffusion coefficient below 15×10 -4 mm 2 /sec, collagens X and XI were detected apart from aggrecan and collagens I and II. The results supplement the concept on the relationship between the microstructure and cell composition of various compartments of the intervertebral disk and parameters of nutrient transport.

Clinical test to detect mecA and antibiotic resistance in Staphylococcus aureus, based on novel biotechnological methods.

PubMed

Shahmohammadi, Mohammad Reza; Nahaei, Mohammad Reza; Akbarzadeh, Abolfazl; Milani, Morteza

2016-09-01

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common organisms isolated from clinical samples, and has been associated with morbidity and mortality among hospitalized patients. The aim of this study was to evaluate the prevalence and antibiotic susceptibility patterns among MRSA and methicillin-sensitive S. aureus (MSSA) isolates collected from four hospitals in Iran. A total of 183 isolates of S. aureus were collected from various clinical specimens of four hospitals in Iran. The isolates were identified by using the conventional biochemical tests. Three methods-oxacillin agar disk diffusion, oxacillin agar screening, and PCR- were applied to determine susceptibility to oxacillin. The conventional disk agar diffusion test was used to evaluate the antibiotic sensitivity of our isolates against 15 antibiotics, according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). Of 183 isolates, 77 isolates (42.1%) were found to be MRSA, by the PCR method. The highest antibiotic resistance was found to be against penicillin, co-trimoxazole, erythromycin, and tetracycline respectively. All isolates were susceptible to vancomycin, according to the results of disk agar diffusion. Among other antibiotics, teicoplanin (84%) and fusidic acid (80.5%) were more active against MRSA isolates. For the different methods evaluated, the sensitivities and specificities were as follows: for disk agar diffusion (84.9% and 95.9%) and for agar screening test with oxacillin concentrations of 0.6 μg/ml (70.8% and 97.4%), 4 μg/ml (96.1%and 97.2%) and 6 μg/ml (96% and 96.3%), respectively. The results of our study showed that 47% of S. aureus isolates were MRSA. Overall, in this research study, resistance to all test antimicrobial agents in MRSA isolates were higher than that of MSSA isolates. Our results also revealed that 85% of mecA-positive isolates and 15% of mecA-negative isolates were resistant to methicillin; while 96% of mecA-negative isolates were sensitive to methicillin. Meanwhile 4% of mecA-positive isolates were also sensitive to methicillin.

Antimicrobial synergy between carprofen and doxycycline against methicillin-resistant Staphylococcus pseudintermedius ST71.

PubMed

Brochmann, Rikke Prejh; Helmfrid, Alexandra; Jana, Bimal; Magnowska, Zofia; Guardabassi, Luca

2016-06-24

New therapeutic strategies are needed to face the rapid spread of multidrug-resistant staphylococci in veterinary medicine. The objective of this study was to identify synergies between antimicrobial and non-antimicrobial drugs commonly used in companion animals as a possible strategy to restore antimicrobial susceptibility in methicillin-resistant Staphylococcus pseudintermedius (MRSP). A total of 216 antimicrobial/non-antimicrobial drug combinations were screened by disk diffusion using a clinical MRSP sequence type (ST) 71 strain resistant to all six antimicrobials tested (ampicillin, ciprofloxacin, clindamycin, doxycycline, oxacillin and trimethoprim/sulfamethoxazole). The most promising drug combination (doxycycline-carprofen) was further assessed by checkerboard testing extended to four additional MRSP strains belonging to ST71 or ST68, and by growth inhibition experiments. Seven non-antimicrobial drugs (bromhexine, acepromazine, amitriptyline, clomipramine, carprofen, fluoxetine and ketoconazole) displayed minimum inhibitory concentrations (MICs) ranging between 32 and >4096 mg/L, and enhanced antimicrobial activity of one or more antimicrobials. Secondary screening by checkerboard assay revealed a synergistic antimicrobial effect between carprofen and doxycycline, with the sum of the fractional inhibitory concentration indexes (ΣFICI) ranging between 0.3 and 0.5 depending on drug concentration. Checkerboard testing of multiple MRSP strains revealed a clear association between synergy and carriage of tetK, which is a typical feature of MRSP ST71. An increased growth inhibition was observed when MRSP ST71 cells in exponential phase were exposed to 0.5/32 mg/L of doxycycline/carprofen compared to individual drug exposure. Carprofen restores in vitro susceptibility to doxycycline in S. pseudintermedius strains carrying tetK such as MRSP ST71. Further research is warranted to elucidate the molecular mechanism behind the identified synergy and its linkage to tetK.

Changes of the Quinolones Resistance to Gram-positive Cocci Isolated during the Past 8 Years in the First Bethune Hospital

NASA Astrophysics Data System (ADS)

Xu, Jiancheng; Chen, Qihui; Yao, Hanxin; Zhou, Qi

This study was to investigate the quinolones resistance to gram-positive cocci isolated in the First Bethune Hospital during the past 8 years. Disk diffusion test was used to study the antimicrobial resistance. The data were analyzed by WHONET 5 software according to Clinical and Laboratory Standards Institute (CLSI). The rates of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococci (MRCNS) were 50.8%∼83.3% and 79.4%∼81.5%during the past 8 years, respectively. In recent 8 years, the quinolones resistance to gram-positive cocci had increased. Monitoring of the quinolones resistance to gram-positive cocci should be strengthened. The change of the antimicrobial resistance should be investigated in order to guide rational drug usage in the clinic and prevent bacterial strain of drug resistance from being transmitted.

Antimicrobial Usage and Antimicrobial Resistance in Animal Production in Southeast Asia: A Review

PubMed Central

Nhung, Nguyen T.; Cuong, Nguyen V.; Thwaites, Guy; Carrique-Mas, Juan

2016-01-01

Southeast Asia is an area of great economic dynamism. In recent years, it has experienced a rapid rise in the levels of animal product production and consumption. The region is considered to be a hotspot for infectious diseases and antimicrobial resistance (AMR). We reviewed English-language peer-reviewed publications related to antimicrobial usage (AMU) and AMR in animal production, as well as antimicrobial residues in meat and fish from 2000 to 2016, in the region. There is a paucity of data from most countries and for most bacterial pathogens. Most of the published work relates to non-typhoidal Salmonella (NTS), Escherichia coli (E. coli), and Campylobacter spp. (mainly from Vietnam and Thailand), Enterococcus spp. (Malaysia), and methicillin-resistant Staphylococcus aureus (MRSA) (Thailand). However, most studies used the disk diffusion method for antimicrobial susceptibility testing; breakpoints were interpreted using Clinical Standard Laboratory Institute (CSLI) guidelines. Statistical models integrating data from publications on AMR in NTS and E. coli studies show a higher overall prevalence of AMR in pig isolates, and an increase in levels of AMR over the years. AMU studies (mostly from Vietnam) indicate very high usage levels of most types of antimicrobials, including beta-lactams, aminoglycosides, macrolides, and quinolones. This review summarizes information about genetic determinants of resistance, most of which are transferrable (mostly plasmids and integrons). The data in this review provide a benchmark to help focus research and policies on AMU and AMR in the region. PMID:27827853

Antimicrobial Susceptibility/Resistance of Streptococcus Pneumoniae

PubMed Central

Karcic, Emina; Aljicevic, Mufida; Bektas, Sabaheta; Karcic, Bekir

2015-01-01

Introduction: Pneumococcal infections are a major cause of morbidity and mortality worldwide, whose treatment is threatened with an increase in the number of strains resistant to antibiotic therapy. Goal: The main goal of this research was to investigate the presence of antimicrobial susceptibility/resistance of S. pneumoniae. Material and methods: Taken are swabs of the nose and nasopharynx, eye and ear. In vitro tests that were made in order to study the antimicrobial resistance of pneumococci are: disk diffusion method and E-test. Results: The resistance to inhibitors of cell wall synthesis was recorded at 39.17%, protein synthesis inhibitors 19.67%, folate antagonists 47.78% and quinolone in 1.11%. S. pneumoniae has shown drug resistance to erythromycin in 45%, clindamycin in 45%, chloramphenicol–0.56%, rifampicin–6.11%, tetracycline–4.67%, penicillin-G in 4.44%, oxacillin in 73.89%, ciprofloxacin in 1.11% and trimethoprim-sulfamethoxazole in 5.34% of cases. Conclusion: The highest resistance pneumococcus showed to erythromycin, clindamycin and trimethoprim-sulfamethoxazole and these should be avoided in the treatment. The least resistance pneumococcus showed to tetracycline, rifampicin, chloramphenicol, penicillin-G and ciprofloxacin. PMID:26236165

Antimicrobial activity of some essential oils against oral multidrug-resistant Enterococcus faecalis in both planktonic and biofilm state

PubMed Central

Benbelaïd, Fethi; Khadir, Abdelmounaïm; Abdoune, Mohamed Amine; Bendahou, Mourad; Muselli, Alain; Costa, Jean

2014-01-01

Objective To evaluate some essential oils in treatment of intractable oral infections, principally caused by biofilm of multidrug-resistant Enterococcus faecalis (E. faecalis), such as persistent endodontic infections in which their treatment exhibits a real challenge for dentists. Methods Ten chemically analyzed essential oils by gas chromatography-mass spectrometry were evaluated for antimicrobial activity against sensitive and resistant clinical strains of E. faecalis in both planktonic and biofilm state using two methods, disk diffusion and broth micro-dilution. Results Studied essential oils showed a good antimicrobial activity and high ability in E. faecalis biofilm eradication, whether for sensitive or multidrug-resistant strains, especially those of Origanum glandulosum and Thymbra capitata with interesting minimum inhibitory concentration, biofilm inhibitory concentration, and biofilm eradication concentration values which doesn't exceed 0.063%, 0.75%, and 1.5%, respectively. Conclusions Findings of this study indicate that essential oils extracted from aromatic plants can be used in treatment of intractable oral infections, especially caused by biofilm of multidrug-resistant E. faecalis. PMID:25182948

New 1,3,4-thiadiazole compounds including pyrazine moiety: Synthesis, structural properties and antimicrobial features

NASA Astrophysics Data System (ADS)

Gür, Mahmut; Şener, Nesrin; Muğlu, Halit; Çavuş, M. Serdar; Özkan, Osman Emre; Kandemirli, Fatma; Şener, İzzet

2017-07-01

In the study, some new 1,3,4-thiadiazole compounds were synthesized and we have reported identification of the structures by using UV-Vis, FT-IR, 1H NMR, 13C NMR and Mass spectroscopic methods. Antimicrobial activities of the compounds against three microorganisms, namely, Candida albicans ATCC 26555, Staphylococcus aureus ATCC 9144, and Escherichia coli ATCC 25922 were investigated by using disk diffusion method. These thiadiazoles exhibited an antimicrobial activity against Staphylococcus aureus and Candida albicans. The experimental data was supported by the quantum chemical calculations. Density functional theory (DFT) calculations were carried out to obtain the ground state optimized geometries of the molecules using the B3LYP, M06 and PBE1PBE methods with 3-21 g, 4-31 g, 6-311++g(2d,2p), cc-pvtz and cc-pvqz basis sets in the different combinations. Frontier molecular orbitals (FMOs) energies, band gap energies and some chemical reactivity parameters were calculated by using the aforementioned methods and basis sets, and the results were also compared with the experimental UV-Vis data.

Dittrichia graveolens (L.) Greuter Essential Oil: Chemical Composition, Multivariate Analysis, and Antimicrobial Activity.

PubMed

Mitic, Violeta; Stankov Jovanovic, Vesna; Ilic, Marija; Jovanovic, Olga; Djordjevic, Aleksandra; Stojanovic, Gordana

2016-01-01

The chemical composition and in vitro antimicrobial activities of Dittrichia graveolens (L.) Greuter essential oil was studied. Moreover, using agglomerative hierarchical cluster (AHC) and principal component analyses (PCA), the interrelationships of the D. graveolens essential-oil profiles characterized so far (including the sample from this study) were investigated. To evaluate the chemical composition of the essential oil, GC-FID and GC/MS analyses were performed. Altogether, 54 compounds were identified, accounting for 92.9% of the total oil composition. The D. graveolens oil belongs to the monoterpenoid chemotype, with monoterpenoids comprising 87.4% of the totally identified compounds. The major components were borneol (43.6%) and bornyl acetate (38.3%). Multivariate analysis showed that the compounds borneol and bornyl acetate exerted the greatest influence on the spatial differences in the composition of the reported oils. The antimicrobial activity against five bacterial and one fungal strain was determined using a disk-diffusion assay. The studied essential oil was active only against Gram-positive bacteria. Copyright © 2016 Verlag Helvetica Chimica Acta AG, Zürich.

Antimicrobial Resistance of Thermotolerant Campylobacter Species Isolated from Humans, Food-Producing Animals, and Products of Animal Origin: A Worldwide Meta-Analysis.

PubMed

Signorini, Marcelo L; Rossler, Eugenia; Díaz David, Diego C; Olivero, Carolina R; Romero-Scharpen, Analía; Soto, Lorena P; Astesana, Diego M; Berisvil, Ayelen P; Zimmermann, Jorge A; Fusari, Marcia L; Frizzo, Laureano S; Zbrun, María V

2018-04-30

The objective of this meta-analysis was to summarize available information on the prevalence of antimicrobial-resistant Campylobacter species in humans, food-producing animals, and products of animal origin. A number of multilevel random-effect meta-analysis models were fitted to estimate mean occurrence rate of antimicrobial-resistant thermotolerant Campylobacter and to compare them throughout the years and among the species, food-producing animals (i.e., bovine, pigs, broilers, hen, goat, and sheep), country of origin, sample type, methodology to determine the antimicrobial susceptibility, and the species of Campylobacter. Among the considered antibiotics, thermotolerant Campylobacter showed the highest resistance to tetracycline (pool estimate [PE] = 0.493; 95% CI 0.466-0.519), nalidixic acid (PE = 0.385; 95% CI 0.348-0.423), and ciprofloxacin (PE = 0.376; 95% CI 0.339-0.415). In general, the prevalence of antimicrobial-resistant Campylobacter spp. was higher in hen, broilers, and swine. Campylobacter coli showed a higher prevalence of antimicrobial resistance than Campylobacter jejuni. Independent of the antimicrobial evaluated, the disk diffusion method showed higher prevalence of antimicrobial-resistant Campylobacter than the methods based on the minimum inhibitory concentration estimation. The meta-analysis showed that the prevalence of antimicrobial-resistant Campylobacter is relevant essentially in foods derived from hens and broilers, and it was observed worldwide. The prevalence of this pathogen is of public health importance and the increase in the prevalence of Campylobacter strains resistant to the antimicrobial of choice worsens the situation, hence, national authorities must monitor the situation in each country with the aim to establish the appropriate risk management measures.

Detection of Methicillin-Resistant Coagulase-Negative Staphylococci by the Vitek 2 System

PubMed Central

Johnson, Kristen N.; Andreacchio, Kathleen

2014-01-01

The accurate performance of the Vitek 2 GP67 card for detecting methicillin-resistant coagulase-negative staphylococci (CoNS) is not known. We prospectively determined the ability of the Vitek 2 GP67 card to accurately detect methicillin-resistant CoNS, with mecA PCR results used as the gold standard for a 4-month period in 2012. Included in the study were 240 consecutively collected nonduplicate CoNS isolates. Cefoxitin susceptibility by disk diffusion testing was determined for all isolates. We found that the three tested systems, Vitek 2 oxacillin and cefoxitin testing and cefoxitin disk susceptibility testing, lacked specificity and, in some cases, sensitivity for detecting methicillin resistance. The Vitek 2 oxacillin and cefoxitin tests had very major error rates of 4% and 8%, respectively, and major error rates of 38% and 26%, respectively. Disk cefoxitin testing gave the best performance, with very major and major error rates of 2% and 24%, respectively. The test performances were species dependent, with the greatest errors found for Staphylococcus saprophyticus. While the 2014 CLSI guidelines recommend reporting isolates that test resistant by the oxacillin MIC or cefoxitin disk test as oxacillin resistant, following such guidelines produces erroneous results, depending on the test method and bacterial species tested. Vitek 2 cefoxitin testing is not an adequate substitute for cefoxitin disk testing. For critical-source isolates, mecA PCR, rather than Vitek 2 or cefoxitin disk testing, is required for optimal antimicrobial therapy. PMID:24951799

Characterization of Clostridium perfringens isolates obtained from 2010 to 2012 from chickens with necrotic enteritis in Korea.

PubMed

Park, Ji Young; Kim, Sara; Oh, Jae Young; Kim, Hye Ryoung; Jang, Il; Lee, Hee Soo; Kwon, Yong Kuk

2015-06-01

Clostridium perfringens produces diverse virulent toxins that cause necrotic enteritis in poultry, resulting in a great negative impact on the poultry industry. To study the characteristics of C. perfringens in chickens, we isolated 88 strains from chickens (1 strain per flock) with necrotic enteritis. The isolated bacterial strains were screened for toxin type and antimicrobial susceptibility. Necropsy of 17 chickens that died from necrotic enteritis revealed that their intestines were dilated with inflammatory exudates and characterized by mucosal necrosis. All the isolated strains were identified as toxin type A using multiplex PCR for toxin typing. We found that the rate of netB-positive strains isolated from dead chickens was significantly higher (8 of 17) than the rate among healthy chickens (2 of 50). We performed antimicrobial susceptibility test with 20 selected antimicrobial agents using the disk diffusion test and found that 30 tested strains were completely resistant to 5 antibiotics and partially resistant to 6 antibiotics whereas all the strains were susceptible to 9 antimicrobial agents. Using pulsed-field gel electrophoresis analysis, the 17 strains were divided into 13 genetic clusters showing high genetic diversity. In conclusion, C. perfringens strains isolated from Korean poultry showed a high resistance to antimicrobial drugs and high genetic diversity, suggesting that continuous monitoring is essential to prevent outbreaks of necrotic enteritis in chickens. © 2015 Poultry Science Association Inc.

Isolation, identification and antimicrobial sensitivity of Ornithobacterium rhinotracheale in broilers chicken flocks of Khuzestan, Iran

PubMed Central

Mayahi, Mansour; Gharibi, Darioush; Ghadimipour, Rahim; Talazadeh, Forough

2016-01-01

Ornithobacterium rhinotracheale (ORT) is a bacterium associated with respiratory disease, growth retardation, decreased egg production and mortality in chickens and turkeys. The objective of this study was isolation, identification and evaluation of antimicrobial susceptibility of ORT bacterium in slaughtered broilers chicken flocks based on cultural and molecular tests in Khuzestan province, south-west of Iran. A total of 210 tracheal swab samples were collected from 21 broiler flocks slaughtered in abattoirs of the province. The results of cultural and biochemical tests showed that 23 (10.95%) isolates from tracheal swabs of 4 flocks (19.04%) were identified as ORT, but according to molecular characterization, 18 (8.57%) ORT isolates were positive in PCR assay and produced the predicted 784 bp amplification product. Finally, using the disk diffusion method, the drug resistance patterns of ORT isolates were determined against a panel of commonly used antimicrobial agents. Antimicrobial susceptibility test revealed that all isolates (100%) were sensitive to tetracycline, florfenicol and cephalexin. The highest antimicrobial resistance (89.00%) was seen for fosfomycin, sultrim and gentamicin. The results of present research showed that there was significant difference between the isolation rates of ORT from various areas of the province. As well, our findings indicated that the simultaneous use of both cultural and molecular techniques results in more comprehensive outcomes in the isolation and identification of the organismfrom understudy hosts. PMID:28144427

Effects of feeding pasteurized waste milk to dairy calves on phenotypes and genotypes of antimicrobial resistance in fecal Escherichia coli isolates before and after weaning.

PubMed

Maynou, G; Migura-Garcia, L; Chester-Jones, H; Ziegler, D; Bach, A; Terré, M

2017-10-01

The aim of this study was to evaluate the effects of feeding pasteurized waste milk (pWM) to calves on antimicrobial resistance of fecal Escherichia coli at both phenotypic and genotypic levels. Fifty-two Holstein female calves (3 ± 1.3 d of age) were fed 1 of the 2 different types of milk: milk replacer (MR) without antimicrobials or pWM with β-lactam residues until weaning at 49 d of age. Fecal swabs of all calves were obtained on d 0, 35, and 56 of the study and 3 E. coli isolates per sample were studied. Phenotypic resistance was tested by the disk diffusion method against a panel of 12 antimicrobials. A total of 13 resistance genes consisting of β-lactam, sulfonamide, tetracycline, and aminoglycoside families were examined by PCR. Feeding pWM to calves increased the presence of phenotypic resistance to ampicillin, cephalotin, ceftiofur, and florfenicol in fecal E. coli compared with MR-fed calves. However, the presence of resistance to sulfonamides, tetracyclines, and aminoglycosides was common in dairy calves independent of their milk-feeding source, suggesting other factors apart from the feeding source are involved in the emergence of antimicrobial resistance. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Examination of bacteria drug resistance utilizing surface plasmon resonance

NASA Astrophysics Data System (ADS)

Chiang, Ya-Ling; Chen, How-Foo; Lin, Chi-Hung; Chen, Shean-Jen

2007-05-01

An antimicrobial testing method using surface plasmon resonance to improve the present techniques is reported in this paper. Different from conventional methods, namely Kirby-Bauer disk diffusion and variations of broth microdilution, the examination time is reduced from 18-24 hours or more to less than one hour after the treatment of antibiotics. E-coli resistant and susceptible to ampicillin are used in the test to demonstrate this innovative method. It is generally known that discovering a method to exam the bacterium resistance rapidly and correctly is very important for patients and for preventing infective disease from spreading. The method reported can benefit this requirement.

The oral microbiota of domestic cats harbors a wide variety of Staphylococcus species with zoonotic potential.

PubMed

Rossi, Ciro César; da Silva Dias, Ingrid; Muniz, Igor Mansur; Lilenbaum, Walter; Giambiagi-deMarval, Marcia

2017-03-01

This study aimed to characterize the species, antimicrobial resistance and dispersion of CRISPR systems in staphylococci isolated from the oropharynx of domestic cats in Brazil. Staphylococcus strains (n=75) were identified by MALDI-TOF and sequencing of rpoB and tuf genes. Antimicrobial susceptibility was assessed by disk diffusion method and PCR to investigate the presence of antimicrobial-resistance genes usually present in mobile genetic elements (plasmids), in addition to plasmid extraction. CRISPR - genetic arrangements that give the bacteria the ability to resist the entry of exogenous DNA - were investigated by the presence of the essential protein Cas1 gene. A great diversity of Staphylococcus species (n=13) was identified. The presence of understudied species, like S. nepalensis and S. pettenkoferi reveals that more than one identification method may be necessary to achieve conclusive results. At least 56% of the strains contain plamids, being 99% resistant to at least one of the eight tested antimicrobials and 12% multidrug resistant. CRISPR were rare among the studied strains, consistent with their putative role as gene reservoirs. Moreover, herein we describe for the first time their existence in Staphylococcus lentus, to which the system must confer additional adaptive advantage. Prevalence of resistance among staphylococci against antimicrobials used in veterinary and human clinical practice and the zoonotic risk highlight the need of better antimicrobial management practices, as staphylococci may transfer resistance genes among themselves, including to virulent species, like S. aureus. Copyright © 2017 Elsevier B.V. All rights reserved.

Highly potent silver-organoalkoxysilane antimicrobial porous nanomembrane

NASA Astrophysics Data System (ADS)

Umar, Sirajo; Liu, Yuanfeng; Wu, Yiguang; Li, Guangtao; Ding, Jiabo; Xiong, Runsong; Chen, Jinchun

2013-04-01

We used a simple electrospinning technique to fabricate a highly potent silver-organoalkoxysilane antimicrobial composite from AgNO3-polyvinylpyrrolidone (PVP)/3-aminopropyltrimethoxysilane (APTMS)/tetraethoxysilane (TEOS) solution. Spectroscopic and microscopic analyses of the composite showed that the fibers contain an organoalkoxysilane `skeleton,' 0.18 molecules/nm2 surface amino groups, and highly dispersed and uniformly distributed silver nanoparticles (5 nm in size). Incorporation of organoalkoxysilanes is highly beneficial to the antimicrobial mat as (1) amino groups of APTMS are adhesive and biocidal to microorganisms, (2) polycondensation of APTMS and TEOS increases the membrane's surface area by forming silicon bonds that stabilize fibers and form a composite mat with membranous structure and high porosity, and (3) the organoalkoxysilanes are also instrumental to the synthesis of the very small-sized and highly dispersed silver metal particles in the fiber mat. Antimicrobial property of the composite was evaluated by disk diffusion, minimum inhibition concentration (MIC), kinetic, and extended use assays on bacteria (Escherichia coli, Bacillus anthracis, Staphylococcus aureus, and Brucella suis), a fungus (Aspergillus niger), and the Newcastle disease virus. The membrane shows quick and sustained broad-spectrum antimicrobial activity. Only 0.3 mg of fibers is required to achieve MIC against all the test organisms. Bacteria are inhibited within 30 min of contact, and the fibers can be used repeatedly. The composite is silver efficient and environment friendly, and its membranous structure is suitable for many practical applications as in air filters, antimicrobial linen, coatings, bioadhesives, and biofilms.

Prevalence and Antimicrobial Resistance of Salmonella Isolates from Chicken Carcasses in Retail Markets in Yangon, Myanmar.

PubMed

Moe, Aung Zaw; Paulsen, Peter; Pichpol, Duangporn; Fries, Reinhard; Irsigler, Herlinde; Baumann, Maximilian P O; Oo, Kyaw Naing

2017-06-01

A cross-sectional investigation was conducted concerning prevalence, antimicrobial resistance, multidrug resistance patterns, and serovar diversity of Salmonella in chicken meat sold at retail in Yangon, Myanmar. The 141 chicken meat samples were collected at 141 retail markets in the Yangon Region, Myanmar, 1 November 2014 to 31 March 2015. Information on hygienic practices (potential risk factors) was retrieved via checklists. Salmonella was isolated and identified according to International Organization for Standardization methods (ISO 6579:2002) with minor modifications. Twelve antimicrobial agents belonging to eight pharmacological groups were used for antimicrobial susceptibility testing (disk diffusion method). Salmonella was recovered from 138 (97.9%) of the 141 samples. The isolates were most frequently resistant to trimethoprim-sulfamethoxazole (70.3% of isolates), tetracycline (54.3%), streptomycin (49.3%), and ampicillin (47.1%). Resistance was also found to chloramphenicol (29.7%), amoxicillin-clavulanic acid (17.4%), ciprofloxacin (9.4%), tobramycin (8.7%), gentamicin (8%), cefazolin (7.2%), lincomycin-spectinomycin (5.8%), and norfloxacin (0.7%). Among the 138 Salmonella isolates, 72 (52.2%) were resistant to three or more antimicrobial agents. Twenty-four serovars were identified among the 138 Salmonella-positive samples; serovars Albany, Kentucky, Braenderup, and Indiana were found in 38, 11, 10, and 8% of samples, respectively. None of the potential risk factors were significantly related to Salmonella contamination of chicken carcasses. This study provides new information regarding prevalence and antimicrobial resistance and Salmonella serovar diversity in retail markets in Yangon, Myanmar.

Comparison of disk diffusion and agar dilution methods for gentamicin susceptibility testing of Neisseria gonorrhoeae.

PubMed

Gianecini, Ricardo; Oviedo, Claudia; Irazu, Lucia; Rodríguez, Marcelo; Galarza, Patricia

2018-03-29

Gentamicin is a promising antibiotic for the treatment of multidrug-resistant gonorrhea. The aim of this study was to analyze the suitability and reliably of disk diffusion to monitor the susceptibility to gentamicin. We studied 237 Neisseria gonorrhoeae isolates obtained in 2013 and 2015. Reference MICs were correlated with inhibition zone diameters (in millimeters) of gentamicin 10 µg disks manufactured by BBL and Oxoid. The Pearson correlation between disk diffusion and agar dilution was r = -.68 (P < 0.001) for BBL disk and r = -.71 (P < 0.001) for Oxoid disk. No very major or major discrepancies were detected. However, a high percentage of minor discrepancies was observed (44.7%, BBL disk) and (21.9%, Oxoid disk). By adjusting the susceptible breakpoint to S ≥ 17 mm, the minor discrepancies rate was reduced to 19.4% (BBL disk) and 10.1% (Oxoid disk). The disk diffusion may be a screening method in clinical laboratories to detect the gentamicin susceptibility of N. gonorrhoeae. Copyright © 2018 Elsevier Inc. All rights reserved.

Identification and Antimicrobial Susceptibility Testing of Anaerobic Bacteria: Rubik’s Cube of Clinical Microbiology?

PubMed Central

Gajdács, Márió; Spengler, Gabriella; Urbán, Edit

2017-01-01

Anaerobic bacteria have pivotal roles in the microbiota of humans and they are significant infectious agents involved in many pathological processes, both in immunocompetent and immunocompromised individuals. Their isolation, cultivation and correct identification differs significantly from the workup of aerobic species, although the use of new technologies (e.g., matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, whole genome sequencing) changed anaerobic diagnostics dramatically. In the past, antimicrobial susceptibility of these microorganisms showed predictable patterns and empirical therapy could be safely administered but recently a steady and clear increase in the resistance for several important drugs (β-lactams, clindamycin) has been observed worldwide. For this reason, antimicrobial susceptibility testing of anaerobic isolates for surveillance purposes or otherwise is of paramount importance but the availability of these testing methods is usually limited. In this present review, our aim was to give an overview of the methods currently available for the identification (using phenotypic characteristics, biochemical testing, gas-liquid chromatography, MALDI-TOF MS and WGS) and antimicrobial susceptibility testing (agar dilution, broth microdilution, disk diffusion, gradient tests, automated systems, phenotypic and molecular resistance detection techniques) of anaerobes, when should these methods be used and what are the recent developments in resistance patterns of anaerobic bacteria. PMID:29112122

Antimicrobial activities of commercial essential oils and their components against food-borne pathogens and food spoilage bacteria

PubMed Central

Mith, Hasika; Duré, Rémi; Delcenserie, Véronique; Zhiri, Abdesselam; Daube, Georges; Clinquart, Antoine

2014-01-01

This study was undertaken to determine the in vitro antimicrobial activities of 15 commercial essential oils and their main components in order to pre-select candidates for potential application in highly perishable food preservation. The antibacterial effects against food-borne pathogenic bacteria (Listeria monocytogenes, Salmonella Typhimurium, and enterohemorrhagic Escherichia coli O157:H7) and food spoilage bacteria (Brochothrix thermosphacta and Pseudomonas fluorescens) were tested using paper disk diffusion method, followed by determination of minimum inhibitory (MIC) and bactericidal (MBC) concentrations. Most of the tested essential oils exhibited antimicrobial activity against all tested bacteria, except galangal oil. The essential oils of cinnamon, oregano, and thyme showed strong antimicrobial activities with MIC ≥ 0.125 μL/mL and MBC ≥ 0.25 μL/mL. Among tested bacteria, P. fluorescens was the most resistant to selected essential oils with MICs and MBCs of 1 μL/mL. The results suggest that the activity of the essential oils of cinnamon, oregano, thyme, and clove can be attributed to the existence mostly of cinnamaldehyde, carvacrol, thymol, and eugenol, which appear to possess similar activities against all the tested bacteria. These materials could be served as an important natural alternative to prevent bacterial growth in food products. PMID:25473498

Identification and Antimicrobial Susceptibility Testing of Anaerobic Bacteria: Rubik's Cube of Clinical Microbiology?

PubMed

Gajdács, Márió; Spengler, Gabriella; Urbán, Edit

2017-11-07

Anaerobic bacteria have pivotal roles in the microbiota of humans and they are significant infectious agents involved in many pathological processes, both in immunocompetent and immunocompromised individuals. Their isolation, cultivation and correct identification differs significantly from the workup of aerobic species, although the use of new technologies (e.g., matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, whole genome sequencing) changed anaerobic diagnostics dramatically. In the past, antimicrobial susceptibility of these microorganisms showed predictable patterns and empirical therapy could be safely administered but recently a steady and clear increase in the resistance for several important drugs (β-lactams, clindamycin) has been observed worldwide. For this reason, antimicrobial susceptibility testing of anaerobic isolates for surveillance purposes or otherwise is of paramount importance but the availability of these testing methods is usually limited. In this present review, our aim was to give an overview of the methods currently available for the identification (using phenotypic characteristics, biochemical testing, gas-liquid chromatography, MALDI-TOF MS and WGS) and antimicrobial susceptibility testing (agar dilution, broth microdilution, disk diffusion, gradient tests, automated systems, phenotypic and molecular resistance detection techniques) of anaerobes, when should these methods be used and what are the recent developments in resistance patterns of anaerobic bacteria.

Antimicrobial activity and partial characterization of bacteriocin-like inhibitory substances produced by Lactobacillus spp. isolated from artisanal Mexican cheese.

PubMed

Heredia-Castro, Priscilia Y; Méndez-Romero, José I; Hernández-Mendoza, Adrián; Acedo-Félix, Evelia; González-Córdova, Aarón F; Vallejo-Cordoba, Belinda

2015-12-01

Lactobacillus spp. from Mexican Cocido cheese were shown to produce bacteriocin-like substances (BLS) active against Staphylococcus aureus,Listeria innocua,Escherichia coli, andSalmonella typhimurium by using the disk diffusion method. Crude extracts of Lactobacillus fermentum showed strong inhibitory activity against Staph. aureus, L. innocua, E. coli, and Salmonella cholerae. Complete inactivation of antimicrobial activity was observed after treatment of crude extracts with proteinase K, pronase, papain, trypsin, and lysozyme, confirming their proteinaceous nature. However, antimicrobial activity was partly lost for some of the crude extracts when treated with α-amylase, indicating that carbohydrate moieties were involved. The antimicrobial activity of the crude extracts was stable at 65°C for 30min over a wide pH range (2-8), and addition of potassium chloride, sodium citrate, ethanol, and butanol did not affect antibacterial activity. However, antimicrobial activity was lost after heating at 121°C for 15min, addition of methanol or Tween 80. Fourteen out of 18 Lactobacillus spp. showed antimicrobial activity against different test microorganisms, and 12 presented bacteriocin-like substances. Generation time and growth rate parameters indicated that the antimicrobial activity of crude extracts from 3 different strains was effective against the 4 indicator microorganisms. One of the crude extracts showed inhibition not only against gram-positive but also against gram-negative bacteria. Bacteriocin-like substances produced by this specific Lactobacillus strain showed potential for application as a food biopreservative. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Supercritical carbon dioxide extraction of compounds with antimicrobial activity from Origanum vulgare L.: determination of optimal extraction parameters.

PubMed

Santoyo, S; Cavero, S; Jaime, L; Ibañez, E; Señoráns, F J; Reglero, G

2006-02-01

Oregano leaves were extracted using a pilot-scale supercritical fluid extraction plant under a wide range of extraction conditions, with the goal of determining the extraction and fractionation conditions to obtain extracts with optimal antimicrobial activity. In this investigation, the essential oil-rich fractions were selectively precipitated in the second separator, and their chemical composition and antimicrobial activity were investigated. Gas chromatography-mass spectrometry analysis of the various fractions resulted in the identification of 27 compounds of the essential oil. The main components of these fractions were carvacrol, trans-sabinene hydrate, cis-piperitol, borneol, terpinen-4-ol, and linalool. Antimicrobial activity was investigated by the disk diffusion and broth dilution methods against six different microbial species, including two gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), two gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), a yeast (Candida albicans), and a fungus (Aspergillus niger). All of the supercritical fluid extraction fractions obtained showed antimicrobial activity against all of the microorganisms tested, although the most active fraction was the one obtained in experiment 5 (fraction was obtained with 7% ethanol at 150 bar and 40 degrees C). C. albicans was the most sensitive microorganism to the oregano extracts, whereas the least susceptible was A. niger. Carvacrol, sabinene hydrate, borneol, and linalool standards also showed antimicrobial activity against all of the microorganisms tested, with carvacrol being the most effective. Consequently, it was confirmed that essential oil from experiment 5, with the best antimicrobial activity, also presented the highest quantity of carvacrol.

Silver nanoparticles: Antimicrobial activity, cytotoxicity, and synergism with N-acetyl cysteine.

PubMed

Hamed, Selwan; Emara, Mohamed; Shawky, Riham M; El-Domany, Ramadan A; Youssef, Tareq

2017-08-01

The fast progression of nanotechnology has led to novel therapeutic interventions. Antimicrobial activities of silver nanoparticles (Ag NPs) were tested against standard ATCC strains of Staphylococcus aureus (ATCC 9144), Escherichia coli (O157:H7), Pseudomonas aeruginosa (ATCC 27853), and Candida albicans (ATCC 90028) in addition to 60 clinical isolates collected from cancer patients. Antimicrobial activity was tested by disk diffusion method and MIC values for Ag NPs alone and in combination with N-acetylcysteine (NAC) against tested pathogens were determined by broth microdilution method. Ag NPs showed a robust antimicrobial activity against all tested pathogens and NAC substantially enhanced the antimicrobial activity of Ag NPs against all tested pathogens. Synergism between Ag NPs and NAC has been confirmed by checkerboard assay. The effect of Ag NPs on tested pathogens was further scrutinized by Transmission Electron Microscope (TEM) which showed disruption of cell wall in both bacteria and fungi. Ag NPs abrogated the activity of respiratory chain dehydrogenase of all tested pathogens and released muramic acid content from S. aureus in culture. The cytotoxic effect of Ag NPs alone and in combination with NAC was examined using human HepG2 cells and this revealed no cytotoxicity at MIC values of Ag NPs and interestingly, NAC reduced the cytotoxic effect of Ag NPs at concentrations higher than their MIC values. Taken together, Ag NPs have robust antimicrobial activity and NAC substantially enhances their antimicrobial activities against MDR pathogens which would provide a novel safe, effective, and inexpensive therapeutic approach to control the prevalence of MDR pathogens. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antimicrobial resistance, heavy metal resistance and integron content in bacteria isolated from a South African tilapia aquaculture system.

PubMed

Chenia, Hafizah Y; Jacobs, Anelet

2017-11-21

Antibacterial compounds and metals co-select for antimicrobial resistance when bacteria harbour resistance genes towards both types of compounds, facilitating the proliferation and evolution of antimicrobial and heavy metal resistance. Antimicrobial and heavy metal resistance indices of 42 Gram-negative bacteria from a tilapia aquaculture system were determined to identify possible correlations between these phenotypes. Agar dilution assays were carried out to determine susceptibility to cadmium, copper, lead, mercury, chromate and zinc, while susceptibility to 21 antimicrobial agents was investigated by disk diffusion assays. Presence of merA, the mercury resistance gene, was determined by dot-blot hybridizations and PCR. Association of mercury resistance with integrons and transposon Tn21 was also investigated by PCR. Isolates displayed a high frequency of antimicrobial (erythromycin: 100%; ampicillin: 85%; trimethoprim: 78%) and heavy metal (Zn2+: 95%; Cd2+: 91%) resistance. No correlation was established between heavy metal and multiple antibiotic resistance indices. Significant positive correlations were observed between heavy metal resistance profiles, indices, Cu2+ and Cr3+ resistance with erythromycin resistance. Significant positive correlations were observed between merA (24%)/Tn21 (24%) presence and heavy metal resistance profiles and indices; however, significant negative correlations were obtained between integron-associated qacE∆1 (43%) and sulI (26%) gene presence and heavy metal resistance indices. Heavy metal and antimicrobial agents co-select for resistance, with fish-associated, resistant bacteria demonstrating simultaneous heavy metal resistance. Thus, care should be taken when using anti-fouling heavy metals as feed additives in aquaculture facilities.

Antimicrobial activity of chemomechanical gingival retraction products.

PubMed

Hsu, Belinda; Lee, Stephanie; Schwass, Donald; Tompkins, Geoffrey

2017-07-01

Application of astringent hemostatic agents is the most widely used technique for gingival retraction, and a variety of products are offered commercially. However, these products may have additional unintended yet clinically beneficial properties. The authors assessed the antimicrobial activities of marketed retraction products against plaque-associated bacteria in both planktonic and biofilm assays, in vitro. The authors assessed hemostatic solutions, gels, pellets, retraction cords, pastes, and their listed active agents against a collection of microorganisms by means of conventional agar diffusion and minimum bacteriostatic and bactericidal concentration determinations. The authors then tested the most active products against monospecies biofilms grown on hydroxyapatite disks. All of the tested retraction products exhibited some antimicrobial activity. The results of the most active products were comparable with those of a marketed mouthwash. The listed retraction-active agents displayed relatively little activity when tested in pure form. At 10% dilution, some products evidenced inhibitory activity against most tested bacteria within 3 minutes of exposure, whereas others displayed variable effects after 10 minutes. The most active agents reduced, but did not completely prevent, the metabolic activity of a monospecies biofilm. Commercial gingival retraction products exhibit antimicrobial effects to various degrees in vitro. Some products display rapid bactericidal activity. The antimicrobial activity is not owing to the retraction-active agents. Biofilm bacteria are less sensitive to the antimicrobial effects of the agents. The rapidity of killing by some hemostatic agents suggests an antimicrobial effect that may be efficacious during clinical placement. The results of this in vitro study suggest that clinicians should be aware of the potential antimicrobial effects of some hemostatic agents, but more research is needed to confirm these observations in clinical use. Copyright © 2017 American Dental Association. Published by Elsevier Inc. All rights reserved.

GALACTIC WINDS DRIVEN BY ISOTROPIC AND ANISOTROPIC COSMIC-RAY DIFFUSION IN DISK GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pakmor, R.; Pfrommer, C.; Simpson, C. M.

2016-06-20

The physics of cosmic rays (CRs) is a promising candidate for explaining the driving of galactic winds and outflows. Recent galaxy formation simulations have demonstrated the need for active CR transport either in the form of diffusion or streaming to successfully launch winds in galaxies. However, due to computational limitations, most previous simulations have modeled CR transport isotropically. Here, we discuss high-resolution simulations of isolated disk galaxies in a 10{sup 11} M {sub ⊙} halo with the moving-mesh code Arepo that include injection of CRs from supernovae, advective transport, CR cooling, and CR transport through isotropic or anisotropic diffusion. Wemore » show that either mode of diffusion leads to the formation of strong bipolar outflows. However, they develop significantly later in the simulation with anisotropic diffusion compared to the simulation with isotropic diffusion. Moreover, we find that isotropic diffusion allows most of the CRs to quickly diffuse out of the disk, while in the simulation with anisotropic diffusion, most CRs remain in the disk once the magnetic field becomes dominated by its azimuthal component, which occurs after ∼300 Myr. This has important consequences for the gas dynamics in the disk. In particular, we show that isotropic diffusion strongly suppresses the amplification of the magnetic field in the disk compared to anisotropic or no diffusion models. We therefore conclude that reliable simulations which include CR transport inevitably need to account for anisotropic diffusion.« less

Bioactive Potential of 3D-Printed Oleo-Gum-Resin Disks: B. papyrifera, C. myrrha, and S. benzoin Loading Nanooxides—TiO2, P25, Cu2O, and MoO3

PubMed Central

Tebcherani, Sergio Mazurek; Kubaski, Evaldo Toniolo; de Almeida Vieira, Rogério

2017-01-01

This experimental study investigates the bioactive potential of filaments produced via hot melt extrusion (HME) and intended for fused deposition modeling (FDM) 3D printing purposes. The oleo-gum-resins from benzoin, myrrha, and olibanum in pure state and also charged with 10% of metal oxide nanoparticles, TiO2, P25, Cu2O, and MoO3, were characterized by ultraviolet-visible (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray microanalysis (EDXMA), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Disks were 3D-printed into model geometries (10 × 5 mm) and the disk-diffusion methodology was used for the evaluation of antimicrobial and antifungal activity of materials in study against the clinical isolates: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans. Due to their intrinsic properties, disks containing resins in pure state mostly prevent surface-associated growth; meanwhile, disks loaded with 10% oxides prevent planktonic growth of microorganisms in the susceptibility assay. The microscopy analysis showed that part of nanoparticles was encapsulated by the biopolymeric matrix of resins, in most cases remaining disorderly dispersed over the surface of resins. Thermal analysis shows that plant resins have peculiar characteristics, with a thermal behavior similar to commercial available semicrystalline polymers, although their structure consists of a mix of organic compounds. PMID:28811751

Bioactive Potential of 3D-Printed Oleo-Gum-Resin Disks: B. papyrifera, C. myrrha, and S. benzoin Loading Nanooxides-TiO2, P25, Cu2O, and MoO3.

PubMed

Horst, Diogo José; Tebcherani, Sergio Mazurek; Kubaski, Evaldo Toniolo; de Almeida Vieira, Rogério

2017-01-01

This experimental study investigates the bioactive potential of filaments produced via hot melt extrusion (HME) and intended for fused deposition modeling (FDM) 3D printing purposes. The oleo-gum-resins from benzoin, myrrha, and olibanum in pure state and also charged with 10% of metal oxide nanoparticles, TiO 2 , P25, Cu 2 O, and MoO 3 , were characterized by ultraviolet-visible (UV-Vis) and Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray microanalysis (EDXMA), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Disks were 3D-printed into model geometries (10 × 5 mm) and the disk-diffusion methodology was used for the evaluation of antimicrobial and antifungal activity of materials in study against the clinical isolates: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli , and Candida albicans . Due to their intrinsic properties, disks containing resins in pure state mostly prevent surface-associated growth; meanwhile, disks loaded with 10% oxides prevent planktonic growth of microorganisms in the susceptibility assay. The microscopy analysis showed that part of nanoparticles was encapsulated by the biopolymeric matrix of resins, in most cases remaining disorderly dispersed over the surface of resins. Thermal analysis shows that plant resins have peculiar characteristics, with a thermal behavior similar to commercial available semicrystalline polymers, although their structure consists of a mix of organic compounds.

Chemical composition and antimicrobial activity of the essential oils from the gum of Turkish pistachio (Pistacia vera L.).

PubMed

Alma, Mehmet Hakki; Nitz, Siegfried; Kollmannsberger, Hubert; Digrak, Metin; Efe, Fatih Tuncay; Yilmaz, Necmettin

2004-06-16

The essential oil from the gum of Pistachio (Pistacia vera L. (Anacardiaceae)) grown in Turkey was obtained by the hydro-distillation method, and its chemical composition was analyzed by GC and GC-MS. Moreover, the antimicrobial activities of the oil against the growth of 13 bacteria and 3 pathogenic yeasts were evaluated using the agar-disk diffusion and minimum inhibitory concentration (MIC) methods. The results showed that the essential oil contained about 89.67% monoterpenes, 8.1% oxygenated monoterpenes and 1.2% diterpenes. alpha-Pinene (75.6%), beta-pinene (9.5%), trans-verbenol (3.0%), camphene (1.4%), trans-pinocarveol (about 1.20%), and limonene (1.0%) were the major components. The antimicrobial results showed that the oil inhibited nine bacteria and all the yeasts studied, and the activities were considerably dependent upon concentration and its bioactive compounds such as carvacrol, camphene, and limonene. Moreover, the essential oil of the gum was found to be more effective yeastcide than Nystatin, synthetic yeastcide. Furthermore, the antibacterial activities of the oil were lower than those of standard antibiotics, ampicillin sodium, and streptomycine sulfate under the conditions studied.

New antibacterial germacrene from Verbesina negrensis.

PubMed

Mora, Flor D; Alpan, Lara; de Tommasi, Nunziatina; McCracken, Vance J; Nieto, Marcelo

2013-05-01

Several health benefits have been attributed to members of the Verbesina genus, including promotion of urinary and gastrointestinal health. Verbesina species are also reported to exhibit antibacterial, antiparasitic, and antioxidant activities. Although members of the Verbesina genus produce various pharmacologically relevant chemicals as secondary metabolites, including eudesmanes, flavonoids, guanidine alkaloids, acetylenic compounds, and germacrenes, the active compounds required for these benefits remain unknown. To investigate potential antimicrobial activities of Verbesina negrensis, crude extracts from plant aerial structures were evaluated. Following chemical fractionation, the chloroformic extract from Verbesina negrensis was subjected to bioassay-guided isolation using disk diffusion assays to determine antimicrobial activity. The active compound was characterized as 6β-cinnamoyloxy-1β-hydroxy-10α-metoxy-3-oxo-germacra-4,5Z-ene (1). Fractions containing 1 inhibited both Enterococcus faecalis (ATCC 29 212) and Staphylococcus aureus (ATCC 29213). The MIC for 1 was determined by microbroth dilution assay to be 64 µg/mL for both E. faecalis and S. aureus. Georg Thieme Verlag KG Stuttgart · New York.

Chemical Composition and In Vitro Antioxidant, Cytotoxic, Antimicrobial, and Larvicidal Activities of the Essential Oil of Mentha piperita L. (Lamiaceae)

PubMed Central

da Silva Ramos, Ryan; Rodrigues, Alex Bruno Lobato; Farias, Ana Luzia Ferreira; Simões, Ranggel Carvalho; Pinheiro, Mayara Tânia; Ferreira, Ricardo Marcelo dos Anjos; Costa Barbosa, Ledayane Mayana; Picanço Souto, Raimundo Nonato; Fernandes, João Batista

2017-01-01

The essential oil was obtained by hydrodistillation and the identification and quantification of components were achieved with the use of GC-MS analysis. The antioxidant activity was evaluated by the method of sequestration of DPPH. Essential oils were used for study the cytotoxic front larvae of Artemia salina. In the evaluation of the antimicrobial activity of essential oils, we employed the disk-diffusion method. The potential larvicide in mosquito larvae of the third stage of development of Aedes aegypti to different concentrations of essential oils was evaluated. The major compounds found in the essential oils of M. piperita were linalool (51.8%) and epoxyocimene (19.3%). The percentage of antioxidant activity was 79.9 ± 1.6%. The essential oil showed LC50 = 414.6 μg/mL front of A. saline and is considered highly toxic. It shows sensitivity and halos significant inhibition against E. coli. The essential possessed partial larvicidal efficiency against A. aegypti. PMID:28116346

Patterns of Antimicrobial Resistance Observed in Escherichia coli Isolates Obtained from Domestic- and Wild-Animal Fecal Samples, Human Septage, and Surface Water

PubMed Central

Sayah, Raida S.; Kaneene, John B.; Johnson, Yvette; Miller, RoseAnn

2005-01-01

A repeated cross-sectional study was conducted to determine the patterns of antimicrobial resistance in 1,286 Escherichia coli strains isolated from human septage, wildlife, domestic animals, farm environments, and surface water in the Red Cedar watershed in Michigan. Isolation and identification of E. coli were done by using enrichment media, selective media, and biochemical tests. Antimicrobial susceptibility testing by the disk diffusion method was conducted for neomycin, gentamicin, streptomycin, chloramphenicol, ofloxacin, trimethoprim-sulfamethoxazole, tetracycline, ampicillin, nalidixic acid, nitrofurantoin, cephalothin, and sulfisoxazole. Resistance to at least one antimicrobial agent was demonstrated in isolates from livestock, companion animals, human septage, wildlife, and surface water. In general, E. coli isolates from domestic species showed resistance to the largest number of antimicrobial agents compared to isolates from human septage, wildlife, and surface water. The agents to which resistance was demonstrated most frequently were tetracycline, cephalothin, sulfisoxazole, and streptomycin. There were similarities in the patterns of resistance in fecal samples and farm environment samples by animal, and the levels of cephalothin-resistant isolates were higher in farm environment samples than in fecal samples. Multidrug resistance was seen in a variety of sources, and the highest levels of multidrug-resistant E. coli were observed for swine fecal samples. The fact that water sample isolates were resistant only to cephalothin may suggest that the resistance patterns for farm environment samples may be more representative of the risk of contamination of surface waters with antimicrobial agent-resistant bacteria. PMID:15746342

The Effect of CuO Nanoparticles on Antimicrobial Effects and Shear Bond Strength of Orthodontic Adhesives

PubMed Central

Toodehzaeim, Mohammad Hossein; Zandi, Hengameh; Meshkani, Hamidreza; Hosseinzadeh Firouzabadi, Azadeh

2018-01-01

Statement of the Problem: Orthodontic appliances facilitate microbial plaque accumulation and increase the chance of white spot lesions. There is a need for new plaque control methods independent of patient's cooperation. Purpose: The aim of this study was to determine the effects of incorporating copper oxide (CuO) nanoparticles on antimicrobial properties and bond strength of orthodontic adhesive. Materials and Method: CuO nanoparticles were added to the composite transbond XT at concentrations of 0.01, 0.5 and 1 wt.%. To evaluate the antimicrobial properties of composites containing nanoparticles, the disk agar diffusion test was used. For this purpose, 10 discs from each concentration of nano-composites (totally 30 discs) and 10 discs from conventional composite (as the control group) were prepared. Then the diameter of streptococcus mutans growth inhibition around each disc was determined in blood agar medium. To evaluate the shear bond strength, with each concentration of nano-composites as well as the control group (conventional composite), 10 metal brackets were bonded to the human premolars and shear bond strength was determined using a universal testing machine. Results: Nano-composites in all three concentrations showed significant antimicrobial effect compared to the control group (p< 0.001). With increasing concentration of nanoparticles, antimicrobial effect showed an upward trend, although statistically was not significant. There was no significant difference between the shear bond strength of nano-composites compared to control group (p= 0.695). Conclusion: Incorporating CuO nanoparticles into adhesive in all three studied concentrations added antimicrobial effects to the adhesive with no adverse effects on shear bond strength. PMID:29492409

The Effect of CuO Nanoparticles on Antimicrobial Effects and Shear Bond Strength of Orthodontic Adhesives.

PubMed

Toodehzaeim, Mohammad Hossein; Zandi, Hengameh; Meshkani, Hamidreza; Hosseinzadeh Firouzabadi, Azadeh

2018-03-01

Orthodontic appliances facilitate microbial plaque accumulation and increase the chance of white spot lesions. There is a need for new plaque control methods independent of patient's cooperation. The aim of this study was to determine the effects of incorporating copper oxide (CuO) nanoparticles on antimicrobial properties and bond strength of orthodontic adhesive. CuO nanoparticles were added to the composite transbond XT at concentrations of 0.01, 0.5 and 1 wt.%. To evaluate the antimicrobial properties of composites containing nanoparticles, the disk agar diffusion test was used. For this purpose, 10 discs from each concentration of nano-composites (totally 30 discs) and 10 discs from conventional composite (as the control group) were prepared. Then the diameter of streptococcus mutans growth inhibition around each disc was determined in blood agar medium. To evaluate the shear bond strength, with each concentration of nano-composites as well as the control group (conventional composite), 10 metal brackets were bonded to the human premolars and shear bond strength was determined using a universal testing machine. Nano-composites in all three concentrations showed significant antimicrobial effect compared to the control group ( p < 0.001). With increasing concentration of nanoparticles, antimicrobial effect showed an upward trend, although statistically was not significant. There was no significant difference between the shear bond strength of nano-composites compared to control group ( p = 0.695). Incorporating CuO nanoparticles into adhesive in all three studied concentrations added antimicrobial effects to the adhesive with no adverse effects on shear bond strength.

Antimicrobial activity of the essential oil from Lippia sidoides, carvacrol and thymol against oral pathogens.

PubMed

Botelho, M A; Nogueira, N A P; Bastos, G M; Fonseca, S G C; Lemos, T L G; Matos, F J A; Montenegro, D; Heukelbach, J; Rao, V S; Brito, G A C

2007-03-01

Dental caries and periodontal disease are associated with oral pathogens. Several plant derivatives have been evaluated with respect to their antimicrobial effects against such pathogenic microorganisms. Lippia sidoides Cham (Verbenaceae), popularly known as "Alecrim-pimenta" is a typical shrub commonly found in the Northeast of Brazil. Many plant species belonging to the genus Lippia yield very fragrant essential oils of potential economic value which are used by the industry for the commercial production of perfumes, creams, lotions, and deodorants. Since the leaves of L. sidoides are also extensively used in popular medicine for the treatment of skin wounds and cuts, the objective of the present study was to evaluate the composition and antimicrobial activity of L. sidoides essential oil. The essential oil was obtained by hydro-distillation and analyzed by GC-MS. Twelve compounds were characterized, having as major constituents thymol (56.7%) and carvacrol (16.7%). The antimicrobial activity of the oil and the major components was tested against cariogenic bacterial species of the genus Streptococcus as well as Candida albicans using the broth dilution and disk diffusion assays. The essential oil and its major components thymol and carvacrol exhibited potent antimicrobial activity against the organisms tested with minimum inhibitory concentrations ranging from 0.625 to 10.0 mg/mL. The most sensitive microorganisms were C. albicans and Streptococcus mutans. The essential oil of L. sidoides and its major components exert promising antimicrobial effects against oral pathogens and suggest its likely usefulness to combat oral microbial growth.

Chemical Composition and Antimicrobial Activities of Iranian Propolis

PubMed Central

Afrouzan, Houshang; Tahghighi, Azar; Zakeri, Sedigheh; Es-haghi, Ali

2018-01-01

Background: With considering the importance of natural products for their remedial and therapeutic value, this research was aimed to analyze the chemical compositions and antimicrobial activity of four propolis samples from different areas of Iran (Chenaran, Taleghan, Morad Beyg, and Kalaleh) with various climates and flora. Methods: Ethanolic (70% EtOH) and dichlromethane (DCM) extracts of Iranian propolis were analyzed by gas chromatography-mass spectrometry (GC-MS) methods, and antimicrobial activity was evaluated against Candida albicans, Escherichia coli, and Staphylococcus aureus using disk diffusion antimicrobial method. Results: The results of GC-MS analysis showed the presence of fatty acids, flavonoids, terpenes, aromatic-aliphatic acids, and their related esters. The total flavonoids in DCM extract of Chenaran, Taleghan, Morad Beyg, and Kalaleh propolis were pinocembrin and pinostrobin chalcone. The common phenolic and terpene compounds detected in all four tested EtOH extracts were P-cumaric acid and dimethyl -1,3,5,6-tetramethyl-[1,3-(13C2)] bicycloce [5.5.0] dodeca-1,3,5,6,8,10-hexaene-9,10-dicarboxylate, respectively. The highest inhibitory diameter zone of the Iranian propolis against C. albicans, E. coli, and S. aureus was for DCM extract of Kalaleh propolis (13.33 mm), Morad Beyg propolis (12 mm), and Kalaleh (11.67 mm), respectively. Conclusion: Iranian propolis showed antimicrobial activities against C. albicans, E. coli, and S. aurous, perhaps due to the presence of flavonoids, phenolic acids, and terpenes as active components that can be used alone or in combination with the selected antibiotics to synergize antibiotic effect, as well as to prevent microbial resistance to available antimicrobial drugs. PMID:28558440

Antimicrobial activity and properties of irreversible hydrocolloid impression materials incorporated with silver nanoparticles.

PubMed

Ginjupalli, Kishore; Alla, Rama Krishna; Tellapragada, Chaitanya; Gupta, Lokendra; Upadhya Perampalli, Nagaraja

2016-06-01

Conventional spray and the immersion disinfection of irreversible hydrocolloid impression materials may lead to dimensional changes. The purpose of this in vitro study was to investigate the antimicrobial activity and properties of irreversible hydrocolloid impression materials incorporated with silver nanoparticles. The antimicrobial activity and properties of 2 commercially available irreversible hydrocolloid impression materials were evaluated after incorporating varying concentrations of silver nanoparticles. Antimicrobial activity was determined using the disk diffusion method. The gel strength, permanent deformation, flow, and gelation time were measured according to American Dental Association specification #18. Analysis of variance was used to identify the significant differences within and across the groups (α=.05). Adding silver nanoparticles to irreversible hydrocolloid impression materials resulted in superior antimicrobial activity without adversely affecting their properties. Adding silver nanoparticles to Zelgan significantly increased the gel strength compared with the control group, except at 5 wt%. However, the gel strength of Tropicalgin was unaffected except at 5 wt%. An increase in the permanent deformation was found with the incorporation of silver nanoparticles in both Zelgan and Tropicalgin. The flow of Zelgan increased with the incorporation of silver nanoparticles, whereas a decrease in the flow of Tropicalgin was observed at 1 wt% and 2 wt%. An increase in the gelation time of both Zelgan and Tropicalgin was observed with the incorporation of silver nanoparticles. Based on this in vitro study, silver nanoparticles can be incorporated into irreversible hydrocolloid impression materials as antimicrobial agents without adversely affecting their properties. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Clonality and antimicrobial resistance gene profiles of multidrug- resistant Salmonella enterica serovar infantis isolates from four public hospitals in Rio de Janeiro, Brazil.

PubMed

Fonseca, E L; Mykytczuk, O L; Asensi, M D; Reis, E M F; Ferraz, L R; Paula, F L; Ng, L K; Rodrigues, D P

2006-08-01

In Brazil, Salmonella enterica serovar Infantis resistant to various antimicrobials, including cephalosporins, has been identified as an etiological agent of severe gastroenteritis in hospitalized children since 1994. In this study, 35 serovar Infantis strains, isolated from children admitted to four different Rio de Janeiro, Brazil, hospitals between 1996 and 2001, were characterized by pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility testing in order to determine their genetic relatedness and antimicrobial resistance profiles. Thirty-four serovar Infantis strains were resistant to at least two antibiotic classes, and all 35 strains were susceptible to fluoroquinolones, cephamycin, and carbapenem. Extended-spectrum beta-lactamase (ESBL) screening by double-disk diffusion indicated that 32 serovar Infantis strains (91.4%) produced beta-lactamases that were inhibited by clavulanic acid. Antimicrobial resistance gene profiles were determined by PCR for a subset of 11 multidrug-resistant serovar Infantis strains, and putative ESBLs were detected by isoelectric focusing. Ten serovar Infantis strains carried bla(TEM), catI, ant(3")Ia and/or ant(3")Ib, sulI and/or sulII, and tet(D) genes as well as an integron-associated aac(6')-Iq cassette. Eight strains possessed at least four different beta-lactamases with pI profiles that confirmed the presence of both ESBLs and non-ESBLs. Our PFGE profiles indicated that 33 serovar Infantis strains isolated from Rio de Janeiro hospitals came from the same genetic lineage.

Anti-microbial resistance stratified by risk factor among Escherichia coli strains isolated from the urinary tract at a rural clinic in Central India.

PubMed

Chatterjee, B; Kulathinal, S; Bhargava, A; Jain, Y; Kataria, R

2009-01-01

The failure of empirical therapy is frequently observed, even in community-acquired urinary tract infections. We, therefore, conducted a prospective, clinic-based study in 2004-2005 to document anti-microbial resistance rates and correlate them with possible risk factors to assist empirical decision-making. Symptomatic patients with pyuria underwent urine culture. Isolates were identified using standard methods and anti-microbial resistance was determined by disk-diffusion. Ultrasonography was used to detect complicating factors. Patients were stratified by the presence of complicating factors and history of invasive procedures for comparison of resistance rates. STATISTICAL METHOD USED: Chi-square or Fisher exact tests, as appropriate. There were 156 E. coli isolates, of which 105 were community-acquired. Twenty-three community-acquired isolates were from patients with complicating factors while 82 were from patients without any. Fifty-one isolates were from patients who had recently undergone invasive procedures on the urinary tract. Thirty-two community-acquired isolates from reproductive-age women without apparent complicating factors had resistance rates of 50% or above against tetracyclines, Co-trimoxazole, aminopenicillins, Nalidixic acid, Ciprofloxacin and 1 st generation cephalosporins. Resistance rates were significantly higher among isolates from patients subjected to invasive procedures, except against Co-trimoxazole, tetracyclines and Amikacin. High rates of anti-microbial resistance in community-acquired uropathogens have made antimicrobial sensitivity testing necessary even in a rural, primary-care setting.

Genotypic and phenotypic virulence characteristics and antimicrobial resistance of Yersinia spp. isolated from meat and milk products.

PubMed

Özdemir, Fatma; Arslan, Seza

2015-06-01

A total of 300 food samples including 180 milk and 120 meat products have been examined for the presence of Yersinia spp. using the ISO 10273 and the cold enrichment method. The overall prevalence of Yersinia spp. was 84 (28%). Yersinia enterocolitica was isolated from 18 (6%) of the 300 samples. The other Yersinia species were detected in the samples Yersinia rohdei 15 (5%), Yersinia intermedia 14 (4.7%), Yersinia pseudotuberculosis 12 (4%), Yersinia ruckeri 12 (4%), Yersinia mollaretii 5 (1.7%), Yersinia bercovieri 4 (1.3%), and atypical Yersinia spp. 4 (1.3%). The conventionally identified Y. enterocolitica strains were also confirmed by the 16S rRNA gene sequencing. All Y. enterocolitica strains biotyped as 1A had negative results in the phenotypic virulence tests. The 84 Yersinia strains were also examined genotypically for the presence of virulence genes. None of the Y. enterocolitica and other Yersinia strains contained the ail, ystA, yadA, and virF except only 1 Y. intermedia and 2 Y. enterocolitica strains that were found to be positive for ystB. Antimicrobial resistance of 84 Yersinia to 16 antimicrobial agents was determined by the disk diffusion method. All strains were sensitive to tobramycine and imipenem while resistant to clindamycin. Although 84.5% of the strains were resistant to at least 3 or more antimicrobial agents, 64.3% of them were resistant to 4 or more antimicrobial agents. © 2015 Institute of Food Technologists®

Antimicrobial and disinfectant resistance of Escherichia coli isolated from giant pandas.

PubMed

Guo, L; Long, M; Huang, Y; Wu, G; Deng, W; Yang, X; Li, B; Meng, Y; Cheng, L; Fan, L; Zhang, H; Zou, L

2015-07-01

The study aims to demonstrate the antimicrobial and disinfectant resistance phenotypes and genotypes of Escherichia coli isolates obtained from giant pandas (Ailuropoda melanoleuca). Antimicrobial testing was performed according to the standard disk diffusion method. The minimal inhibitory concentrations (MICs) of disinfectants were determined using the agar dilution method. All isolates were screened for the presence of antimicrobial and disinfectant resistance genes and further analysed for genetic relatedness by pulse-field gel electrophoresis (PFGE). Results showed that 46·6% of the isolates were resistant to at least one antimicrobial. Escherichia coli isolates showed resistance to fewer antimicrobials as panda age increased. Among antimicrobial-resistant E. coli isolates, the antimicrobial resistance genes blaCTX-M (88·2%) and sul1 (92·3%) were most prevalent. The disinfectant resistance genes emrE, ydgE/ydgF, mdfA and sugE(c) were commonly present (68·2-98·9%), whereas qac and sugE(p) were relatively less prevalent (0-21·3%). The frequencies of resistance genes tended to be higher in E. coli isolated in December than in July, and PFGE profiles were also more diverse in isolates in December. The qacEΔ1 and sugE(p) genes were higher in adolescent pandas than in any other age groups. PFGE revealed that antimicrobial resistance correlated well with sampling time and habitat. This study demonstrated that antimicrobial and disinfectant resistance was common in giant panda-derived E. coli, and the antimicrobial resistance was associated with sampling time and habitat. Escherichia coli could serve as a critical vector in spreading disinfectant and antimicrobial resistance. This is the first study that demonstrated the phenotypic and genetic characterizations of antimicrobial and disinfectant resistance in E. coli isolates from more than 60 giant pandas. Frequent transfer of pandas to other cages may lead to the dissemination of antimicrobial resistance. The study highlights the need for regularly monitoring the antimicrobial and disinfectant resistance in bacteria from giant pandas. © 2015 The Society for Applied Microbiology.

Antimicrobial Testing Methods & Procedures: MB-31

EPA Pesticide Factsheets

Information about ATMP - SOP Quantitative Disk Carrier Test Method (QCT-2) Modified for Testing Antimicrobial Products Against Spores of Clostridium difficile (ATCC 43598) on Inanimate, Hard, Non-porous Surfaces - MB-31-Final

Disk Diffusion Testing Using Candida sp. Colonies Taken Directly from CHROMagar Candida Medium May Decrease Time Required To Obtain Results

PubMed Central

Klevay, Michael; Ebinger, Alex; Diekema, Daniel; Messer, Shawn; Hollis, Richard; Pfaller, Michael

2005-01-01

We compared results of disk diffusion antifungal susceptibility testing from Candida sp. strains passaged on CHROMagar and on potato dextrose agar. The overall categorical agreements for fluconazole and voriconazole disk testing were 95% and 98% with 0% and 0.5% very major errors, respectively. Disk diffusion testing by the CLSI (formerly NCCLS) M44-A method can be performed accurately by taking inocula directly from CHROMagar. PMID:16000489

Antimicrobial Testing Methods & Procedures: MB-31-03

EPA Pesticide Factsheets

Information about ATMP - SOP Quantitative Disk Carrier Test Method (QCT-2) Modified for Testing Antimicrobial Products Against Spores of Clostridium difficile (ATCC 43598) on Inanimate, Hard, Non-porous Surfaces - MB-31-03

Streptococcus suis in employees and the environment of swine slaughterhouses in São Paulo, Brazil: Occurrence, risk factors, serotype distribution, and antimicrobial susceptibility.

PubMed

Soares, Taíssa Cook Siqueira; Gottschalk, Marcelo; Lacouture, Sonia; Megid, Jane; Ribolla, Paulo Eduardo Martins; Pantoja, José Carlos de Figueiredo; Paes, Antonio Carlos

2015-10-01

Streptococcus suis is an important pathogen in the swine industry. This article is the first to report the occurrence, risk factors, serotype distribution, and antimicrobial susceptibility of S. suis recovered from employees and environmental samples of swine slaughterhouses in Brazil. Tonsillar swabs from all 139 pig-slaughtering employees and 261 environmental swabs were collected for detection of S. suis and serotyping by monoplex and multiplex polymerase chain reaction, respectively. Antimicrobial susceptibility was determined by the disk-diffusion method. Although S. suis was not detected in any of the tested employees, it was isolated from 25% of the environmental samples. Significant differences (P < 0.05) in the occurrence of S. suis were observed between slaughterhouses and between areas of low, medium, and high risk. The most frequent serotypes were 4 and 29, each accounting for 12% of the isolates, followed by 5, 12, 21, and 31, each accounting for 6%. High rates of susceptibility to the antimicrobials doxycycline (100%), ceftiofur (94%), ampicillin (81%), and cephalexin (75%) were observed. However, multidrug resistance was observed in all the isolates. Because S. suis is present in the environment of swine slaughterhouses, on carcasses and knives, as well as on the hands of employees in all areas, all employees are at risk of infection.

Streptococcus suis in employees and the environment of swine slaughterhouses in São Paulo, Brazil: Occurrence, risk factors, serotype distribution, and antimicrobial susceptibility

PubMed Central

Soares, Taíssa Cook Siqueira; Gottschalk, Marcelo; Lacouture, Sonia; Megid, Jane; Ribolla, Paulo Eduardo Martins; de Figueiredo Pantoja, José Carlos; Paes, Antonio Carlos

2015-01-01

Streptococcus suis is an important pathogen in the swine industry. This article is the first to report the occurrence, risk factors, serotype distribution, and antimicrobial susceptibility of S. suis recovered from employees and environmental samples of swine slaughterhouses in Brazil. Tonsillar swabs from all 139 pig-slaughtering employees and 261 environmental swabs were collected for detection of S. suis and serotyping by monoplex and multiplex polymerase chain reaction, respectively. Antimicrobial susceptibility was determined by the disk-diffusion method. Although S. suis was not detected in any of the tested employees, it was isolated from 25% of the environmental samples. Significant differences (P < 0.05) in the occurrence of S. suis were observed between slaughterhouses and between areas of low, medium, and high risk. The most frequent serotypes were 4 and 29, each accounting for 12% of the isolates, followed by 5, 12, 21, and 31, each accounting for 6%. High rates of susceptibility to the antimicrobials doxycycline (100%), ceftiofur (94%), ampicillin (81%), and cephalexin (75%) were observed. However, multidrug resistance was observed in all the isolates. Because S. suis is present in the environment of swine slaughterhouses, on carcasses and knives, as well as on the hands of employees in all areas, all employees are at risk of infection. PMID:26424907

Prevalence and antimicrobial resistance of Campylobacter species isolated from chicken carcasses during processing in Iran.

PubMed

Rahimi, E; Momtaz, H; Ameri, M; Ghasemian-Safaei, H; Ali-Kasemi, M

2010-05-01

The objective of this study was to determine the prevalence and antimicrobial resistance of Campylobacter spp. isolated from chicken carcasses during different stages of broiler processing in a major commercial poultry processing plant in southwestern Iran. Overall, 84 chicken carcasses were sampled from 4 sites along the processing line during a total of 7 visits. In addition, 14 water samples from the chiller tank were taken. Using the cultural method, 186 of 336 (55.4%) carcasses were positive for Campylobacter. Campylobacter jejuni was more frequently isolated (89.4%) than Campylobacter coli (10.6%). The frequency of Campylobacter spp. on carcasses was 54.8% after defeathering, 51.2% after evisceration, 69.0% 20 min after the chilling period started, and 46.4% 24 h after the chilling period completed. Campylobacter was positive in 85.7% of the samples taken from the chilling water. The frequency of Campylobacter spp.-positive carcasses was reduced in complete chilled chickens but not during the slaughtering process. Susceptibilities of Campylobacter isolates were determined for 10 antimicrobial drugs using the disk diffusion method. Of the 198 Campylobacter isolates tested, 92.9% were resistant to one or more antimicrobial agents. Resistance to tetracycline was the most common finding (78.3%), followed by resistance to ciprofloxacin (62.1%), nalidixic acid (58.6%), and enrofloxacin (44.4%).

Reevaluation of interpretive criteria for Haemophilus influenzae by using meropenem (10-microgram), imipenem (10-microgram), and ampicillin (2- and 10-microgram) disks.

PubMed Central

Zerva, L; Biedenbach, D J; Jones, R N

1996-01-01

A collection of 300 Haemophilus influenzae clinical strains was used to assess in vitro susceptibility to carbapenems (meropenem, imipenem) by MIC and disk diffusion methods and to compare disk diffusion test results with two potencies of ampicillin disks (2 and 10 micrograms). The isolates included ampicillin-susceptible or- intermediate (167 strains), beta-lactamase-positive (117 strains), and beta-lactamase-negative ampicillin-resistant (BLNAR; 16 strains) organisms. Disk diffusion testing was performed with 10-micrograms meropenem disks from two manufacturers. Meropenem was highly active against H. influenzae strains (MIC50, 0.06 microgram/ml; MIC90, 0.25 microgram/ml; MIC50 and MIC90, MICs at which 50 and 90%, respectively, of strains are inhibited) and was 8- to 16-fold more potent than imipenem (MIC50, 1 microgram/ml; MIC90, 2 micrograms/ml). Five non-imipenem-susceptible strains were identified (MIC, 8 micrograms/ml), but the disk diffusion test indicated susceptibility (zone diameters, 18 to 21 mm). MIC values of meropenem, doxycycline, ceftazidime, and ceftriaxone for BLNAR strains were two- to fourfold greater than those for other strains. The performance of both meropenem disks was comparable and considered acceptable. A single susceptible interpretive zone diameter of > or = 17 mm (MIC, < = or 4 micrograms/ml) was proposed for meropenem. Testing with the 2-micrograms ampicillin disk was preferred because of an excellent correlation between MIC values and zone diameters (r = 0.94) and superior interpretive accuracy with the susceptible criteria at > or = 17 mm (MIC, < or = 1 microgram/ml) and the resistant criteria at < or = 13 mm (MIC, > or = 4 micrograms/ml). Among the BLNAR strains tested, 81.3% were miscategorized as susceptible or intermediate when the 10-micrograms ampicillin disk was used, while the 2-micrograms disk produced only minor interpretive errors (12.5%). Use of these criteria for testing H. influenzae against meropenem and ampicillin should maximize reference test and standardized disk diffusion test performance with the Haemophilus Test Medium. The imipenem disk diffusion test appears compromised and should be used with caution for detecting strains for which imipenem MICs are elevated. PMID:8818892

Self-gravity, Resonances, and Orbital Diffusion in Stellar Disks

NASA Astrophysics Data System (ADS)

Fouvry, Jean-Baptiste; Binney, James; Pichon, Christophe

2015-06-01

Fluctuations in a stellar system's gravitational field cause the orbits of stars to evolve. The resulting evolution of the system can be computed with the orbit-averaged Fokker-Planck equation once the diffusion tensor is known. We present the formalism that enables one to compute the diffusion tensor from a given source of noise in the gravitational field when the system's dynamical response to that noise is included. In the case of a cool stellar disk we are able to reduce the computation of the diffusion tensor to a one-dimensional integral. We implement this formula for a tapered Mestel disk that is exposed to shot noise and find that we are able to explain analytically the principal features of a numerical simulation of such a disk. In particular the formation of narrow ridges of enhanced density in action space is recovered. As the disk's value of Toomre's Q is reduced and the disk becomes more responsive, there is a transition from a regime of heating in the inner regions of the disk through the inner Lindblad resonance to one of radial migration of near-circular orbits via the corotation resonance in the intermediate regions of the disk. The formalism developed here provides the ideal framework in which to study the long-term evolution of all kinds of stellar disks.

Antimicrobial Air Filters Using Natural Euscaphis japonica Nanoparticles

PubMed Central

Yun, Ji Ho; Lee, Jung Eun; Lee, Hee Ju; Nho, Chu Won; Bae, Gwi- Nam; Jung, Jae Hee

2015-01-01

Controlling bioaerosols has become more important with increasing participation in indoor activities. Treatments using natural-product nanomaterials are a promising technique because of their relatively low toxicity compared to inorganic nanomaterials such as silver nanoparticles or carbon nanotubes. In this study, antimicrobial filters were fabricated from natural Euscaphis japonica nanoparticles, which were produced by nebulizing E. japonica extract. The coated filters were assessed in terms of pressure drop, antimicrobial activity, filtration efficiency, major chemical components, and cytotoxicity. Pressure drop and antimicrobial activity increased as a function of nanoparticle deposition time (590, 855, and 1150 µg/cm2filter at 3-, 6-, and 9-min depositions, respectively). In filter tests, the antimicrobial efficacy was greater against Staphylococcus epidermidis than Micrococcus luteus; ~61, ~73, and ~82% of M. luteus cells were inactivated on filters that had been coated for 3, 6, and 9 min, respectively, while the corresponding values were ~78, ~88, and ~94% with S. epidermidis. Although statistically significant differences in filtration performance were not observed between samples as a function of deposition time, the average filtration efficacy was slightly higher for S. epidermidis aerosols (~97%) than for M. luteus aerosols (~95%). High-performance liquid chromatography (HPLC) and electrospray ionization-tandem mass spectrometry (ESI/MS) analyses confirmed that the major chemical compounds in the E. japonica extract were 1(ß)-O-galloyl pedunculagin, quercetin-3-O-glucuronide, and kaempferol-3-O-glucoside. In vitro cytotoxicity and disk diffusion tests showed that E. japonica nanoparticles were less toxic and exhibited stronger antimicrobial activity toward some bacterial strains than a reference soluble nickel compound, which is classified as a human carcinogen. This study provides valuable information for the development of a bioaerosol control system that is environmental friendly and suitable for use in indoor environments. PMID:25974109

Determination of Antimicrobial Activity of Sorrel (Hibiscus sabdariffa) on Esherichia coli O157:H7 Isolated from Food, Veterinary, and Clinical Samples

PubMed Central

Fullerton, Marjorie; Khatiwada, Janak; Johnson, Jacqueline U.; Davis, Shurrita

2011-01-01

Abstract The use of medicinal plants as natural antimicrobial agents is gaining popularity. Sorrel (Hibiscus sabdariffa) is widely used for the treatment of diseases. The objective of this study was to investigate the antimicrobial activity of sorrel on Escherichia coli O157:H7 isolates from food, veterinary, and clinical samples. Phenolics of the calyces were extracted from 10 g of ground, freeze-dried samples using 100 mL of 80% aqueous methanol. Concentrations of 10%, 5%, and 2.5% methanol extract of sorrel were investigated for its antimicrobial activity. Inhibition zones were indicated by a lack of microbial growth due to inhibitory concentrations of sorrel diffused into semisolid culture medium beneath the sorrel-impregnated disk. The results of this experiment showed that the most potent sorrel concentration was 10%, then 5%, and finally 2.5%. The overall mean zone of inhibition for the sorrel extract was 12.66 mm for 10%, 10.75 mm for 5%, and 8.9 mm for 2.5%. The highest inhibition zones (11.16 mm) were observed in veterinary samples, and the lowest (10.57 mm) in the food samples. There were significant (P<.05) differences among mean zones of inhibition found in the food, veterinary, and clinical sources. Based on the source of samples and concentration of sorrel extract, the lowest mean inhibition was 7.00±0.04 mm from clinical samples, and the highest was 15.37±0.61 mm from a food source. These findings indicated that sorrel was effective at all levels in inhibiting E. coli O157:H7; thus it possesses antimicrobial activity and hold great promise as an antimicrobial agent. PMID:21548802

Comparative assessment of antimicrobial efficacy of different hand sanitizers: An in vitro study.

PubMed

Jain, Vardhaman Mulchand; Karibasappa, Gundabaktha Nagappa; Dodamani, Arun Suresh; Prashanth, Vishwakarma K; Mali, Gaurao Vasant

2016-09-01

To evaluate the antimicrobial efficacy of four different hand sanitizers against Staphylococcus aureus , Staphylococcus epidermidis , Pseudomonas aeruginosa , Escherichia coli , and Enterococcus faecalis as well as to assess and compare the antimicrobial effectiveness among four different hand sanitizers. The present study is an in vitro study to evaluate antimicrobial efficacy of Dettol, Lifebuoy, PureHands, and Sterillium hand sanitizers against clinical isolates of the aforementioned test organisms. The well variant of agar disk diffusion test using Mueller-Hinton agar was used for evaluating the antimicrobial efficacy of hand sanitizers. McFarland 0.5 turbidity standard was taken as reference to adjust the turbidity of bacterial suspensions. Fifty microliters of the hand sanitizer was introduced into each of the 4 wells while the 5 th well incorporated with sterile water served as a control. This was done for all the test organisms and plates were incubated in an incubator for 24 h at 37΀C. After incubation, antimicrobial effectiveness was determined using digital caliper (mm) by measuring the zone of inhibition. The mean diameters of zones of inhibition (in mm) observed in Group A (Sterillium), Group B (PureHands), Group C (Lifebuoy), and Group D (Dettol) were 22 ± 6, 7.5 ± 0.5, 9.5 ± 1.5, and 8 ± 1, respectively. Maximum inhibition was found with Group A against all the tested organisms. Data were statistically analyzed using analysis of variance, followed by post hoc test for group-wise comparisons. The difference in the values of different sanitizers was statistically significant at P < 0.001. Sterillium was the most effective hand sanitizer to maintain the hand hygiene.

Comparative assessment of antimicrobial efficacy of different hand sanitizers: An in vitro study

PubMed Central

Jain, Vardhaman Mulchand; Karibasappa, Gundabaktha Nagappa; Dodamani, Arun Suresh; Prashanth, Vishwakarma K.; Mali, Gaurao Vasant

2016-01-01

Background: To evaluate the antimicrobial efficacy of four different hand sanitizers against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis as well as to assess and compare the antimicrobial effectiveness among four different hand sanitizers. Materials and Methods: The present study is an in vitro study to evaluate antimicrobial efficacy of Dettol, Lifebuoy, PureHands, and Sterillium hand sanitizers against clinical isolates of the aforementioned test organisms. The well variant of agar disk diffusion test using Mueller-Hinton agar was used for evaluating the antimicrobial efficacy of hand sanitizers. McFarland 0.5 turbidity standard was taken as reference to adjust the turbidity of bacterial suspensions. Fifty microliters of the hand sanitizer was introduced into each of the 4 wells while the 5th well incorporated with sterile water served as a control. This was done for all the test organisms and plates were incubated in an incubator for 24 h at 37΀C. After incubation, antimicrobial effectiveness was determined using digital caliper (mm) by measuring the zone of inhibition. Results: The mean diameters of zones of inhibition (in mm) observed in Group A (Sterillium), Group B (PureHands), Group C (Lifebuoy), and Group D (Dettol) were 22 ± 6, 7.5 ± 0.5, 9.5 ± 1.5, and 8 ± 1, respectively. Maximum inhibition was found with Group A against all the tested organisms. Data were statistically analyzed using analysis of variance, followed by post hoc test for group-wise comparisons. The difference in the values of different sanitizers was statistically significant at P < 0.001. Conclusion: Sterillium was the most effective hand sanitizer to maintain the hand hygiene. PMID:27857768

Determination of antimicrobial activity of sorrel (Hibiscus sabdariffa) on Escherichia coli O157:H7 isolated from food, veterinary, and clinical samples.

PubMed

Fullerton, Marjorie; Khatiwada, Janak; Johnson, Jacqueline U; Davis, Shurrita; Williams, Leonard L

2011-09-01

The use of medicinal plants as natural antimicrobial agents is gaining popularity. Sorrel (Hibiscus sabdariffa) is widely used for the treatment of diseases. The objective of this study was to investigate the antimicrobial activity of sorrel on Escherichia coli O157:H7 isolates from food, veterinary, and clinical samples. Phenolics of the calyces were extracted from 10 g of ground, freeze-dried samples using 100 mL of 80% aqueous methanol. Concentrations of 10%, 5%, and 2.5% methanol extract of sorrel were investigated for its antimicrobial activity. Inhibition zones were indicated by a lack of microbial growth due to inhibitory concentrations of sorrel diffused into semisolid culture medium beneath the sorrel-impregnated disk. The results of this experiment showed that the most potent sorrel concentration was 10%, then 5%, and finally 2.5%. The overall mean zone of inhibition for the sorrel extract was 12.66 mm for 10%, 10.75 mm for 5%, and 8.9 mm for 2.5%. The highest inhibition zones (11.16 mm) were observed in veterinary samples, and the lowest (10.57 mm) in the food samples. There were significant (P<.05) differences among mean zones of inhibition found in the food, veterinary, and clinical sources. Based on the source of samples and concentration of sorrel extract, the lowest mean inhibition was 7.00±0.04 mm from clinical samples, and the highest was 15.37±0.61 mm from a food source. These findings indicated that sorrel was effective at all levels in inhibiting E. coli O157:H7; thus it possesses antimicrobial activity and hold great promise as an antimicrobial agent.

CLSI performance standards for antimicrobial susceptibility testing of bacteria isoloated from aquatic animals; second information supplement. CLSI document VET03/VET04-S2

USDA-ARS?s Scientific Manuscript database

The supplemental information presented in this document is intended for use with the antimicrobial susceptibility testing procedures published in the following Clinical and Laboratory Standards Institute (CLSI) approved documents VET03-A Methods for Antimicrobial Disk Susceptibility Testing of Bacte...

Antibacterial activity against Clostridium genus and antiradical activity of the essential oils from different origin.

PubMed

Kačániová, Miroslava; Vukovič, Nenad; Horská, Elena; Salamon, Ivan; Bobková, Alica; Hleba, Lukáš; Fiskelová, Martina; Vatľák, Alexander; Petrová, Jana; Bobko, Marek

2014-01-01

In the present study, the antimicrobial and antiradical activities of 15 essential oils were investigated. The antimicrobial activities were determined by using agar disc diffusion and broth microdilution methods against Clostridium genus and antioxidant properties of essential oils by testing their scavenging effect on DPPH radicals activities. We determined the antibacterial activity of Clostridium butyricum, Clostridium hystoliticum, Clostridium intestinale, Clostridium perfringens and Clostridium ramosum. We obtained the original commercial essential oils samples of Lavandula angustifolia, Carum carvi, Pinus montana, Mentha piperita, Foeniculum vulgare Mill., Pinus sylvestris, Satureia montana, Origanum vulgare L. (2 samples), Pimpinella anisum, Rosmarinus officinalis L., Salvia officinalis L., Abies alba Mill., Chamomilla recutita L. Rausch and Thymus vulgaris L. produced in Slovakia (Calendula a.s., Nova Lubovna, Slovakia). The results of the disk diffusion method showed very high essential oils activity against all tested strains of microorganisms. The best antimicrobial activity against C. butyricum was found at Pimpinella anisum, against C. hystoliticum was found at Pinus sylvestris, against C. intestinale was found at Satureia hortensis L., against C. perfringens was found at Origanum vulgare L. and against C. ramosum was found at Pinus sylvestris. The results of broth microdilution assay showed that none of the essential oils was active against C. hystoliticum. The best antimicrobial activity against C. butyricum was found at Abies alba Mill., against C. intestinale was found at Abies alba Mill., against C. perfringens was found at Satureia montana and against C. ramosum was found at Abius alba and Carum carvi. Antioxidant DPPH radical scavenging activity was determined at several solutions of oil samples (50 μL.mL(-1)-0.39 μL.mL(-1)) and the best scavenging effect for the highest concentration (50 μL.mL(-1)) was observed. The antioxidant properties were different in particular plant species. The highest% of inhibition after 30 min. of reaction was observed at Origanum vulgare (93%), Satureia montana (90.66%) and Lavandula augustifolia (90.22%).

Physico-chemical and Biological Evaluation of Flavonols: Fisetin, Quercetin and Kaempferol Alone and Incorporated in beta Cyclodextrins.

PubMed

Corina, Danciu; Bojin, Florina; Ambrus, Rita; Muntean, Delia; Soica, Codruta; Paunescu, Virgil; Cristea, Mirabela; Pinzaru, Iulia; Dehelean, Cristina

2017-01-01

Fisetin,quercetin and kaempferol are among the important representatives of flavonols, biological active phytocomounds, with low water solubility. To evaluate the antimicrobial effect, respectively the antiproliferative and pro apoptotic activity on the B164A5 murine melanoma cell line of pure flavonols and their beta cyclodextrins complexes. Incorporation of fisetin, quercetin and kaempferol in beta cyclodextrins was proved by scanning electron microscopy (SEM), differencial scanning calorimetry (DSC) and X-ray powder diffraction (XRPD). Pure compounds and their complexes were tested for antiproliferative (MTT) and pro-apoptotic activity (Annexin V-PI) on the B164A5 murine melanoma cell line and for the antimicrobial properties (Disk Diffusion Method) on the selected strains. The phytocompounds presented in a different manner in vitro chemopreventive activity against B164A5 murine melanoma cell line and weak antimicrobial effect. The three flavonols: fisetin, quercetin and kaempferol were successfully incorporated in beta-cyclodextrin (BCD) and hydroxylpropyl-beta-cyclodextrin (HPBCD). Incorporation in beta cyclodextrins had a mix effect on the biological activity conducing to decrease, increase or consistent effect compared to pure phytocompound, depending on the screened process and on the chosen combination. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Rauvolfia Grandiflora (Apocynaceae) Extract Interferes With Staphylococcal Density, Enterotoxin Production And Antimicrobial Activity

PubMed Central

de Almeida Carlos, Lanamar; da Silva Amaral, Kenas Aguiar; Curcino Vieira, Ivo José; Mathias, Leda; Braz-Filho, Raimundo; Silva Samarão, Solange; Vieira-da-Motta, Olney

2010-01-01

Staphylococci bacteria are involved in many human and animal infections and development of alternative antimicrobial drugs against pathogenic bacteria is of great interest to the pharmaceutical industry. This study investigated the in vitro effect of Rauvolfia grandiflora methanol extract (root bark fraction) (RGE) on the density of ATCC strains of Staphylococcus aureus and Staphylococcus epidermidis, and a clinical enterotoxin-producer, S. aureus bovine strain. The alkaloid, isoreserpiline, obtained from dichloromethane extract of R. grandiflora was ineffective against the strains tested. After incubation of staphylococci strains in the presence of 1.2 μg.mL-1 RGE, a significant inhibition of cell growth was observed using both spectrophotometry and ELISA assays. Twelve drugs were evaluated for their antimicrobial effects on culture RGE-treated cells using the disk diffusion method. Penicillin resistant strains became sensitive to the drug after RGE treatment. Furthermore, enterotoxin production by RGE-treated S. aureus was evaluated using a standardized ELISA method. Although staphylococcal LSA 88 bovine strain cells remained viable after exposure to the extract, enterotoxin production was precluded in 20% after RGE treatment. Significant interference in staphylococci cell density, drug sensitivity and enterotoxin secretion was observed after treatment. The study highlights the necessity to find new methods of disease prevention and new antibiotic therapies against staphylococcal infections. PMID:24031536

Rauvolfia grandiflora (apocynaceae) extract interferes with staphylococcal density, enterotoxin production and antimicrobial activity.

PubMed

de Almeida Carlos, Lanamar; da Silva Amaral, Kenas Aguiar; Curcino Vieira, Ivo José; Mathias, Leda; Braz-Filho, Raimundo; Silva Samarão, Solange; Vieira-da-Motta, Olney

2010-07-01

Staphylococci bacteria are involved in many human and animal infections and development of alternative antimicrobial drugs against pathogenic bacteria is of great interest to the pharmaceutical industry. This study investigated the in vitro effect of Rauvolfia grandiflora methanol extract (root bark fraction) (RGE) on the density of ATCC strains of Staphylococcus aureus and Staphylococcus epidermidis, and a clinical enterotoxin-producer, S. aureus bovine strain. The alkaloid, isoreserpiline, obtained from dichloromethane extract of R. grandiflora was ineffective against the strains tested. After incubation of staphylococci strains in the presence of 1.2 μg.mL(-1) RGE, a significant inhibition of cell growth was observed using both spectrophotometry and ELISA assays. Twelve drugs were evaluated for their antimicrobial effects on culture RGE-treated cells using the disk diffusion method. Penicillin resistant strains became sensitive to the drug after RGE treatment. Furthermore, enterotoxin production by RGE-treated S. aureus was evaluated using a standardized ELISA method. Although staphylococcal LSA 88 bovine strain cells remained viable after exposure to the extract, enterotoxin production was precluded in 20% after RGE treatment. Significant interference in staphylococci cell density, drug sensitivity and enterotoxin secretion was observed after treatment. The study highlights the necessity to find new methods of disease prevention and new antibiotic therapies against staphylococcal infections.

Analysis of Polyphenolic Compounds in Extracts from Leaves of Some Malus domestica Cultivars: Antiradical and Antimicrobial Analysis of These Extracts

PubMed Central

Sowa, Alina; Zgórka, Grażyna; Szykuła, Aleksandra; Franiczek, Roman; Żbikowska, Beata; Gamian, Andrzej

2016-01-01

In this study, methanol, ethyl acetate, water extracts, and precipitate were obtained from leaves of Malus domestica cultivars: Golden delicious, Jonagold, Elstar, Ligol, and Mutsu. Antiradical activity of these extracts was measured using the ABTS+∙ radical, and antimicrobial activity was measured with the disk-diffusion method. Phenolic compounds were measured with the colorimetric method and identified with high performance liquid chromatography (HPLC). The highest antiradical activity was observed for the Jonagold variety, and in particular strong activity was noted for ethyl acetate extracts. Antimicrobial activity was observed against strains of Staphylococcus aureus, Enterococcus faecalis, and the fungus Candida glabrata. Particularly susceptible to the extracts activity appeared to be Staphylococcus aureus, but the growth of Candida glabrata was inhibited in the presence of ethyl acetate extracts. With the HPLC method we identified a high amount of phloridzin (above 500 mg per g of ethyl acetate extracts), lower amounts of hyperoside, isoquercitrin, and quercitrin, and traces of p-hydroxybenzoic and chlorogenic acids. The contribution of phloridzin to antiradical activity of methanol and ethyl acetate extracts was very high (above 90%). In water extract the contribution of phloridzin was between 38.9 and 55.2%, chlorogenic acid 22.7 and 36.1%, and hyperoside 12.2 and 13.3%. PMID:28097143

Analysis of Polyphenolic Compounds in Extracts from Leaves of Some Malus domestica Cultivars: Antiradical and Antimicrobial Analysis of These Extracts.

PubMed

Sowa, Alina; Zgórka, Grażyna; Szykuła, Aleksandra; Franiczek, Roman; Żbikowska, Beata; Gamian, Andrzej; Sroka, Zbigniew

2016-01-01

In this study, methanol, ethyl acetate, water extracts, and precipitate were obtained from leaves of Malus domestica cultivars: Golden delicious, Jonagold, Elstar, Ligol, and Mutsu. Antiradical activity of these extracts was measured using the ABTS +∙ radical, and antimicrobial activity was measured with the disk-diffusion method. Phenolic compounds were measured with the colorimetric method and identified with high performance liquid chromatography (HPLC). The highest antiradical activity was observed for the Jonagold variety, and in particular strong activity was noted for ethyl acetate extracts. Antimicrobial activity was observed against strains of Staphylococcus aureus , Enterococcus faecalis , and the fungus Candida glabrata . Particularly susceptible to the extracts activity appeared to be Staphylococcus aureus , but the growth of Candida glabrata was inhibited in the presence of ethyl acetate extracts. With the HPLC method we identified a high amount of phloridzin (above 500 mg per g of ethyl acetate extracts), lower amounts of hyperoside, isoquercitrin, and quercitrin, and traces of p -hydroxybenzoic and chlorogenic acids. The contribution of phloridzin to antiradical activity of methanol and ethyl acetate extracts was very high (above 90%). In water extract the contribution of phloridzin was between 38.9 and 55.2%, chlorogenic acid 22.7 and 36.1%, and hyperoside 12.2 and 13.3%.

Clinical features and antimicrobial resistance profiles of important Enterobacteriaceae pathogens in Guangzhou representative of Southern China, 2001-2015.

PubMed

Xie, Jinhong; Peters, Brian M; Li, Bing; Li, Lin; Yu, Guangchao; Xu, Zhenbo; Shirtliff, Mark E

2017-06-01

This surveillance aimed to investigate the antimicrobial resistance profiles of Enterobacteriaceae pathogens in Southern China during 2001-2015. A total of 6858 Enterobacteriaceae isolates were collected, including 4276 E. coli, 1992 K. pneumoniae and 590 Enterobacter spp. Disk diffusion method and minimum inhibitory concentrations method were used for susceptibility testing, with results interpreted by the CLSI (2015). Urinary tract remained the dominant isolated site among E. coli (49.88%), whereas 53.26% K. pneumoniae and 45.25% Enterobacter spp. were from Sputum. The carbapenems maintained the highest antimicrobial activity (resistance rates <15%), followed by piperacillin-tazobactam and amikacin. Gentle increases were obtained in carbapenems-resistant K. pneumoniae and Enterobacter spp. (eg. from 4.5% to 11.2% and 3.2% to 14.5% in imipenem, repestively). The third-generation cephalosporins showed high and stable resistance among Enterobacteriaceae pathogens during the studied period, with ceftazidime as the most active third-generation cephalosporin against Enterobacteriaceae. Isolates from ICU department showed higher or similar resistance rates among Enterobacteriaceae pathogens compared to other wards. Carbapenems are the most potent antibiotic agents against Enterobacteriaceae pathogens. Due to the complicated susceptibility profiles, prescribing guidelines should be based on the knowledge of antibiogram of pathogens. Copyright © 2017 Elsevier Ltd. All rights reserved.

Antimicrobial resistance in Escherichia coli and Salmonella spp. isolates from fresh produce and the impact to food safety.

PubMed

Vital, Pierangeli G; Caballes, Marie Bernadine D; Rivera, Windell L

2017-09-02

Foodborne diseases associated with fresh produce consumption have escalated worldwide, causing microbial safety of produce of critical importance. Bacteria that have increasingly been detected in fresh produce are Escherichia coli and Salmonella spp., both of which have been shown to progressively display antimicrobial resistance. The study focused on the assessment of antimicrobial resistance of these enteric bacteria from different kinds of fresh produce from various open air markets and supermarkets in the Philippines. Using the disk diffusion assay on a total of 50 bacterial isolates obtained from 410 fresh produce surveyed, monoresistance to tetracycline was observed to be the most prevalent (38%), followed by multidrug resistance to tetracycline, chloramphenicol, ciprofloxacin, and nalidixic acid (4%), and lastly by dual resistance to tetracycline and chloramphenicol (2%). Using multiplex and simplex polymerase chain reaction (PCR) assays, tetA (75%) and tetB (9%) were found in tetracycline resistant isolates, whereas catI (67%) and catIII (33%) were detected in chloramphenicol resistant isolates. Sequence analysis of gyr and par genes from the ciprofloxacin and nalidixic acid resistant isolates revealed different mutations. Based on the results, fresh produce act as a reservoir of these antibiotic resistant bacteria which may pose health threat to consumers.

Isolation and identification of local bacteria endophyte and screening of its antimicrobial property against pathogenic bacteria and fungi

NASA Astrophysics Data System (ADS)

Fikri, Ahmad Syairazie Ibrahim; Rahman, Irman Abdul; Nor, Norefrina Shafinaz Md; Hamzah, Ainon

2018-04-01

Endophytes are organisms, often fungi and bacteria that live in living plant cells. These organisms reside in the living tissues of the host plant in a variety of relationships, ranging from symbiotic to slightly pathogenic. The endophytes may produce a plethora of substances that have potential to be used in modern medicine, agriculture and industry. The aims of this study are to isolate, identify and screening antimicrobial activity of bacterial endophytes. The endophytes were isolated using nutrient agar, incubated at 37°C for 48 hours. Identification of the isolates were done based on morphological characteristics, biochemical tests and 16S rDNA molecular analysis. Disk diffusion method was used to screen for antimicrobial activity of metabolites from endophytes against pathogenic bacteria. Screening for antifungal activity of selected endophytes was done using dual culture method againts pathogenic fungi followed by Kirby-Bauer method. Results showed endophytes designated as B2c and B7b have positive antimicrobial activity. The metabolites from isolate B2c showed antimicrobial activity against pathogenic bacteria methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus aureus and Staphylococcus epidermis, while isolate B7b have positive activities againts MRSA, S. aureus and Pseudomonas aeruginosa. Isolates B2c displayed antifungal activity against Fusarium oxysporum, Fusarium solani, Phytophthora palmivora and Colletotrichum gloeosporioides. Identification using biochemical tests and 16S rDNA sequences identified isolate B2c as Pseudomonas resinovorans with 97% homology and isolate B7b as Bacillus subtilis with 98% homology.

Black Zira essential oil: Chemical compositions and antimicrobial activity against the growth of some pathogenic strain causing infection.

PubMed

Noshad, Mohammad; Hojjati, Mohammad; Alizadeh Behbahani, Behrooz

2018-03-01

The aim of this study was to perform chemical compositions and phytochemical analysis of Black Zira essential oil and other goal of this research was to investigate the antimicrobial effects of Black Zira essential oil against Enterobacter aerogenes, Pseudomonas aeruginosa, Escherichia coli, Shigella flexneri, Staphylococcus epidermidis, Streptococcus pyogenes and Candida albicans. Black Zira essential oil was extracted by hydrodistillation method using clevenger apparatus. Black Zira essential oil chemical composition was identified through gas chromatography/mass spectrometry. γ-terpinene with a percentage of 24.8% was the major compound of Black Zira essential oil. The antimicrobial effect Black Zira essential oil was evaluated by several qualitative and quantitative methods (disk diffusion, well diffusion, microdilution broth, agar dilution and minimum bactericidal/fungicidal concentration). Phytochemical analysis Black Zira essential oil were appraised based on qualitative methods. Antioxidant activity (2,2-diphenyl-1-picrylhydrazyl and β-carotene/linoleic acid inhibition) and total phenolic content (Folin-Ciocalteu) were examined. The results of phytochemical analysis of Black Zira essential oil showed the existence of phenolic, flavonoids, saponins, alkaloids and tannins. The total phenolic content and antioxidant activity (reported as IC 50 ) of Black Zira essential oil were equal to 120.50 ± 0.50 mg GAE/g and 11.55 ± 0.25 μg/ml, respectively. The MIC of the Black Zira essential oil ranged from 1 mg/ml to 8 mg/ml, while its MBC and MFC ranged from 1 mg/ml to 16 mg/ml. The results presented that the longest and the shortest inhibition zone diameter at the concentration of 8 mg/ml pertained to C. albicans and E. aerogenes, respectively. Copyright © 2018. Published by Elsevier Ltd.

Pseudomonas aeruginosa-producing Metallo-β-lactamases (VIM, IMP, SME, and AIM) in the Clinical Isolates of Intensive Care Units, a University Hospital in Isfahan, Iran.

PubMed

Khorvash, Farzin; Yazdani, Mohammadreza; Shabani, Shiva; Soudi, Aliasghar

2017-01-01

Pseudomonas aeruginosa is a severe challenge for antimicrobial therapy, due to the chromosomal mutations or exhibition of intrinsic resistance to various antimicrobial agents such as most β-lactams. We undertook this study to evaluate the existence of SME, IMP, AIM, and VIM metallo-β-lactamases (MBL) encoding genes among P. aeruginosa strains isolated from Intensive Care Unit (ICU) patients in Al-Zahra Hospital in Isfahan, Iran. In a retrospective cross-sectional study that was conducted between March 2012 and April 2013, a total of 48 strains of P. aeruginosa were collected from clinical specimens of bedridden patients in ICU wards. Susceptibility test was performed by disc diffusion method. All of the meropenem-resistant strains were subjected to modified Hodge test for detection of carbapenemases. Multiplex polymerase chain reaction was performed for detection of blaVIM, blaIMP, blaAIM, and blaSME genes. In disk diffusion method, imipenem and meropenem showed the most and colistin the least resistant antimicrobial agents against P. aeruginosa strains. Of the 48 isolates, 36 (75%) were multidrug resistant (MDR). Amplification of β-lactamase genes showed the presence of blaVIM genes in 7 (%14.6) strains and blaIMP genes in 15 (31.3%) strains. All of the isolates were negative for blaSME and blaAIM genes. We could not find any statistically significant difference among the presence of this gene and MDR positive, age, or source of the specimen. As patients with infections caused by MBL-producing bacteria are at an intensified risk of treatment failure, fast determination of these organisms is necessary. Our findings may provide useful insights in replace of the appropriate antibiotics and may also prevent MBLs mediated resistance problem.

In vitro antimicrobial activity of ethanolic fractions of Cryptolepis sanguinolenta

PubMed Central

2012-01-01

Background Following claims that some plants have antimicrobial activities against infectious microbes, the in vitro antimicrobial activities of different solvent fractions of ethanolic extract of Cryptolepis sanguinolenta were evaluated against eight standard bacteria and clinical isolates. Methods The solvent partitioning protocol involving ethanol, petroleum ether, chloroform, ethyl acetate and water, was used to extract various fractions of dried pulverized Cryptolepis sanguinolenta roots. Qualitative phyto-constituents screening was performed on the ethanol extract, chloroform fraction and the water fraction. The Kirby Bauer disk diffusion method was employed to ascertain the antibiogram of the test organisms while the agar diffusion method was used to investigate the antimicrobial properties of the crude plant extracts. The microplate dilution method aided in finding the MICs while the MBCs were obtained by the method of Nester and friends. The SPSS 16.0 version was used to analyze the percentages of inhibitions and bactericidal activities. Results The phytochemical screening revealed the presence of alkaloids, reducing sugars, polyuronides, anthocyanosides and triterpenes. The ethanol extract inhibited 5 out of 8 (62.5%) of the standard organisms and 6 out of 8 (75%) clinical isolates. The petroleum ether fraction inhibited 4 out of 8 (50%) of the standard microbes and 1 out of 8 (12.5%) clinical isolates. It was also observed that the chloroform fraction inhibited the growth of all the organisms (100%). Average inhibition zones of 14.0 ± 1.0 mm to 24.67 ± 0.58 mm was seen in the ethyl acetate fraction which halted the growth of 3 (37.5%) of the standard organisms. Inhibition of 7 (87.5%) of standard strains and 6 (75%) of clinical isolates were observed in the water fraction. The chloroform fraction exhibited bactericidal activity against all the test organisms while the remaining fractions showed varying degrees of bacteriostatic activity. Conclusion The study confirmed that fractions of Cryptolepis sanguinolenta have antimicrobial activity. The chloroform fraction had the highest activity, followed by water, ethanol, petroleum ether and ethyl acetate respectively. Only the chloroform fraction exhibited bactericidal activity and further investigations are needed to ascertain its safety and prospects of drug development. PMID:22709723

Antimicrobial isothiocyanates from the seeds of Moringa oleifera Lam.

PubMed

Padla, Eleanor P; Solis, Ludivina T; Levida, Ruel M; Shen, Chien-Chang; Ragasa, Consolacion Y

2012-01-01

4-(alpha-L-Rhamnosyloxy)benzyl isothiocyanate (1) and 4-(4'-O-acetyl-alpha-L-rhamnosyloxy)-benzyl isothiocyanate (2) isolated from Moringa oleifera seeds were screened for their antibacterial activities against Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae, and Pseudomonas aeruginosa, and for their antifungal activities against Candida albicans, Trichophyton rubrum, and Epidermophyton floccosum using the disk diffusion method. Isothiocyanates 1 and 2 were found active at the lowest inhibitory concentration of 1 mg/ml against all Gram-positive bacteria tested (S. aureus, S. epidermidis, B. subtilis) and against the dermatophytic fungi E. floccosum and T. rubrum. Statistically significant differences were found between the mean inhibition zones (IZ) of 1 and 2 and the standard drugs, ofloxacin and clotrimazole. The minimum inhibitory concentration (MIC) values confirmed the good antimicrobial activity of 1 and 2 against S. aureus, good to moderate activity against S. epidermidis, moderate activity against B. subtilis, and weak activity against E. floccosum and T. rubrum. The in vitro bactericidal effect of 1 and 2 against the Gram-positive bacterial strains tested is suggested by MBC:MIC ratios of 2:1.

Antibiotic Resistance of Gram Negatives isolates from loggerhead sea turtles (Caretta caretta) in the central Mediterranean Sea.

PubMed

Foti, M; Giacopello, C; Bottari, Teresa; Fisichella, V; Rinaldo, D; Mammina, C

2009-09-01

Previous studies on fish and marine mammals support the hypothesis that marine species harbor antibiotic resistance and therefore may serve as reservoirs for antibiotic-resistance genetic determinants. The aim of this study was to assess the resistance to antimicrobial agents of Gram negative strains isolated from loggerhead sea turtles (Carettacaretta). Oral and cloacal swabs from 19 live-stranded loggerhead sea turtles, with hooks fixed into the gut, were analyzed. The antimicrobial resistance of the isolates to 31 antibiotics was assessed using the disk-diffusion method. Conventional biochemical tests identified Citrobacter spp., Proteus spp., Enterobacter spp., Escherichia spp., Providencia spp., Morganella spp., Pantoea spp., Pseudomonas spp. and Shewanella spp. Highest prevalences of resistance was detected to carbenicillin (100%), cephalothin (92.6%), oxytetracycline (81.3%) and amoxicillin (77.8%). The isolates showing resistance to the widest range of antibiotics were identified as Citrobacterfreundii, Proteusvulgaris, Providenciarettgeri and Pseudomonasaeruginosa. In this study, antibiotic resistant bacteria reflect marine contamination by polluted effluents and C.caretta is considered a bioindicator which can be used as a monitor for pollution.

Antimicrobial susceptibility of Histophilus somni isolated from clinically affected cattle in Australia.

PubMed

Goldspink, Lauren K; Mollinger, Joanne L; Barnes, Tamsin S; Groves, Mitchell; Mahony, Timothy J; Gibson, Justine S

2015-02-01

This study investigated antimicrobial resistance traits, clonal relationships and epidemiology of Histophilus somni isolated from clinically affected cattle in Queensland and New South Wales, Australia. Isolates (n = 53) were subjected to antimicrobial susceptibility testing against six antimicrobial agents (ceftiofur, enrofloxacin, florfenicol, tetracycline, tilmicosin and tulathromycin) using disc diffusion and minimum inhibitory concentration (MIC) assays. Clonal relationships were assessed using repetitive sequence PCR and descriptive epidemiological analysis was performed. The H. somni isolates appeared to be geographically clonal, with 27/53 (47%) isolates grouping in one cluster from one Australian state. On the basis of disc diffusion, 34/53 (64%) isolates were susceptible to all antimicrobial agents tested; there was intermediate susceptibility to tulathromycin in 12 isolates, tilmicosin in seven isolates and resistance to tilmicosin in one isolate. Using MIC, all but one isolate was susceptible to all antimicrobial agents tested; the non-susceptible isolate was resistant to tetracycline, but this MIC result could not be compared to disc diffusion, since there are no interpretative guidelines for disc diffusion for H. somni against tetracycline. In this study, there was little evidence of antimicrobial resistance in H. somni isolates from Australian cattle. Disc diffusion susceptibility testing results were comparable to MIC results for most antimicrobial agents tested; however, results for isolates with intermediate susceptibility or resistance to tilmicosin and tulathromycin on disc diffusion should be interpreted with caution in the absence of MIC results. Copyright © 2014 Elsevier Ltd. All rights reserved.

Antimicrobial profile of essential oils extracted from wild versus cultivated Origanum ehrenberjii against enteric bacteria.

PubMed

Barbour, Elie K; Dankar, Samar K; Shaib, Houssam A; Kumosani, Taha; Azhar, Esam; Masaudi, Saad; Iyer, Archana; Harakeh, Steve

2014-10-15

The role of Origanum ehrenberjii against bacteria that cause enteric diseases is well known. Salmonella and Enterococcus cause high rates of enteric infections around the world. The aim of this study was to extract essential oils from cultivated and naturally growing O. ehrenberjii, compare the chemical profiles of the extracts and estimate their antimicrobial efficacy against enteric pathogens. Sixteen compounds were recovered consistently from essential oils extracted from O. ehrenberjii of wild and cultivated origin. The chemical profiles were determined using GC-MS. Safety of the essential oils was determined by observing mortality of chicks after intramuscular administration of the oils. The antimicrobial efficacy of the oils against the enteric pathogens was determined by the Kirby-Bauer Single Disk Diffusion assay. The levels of thymol, carvacrol, para cymene and γ-terpinene were significantly different in the two oils. A significant difference in in vitro antimicrobial activity of the two oils against Salmonella enterica serovar Typhimurium was observed. Intramuscular administration of the two oils in one day-old chicks resulted in significant differences in mortality of 60% vs. 5% (p < 0.05) for wild and cultivated herbs respectively, reflecting the higher safety of the cultivated herb due to the differences in the levels of certain active ingredients. The chemical profile of essential oil of wild vs. cultivated O. ehrenberjii differ significantly at compound level, suggesting the reason for their significant difference in efficacy against Salmonella enterica serovar Typhimurium, and also significant differences in the toxicity of the two oils.

Phenotypic and Molecular Antibiotic Resistance Determination of Airborne Coagulase Negative Staphylococcus spp. Strains from Healthcare Facilities in Southern Poland.

PubMed

Lenart-Boroń, Anna; Wolny-Koładka, Katarzyna; Stec, Joanna; Kasprowic, Andrzej

2016-10-01

This study assessed the antimicrobial resistance of airborne Staphylococcus spp. strains isolated from healthcare facilities in southern Poland. A total of 55 isolates, belonging to 10 coagulase-negative staphylococci (CoNS) species, isolated from 10 healthcare facilities (including hospitals and outpatient units) were included in the analysis. The most frequently identified species were Staphylococcus saprophyticus and Staphylococcus warneri, which belong to normal human skin flora, but can also be the cause of common and even severe nosocomial infections. Disk diffusion tests showed that the bacterial strains were most frequently resistant to erythromycin and tetracycline and only 18% of strains were susceptible to all tested antimicrobials. Polymerase chain reaction amplification of specific gene regions was used to determine the presence of the Macrolide-Lincosamide-Streptogramin resistance mechanisms in CoNS. The molecular analysis, conducted using specific primer pairs, identified the msrA1 gene, encoding active efflux pumps in bacterial cells, as the most frequent resistance gene. As many as seven antibiotic resistance genes were found in one isolate, whereas the most common number of resistance genes per isolate was five (n = 17). It may be concluded that drug resistance was widely spread among the tested strains, but the resulting antimicrobial resistance profile indicates that in the case of infection, the use of antibiotics from the basic antibiogram group will be effective in therapy. However, before administering treatment, determination of the specific antimicrobial resistance should be conducted, particularly in the case of hospitalized patients.

Antimicrobial activity of the imipenem/rifampicin combination against clinical isolates of Acinetobacter baumannii grown in planktonic and biofilm cultures.

PubMed

Wang, Yang; Bao, Wanguo; Guo, Na; Chen, Haiying; Cheng, Wei; Jin, Kunqi; Shen, Fengge; Xu, Jiancheng; Zhang, Qiaoli; Wang, Chao; An, Yanan; Zhang, Kaiyu; Wang, Feng; Yu, Lu

2014-12-01

To investigate the antimicrobial activity of imipenem and rifampicin alone and in combination against clinical isolates of Acinetobacter baumannii grown in planktonic and biofilm cultures. Minimum inhibitory concentrations were determined for each isolate grown in suspension and in biofilm using a microbroth dilution method. Chequerboard assays and the agar disk diffusion assay were used to determine synergistic, indifferent or antagonistic interactions between imipenem and rifampicin. We used the tissue culture plate method for A. baumannii biofilm formation to measure the percentage of biofilm inhibition and the amount of extracellular DNA after the treatment. To understand the synergistic mechanisms, we conducted hydroxyl radical formation assays. The results were verified by confocal laser scanning microscopy. Imipenem and rifampicin showed effective antimicrobial activity against suspensions and biofilm cultures of A. baumannii, respectively. Synergistic antimicrobial effects between imipenem and rifampicin were observed in 13 and 17 of the 20 clinical isolates when in suspension and in biofilms, respectively. Imipenem and rifampicin alone and in combination generated hydroxyl radicals, which are highly reactive oxygen forms and the major components of bactericidal agents. Furthermore, treatment with imipenem and rifampicin individually or in combination has obvious antibiofilm effects. The synergistic activity of imipenem and rifampicin against clinical isolates of A. baumannii (in suspension and in biofilms) was observed in vitro. Therefore, we conclude that imipenem combined with rifampicin has the potential to be used as a combinatorial therapy for the treatment of infectious diseases caused by A. baumannii.

Antimicrobial potential of actinobacteria isolated from the rhizosphere of the Caatinga biome plant Caesalpinia pyramidalis Tul.

PubMed

Silva-Lacerda, G R; Santana, R C F; Vicalvi-Costa, M C V; Solidônio, E G; Sena, K X F R; Lima, G M S; Araújo, J M

2016-03-04

Actinobacteria are known to produce various secondary metabolites having antibiotic effects. This study assessed the antimicrobial potential of actinobacteria isolated from the rhizosphere of Caesalpinia pyramidalis Tul. from the Caatinga biome. Sixty-eight actinobacteria isolates were evaluated for antimicrobial activity against different microorganisms by disk diffusion and submerged fermentation, using different culture media, followed by determination of minimum inhibitory concentration (MIC) and chemical prospecting of the crude extract. Of the isolates studied, 52.9% of those isolated at 37°C and 47.05% of those isolated at 45°C had activity against Bacillus subtilis, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Fusarium moniliforme, and Candida albicans. When compared with others actinobacteria, the isolate C1.129 stood out with better activity and was identified by 16S rDNA gene analysis as Streptomyces parvulus. The crude ethanol extract showed an MIC of 0.97 μg/mL for MRSA and B. subtilis, while the ethyl acetate extract showed MIC of 3.9 μg/mL for S. aureus and MRSA, showing the greatest potential among the metabolites produced. Chemical prospecting revealed the presence of mono/sesquiterpenes, proanthocyanidin, triterpenes, and steroids in both crude extracts. This study evaluates S. parvulus activity against multi-resistant microorganisms such as MRSA. Thus, it proves that low-fertility soil, as is found in the Caatinga, may contain important microorganisms for the development of new antimicrobial drugs.

Antimicrobial resistance patterns of bacteria isolated from canine urinary samples submitted to a New Zealand veterinary diagnostic laboratory between 2005-2012.

PubMed

McMeekin, C H; Hill, K E; Gibson, I R; Bridges, J P; Benschop, J

2017-03-01

To identify and describe culture and antimicrobial resistance (AMR) patterns in bacteria isolated from canine urinary samples submitted to a New Zealand veterinary diagnostic laboratory. Records from a veterinary diagnostic laboratory were examined for bacterial isolates cultured from canine urine samples between January 2005 and December 2012. Culture and susceptibility results were compiled with information on the age, sex and breed of dog. Repeat submissions were removed. Susceptibility was assessed using results of the Kirby-Bauer disk diffusion method, for a standard panel including amoxicillin-clavulanic acid (AMC), cefovecin (from 2010-2012), cephalothin, clindamycin, enrofloxacin and trimethoprim-sulphonamide (TMS). A total of 5,786 urine samples were submitted for analysis, and 3,135 bacterial isolates were cultured from 2,184 samples. Of these 3,135 isolates, 1,104 (35.2%) were Escherichia coli, 442 (14.1%) were Staphylococcus spp., 357 (11.4%) Proteus mirabilis and 276 (8.8%) were Enterococcus spp. The frequency of culture-positive samples increased with increasing age in both female and male dogs (p<0.001). The percentage of E. coli isolates resistant to AMC and cephalothin increased between 2005 and 2012 (p<0.001), as did resistance to enrofloxacin (p=0.022), but there was no change in resistance to TMS (p=0.696). Enrofloxacin was the antimicrobial with the least resistance shown by the four most common bacteria isolated during the course of the study. The results of this study provide important regional information regarding the prevalence of bacterial uropathogens and their susceptibility patterns. There was an increase in resistance to some commonly used antimicrobials in the treatment of urinary tract infections. Having access to regional antimicrobial susceptibility results is crucial when forming guidelines for the use of antimicrobials for the treatment of urinary tract infections. Given changes in practising habits and antimicrobial usage over time, ongoing monitoring and surveillance of resistance in pathogens is needed.

Influence of housing systems on microbial load and antimicrobial resistance patterns of Escherichia coli isolates from eggs produced for human consumption.

PubMed

Alvarez-Fernández, Elena; Domínguez-Rodríguez, Jessica; Capita, Rosa; Alonso-Calleja, Carlos

2012-05-01

Microbial counts (aerobic bacteria, psychrotrophs, Enterobacteriaceae, coliforms, Pseudomonas spp., Enterococcus spp., Staphylococcus spp., and molds and yeasts) were obtained for the shells of 240 table eggs in northwestern Spain. Eggs from six sources (40 samples in each) were analyzed: chicken eggs from five different housing systems (conventional battery cages, barn, free range, organic, and domestic breeding) and quail eggs (cages). A total of 120 Escherichia coli strains (20 from each source) were tested by the disk diffusion method for resistance to 12 antimicrobial drugs of veterinary and human health significance. Aerobic plate counts ranged from 1.96 ± 1.0 (barn) to 3.69 ± 0.7 (domestic) log CFU/cm(2). Counts for most microbial groups differed significantly between sources. Eggs from domestic production had the highest contamination loads (P < 0.05) for aerobic bacteria, Enterococcus spp., and molds and yeasts and the highest prevalence of E. coli. Twenty-three E. coli isolates (19.17%) were susceptible to all antimicrobials tested, and 80.83 % were resistant to one (22.50%) or more (58.33%) antimicrobials. The housing system had a significant influence (P < 0.05) on the average resistance per strain, with the highest resistance in conventional cage (2.85) and barn (3.10) systems followed by free range (1.55) and quail (1.95). Eggs from organic (1.00) and domestic (0.75) production systems had the lowest resistance per strain. The highest prevalence of resistance was observed for the groups of antimicrobials more frequently used on poultry farms. Our results suggest that a relationship exists between the prevalence of antimicrobial resistance in E. coli strains and the more frequent use of antimicrobials in conventional (cage, barn, and free range) than in domestic and organic chicken housing systems. Education covering good sanitary practices for handling eggs to avoid cross-contamination or inadequate cooking is needed.

Antagonistic Activity of Nocardia brasiliensis PTCC 1422 Against Isolated Enterobacteriaceae from Urinary Tract Infections.

PubMed

Jalali, Hossnieh Kafshdar; Salamatzadeh, Abdolreza; Jalali, Arezou Kafshdar; Kashani, Hamed Haddad; Asbchin, Salman Ahmadi; Issazadeh, Khosro

2016-03-01

The main drawback of current antibiotic therapies is the emergence and rapid increase in antibiotic resistance. Nocardiae are aerobic, Gram-positive, catalase-positive, non-motile actinomycetes. Nocardia brasiliensis was reported as antibiotic producer. The purpose of the study was to determine antibacterial activity of N. brasiliensis PTCC 1422 against isolated Enterobacteriaceae from urinary tract infections (UTIs). The common bacteria from UTIs were isolated from hospital samples. Antimicrobial susceptibility test was performed for the isolated pathogens using Kirby-Bauer disk diffusion method according to clinical and Laboratory Standards Institute guideline. Antagonistic activity of N. brasiliensis PTCC 1422 was examined with well diffusion methods. Supernatant of N. brasiliensis PTCC 1422 by submerged culture was analyzed with gas chromatography-mass spectrometry. Isolated strains included Escherichia coli, Klebsiella pneumoniae, Serratia marcescens and Proteus mirabilis. The most common pathogen isolated was E. coli (72.5%). Bacterial isolates revealed the presence of high levels of antimicrobial resistances to ceftriaxone and low levels of resistance to cephalexin. Supernatant of N. brasiliensis PTCC 1422 showed antibacterial activity against all of the isolated microorganisms in well diffusion method. The antibiotic resistance among the uropathogens is an evolving process, so a routine surveillance to monitor the etiologic agents of UTI and the resistance pattern should be carried out timely to choose the most effective empirical treatment by the physicians. Our present investigation indicates that the substances present in the N. brasiliensis PTCC 1422 could be used to inhibit the growth of human pathogen. Antibacterial resistance among bacterial uropathogen is an evolving process. Therefore, in the field on the need of re-evaluation of empirical treatment of UTIs, our present. The study has demonstrated that N. brasiliensis PTCC 1422 has a high potential for the treatment of UTIs.

Comparison of the antibacterial activity of an ozonated oil with chlorhexidine digluconate and povidone-iodine. A disk diffusion test.

PubMed

Montevecchi, Marco; Dorigo, Antonio; Cricca, Monica; Checchi, Luigi

2013-07-01

Ozonated oils are antiseptics obtained from the chemical reaction between ozone and unsaturated fatty acids of vegetable oils. The aim of this study was to investigate the antimicrobial effectiveness of a commercially available ozonated oil (O3-Oil), in comparison with 0.2% chlorhexidine digluconate (CHX) and 10% povidone-iodine (PVP-I) through a disk diffusion test. For each antiseptic a series of two-fold dilutions was made, obtaining seven dilutions: 1:2, 1:4, 1:8, 1:16, 1:32, 1:64 and 1:128. The undiluted antiseptics and the seven dilutions were tested against two freeze-dried bacterial strains: Staphylococcus aureus (Sa) and Porphyromonas gingivalis (Pg). O3-Oil showed significantly greater diameters of growth inhibition (p<0.01) than CHX and PVP-I in all dilutions for both tested strains. CHX lost any antibacterial efficacy when diluted more than 1:32. At the highest dilution, the diameters of growth inhibition against Sa were 20.67±0.58 mm and 15.33±0.58 mm, for O3-Oil and PVP-I, respectively. At the same dilution, the diameters of growth inhibition against Pg were: 19.00 mm for O3-Oil and 13.67±0.58 mm for PVP-I. The promising results obtained for the O3-Oil, against the opportunistic Sa, and Pg, one of the main periodontal pathogens, suggest its potential applicability for periodontal treatment. Further preclinical and clinical investigations are warranted.

Differentiation of farmed and wild turbot (Psetta maxima): proximate chemical composition, fatty acid profile, trace minerals and antimicrobial resistance of contaminant bacteria.

PubMed

Martínez, B; Miranda, J M; Nebot, C; Rodriguez, J L; Cepeda, A; Franco, C M

2010-10-01

The proximate, cholesterol, fatty acid and trace mineral compositions in the flesh of farmed and wild turbot (Psetta maxima) were evaluated. Additionally, the potential influence of the use of antimicrobial agents in the bacteria carried by farmed turbot was investigated. For this purpose, a total of 144 Pseudomonas spp. and 127 Aeromonas spp. were isolated and tested for their susceptibility to 12 antimicrobials by a disk diffusion method. Farmed turbot contained higher fat, cholesterol and calories as well as lower moisture content than its wild counterpart. The fatty acid profile of farmed turbot included higher levels of myristic, pentadecanoic, palmitoleic, gadoleic, cetoleic, linoleic, linolenic, stearidonic, eicosadienoic and eicosapentaenoic acids, and lower levels of stearic, arachidonic, docosapentaenoic and docosahexaenoic acids than its wild counterpart. The proportions of polyunsaturated fatty acids and n-3/n-6 ratios were higher in wild turbot than in farmed turbot. With respect to trace minerals, no toxic levels were found, and higher amounts of Cd, Co, Cu, Fe, Mn, Pb and Zn, as well as lower amounts of Cr, were found in farmed turbot relative to wild turbot. The antimicrobial resistance of Pseudomonas spp. and Aeromonas spp. were quite similar, with only the trimethoprim-sulfamethoxazole resistance of Aeromonas spp. isolated from farmed turbot being higher than those isolated from wild turbot. In the case of ampicillin, Pseudomonas spp. isolated from wild turbot showed higher resistance levels than those of their counterparts isolated from farmed turbot. In conclusion, the nutritional parameters of wild turbot are more adequate with respect to nutritional recommendations, while no differences were observed in food safety derived from trace mineral concentrations or the antimicrobial resistance of bacteria isolated from wild and farmed turbot.

Molecular detection of six virulence genes in Pseudomonas aeruginosa isolates detected in children with urinary tract infection.

PubMed

Badamchi, Ali; Masoumi, Hossein; Javadinia, Shima; Asgarian, Ramin; Tabatabaee, Azardokht

2017-06-01

Although a vast majority of Urinary tract infections (UTIs) are caused by E. coli, epidemiological reports have indicated an increasing rate of such infections caused by some other opportunistic organisms including Pseudomonas aeruginosa. Antimicrobial susceptibility and pathogenesis mechanisms of P. aeruginosa are poorly understood. The aim of this study was to detect some virulence factor genes and antimicrobial susceptibility patterns of P. aeruginosa isolates detected in patients with UTI, in children hospital of Tehran, Tehran, Iran. Eighty-four Pseudomonas aeruginosa were isolated. Then, the presence of six virulence genes, in the genome of the isolates was evaluated using PCR amplifications techniques. Finally, antimicrobial susceptibility pattern of the isolates was determined by disk diffusion method. According to the results, lasB was the most prevalent virulence gene that could be detected in the P. aeruginosa isolates (92.9%) used in this study. This was followed by aprA (81.2%), toxA (69.4%), and algD (60%) genes. Two genes, plcH and plcN, were detected in about 38.8% of the isolates. Additionally, Imipenem was found as the most active agent against the P. aeruginosa isolates used in this research. However, Cefotaxime resistance was observed in most of the isolates. Our P. aeruginosa isolates exhibited a great degree of heterogeneity not only in their virulence genes but also in their antimicrobial susceptibility profiles. Imipenem therapies tend to be among the best choices in the management of UTI caused by P. aeruginosa. As a conclusion, assessment of antimicrobial susceptibility pattern and also analyzing the virulence factors can be highly helpful to develop effective treatment strategies against P. aeruginosa urinary infections. Copyright © 2017. Published by Elsevier Ltd.

Diffusion of Antimicrobials Across Silicone Hydrogel Contact Lenses.

PubMed

Zambelli, Alison M; Brothers, Kimberly M; Hunt, Kristin M; Romanowski, Eric G; Nau, Amy C; Dhaliwal, Deepinder K; Shanks, Robert M Q

2015-09-01

To measure the diffusion of topical preparations of moxifloxacin, amphotericin B (AmB), and polyhexamethylene biguanide (PHMB) through silicone hydrogel (SH) contact lenses (CLs) in vitro. Using an in vitro model, the diffusion of three antimicrobials through SH CLs was measured. Diffused compounds were measured using a spectrophotometer at set time points over a period of 4 hr. The amount of each diffused antimicrobial was determined by comparing the experimental value with a standard curve. A biological assay was performed to validate the CL diffusion assay by testing antimicrobial activity of diffused material against lawns of susceptible bacteria (Staphylococcus epidermidis) and yeast (Saccharomyces cerevisiae). Experiments were repeated at least two times with a total of at least four independent replicates. Our data show detectable moxifloxacin and PHMB diffusion through SH CLs at 30 min, whereas AmB diffusion remained below the limit of detection within the 4-hr experimental period. In the biological assay, diffused moxifloxacin demonstrated microbial killing starting at 20 min on bacterial lawns, whereas PHMB and AmB failed to demonstrate killing on microbial lawns over the course of the 60-min experiment. In vitro diffusion assays demonstrate limited penetration of certain anti-infective agents through SH CLs. Further studies regarding the clinical benefit of using these agents along with bandage CL for corneal pathologic condition are warranted.

Disk diffusion quality control guidelines for NVP-PDF 713: a novel peptide deformylase inhibitor.

PubMed

Anderegg, Tamara R; Jones, Ronald N

2004-01-01

NVP-PDF713 is a peptide deformylase inhibitor that has emerged as a candidate for treating Gram-positive infections and selected Gram-negative species that commonly cause community-acquired respiratory tract infections. This report summarizes the results of a multi-center (seven participants) disk diffusion quality control (QC) investigation for NVP PDF-713 using guidelines of the National Committee for Clinical Laboratory Standards and the standardized disk diffusion method. A total of 420 NVP-PDF 713 zone diameter values were generated for each QC organism. The proposed zone diameter ranges contained 97.6-99.8% of the reported participant results and were: Staphylococcus aureus ATCC 25923 (25-35 mm), Streptococcus pneumoniae ATCC 49619 (30-37 mm), and Haemophilus influenzae ATCC 49247 (24-32 mm). These QC criteria for the disk diffusion method should be applied during the NVP-PDF 713 clinical trials to maximize test accuracy.

Antimicrobial Properties of Diamond-Like Carbon/Silver Nanocomposite Thin Films Deposited on Textiles: Towards Smart Bandages

PubMed Central

Juknius, Tadas; Ružauskas, Modestas; Tamulevičius, Tomas; Šiugždinienė, Rita; Juknienė, Indrė; Vasiliauskas, Andrius; Jurkevičiūtė, Aušrinė; Tamulevičius, Sigitas

2016-01-01

In the current work, a new antibacterial bandage was proposed where diamond-like carbon with silver nanoparticle (DLC:Ag)-coated synthetic silk tissue was used as a building block. The DLC:Ag structure, the dimensions of nanoparticles, the silver concentration and the silver ion release were studied systematically employing scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic absorption spectroscopy, respectively. Antimicrobial properties were investigated using microbiological tests (disk diffusion method and spread-plate technique). The DLC:Ag layer was stabilized on the surface of the bandage using a thin layer of medical grade gelatin and cellulose. Four different strains of Staphylococcus aureus extracted from humans’ and animals’ infected wounds were used. It is demonstrated that the efficiency of the Ag+ ion release to the aqueous media can be increased by further RF oxygen plasma etching of the nanocomposite. It was obtained that the best antibacterial properties were demonstrated by the plasma-processed DLC:Ag layer having a 3.12 at % Ag surface concentration with the dominating linear dimensions of nanoparticles being 23.7 nm. An extra protective layer made from cellulose and gelatin with agar contributed to the accumulation and efficient release of silver ions to the aqueous media, increasing bandage antimicrobial efficiency up to 50% as compared to the single DLC:Ag layer on textile. PMID:28773494

Antimicrobial Properties of Diamond-Like Carbon/Silver Nanocomposite Thin Films Deposited on Textiles: Towards Smart Bandages.

PubMed

Juknius, Tadas; Ružauskas, Modestas; Tamulevičius, Tomas; Šiugždinienė, Rita; Juknienė, Indrė; Vasiliauskas, Andrius; Jurkevičiūtė, Aušrinė; Tamulevičius, Sigitas

2016-05-13

In the current work, a new antibacterial bandage was proposed where diamond-like carbon with silver nanoparticle (DLC:Ag)-coated synthetic silk tissue was used as a building block. The DLC:Ag structure, the dimensions of nanoparticles, the silver concentration and the silver ion release were studied systematically employing scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic absorption spectroscopy, respectively. Antimicrobial properties were investigated using microbiological tests (disk diffusion method and spread-plate technique). The DLC:Ag layer was stabilized on the surface of the bandage using a thin layer of medical grade gelatin and cellulose. Four different strains of Staphylococcus aureus extracted from humans' and animals' infected wounds were used. It is demonstrated that the efficiency of the Ag⁺ ion release to the aqueous media can be increased by further RF oxygen plasma etching of the nanocomposite. It was obtained that the best antibacterial properties were demonstrated by the plasma-processed DLC:Ag layer having a 3.12 at % Ag surface concentration with the dominating linear dimensions of nanoparticles being 23.7 nm. An extra protective layer made from cellulose and gelatin with agar contributed to the accumulation and efficient release of silver ions to the aqueous media, increasing bandage antimicrobial efficiency up to 50% as compared to the single DLC:Ag layer on textile.

[The possibilities for diagnostics of prescription of death coming based on the changes in the lumbar intervertebral disks (the comparison of the morphological, immunohistochemical and topographical findings)].

PubMed

Byval'tsev, V A; Stepanov, I A; Semenov, A V; Perfil'ev, D V; Belykh, E G; Bardonova, L A; Nikiforov, S B; Sudakov, N P; Bespyatykh, I V; Antipina, S L

The objective of the present study was the comprehensive analysis of the postmortem changes in the lumbar intervertebral disks within different periods after death. A total of seven vertebromotor segments were distinguished in the lumbosacral region of the vertebral column based on the examination of 7 corpses. All these segments were divided into three groups in accordance with the prescription of death coming as follows: up to 12 hours (group 1), between 12 and 24 hours (group 2), and between 24 and 36 hours (group 3) after death. The models of the segments thus obtained were subjected to the study by means of diffusion weighted MRI. The removed intervertebral disks were used for morphological and immunohistochemical investigations. The comparison of the diffusion coefficients (DI) revealed the significant difference between the intervertebral disks assigned to groups 1 and 2 (p<0.01). The number of the cells in the pulpal core, the vertebral end plate, and the fibrous ring in all the above groups of the intervertebral disks was significantly reduced (p<0.01). The analysis of the correlation dependence between cell density and diffusion coefficients has demonstrated the well apparent relationship between these characteristics of the intervertebral disks comprising groups 1 and 2. It is concluded that diffusion weighted MRI in the combination with the calculation of diffusion coefficients for the intervertebral disks provides a tool for diagnostics of prescription of death coming as confirmed by the results of the morphometric studies and immunohistochemical analysis.

Antimicrobial susceptibilities and population structure of Staphylococcus epidermidis associated with ovine mastitis.

PubMed

Onni, Toniangelo; Sanna, Giovanna; Larsen, Jesper; Tola, Sebastiana

2011-02-24

Intramammary infections are a serious problem for dairy sheep farms, and Staphylococcus epidermidis is one of the main etiological agents of ovine mastitis. In this work, 131 S. epidermidis isolates, collected from 2201 dairy Sarda sheep belonging to 14 flocks with high somatic cell count scores, were studied. The flocks were located in diverse geographical areas of Sardinia, Italy. The aim of study was to assess the susceptibility of isolates to 13 antimicrobial agents, many of which are frequently used in mastitis therapy. Oxacillin was used for detecting methicillin-resistant S. epidermidis (MRSE) by disk diffusion test. Thirty-eight percent of the isolates (n=50) were resistant to penicillin, 7.6% (n=10) were resistant to tetracycline, and 2.3% (n=3) were resistant to both penicillin and tetracycline (PTRSE). Two isolates were resistant to five antimicrobials including methicillin. Analysis of staphylococcal cassette chromosome mec (SCCmec) elements showed that both MRSE isolates harbored SCCmec type IVa. Based on pulsed-field gel electrophoresis (PFGE) typing by SmaI macrorestriction, S. epidermidis isolates were grouped into four clusters at 75% similarity level. The two multi-drug resistant MRSE isolates displayed distinct PFGE patters. This study indicates that S. epidermidis isolates from sheep milk samples may accumulate resistance markers for different antimicrobial agents. Furthermore, the occurrence of PTRSE and MRSE suggests to adopt adequate hygienic measures when handling animals with intramammary infections, in order to prevent spreading PTRSE and MRSE strains to humans through direct contact and/or consumption of contaminated food. Copyright © 2010 Elsevier B.V. All rights reserved.

Antimicrobial activity, cytotoxicity and chemical analysis of lemongrass essential oil (Cymbopogon flexuosus) and pure citral.

PubMed

Adukwu, Emmanuel C; Bowles, Melissa; Edwards-Jones, Valerie; Bone, Heather

2016-11-01

The aim of this study was to determine the antimicrobial effects of lemongrass essential oil (C. flexuosus) and to determine cytotoxic effects of both test compounds on human dermal fibroblasts. Antimicrobial susceptibility screening was carried out using the disk diffusion method. Antimicrobial resistance was observed in four of five Acinetobacter baumannii strains with two strains confirmed as multi-drug-resistant (MDR). All the strains tested were susceptible to both lemongrass and citral with zones of inhibition varying between 17 to 80 mm. The mean minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of citral (mic-0.14 % and mbc-0.3 % v/v) was lower than that of Lemongrass (mic-0.65 % and mbc-1.1 % v/v) determined using the microtitre plate method. Cell viability using human dermal fibroblasts (HDF; 106-05a) was determined following exposure to both compounds and a control (Grapeseed oil) using the XTT assay and the IC 50 determined at 0.095 % (v/v) for citral and 0.126 % (v/v) for lemongrass. Grapeseed oil had no effect on cell viability. Live cell imaging was performed using the LumaScope 500 imaging equipment and changes in HDF cell morphology such as necrotic features and shrinkage were observed. The ability of lemongrass essential oil (EO) and citral to inhibit and kill MDR A. baumannii highlights its potential for use in the management of drug-resistant infections; however, in vitro cytotoxicity does suggest further tests are needed before in vivo or ex vivo human exposure.

Characterization of antimicrobial resistance of Escherichia coli recovered from foods of animal and fish origin in Korea.

PubMed

Koo, Hyon-Ji; Woo, Gun-Jo

2012-05-01

Antimicrobial-resistant Escherichia coli is transferred from food-producing animals to humans through the food chain. We investigated the prevalence of antimicrobial resistance and resistance determinants and characterized the integrons of foodborne E. coli in Korea. In total, 162 E. coli isolates from commercial foods (raw meat, fish, and processed foods) were collected by the National Antimicrobial Resistance Management Program from 2004 to 2006. Susceptibility to 20 antibiotics was tested by disk diffusion, and resistance determinants were detected using PCR and genomic sequence analysis. The isolates were highly resistant to antibiotics commonly used in livestock farming. Resistance to tetracycline (74.7%) was the most frequently observed, followed by streptomycin (71%) and ampicillin (51.2%). Class 1 integrons were detected in 13 isolates (8%), and nine of these integrons were located on conjugative plasmids. None of the isolates produced extended-spectrum β -lactamase. One isolate (0.6%) harbored bla(CMY-2), which was located on a conjugative plasmid. Although the qnr gene was not detected, aac(6'9)-Ib-cr was present in two isolates (1.2%). This is the first report of aac(6'9)-Ib-cr in food isolates. Three or four amino acid substitutions at positions 83 and 87 in gyrA and at positions 80 and/or 84 in parC were found in six isolates, representing high resistance to ciprofloxacin (MIC ≥ 16 mg/liter). These results suggest that E. coli isolates carrying resistance genes and integrons are present in the Korean food chain.

Diffusion of Antimicrobials Across Silicone Hydrogel Contact Lenses

PubMed Central

Zambelli, Alison M.; Brothers, Kimberly M.; Hunt, Kristin M.; Romanowski, Eric G.; Nau, Amy C.; Dhaliwal, Deepinder K.; Shanks, Robert M. Q.

2014-01-01

Objectives To measure the diffusion of topical preparations of moxifloxacin, amphotericin B (AmB), and polyhexamethylene biguanide (PHMB) through silicone hydrogel (SH) contact lenses in vitro. Methods Using an in vitro model, the diffusion of three antimicrobials through SH contact lenses was measured. Diffused compounds were measured using a spectrophotometer at set time points over a period of four hours. The amount of each diffused antimicrobial was determined by comparing the experimental value to a standard curve. A biological assay was performed to validate the contact lens diffusion assay by testing antimicrobial activity of diffused material against lawns of susceptible bacteria (Staphylococcus epidermidis) and yeast (Saccharomyces cerevisiae). Experiments were repeated at least two times with a total of at least 4 independent replicates. Results Our data show detectable moxifloxacin and PHMB diffusion through SH contact lenses at 30 minutes, while amphotericin B diffusion remained below the limit of detection within the 4 hour experimental period. In the biological assay, diffused moxifloxacin demonstrated microbial killing starting at 20 minutes on bacterial lawns, whereas PHMB and amphotericin B failed to demonstrate killing on microbial lawns over the course of the 60 minute experiment. Conclusions In vitro diffusion assays demonstrate limited penetration of certain anti-infective agents through silicone hydrogel contact lenses. Further studies regarding the clinical benefit of using these agents along with bandage contact lens use for corneal pathology are warranted. PMID:25806673

Isolation of Multidrug-Resistant Escherichia coli O157 from Goats in the Somali Region of Ethiopia: A Cross-Sectional, Abattoir-Based Study.

PubMed

Dulo, Fitsum; Feleke, Aklilu; Szonyi, Barbara; Fries, Reinhard; Baumann, Maximilian P O; Grace, Delia

2015-01-01

Toxigenic Escherichia coli (E. coli) are an important cause of gastroenteritis in developing countries. In Ethiopia, gastroenteritis due to food-borne disease is a leading cause of death. Yet, there is no surveillance for E. coli O157 and little is known about the carriage of this pathogen in Ethiopia's livestock. This study aimed to assess the prevalence and levels of antimicrobial resistance of E. coli O157 in goat meat, feces, and environmental samples collected at a large abattoir in the Somali region of Ethiopia. The samples were enriched in modified tryptone broth containing novobiocin, and plated onto sorbitol MacConkey agar. Isolates were confirmed using indole test and latex agglutination. Antimicrobial susceptibility testing was conducted using the disk diffusion method. A total of 235 samples, including 93 goat carcass swabs, 93 cecal contents, 14 water, 20 hand, and 15 knife swabs were collected. Overall, six (2.5%) samples were contaminated with E. coli O157 of which two (2.1%) were isolated from cecal contents, three (3.2%) from carcass swabs, and one (7.1%) from water. All isolates were resistant to at least two of the 18 antimicrobials tested. Two isolates (33.3%) were resistant to more than five antimicrobials. Abattoir facilities and slaughter techniques were conducive to carcass contamination. This study highlights how poor hygiene and slaughter practice can result in contaminated meat, which is especially risky in Ethiopia because of the common practice of eating raw meat. We detect multi-resistance to drugs not used in goats, suggesting that drugs used to treat human infections may be the originators of antimicrobial resistance in livestock in this ecosystem. The isolation of multidrug-resistant E. coli O157 from goats from a remote pastoralist system highlights the need for global action on regulating and monitoring antimicrobial use in both human and animal populations.

Isolation of Multidrug-Resistant Escherichia coli O157 from Goats in the Somali Region of Ethiopia: A Cross-Sectional, Abattoir-Based Study

PubMed Central

Dulo, Fitsum; Feleke, Aklilu; Szonyi, Barbara; Fries, Reinhard; Baumann, Maximilian P. O.; Grace, Delia

2015-01-01

Toxigenic Escherichia coli (E. coli) are an important cause of gastroenteritis in developing countries. In Ethiopia, gastroenteritis due to food-borne disease is a leading cause of death. Yet, there is no surveillance for E. coli O157 and little is known about the carriage of this pathogen in Ethiopia’s livestock. This study aimed to assess the prevalence and levels of antimicrobial resistance of E. coli O157 in goat meat, feces, and environmental samples collected at a large abattoir in the Somali region of Ethiopia. The samples were enriched in modified tryptone broth containing novobiocin, and plated onto sorbitol MacConkey agar. Isolates were confirmed using indole test and latex agglutination. Antimicrobial susceptibility testing was conducted using the disk diffusion method. A total of 235 samples, including 93 goat carcass swabs, 93 cecal contents, 14 water, 20 hand, and 15 knife swabs were collected. Overall, six (2.5%) samples were contaminated with E. coli O157 of which two (2.1%) were isolated from cecal contents, three (3.2%) from carcass swabs, and one (7.1%) from water. All isolates were resistant to at least two of the 18 antimicrobials tested. Two isolates (33.3%) were resistant to more than five antimicrobials. Abattoir facilities and slaughter techniques were conducive to carcass contamination. This study highlights how poor hygiene and slaughter practice can result in contaminated meat, which is especially risky in Ethiopia because of the common practice of eating raw meat. We detect multi-resistance to drugs not used in goats, suggesting that drugs used to treat human infections may be the originators of antimicrobial resistance in livestock in this ecosystem. The isolation of multidrug-resistant E. coli O157 from goats from a remote pastoralist system highlights the need for global action on regulating and monitoring antimicrobial use in both human and animal populations. PMID:26561414

Prevalence and Antimicrobial Resistance of Enterobacteriaceae in Shell Eggs from Small-Scale Poultry Farms and Farmers' Markets.

PubMed

Kilonzo-Nthenge, A; Nahashon, S N; Godwin, S; Liu, S; Long, D

2016-12-01

Public health concerns over the emergence of antimicrobial resistant bacteria have increased recently. The purpose of this study was to investigate the prevalence of antimicrobial resistant Enterobacteriaceae in shell eggs purchased from small poultry farms and farmers' markets. A total of 504 eggs were pooled to make 252 composite samples, consisting of 2 eggs per composite. The microbial quality of shell eggs was determined by standard quantitative, biochemical, and PCR techniques. Susceptibility to 13 antimicrobial agents was determined by the Kirby-Bauer disk diffusion technique, and results were interpreted based on Clinical and Laboratory Standards Institute values. Shell eggs and egg contents were positive for Escherichia coli (11.9 and 5.2%, respectively), Enterobacter (9.1 and 7.9%), and Serratia (11.5 and 4.8%). Salmonella was isolated from 3.6% of egg shells but not from egg contents. Mean (±SD) Enterobacteriaceae levels (4.4 ± 2.0 log CFU per eggshell) on shell eggs from poultry farms was significantly higher (P ≤ 0.05) than that on shell eggs from farmers' markets (2.1 ± 1.3 log CFU per eggshell). Of the 134 isolates recovered, resistance among isolates from farm and market shell eggs to erythromycin was most common (48.5 and 32.8%, respectively) followed by ampicillin (44.8 and 17.2%), and tetracycline (29.9 and 17.2%). The multiple antibiotic resistance index value for E. coli and Pantoea was 0.62, and that for Salmonella and Klebsiella terrigena was 0.08, indicating that Enterobacteriaceae in shell eggs can be resistant to multiple antimicrobial agents. These data reveal that shell eggs from small poultry farms and farmers' markets can harbor antimicrobial resistant pathogenic and commensal bacteria. Thus, failure to properly handle shell eggs poses a potential health hazard to consumers.

Chemical constituents of Helichrysum italicum (Roth) G. Don essential oil and their antimicrobial activity against Gram-positive and Gram-negative bacteria, filamentous fungi and Candida albicans.

PubMed

Djihane, Bouzid; Wafa, Nouioua; Elkhamssa, Soltani; Pedro, De Haro Juan; Maria, Angeles Esteban; Mohamed Mihoub, Zerroug

2017-07-01

The aerial parts of Helichrysum italicum (Roth) G. Don were subjected to hydrodistillation to obtain essential oils which had been analyzed by gas chromatography and gas chromatography coupled with mass spectrometry and tested for antimicrobial activity against 12 bacteria, two yeasts and four fungi by agar diffusion method. The essential oil yielded 0.44% (v/w) and 67 compounds accounting for 99.24% of the oil were identified with a high content of oxygenated sesquiterpenes (61.42%). The most oxygenated sesquiterpene compounds were α-Cedrene (13.61%), α-Curcumene (11.41%), Geranyl acetate (10.05%), Limonene (6.07%), Nerol (5.04%), Neryl acetate (4.91%) and α-Pinene (3.78%). The antimicrobial activity of the essential oil was assayed by using the disk diffusion method on Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538, Micrococcus luteus ATCC 4698, Klebsiella pneumonia ATCC 4352, Enterococcus cereus ATCC 2035, Bacillus cereus ATCC 10876, Staphylococcus epidermidis ATCC 12228, Bacillus subtilis ATCC 9372, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 49452, Proteus mirabilis ATCC 35659, Listeria monocytogenes ATCC 15313 and yeasts Candida albicans ATCC 10231, Saccharomyces cerevisiae ATCC 9763 and fungi, Fusarium solani var. coeruleum , Aspergillus niger , Alternaria alternata , Ascochyta rabiei . H. italicum inhibited the growth of all the tested microorganisms except three bacteria, E. coli ATCC 25922, K. pneumonia ATCC 4352 and L. monocytogenes ATCC 15313. The most sensitive bacterium was E. cereus ATCC 2035 with minimum inhibitory and bactericidal concentrations of 0.79 μg ml -1 . A minimum fungistatic and fungicide concentration of 6.325 μg ml -1 and 12.65 μg ml -1 respectively was obtained with C. albicans ATCC 10231 and S. cerevisiae ATCC 9763. However the four fungi were more resistant with fungistatic minimum concentration ranging from 6.325 μg ml -1 to 50.6 μg ml -1 and a fungicide minimum concentration of 50.6 μg ml -1 . This antimicrobial activity could be attributed to the essential oil chemical composition. Thus this study represents a first step in the study of the chemical composition of H. italicum (Roth) G. Don collected from north Algeria and its antimicrobial properties.

Assessment of Metronidazole Susceptibility in Helicobacter pylori: Statistical Validation and Error Rate Analysis of Breakpoints Determined by the Disk Diffusion Test

PubMed Central

Chaves, Sandra; Gadanho, Mário; Tenreiro, Rogério; Cabrita, José

1999-01-01

Metronidazole susceptibility of 100 Helicobacter pylori strains was assessed by determining the inhibition zone diameters by disk diffusion test and the MICs by agar dilution and PDM Epsilometer test (E test). Linear regression analysis was performed, allowing the definition of significant linear relations, and revealed correlations of disk diffusion results with both E-test and agar dilution results (r2 = 0.88 and 0.81, respectively). No significant differences (P = 0.84) were found between MICs defined by E test and those defined by agar dilution, taken as a standard. Reproducibility comparison between E-test and disk diffusion tests showed that they are equivalent and with good precision. Two interpretative susceptibility schemes (with or without an intermediate class) were compared by an interpretative error rate analysis method. The susceptibility classification scheme that included the intermediate category was retained, and breakpoints were assessed for diffusion assay with 5-μg metronidazole disks. Strains with inhibition zone diameters less than 16 mm were defined as resistant (MIC > 8 μg/ml), those with zone diameters equal to or greater than 16 mm but less than 21 mm were considered intermediate (4 μg/ml < MIC ≤ 8 μg/ml), and those with zone diameters of 21 mm or greater were regarded as susceptible (MIC ≤ 4 μg/ml). Error rate analysis applied to this classification scheme showed occurrence frequencies of 1% for major errors and 7% for minor errors, when the results were compared to those obtained by agar dilution. No very major errors were detected, suggesting that disk diffusion might be a good alternative for determining the metronidazole sensitivity of H. pylori strains. PMID:10203543

Variation of the chemical composition and antimicrobial activity of the essential oils of natural populations of Tunisian Daucus carota L. (Apiaceae).

PubMed

Rokbeni, Nesrine; M'rabet, Yassine; Dziri, Salma; Chaabane, Hedia; Jemli, Marwa; Fernandez, Xavier; Boulila, Abdennacer

2013-12-01

The essential oils of Daucus carota L. (Apiaceae) seeds sampled from ten wild populations spread over northern Tunisia were characterized by GC-FID and GC/MS analyses. In total, 36 compounds were identified in the D. carota seed essential oils, with a predominance of sesquiterpene hydrocarbons in most samples (22.63-89.93% of the total oil composition). The main volatile compounds identified were β-bisabolene (mean content of 39.33%), sabinene (8.53%), geranyl acetate (7.12%), and elemicin (6.26%). The volatile composition varied significantly across the populations, even for oils of populations harvested in similar areas. The chemometric principal component analysis and the hierarchical clustering identified four groups, each corresponding to a composition-specific chemotype. The in vitro antimicrobial activity of the isolated essential oils was preliminarily evaluated, using the disk-diffusion method, against one Gram-positive (Staphylococcus aureus) and two Gram-negative bacteria (Escherichia coli and Salmonella typhimurium), as well as against a pathogenic yeast (Candida albicans). All tested essential oils exhibited interesting antibacterial and antifungal activities against the assayed microorganisms. Copyright © 2013 Verlag Helvetica Chimica Acta AG, Zürich.

Green synthesis of copper nanoparticles by Citrus medica Linn. (Idilimbu) juice and its antimicrobial activity.

PubMed

Shende, Sudhir; Ingle, Avinash P; Gade, Aniket; Rai, Mahendra

2015-06-01

We report an eco-friendly method for the synthesis of copper nanoparticles (CuNPs) using Citron juice (Citrus medica Linn.), which is nontoxic and cheap. The biogenic copper nanoparticles were characterized by UV-Vis spectrophotometer showing a typical resonance (SPR) at about 631 nm which is specific for CuNPs. Nanoparticles tracking analysis by NanoSight-LM20 showed the particles in the range of 10-60 nm with the concentration of 2.18 × 10(8) particles per ml. X-ray diffraction revealed the FCC nature of nanoparticles with an average size of 20 nm. The antimicrobial activity of CuNPs was determined by Kirby-Bauer disk diffusion method against some selected species of bacteria and plant pathogenic fungi. It was reported that the synthesized CuNPs demonstrated a significant inhibitory activity against Escherichia coli followed by Klebsiella pneumoniae, Pseudomonas aeruginosa, Propionibacterium acnes and Salmonella typhi. Among the plant pathogenic fungi tested, Fusarium culmorum was found to be most sensitive followed by F. oxysporum and F. graminearum. The novelty of this work is that for the first time citron juice was used for the synthesis of CuNPs.

Simple biosynthesis of zinc oxide nanoparticles using nature's source, and it's in vitro bio-activity

NASA Astrophysics Data System (ADS)

Zare, Elham; Pourseyedi, Shahram; Khatami, Mehrdad; Darezereshki, Esmaeel

2017-10-01

Nanoparticles with antimicrobial activity, especially as a new class of biomedical materials for use in increasing the level of public health in daily life have emerged. In this study, green synthesis of zinc oxide) ZnO(nanoparticles was studied by Cuminum cyminum (cumin) as novel natural source and zinc nitrate [Zn(NO3)2] as Zn2+ source. The results showed that parameters such as concentration, time, temperature and pH have a direct impact on the synthesis of zinc nanoparticles and change in any of the factors causing the change in the process of synthesis. The properties of synthesized nanoparticles were examined by UV-visible Spectrophotometer, X-ray diffraction spectroscopy and transmission electron microscopy (TEM). The UV-visible spectroscopy presented the absorption peak in the range of 370 nm. Transmission electron microscopy images of synthesized nanoparticles are mainly spherical or oval with an average size of about 7 nm. The effect of antimicrobial nanoparticles calculated using disk diffusion method and broth MIC and MBC in different strains of bacteria, which showed that gram positive and negative were sensitive to zinc oxide nanoparticles. The sensitivity of gram-negative bacteria was more.

The anti-biofilm activity of lemongrass (Cymbopogon flexuosus) and grapefruit (Citrus paradisi) essential oils against five strains of Staphylococcus aureus.

PubMed

Adukwu, E C; Allen, S C H; Phillips, C A

2012-11-01

To determine the sensitivity of five strains of Staphylococcus aureus to five essential oils (EOs) and to investigate the anti-biofilm activity of lemongrass and grapefruit EOs. Antimicrobial susceptibility screening was carried out using the disk diffusion method. All of the strains tested were susceptible to lemongrass, grapefruit, bergamot and lime EOs with zones of inhibition varying from 2·85 to 8·60 cm although they were resistant to lemon EO. Lemongrass EO inhibited biofilm formation at 0·125% (v/v) as measured by colorimetric assay and at 0·25% (v/v) no metabolic activity was observed as determined by 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction. Grapefruit EO did not show any anti-biofilm activity. Following exposure to lemongrass EO extensive disruption to Staph. aureus biofilms was shown under scanning electron microscopy. In comparison to the other EOs tested, lemongrass exhibited the most effective antimicrobial and anti-biofilm activity. The effect of lemongrass EO highlights its potential against antibiotic resistant Staph. aureus in the healthcare environment. © 2012 The Authors Journal of Applied Microbiology © 2012 The Society for Applied Microbiology.

Diversity of methicillin-resistant Staphylococcus aureus (MRSA) isolated from Austrian ruminants and New World camelids.

PubMed

Schauer, B; Krametter-Frötscher, R; Knauer, F; Ehricht, R; Monecke, S; Feßler, A T; Schwarz, S; Grunert, T; Spergser, J; Loncaric, I

2018-02-01

The aim of this study was to determine the prevalence, the antimicrobial resistance patterns and the genetic diversity of methicillin-resistant Staphylococcus aureus (MRSA) from Austrian ruminants and New World camelids that were treated at the University of Veterinary Medicine, Vienna. Between April 2014 and January 2017, 723 nasal swabs originating from ruminants and New World camelids were examined. MRSA isolates were characterized by mecA/mecA1/mecC PCRs and by DNA microarray analysis. They were genotyped by spa typing, dru typing, MLST and MLVA. Glycopolymer fingerprinting by FTIR spectroscopy was also performed. Antimicrobial susceptibility testing was conducted by agar disk diffusion. Twelve MRSA isolates were mecA-positive, whereas three were mecC-positive. The MRSA isolates carried five different SCCmec elements, and belonged to three sequence types (ST45, ST130, ST398). The MRSA isolates displayed seven different resistance phenotypes. The present study describes for the first time mecC-carrying MRSA isolates originating from domesticated animals in Austria. More systematic studies are needed to unravel the role of ruminants and New World camelids as reservoirs for MRSA as a potential risk for zooanthropogenic transmission. Copyright © 2018 Elsevier B.V. All rights reserved.

Biosynthesis, characterization, and evaluation of bioactivities of leaf extract-mediated biocompatible silver nanoparticles from an early tracheophyte, Pteris tripartita Sw.

PubMed Central

Baskaran, Xavierravi; Geo Vigila, Antony Varuvel; Parimelazhagan, Thangaraj; Muralidhara-Rao, Doulathabad; Zhang, Shouzhou

2016-01-01

The objective of the study was to characterize silver nanoparticles (Ag-NPs) and their bioactivities in early tracheophytes (Pteridophyta). Aqueous leaf extract of a critically endangered fern, Pteris tripartita Sw., was used for one-step green synthesis of Ag-NPs. The biosynthesized Ag-NPs were characterized using ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy. Morphologically, the Ag-NPs showed hexagonal, spherical, and rod-shaped structures. Size distributions of Ag-NPs, calculated using Scherrer’s formula, showed an average size of 32 nm. Ag-NPs were studied for in vitro antioxidant, antimicrobial, and in vivo anti-inflammatory activities. Ag-NPs exhibited significant anti-inflammatory activity in carrageenan-induced paw volume tests performed in female Wistar albino rats. Furthermore, Ag-NPs showed significant antimicrobial activity against 12 different microorganisms in three different assays (disk diffusion, time course growth, and minimum inhibitory concentration). This study reports that colloidal Ag-NPs can be synthesized by simple, nonhazardous methods, and that biosynthesized Ag-NPs have significant therapeutic properties. PMID:27895478

Methicillin-resistant Staphylococcus sp. colonizing health care workers of a cancer hospital

PubMed Central

Costa, Dayane de Melo; Kipnis, André; Leão-Vasconcelos, Lara Stefânia Netto de Oliveira; Rocha-Vilefort, Larissa Oliveira; Telles, Sheila Araújo; André, Maria Cláudia Dantas Porfírio Borges; Tipple, Anaclara Ferreira Veiga; Lima, Ana Beatriz Mori; Ribeiro, Nádia Ferreira Gonçalves; Pereira, Mayara Regina; Prado-Palos, Marinésia Aparecida

2014-01-01

The aim of the study was to analyze epidemiological and microbiological aspects of oral colonization by methicillin-resistant Staphylococcus of health care workers in a cancer hospital. Interview and saliva sampling were performed with 149 health care workers. Antimicrobial resistance was determined by disk diffusion and minimum inhibitory concentration. Polymerase Chain Reaction, Internal Transcribed Spacer-Polymerase Chain Reaction and Pulsed Field Gel Electrophoresis were performed for genotypic characterization of methicillin-resistant Staphylococcus. Risk factors were determined by logistic regression. Methicillin-resistant Staphylococcus colonization prevalence was 19.5%, denture wearing (p = 0.03), habit of nail biting (p = 0.04) and preparation and administration of antimicrobial (p = 0.04) were risk factors identified. All methicillin-resistant Staphylococcus were S. epidermidis, 94.4% of them had mecA gene. Closely related and indistinguishable methicillin-resistant S. epidermidis were detected. These results highlight that HCWs which have contact with patient at high risk for developing infections were identified as colonized by MRSE in the oral cavity, reinforcing this cavity as a reservoir of these bacteria and the risk to themselves and patients safety, because these microorganisms may be spread by coughing and talking. PMID:25477910

Pattern Formation in Diffusion Flames Embedded in von Karman Swirling Flows

NASA Technical Reports Server (NTRS)

Nayagam, Vedha

2006-01-01

Pattern formation is observed in nature in many so-called excitable systems that can support wave propagation. It is well-known in the field of combustion that premixed flames can exhibit patterns through differential diffusion mechanism between heat and mass. However, in the case of diffusion flames where fuel and oxidizer are separated initially there have been only a few observations of pattern formation. It is generally perceived that since diffusion flames do not possess an inherent propagation speed they are static and do not form patterns. But in diffusion flames close to their extinction local quenching can occur and produce flame edges which can propagate along stoichiometric surfaces. Recently, we reported experimental observations of rotating spiral flame edges during near-limit combustion of a downward-facing polymethylmethacrylate disk spinning in quiescent air. These spiral flames, though short-lived, exhibited many similarities to patterns commonly found in quiescent excitable media including compound tip meandering motion. Flame disks that grow or shrink with time depending on the rotational speed and in-depth heat loss history of the fuel disk have also been reported. One of the limitations of studying flame patterns with solid fuels is that steady-state conditions cannot be achieved in air at normal atmospheric pressure for experimentally reasonable fuel thickness. As a means to reproduce the flame patterns observed earlier with solid fuels, but under steady-state conditions, we have designed and built a rotating, porous-disk burner through which gaseous fuels can be injected and burned as diffusion flames. The rotating porous disk generates a flow of air toward the disk by a viscous pumping action, generating what is called the von K rm n boundary layer which is of constant thickness over the entire burner disk. In this note we present a map of the various dynamic flame patterns observed during the combustion of methane in air as a function of fuel flow rate and the burner rotational speed.

Levofloxacin susceptibility testing against Helicobacter pylori: evaluation of a modified disk diffusion method compared to E test.

PubMed

Boyanova, Lyudmila; Ilieva, Juliana; Gergova, Galina; Mitov, Ivan

2016-01-01

We compared levofloxacin (1 μg/disk) disk diffusion method to E test against 212 Helicobacter pylori strains. Using diameter breakpoints for susceptibility (≥15 mm) and resistance (≤9 mm), very major error, major error rate, and categoric agreement were 0.0%, 0.6%, and 93.9%, respectively. The method may be useful in low-resource laboratories. Copyright © 2016 Elsevier Inc. All rights reserved.

Effect of TiO2 nanoparticles incorporation on antibacterial properties and shear bond strength of dental composite used in Orthodontics

PubMed Central

Sodagar, Ahmad; Akhoundi, Mohamad Sadegh Ahmad; Bahador, Abbas; Jalali, Yasamin Farajzadeh; Behzadi, Zahra; Elhaminejad, Farideh; Mirhashemi, Amir Hossein

2017-01-01

ABSTRACT Introduction: Plaque accumulation and bond failure are drawbacks of orthodontic treatment, which requires composite for bonding of brackets. As the antimicrobial properties of TiO2 nanoparticles (NPs) have been proven, the aim of this study was to evaluate the antimicrobial and mechanical properties of composite resins modified by the addition of TiO2 NPs. Methods: Orthodontics composite containing 0%, 1%, 5% and 10% NPs were prepared. 180 composite disks were prepared for elution test, disk agar diffusion test and biofilm inhibition test to collect the counts of microorganisms on three days, measure the inhibition diameter and quantify the viable counts of colonies consequently. For shear bond strength (SBS) test, 48 intact bovine incisors were divided into four groups. Composites containing 0%, 1%, 5% and 10% NPs were used for bonding of bracket. The bracket/tooth SBS was measured by using an universal testing machine. Results: All concentration of TiO2 NPs had a significant effect on creation and extension of inhibition zone. For S. mutans and S. sanguinis, all concentration of TiO2 NPs caused reduction of the colony counts. Composite containing 10% TiO2 NPs had significant effect on reduction of colony counts for S. mutans and S. sanguinis in all three days. The highest mean shear bond strength belonged to the control group, while the lowest value was seen in 10% NPs composite. Conclusions: Incorporating TiO2 nanoparticles into composite resins confer antibacterial properties to adhesives, while the mean shear bond of composite containing 1% and 5% NPs still in an acceptable range. PMID:29160346

Molecular detection of metallo-β-lactamase gene blaVIM-1 in imipenem-resistant Pseudomonas aeruginosa strains isolated from hospitalized patients in the hospitals of Isfahan.

PubMed

Sedighi, Mansour; Vaez, Hamid; Moghoofeie, Mohsen; Hadifar, Shima; Oryan, Golfam; Faghri, Jamshid

2015-01-01

Pseudomonas aeruginosa is an opportunistic human pathogen that causes serious problems, especially in people, who have immunodeficiency. In recent times, metallo-β-lactamase (MBLs) resistance in this bacterium has led to some difficulties in treating bacterial infections. The metallo-beta-lactamase family of genes, including blaVIM-1, is being reported with increasing frequency worldwide. The aim of this study is the detection of the metallo-β-lactamase gene blaVIM-1 in imipenem-resistant P. aeruginosa (IRPA) strains isolated from hospitalized patients. In this study, 106 P. aeruginosa samples were isolated from various nosocomial infections. The isolates were identified, tested for susceptibility to various antimicrobial agents by the Kirby-Bauer disk diffusion method, and all the imipenem-resistant isolates were screened for the presence of MBLs by using the combined disk (IMP-EDTA). The minimal inhibitory concentration (MIC) of imipenem was determined by E-test on the Mueller-Hinton agar. To detect the blaVIM-1 gene, the isolates were subjected to a polymerase chain reaction (PCR). Of all the P. aeruginosa isolates, 62 (58.5%) were found to be imipenem-resistant P. aeruginosa (MIC ≥32 μg/ml). Twenty-six (42%) of the imipenem-resistant isolates were MBL positive. None of these isolates carried the blaVIM-1 gene using the PCR assay. The results demonstrated the serious therapeutic threat of the MBL-producing P. aeruginosa populations. The rate of imipenem resistance due to MBL was increased dramatically. Early detection and infection-control practices are the best antimicrobial strategies for this organism. None of MBL-producing isolates in this study carry the blaVIM-1 gene; therefore, another gene in the MBL family should be investigated.

Evaluation of CLSI M44-A2 Disk Diffusion and Associated Breakpoint Testing of Caspofungin and Micafungin Using a Well-Characterized Panel of Wild-Type and fks Hot Spot Mutant Candida Isolates▿

PubMed Central

Arendrup, Maiken Cavling; Park, Steven; Brown, Steven; Pfaller, Michael; Perlin, David S.

2011-01-01

Disk diffusion testing has recently been standardized by the CLSI, and susceptibility breakpoints have been established for several antifungal compounds. For caspofungin, 5-μg disks are approved, and for micafungin, 10-μg disks are under evaluation. We evaluated the performances of caspofungin and micafungin disk testing using a panel of Candida isolates with and without known FKS echinocandin resistance mechanisms. Disk diffusion and microdilution assays were performed strictly according to CLSI documents M44-A2 and M27-A3. Eighty-nine clinical Candida isolates were included: Candida albicans (20 isolates/10 mutants), C. glabrata (19 isolates/10 mutants), C. dubliniensis (2 isolates/1 mutant), C. krusei (16 isolates/3 mutants), C. parapsilosis (14 isolates/0 mutants), and C. tropicalis (18 isolates/4 mutants). Quality control strains were C. parapsilosis ATCC 22019 and C. krusei ATCC 6258. The correlations between zone diameters and MIC results were good for both compounds, with identical susceptibility classifications for 93.3% of the isolates by applying the current CLSI breakpoints. However, the numbers of fks hot spot mutant isolates misclassified as being susceptible (S) (very major errors [VMEs]) were high (61% for caspofungin [S, ≥11 mm] and 93% for micafungin [S, ≥14 mm]). Changing the disk diffusion breakpoint to S at ≥22 mm significantly improved the discrimination. For caspofungin, 1 VME was detected (a C. tropicalis isolate with an F76S substitution) (3.5%), and for micafungin, 10 VMEs were detected, the majority of which were for C. glabrata (8/10). The broadest separation between zone diameter ranges for wild-type (WT) and mutant isolates was seen for caspofungin (6 to 12 mm versus −4 to 7 mm). In conclusion, caspofungin disk diffusion testing with a modified breakpoint led to excellent separation between WT and mutant isolates for all Candida species. PMID:21357293

Correlation between microdilution, Etest, and disk diffusion methods for antifungal susceptibility testing of fluconazole against Candida sp. blood isolates.

PubMed

Menezes, Everardo Albuquerque; Vasconcelos Júnior, Antônio Alexandre de; Ângelo, Maria Rozzelê Ferreira; Cunha, Maria da Conceição dos Santos Oliveira; Cunha, Francisco Afrânio

2013-01-01

Antifungal susceptibility testing assists in finding the appropriate treatment for fungal infections, which are increasingly common. However, such testing is not very widespread. There are several existing methods, and the correlation between such methods was evaluated in this study. The susceptibility to fluconazole of 35 strains of Candida sp. isolated from blood cultures was evaluated by the following methods: microdilution, Etest, and disk diffusion. The correlation between the methods was around 90%. The disk diffusion test exhibited a good correlation and can be used in laboratory routines to detect strains of Candida sp. that are resistant to fluconazole.

Epidemiology, Clinical Characteristics, and Antimicrobial Susceptibility Profiles of Human Clinical Isolates of Staphylococcus intermedius Group.

PubMed

Yarbrough, Melanie L; Lainhart, William; Burnham, C A

2018-03-01

The veterinary pathogens in the Staphylococcus intermedius group (SIG) are increasingly recognized as causes of human infection. Shared features between SIG and Staphylococcus aureus may result in the misidentification of SIG in human clinical cultures. This study examined the clinical and microbiological characteristics of isolates recovered at a tertiary-care academic medical center. From 2013 to 2015, 81 SIG isolates were recovered from 62 patients. Patients were commonly ≥50 years old, diabetic, and/or immunocompromised. Documentation of dog exposure in the electronic medical record was not common. Of the 81 SIG isolates, common sites of isolation included 37 (46%) isolates from wound cultures and 17 (21%) isolates from respiratory specimens. Although less common, 10 (12%) bloodstream infections were documented in 7 unique patients. The majority of SIG (65%) isolates were obtained from polymicrobial cultures. In comparison to S. aureus isolates from the same time period, significant differences were noted in proportion of SIG isolates that were susceptible to doxycycline (74% versus 97%, respectively; P < 0.001), trimethoprim-sulfamethoxazole (65% versus 97%, respectively; P < 0.001), and ciprofloxacin (78% versus 59%, respectively; P < 0.01). Methicillin resistance (MR) was detected in 12 (15%) of 81 SIG isolates. All MR isolates detected by an oxacillin disk diffusion test would have been misclassified as methicillin susceptible using a cefoxitin disk diffusion test. Thus, SIG is recovered from human clinical specimens, and distinction of SIG from S. aureus is critical for the accurate characterization of MR status in these isolates. Copyright © 2018 American Society for Microbiology.

Escherichia coli Overexpressing a Baeyer-Villiger Monooxygenase from Acinetobacter radioresistens Becomes Resistant to Imipenem

PubMed Central

Minerdi, Daniela; Zgrablic, Ivan; Castrignanò, Silvia; Catucci, Gianluca; Medana, Claudio; Terlizzi, Maria Elena; Gribaudo, Giorgio; Gilardi, Gianfranco

2015-01-01

Antimicrobial resistance is a global issue currently resulting in the deaths of hundreds of thousands of people a year worldwide. Data present in the literature illustrate the emergence of many bacterial species that display resistance to known antibiotics; Acinetobacter spp. are a good example of this. We report here that Acinetobacter radioresistens has a Baeyer-Villiger monooxygenase (Ar-BVMO) with 100% amino acid sequence identity to the ethionamide monooxygenase of multidrug-resistant (MDR) Acinetobacter baumannii. Both enzymes are only distantly phylogenetically related to other canonical bacterial BVMO proteins. Ar-BVMO not only is capable of oxidizing two anticancer drugs metabolized by human FMO3, danusertib and tozasertib, but also can oxidize other synthetic drugs, such as imipenem. The latter is a member of the carbapenems, a clinically important antibiotic family used in the treatment of MDR bacterial infections. Susceptibility tests performed by the Kirby-Bauer disk diffusion method demonstrate that imipenem-sensitive Escherichia coli BL21 cells overexpressing Ar-BVMO become resistant to this antibiotic. An agar disk diffusion assay proved that when imipenem reacts with Ar-BVMO, it loses its antibiotic property. Moreover, an NADPH consumption assay with the purified Ar-BVMO demonstrates that this antibiotic is indeed a substrate, and its product is identified by liquid chromatography-mass spectrometry to be a Baeyer-Villiger (BV) oxidation product of the carbonyl moiety of the β-lactam ring. This is the first report of an antibiotic-inactivating BVMO enzyme that, while mediating its usual BV oxidation, also operates by an unprecedented mechanism of carbapenem resistance. PMID:26459905

Escherichia coli Overexpressing a Baeyer-Villiger Monooxygenase from Acinetobacter radioresistens Becomes Resistant to Imipenem.

PubMed

Minerdi, Daniela; Zgrablic, Ivan; Castrignanò, Silvia; Catucci, Gianluca; Medana, Claudio; Terlizzi, Maria Elena; Gribaudo, Giorgio; Gilardi, Gianfranco; Sadeghi, Sheila J

2016-01-01

Antimicrobial resistance is a global issue currently resulting in the deaths of hundreds of thousands of people a year worldwide. Data present in the literature illustrate the emergence of many bacterial species that display resistance to known antibiotics; Acinetobacter spp. are a good example of this. We report here that Acinetobacter radioresistens has a Baeyer-Villiger monooxygenase (Ar-BVMO) with 100% amino acid sequence identity to the ethionamide monooxygenase of multidrug-resistant (MDR) Acinetobacter baumannii. Both enzymes are only distantly phylogenetically related to other canonical bacterial BVMO proteins. Ar-BVMO not only is capable of oxidizing two anticancer drugs metabolized by human FMO3, danusertib and tozasertib, but also can oxidize other synthetic drugs, such as imipenem. The latter is a member of the carbapenems, a clinically important antibiotic family used in the treatment of MDR bacterial infections. Susceptibility tests performed by the Kirby-Bauer disk diffusion method demonstrate that imipenem-sensitive Escherichia coli BL21 cells overexpressing Ar-BVMO become resistant to this antibiotic. An agar disk diffusion assay proved that when imipenem reacts with Ar-BVMO, it loses its antibiotic property. Moreover, an NADPH consumption assay with the purified Ar-BVMO demonstrates that this antibiotic is indeed a substrate, and its product is identified by liquid chromatography-mass spectrometry to be a Baeyer-Villiger (BV) oxidation product of the carbonyl moiety of the β-lactam ring. This is the first report of an antibiotic-inactivating BVMO enzyme that, while mediating its usual BV oxidation, also operates by an unprecedented mechanism of carbapenem resistance. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Pseudomonas aeruginosa-producing Metallo-β-lactamases (VIM, IMP, SME, and AIM) in the Clinical Isolates of Intensive Care Units, a University Hospital in Isfahan, Iran

PubMed Central

Khorvash, Farzin; Yazdani, Mohammadreza; Shabani, Shiva; Soudi, Aliasghar

2017-01-01

Background: Pseudomonas aeruginosa is a severe challenge for antimicrobial therapy, due to the chromosomal mutations or exhibition of intrinsic resistance to various antimicrobial agents such as most β-lactams. We undertook this study to evaluate the existence of SME, IMP, AIM, and VIM metallo-β-lactamases (MBL) encoding genes among P. aeruginosa strains isolated from Intensive Care Unit (ICU) patients in Al-Zahra Hospital in Isfahan, Iran. Materials and Methods: In a retrospective cross-sectional study that was conducted between March 2012 and April 2013, a total of 48 strains of P. aeruginosa were collected from clinical specimens of bedridden patients in ICU wards. Susceptibility test was performed by disc diffusion method. All of the meropenem-resistant strains were subjected to modified Hodge test for detection of carbapenemases. Multiplex polymerase chain reaction was performed for detection of blaVIM, blaIMP, blaAIM, and blaSME genes. Results: In disk diffusion method, imipenem and meropenem showed the most and colistin the least resistant antimicrobial agents against P. aeruginosa strains. Of the 48 isolates, 36 (75%) were multidrug resistant (MDR). Amplification of β-lactamase genes showed the presence of blaVIM genes in 7 (%14.6) strains and blaIMP genes in 15 (31.3%) strains. All of the isolates were negative for blaSME and blaAIM genes. We could not find any statistically significant difference among the presence of this gene and MDR positive, age, or source of the specimen. Conclusion: As patients with infections caused by MBL-producing bacteria are at an intensified risk of treatment failure, fast determination of these organisms is necessary. Our findings may provide useful insights in replace of the appropriate antibiotics and may also prevent MBLs mediated resistance problem. PMID:29285477

Solid- and vapor-phase antimicrobial activities of six essential oils: susceptibility of selected foodborne bacterial and fungal strains.

PubMed

López, P; Sánchez, C; Batlle, R; Nerín, C

2005-08-24

The antimicrobial activity of essential oils (EOs) of cinnamon (Cinnamon zeylanicum), clove (Syzygium aromaticum), basil (Ocimum basillicum), rosemary (Rosmarinus officinalis), dill (Anethum graveolens), and ginger (Zingiber officinalis) was evaluated over a range of concentrations in two types of contact tests (solid and vapor diffusion). The EOs were tested against an array of four Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, and Listeria monocytogenes), four Gram-negative bacteria (Escherichia coli, Yersinia enterocolitica, Salmonella choleraesuis, and Pseudomonas aeruginosa), and three fungi (a yeast, Candida albicans, and two molds, Penicillium islandicum and Aspergillus flavus). The rationale for this work was to test the possibility of creating a protective atmosphere by using natural compounds that could extend the shelf life of packaged foodstuffs while minimizing organoleptic alterations. In the solid diffusion tests, cinnamon and clove gave the strongest (and very similar) inhibition, followed by basil and rosemary, with dill and ginger giving the weakest inhibition. The fungi were the most sensitive microorganisms, followed by the Gram-positive bacterial strains. The Gram-negative strain P. aeruginosa was the least inhibited. The composition of the atmosphere generated by the EOs, and their minimum inhibitory concentrations (MICs), were determined using a disk volatilization method, in which no inhibition from rosemary or basil was observed. Cinnamon and clove, once again, gave similar results for every microorganism. As a general rule, MIC (fungi) < MIC (bacteria) with no clear differences between Gram-positive or -negative strains except for P. aeruginosa, which was not inhibited by any of the EOs in the vapor phase. The atmosphere generated from the EOs was analyzed by means of solid-phase microextraction combined with gas chromatography-ion trap mass spectrometry. Differences among the volatiles in the EOs, which may be responsible for the differences in their antimicrobial performances, were found.

Extended-spectrum beta-lactamase- and carbapenemase-producing Enterobacteriaceae among Ethiopian children

PubMed Central

Legese, Melese Hailu; Weldearegay, Gebru Mulugeta; Asrat, Daniel

2017-01-01

Background Infections by extended-spectrum beta-lactamase- (ESBL) and carbapenem-resistant Enterobacteriaceae (CRE) are an emerging problem in children nowadays. Hence, the aim of this study was to determine the prevalence of ESBL- and carbapenemase-producing Enterobacteriaceae among children suspected of septicemia and urinary tract infections (UTIs). Methods A cross-sectional study was conducted from January to March 2014. A total of 322 study participants suspected of septicemia and UTIs were recruited. All blood and urine samples were cultured on blood and MacConkey agar. All positive cultures were characterized by colony morphology, Gram stain, and standard biochemical tests. Antimicrobial susceptibility test was performed on Muller-Hinton agar using disk diffusion. ESBL was detected using combination disk and double-disk synergy methods, and the results were compared. Carbapenemase was detected by modified Hodge method using meropenem. Data were analyzed using SPSS version 20. Results The overall prevalence of ESBL- and carbapenemase-producing Enterobacteriaceae was 78.57% (n=22/28) and 12.12%, respectively. Among the Enterobacteriaceae tested, Klebsiella pneumoniae (84.2%, n=16/19), Escherichia coli (100%, n=5/5), and Klebsiella oxytoca (100%, n=1/1) were positive for ESBL. Double-disk synergy method showed 90.9% sensitivity, 66.7% specificity, 95.2% positive predictive value, and 50% negative predictive value. Carbapenemase-producing Enterobacteriaceae were K. pneumoniae (9.09%, n=3/33) and Morganella morganii (3.03%, n=1/33). Conclusion Screening Enterobacteriaceae for ESBL production is essential for better antibiotics selection and preventing its further emergence and spread. In resource-limited settings, double-disk synergy method can be implemented for screening and confirming ESBL production. Moreover, occurrence of CRE in countries where no carbapenems are sold is worrying microbiologists as well as clinicians. Hence, identifying factors that induce carbapenemase production in the absence of carbapenems prescription is essential for control of CRE dissemination within the community. PMID:28182124

Comparative analysis of antimicrobial resistance in enterotoxigenic Escherichia coli isolates from two paediatric cohort studies in Lima, Peru

PubMed Central

Medina, Anicia M.; Rivera, Fulton P.; Pons, Maria J.; Riveros, Maribel; Gomes, Cláudia; Bernal, María; Meza, Rina; Maves, Ryan C.; Huicho, Luis; Chea-Woo, Elsa; Lanata, Claudio F.; Gil, Ana I.; Ochoa, Theresa J.; Ruiz, Joaquim

2015-01-01

Background Antibiotic resistance is increasing worldwide, being of special concern in low- and middle-income countries. The aim of this study was to determine the antimicrobial susceptibility and mechanisms of resistance in 205 enterotoxigenic Escherichia coli (ETEC) isolates from two cohort studies in children <24 months in Lima, Peru. Methods ETEC were identified by an in-house multiplex real-time PCR. Susceptibility to 13 antimicrobial agents was tested by disk diffusion; mechanisms of resistance were evaluated by PCR. Results ETEC isolates were resistant to ampicillin (64%), cotrimoxazole (52%), tetracycline (37%); 39% of the isolates were multidrug-resistant. Heat-stable toxin producing (ETEC-st) (48%) and heat-labile toxin producing ETEC (ETEC-lt) (40%) had higher rates of multidrug resistance than isolates producing both toxins (ETEC-lt-st) (21%), p<0.05. Only 10% of isolates were resistant to nalidixic acid and none to ciprofloxacin or cefotaxime. Ampicillin and sulfamethoxazole resistance were most often associated with blaTEM (69%) and sul2 genes (68%), respectively. Tetracycline resistance was associated with tet(A) (49%) and tet(B) (39%) genes. Azithromycin inhibitory diameters were ≤15 mm in 36% of isolates, with 5% of those presenting the mph(A) gene. Conclusions ETEC from Peruvian children are often resistant to older, inexpensive antibiotics, while remaining susceptible to ciprofloxacin, cephalosporins and furazolidone. Fluoroquinolones and azithromycin remain the drugs of choice for ETEC infections in Peru. However, further development of resistance should be closely monitored. PMID:26175267

Evaluating the antimicrobial potential of green cardamom essential oil focusing on quorum sensing inhibition of Chromobacterium violaceum.

PubMed

Abdullah; Asghar, Ali; Butt, Masood Sadiq; Shahid, Muhammad; Huang, Qingrong

2017-07-01

Spices are well known for their taste and flavor imparting properties. Green cardamom ( Elletaria cardamomum ), a herb spice belongs to family Zingiberaceae . In current study, GC-MS analysis of green cardamom essential oil (CEO) resulted in identification of twenty-six compounds with α -terpinyl acetate (38.4%), 1,8-cineole (28.71%), linalool acetate (8.42%), sabinene (5.21%), and linalool (3.97%) as major bioactive components. Present study also described the antimicrobial properties like zone of inhibition, minimum inhibitory concentration against microbial strains with special emphasis on quorum sensing inhibition. Disk diffusion assay showed that C. albicans and S. mutans were the most sensitive microorganisms followed by S. aureus , L. monocytogenes , B. cereus and S. typhimurium sensor strains, respectively. Whilst P. aeruginosa was found most resistant strain as CEO did not inhibited its growth. The minimum inhibitory concentration (MIC) values of CEO against tested strains were 10 ± 0.00 mg/mL against S. typhimurium , S. aureus and 5 ± 0.00 mg/mL against S. mutans , C. albicans strains, respectively. Regarding quorum sensing inhibition the tested concentrations 0.625 and 0.313 mg/mL of CEO inhibited violacein production with very little effect on growth of C. violaceum . Conclusively, study proved that quorum sensing inhibition values of CEO were much lower compared to MIC revealed values. Hence, cardamom bioactive constituents can effectively be used to develop novel antimicrobial drugs against conventional antibiotics.

Antimicrobial susceptibility and genotyping of Staphylococcus aureus isolates collected between 1986 and 2015 from ovine mastitis.

PubMed

Azara, Elisa; Piras, Maria Giovanna; Parisi, Antonio; Tola, Sebastiana

2017-06-01

In this research, 330 Staphylococcus aureus isolates, collected in Sardinia (Italy) in the period 1986-2015 from clinical ovine mastitis and used for the preparation of inactivated autogenous vaccines, were analyzed. Susceptibility to 12 antimicrobial agents was tested by disk diffusion, according to CLSI recommendations. Resistance genes were detected by PCR assays. The most of isolates (85.2%) were susceptible to all antimicrobials tested, suggesting that did not exist change of resistance over time. Two isolates were multidrug-resistant (MDR), one of them (isolate 1496) showed resistance to seven antibiotics including oxacillin and erythromycin. This MRSA harboured SCCmec type IV and the erm(C) gene. Isolates were characterized by spa typing and MLST. Isolates belonged to 29 spa types: t1773 (n=186), t2678 (n=53), t7754 (n=14), t1532 (n=5), t524 (n=5) and t6060 (n=4) were the most frequent spa types found in Sardinia. The majority of ovine isolates (t1773, t7754 and t1532) was grouped in MLST CC130 (n=205) followed by CC133 (n=57). MRSA 1496 was classified as t3896, ST1 and CC1, a clonal complex common in human and also reported in cattle and pig. This study suggests that the CC130/ST700/t1773 is the prevalent S. aureus lineage associated with ovine mastitis in Sardinia. Copyright © 2017 Elsevier B.V. All rights reserved.

Alkaloid (Meleagrine and Chrysogine) from endophytic fungi (Penicillium sp.) of Annona squamosa L.

PubMed

Yunianto, Prasetyawan; Rusman, Yudi; Saepudin, Endang; Suwarso, Wahyudi Priyono; Sumaryono, Wahono

2014-05-01

Several endophytic fungal strains from Srikaya plants (Annona squamosa L.) have been isolated and one of them was identified as Penicillium sp. Penicillium has been proven as an established source for a wide array of unique bioactive secondary metabolites that exhibit a variety of biological activities. The aim of this study is isolation of secondary metabolite from Penicillium, an endophytic of A. squamosa L. Penicillium sp. from endophytic of A. squamosa L. was fermented in Wicherham media. The whole extract from both liquid media and mycelium was partitioned by ethyl acetate and evaporated to obtain crude ethyl acetate extract. The ethyl acetate extract was then brokedown using column chromatography with silica as stationary phase and mixture of ethyl acetate/methanol (98%:2%) as mobile phase and then was separated by sephadex column. Structure elucidation of isolated compounds were mainly done by analysis of one and two dimensional NMR (Nuclear Magnetic Resonance) data and supported by HPLC (High performance Liquid Chromatography) and MS-TOF (Mass Spectrometer-Time of Flight). Isolated secondary metabolites were tested using in vitro assays for anticancer and antimicrobial activity. For anticancer activity, the metabolites were tested against breast cancer cells (MCF-7) using MTT assay, while for antimicrobial activity was performed using disk diffusion assays. From these physical, chemical and spectral evidences that the secondary metabolites were confirmed as Chrysogine and Meleagrine. Chrysogine and Meleagrine have no activity as anticancer and antimicrobial.

Antibacterial activity of jalapeño pepper (Capsicum annuum var. annuum) extract fractions against select foodborne pathogens.

PubMed

Bacon, Karleigh; Boyer, Renee; Denbow, Cynthia; O'Keefe, Sean; Neilson, Andrew; Williams, Robert

2017-05-01

Capsicum annuum fruits have been investigated for antimicrobial activity in a number of studies. Capsaicin or other cinnamic acid pathway intermediates are often suggested to be the antimicrobial component, however there are conflicting results. No research has specifically fractionated jalapeño pepper ( Capsicum annuum var. annuum ) extract to isolate and identify compound(s) responsible for inhibition. In this study, fractions were collected from jalapeño pepper extracts using reverse-phase HPLC and tested for antibacterial activity using the disk diffusion method. Following initial fractionation, two fractions (E and F) displayed antibacterial activity against all three pathogens ( p  >   .05). Commercial standards were screened to determine when they elude and it was found that capsaicin elutes at the same time as fraction E. Fractions E and F were subject to further HPLC fractionation and antibacterial analysis using two methods. The only fraction to display clear inhibition using both was fraction E1, inhibiting the growth of L. monocytogenes . Fraction E1 was analyzed using HPLC-MS. The resulting mass spectra revealed fraction E1 contained compounds belonging to a group of C. annuum -specific compounds known as capsianosides. Limited research is available on antibacterial activity of capsianosides, and a pure commercial standard is not available. In order to confirm the potential antimicrobial activity of the compound(s) isolated, methods need to be developed to isolate and purify capsianosides specifically from jalapeño peppers.

Antimicrobial activity of sodium hypochlorite-based irrigating solutions.

PubMed

Poggio, Claudio; Arciola, Carla Renata; Dagna, Alberto; Chiesa, Marco; Sforza, Dario; Visai, Livia

2010-09-01

The objective of the present study was the in vitro evaluation of the antimicrobial activity of three different NaOCl-based endodontic irrigating solutions: a 5.25% conventional sodium hypochlorite solution; and two new irrigating solutions, a 5.25% sodium hypochlorite solution with the addition of a proteolytic enzyme and a surfactant; and a 5.25% sodium hypochlorite gel with inorganic silicate. Enterococcus faecalis, Staphylococcus aureus and Streptococcus mutans strains were selected to evaluate the antimicrobial activity of the endodontic irrigating solutions by the agar disc diffusion test. Paper disks were saturated with each one of the tested solutions (at room temperature and pre-warmed at 45°C) and placed onto culture agar-plates pre-adsorbed with bacterial cells and further incubated for 24 h at 37°C. The growth inhibition zones around each irrigating solution were recorded and compared for each bacterial strain. The results were significantly different among the tested irrigating solutions: 5.25% sodium hypochlorite solution produced the highest inhibition areas; 5.25% sodium hypochlorite solution with a proteolytic enzyme and a surfactant, and 5.25% sodium hypochlorite gel with inorganic silicate showed the lowest zones of inhibition. Even if all tested irrigating solution possessed antibacterial activity versus all tested bacterial strains, 5.25% sodium hypochlorite solution with a proteolytic enzyme and a surfactant, and 5.25% sodium hypochlorite gel with inorganic silicate showed lower in vitro efficacy than 5.25% conventional sodium hypochlorite solution.

Expanded spectrum β-lactamase producing Escherichia coli isolated from chickens with colibacillosis in Egypt.

PubMed

El-Shazly, D A; Nasef, S A; Mahmoud, F F; Jonas, Daniel

2017-07-01

Throughout the world, expanded spectrum β-lactamases (ESBL) are increasing among clinical isolates of Enterobacteriaceae, both in humans and animals. Unfortunately, there is a paucity of data on ESBL or Ampicillin class C β-lactamase (AmpC) in Egypt, although antimicrobial consumption is high in this developing country. This study aims to characterize the resistance mechanisms to expanded spectrum cephalosporins among resistant veterinary Escherichia coli isolates in Egypt. We investigated 50 clinical multi-resistant E. coli strains isolated from 20 chicken farms for production of ESBL or AmpC. Antibiotic susceptibility was tested by Clinical and Laboratory Standards Institute (CLSI) disk diffusion and ESBL confirmatory tests. PCR and sequencing were performed to screen for plasmid mediated ESBL genes and genes encoding AmpC β-lactamases. All the isolates were phylogentically classified, investigated for harboring class 1 integrons, and genotyped by amplified fragment length polymorphism (AFLP). Three strains showed ESBL and 6 strains AmpC phenotypic patterns, respectively, with confirmed ESBL genes of blaTEM-57, blaSHV-12, blaCTX-M-14, and blaCMY-2 for AmpC producing strains. All ESBL strains belonged to phylogroup D with different clones isolated from different flocks, while most of the AmpC strains belonged to phylogroup B1 (4/6) and were assigned to the same genotype distributed in 2 different farms. Class 1 integrons were disseminated in 60% of all tested strains and in 100% of ESBL and AmpC strains. These results highlight the antimicrobial resistance problem in Egypt, caused in all probability by unwise use of antimicrobials in animal husbandry. The results call for a nationwide surveillance program to monitor antimicrobial resistance. © 2017 Poultry Science Association Inc.

[Statistical approach to evaluate the occurrence of out-of acceptable ranges and accuracy for antimicrobial susceptibility tests in inter-laboratory quality control program].

PubMed

Ueno, Tamio; Matuda, Junichi; Yamane, Nobuhisa

2013-03-01

To evaluate the occurrence of out-of acceptable ranges and accuracy of antimicrobial susceptibility tests, we applied a new statistical tool to the Inter-Laboratory Quality Control Program established by the Kyushu Quality Control Research Group. First, we defined acceptable ranges of minimum inhibitory concentration (MIC) for broth microdilution tests and inhibitory zone diameter for disk diffusion tests on the basis of Clinical and Laboratory Standards Institute (CLSI) M100-S21. In the analysis, more than two out-of acceptable range results in the 20 tests were considered as not allowable according to the CLSI document. Of the 90 participating laboratories, 46 (51%) experienced one or more occurrences of out-of acceptable range results. Then, a binomial test was applied to each participating laboratory. The results indicated that the occurrences of out-of acceptable range results in the 11 laboratories were significantly higher when compared to the CLSI recommendation (allowable rate < or = 0.05). The standard deviation indices(SDI) were calculated by using reported results, mean and standard deviation values for the respective antimicrobial agents tested. In the evaluation of accuracy, mean value from each laboratory was statistically compared with zero using a Student's t-test. The results revealed that 5 of the 11 above laboratories reported erroneous test results that systematically drifted to the side of resistance. In conclusion, our statistical approach has enabled us to detect significantly higher occurrences and source of interpretive errors in antimicrobial susceptibility tests; therefore, this approach can provide us with additional information that can improve the accuracy of the test results in clinical microbiology laboratories.

Gas Chromatography, GC/Mass Analysis and Bioactivity of Essential Oil from Aerial Parts of Ferulago trifida: Antimicrobial, Antioxidant, AChE Inhibitory, General Toxicity, MTT Assay and Larvicidal Activities

PubMed Central

Tavakoli, Saeed; Vatandoost, Hassan; Zeidabadinezhad, Reza; Hajiaghaee, Reza; Hadjiakhoondi, Abbas; Abai, Mohammad Reza; Yassa, Narguess

2017-01-01

Background: We aimed to investigate different biological properties of aerial parts essential oil of Ferulago trifida Boiss and larvicidal activity of its volatile oils from all parts of plant. Methods: Essential oil was prepared by steam distillation and analyzed by Gas chromatography and GC/Mass. Antioxidant, antimicrobial, cytotoxic effects and AChE inhibitory of the oil were investigated using DPPH, disk diffusion method, MTT assay and Ellman methods. Larvicidal activity of F. trifida essential oil against malaria vector Anopheles stephensi was carried out according to the method described by WHO. Results: In GC and GC/MS analysis, 58 compounds were identified in the aerial parts essential oil, of which E-verbenol (9.66%), isobutyl acetate (25.73%) and E-β-caryophyllene (8.68%) were main compounds. The oil showed (IC50= 111.2μg/ml) in DPPH and IC50= 21.5 mg/ml in the investigation of AChE inhibitory. Furthermore, the oil demonstrated toxicity with (LD50= 1.1μg/ml) in brine shrimp lethality test and with (IC50= 22.0, 25.0 and 42.55 μg/ml) on three cancerous cell lines (MCF-7, A-549 and HT-29) respectively. LC50 of stem, root, aerial parts, fruits, and flowers essential oils against larvae of An. stephensi were equal with 10.46, 22.27, 20.50, 31.93 and 79.87ppm respectively. In antimicrobial activities, essential oil was effective on all specimens except Escherichia coli, Aspergillus niger and Candida albicans. Conclusion: The essential oil showed moderate antioxidant activity, strong antimicrobial properties and good toxic effect in brine shrimp test and MTT assay on three cancerous cell lines. PMID:29322058

Gas Chromatography, GC/Mass Analysis and Bioactivity of Essential Oil from Aerial Parts of Ferulago trifida: Antimicrobial, Antioxidant, AChE Inhibitory, General Toxicity, MTT Assay and Larvicidal Activities.

PubMed

Tavakoli, Saeed; Vatandoost, Hassan; Zeidabadinezhad, Reza; Hajiaghaee, Reza; Hadjiakhoondi, Abbas; Abai, Mohammad Reza; Yassa, Narguess

2017-09-01

We aimed to investigate different biological properties of aerial parts essential oil of Ferulago trifida Boiss and larvicidal activity of its volatile oils from all parts of plant. Essential oil was prepared by steam distillation and analyzed by Gas chromatography and GC/Mass. Antioxidant, antimicrobial, cytotoxic effects and AChE inhibitory of the oil were investigated using DPPH, disk diffusion method, MTT assay and Ellman methods. Larvicidal activity of F. trifida essential oil against malaria vector Anopheles stephensi was carried out according to the method described by WHO. In GC and GC/MS analysis, 58 compounds were identified in the aerial parts essential oil, of which E-verbenol (9.66%), isobutyl acetate (25.73%) and E-β-caryophyllene (8.68%) were main compounds. The oil showed (IC 50 = 111.2μg/ml) in DPPH and IC 50 = 21.5 mg/ml in the investigation of AChE inhibitory. Furthermore, the oil demonstrated toxicity with (LD 50 = 1.1μg/ml) in brine shrimp lethality test and with (IC 50 = 22.0, 25.0 and 42.55 μg/ml) on three cancerous cell lines (MCF-7, A-549 and HT-29) respectively. LC 50 of stem, root, aerial parts, fruits, and flowers essential oils against larvae of An. stephensi were equal with 10.46, 22.27, 20.50, 31.93 and 79.87ppm respectively. In antimicrobial activities, essential oil was effective on all specimens except Escherichia coli , Aspergillus niger and Candida albicans. The essential oil showed moderate antioxidant activity, strong antimicrobial properties and good toxic effect in brine shrimp test and MTT assay on three cancerous cell lines.

Prevalence of antimicrobial-resistant Escherichia coli from raw vegetables in Lebanon.

PubMed

Faour-Klingbeil, Dima; Kuri, Victor; Fadlallah, Sukayna; Matar, Ghassan M

2016-04-28

Fresh produce has been implicated in a number of documented outbreaks of foodborne illness caused by bacteria, viruses, and parasites. Shiga toxin-producing Escherichia coli (STEC) have been detected on vegetables, raising concerns about the prevalence of E. coli contamination in produce, which can take place at various points from farm to fork. This study aimed to detect the presence of STEC and multidrug-resistant (MDR) E. coli on fresh vegetables and water from different sources along the fresh produce supply chain in Lebanon. E. coli isolates (n = 60) were group serotyped using trivalent antisera (trivalent 1 [O111+O55+O26], trivalent 2 [O86+O119+O127], trivalent 3 [O125; O126; O128], and trivalent 4 [O114+O124+O142]) and tested for stx1 and stx2 genes by polymerase chain reaction (PCR) assay. Resistance to antimicrobial agents was determined using the disk diffusion method. The virulence genes stx1 and stx2 were not detected in any of the isolates. However, 60% of the isolates were MDR and predominantly observed in trivalent 2 (32%). It is postulated that the inadequate post-harvest washing contributed to transmission of antimicrobial-resistant E. coli at wholesale and retail levels. Fresh vegetables harbor MDR E. coli and their consumption poses risks of increasing the reservoir of antimicrobial resistance in the intestines of the Lebanese population. Greater emphasis should be placed on vigilant sanitation measures at the consumption level, and effective national risk mitigation strategies are crucial to minimize fecal contamination in the early stages of production, particularly in the post-harvest washing processes.

Antimicrobial susceptibility of travel-related Salmonella enterica serovar Typhi isolates detected in Switzerland (2002-2013) and molecular characterization of quinolone resistant isolates.

PubMed

Nüesch-Inderbinen, Magdalena; Abgottspon, Helga; Sägesser, Grethe; Cernela, Nicole; Stephan, Roger

2015-05-12

Typhoid fever is an acute, invasive, and potentially fatal systemic infection caused by Salmonella enterica subspecies enterica serotype Typhi (S. Typhi). Drug resistance to antimicrobials such as ciprofloxacin is emerging in developing countries, threatening the efficacy of treatment of patients in endemic regions as well as of travellers returning from these countries. We compared the antimicrobial resistance profiles of 192 S. Typhi isolated from patients over a time span of twelve years. Susceptibility testing was done by the disk diffusion method. A representative selection of isolates (n = 41) was screened by PCR for mutations in the quinolone resistance-determining regions (QRDRs) of the gyrA and parC genes and all 192 isolates were screened for plasmid-mediated quinolone resistance (PMQR) genes. Multilocus sequence typing (MLST) was used to investigate the sequence type of isolates from patients with a known history of international travel. Resistance rates for nalidixic acid increased from 20 % to 66.7 % between 2002 and 2013. Resistance to ciprofloxacin was detected in 55.6 % of the isolates by 2013. Ciprofloxacin resistance was predominantly associated with the triple substitutions Ser83 → Phe and Asp87 → Asn in GyrA and Ser80 → Ile in ParC. The plasmid-mediated resistance gene qnrS1 was detected in two isolates. Sequence type ST1 was associated with the Indian subcontinent, while ST2 was distributed internationally. Multidrug resistance was noted for 11.5 % of the isolates. Fluoroquinolone resistant S. Typhi constitute a serious public health concern in endemic areas as well as in industrialized countries. Increased surveillance of global patterns of antimicrobial resistance is necessary and the control of resistant strains is of the utmost importance to maintain treatment options.

Genetic Diversity and Antibiotic Resistance of Escherichia coli Isolates from Different Leafy Green Production Systems.

PubMed

Jongman, Mosimanegape; Korsten, Lise

2016-11-01

Foodborne disease outbreaks linked to contaminated irrigation water and fresh produce are a public health concern. The presence of Escherichia coli isolates from irrigation water and leafy green vegetables in different food production systems (large commercial farms, small-scale farms, and homestead gardens) was investigated. The prevalence of antibiotic resistance and virulence in these isolates was further assessed, and links between water source and irrigated crops were identified using antimicrobial and genotypic analyses. Presumptive E. coli isolates were identified by matrix-assisted laser desorption ionization time-of-flight mass spectroscopy, and identities were confirmed by PCR using the uidA gene. Antimicrobial susceptibility was evaluated with the Kirby Bauer disk diffusion test; the presence of virulence genes was determined with enterobacterial repetitive intergenic consensus PCR assays. Of the 130 E. coli isolates from water (n =60) and leafy green vegetables (n =70), 19 (14.6%) were resistant to one antibiotic (tetracycline) and 92 (70.7%) were resistant to various antibiotics (including ampicillin, cefoxitin, and nalidixic acid). All E. coli isolates were susceptible to ceftriaxone and gentamicin. The virulence gene stx 2 was detected in E. coli isolates from irrigation water (8 [13.3%] of 60 isolates) and cabbages (3 [7.5%] of 40), but the virulence genes eae and stx 1 were not detected in any tested isolates from irrigation water and fresh produce samples. The prevalence of multidrug-resistant E. coli was lower in isolates from GLOBALG.A.P.-certified farms than in isolates from noncertified commercial and small-scale farms and homestead gardens. A link between the E. coli isolates from irrigation water sources and leafy green vegetables was established with phenotypic (antimicrobial) and genotypic (DNA fingerprinting) analyses. However, a link between virulence genes and the prevalence of antimicrobial resistance could not be established.

[Neisseria gonorrhoeae: antimicrobial resistance and study of population dynamics. Situation in Barcelona in 2011].

PubMed

Serra-Pladevall, Judit; Barberá-Gracia, María Jesús; Roig-Carbajosa, Glòria; Juvé-Saumell, Rosa; Gonzalez-Lopez, Juan José; Bartolomé-Comas, Rosa; Andreu-Domingo, Antònia

2013-11-01

Due to the high rates of antimicrobial resistance to certain antibiotics, together with the emergence of Neisseria gonorrhoeae (NG) with reduced susceptibility and resistance to third-generation cephalosporins, gonococcal infection is becoming a public health problem. The objectives of the study were: To keep track of the antimicrobial susceptibility of NG strains obtained from January to August 2011. To study the population dynamics. The antimicrobial susceptibility was studied by disk-diffusion and E-test. The genotyping was performed by NG-MAST method. Of a total of 100strains studied, 59% showed intermediate sensitivity to penicillin and 9% were resistant. According to EUCAST, we detected 3gonococci with reduced susceptibility to ceftriaxone, 10 to cefixime and one with high-level resistance to both antibiotics (MIC 1.5μg/ml). MIC50 and MIC90 to cefixime were 0.016 and 0.125μg/ml, respectively, whereas to ceftriaxone they were <0.016 and 0.064μg/ml, respectively. Almost all (99%) of the strains were resistant to doxycycline, 53% to ciprofloxacin, 3% to azithromycin, and 1% to spectinomycin. The most prevalent ST was ST1407, predominantly associated to resistance or reduced sensitivity to cephalosporins or macrolides. NG has developed significant rates of resistance to various antibiotics. One strain has been detected with high level resistance to third generation cephalosporins, and several strains with reduced susceptibility. An increase in MIC50 and MIC90 to these antibiotics has also been observed. NG population structure remains stable and common to the rest of Europe, although two new ST (ST7226 and ST7227) have been identified that could be selected and acquire high levels of resistance to cephalosporins. Copyright © 2012 Elsevier España, S.L. All rights reserved.

Diversity and antimicrobial susceptibility profiling of staphylococci isolated from bovine mastitis cases and close human contacts.

PubMed

Schmidt, T; Kock, M M; Ehlers, M M

2015-09-01

The objectives of this study were to examine the diversity of Staphylococcus spp. recovered from bovine intramammary infections and humans working in close contact with the animals and to evaluate the susceptibility of the staphylococcal isolates to different antimicrobials. A total of 3,387 milk samples and 79 human nasal swabs were collected from 13 sampling sites in the KwaZulu-Natal province of South Africa. In total, 146 Staph. aureus isolates and 102 coagulase-negative staphylococci (CNS) were recovered from clinical and subclinical milk samples. Staphylococcusaureus was isolated from 12 (15.2%) of the human nasal swabs and 95 representative CNS were recovered for further characterization. The CNS were identified using multiplex-PCR assays, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and tuf gene sequencing. Seven Staphylococcus spp. were identified among the CNS of bovine origin, with Staph.chromogenes (78.4%) predominating. The predominant CNS species recovered from the human nasal swabs was Staph.epidermidis (80%) followed by Staph.chromogenes (6.3%). The antimicrobial susceptibility of all staphylococcal isolates was evaluated using disk diffusion and was supplemented by screening for specific antimicrobial resistance genes. Ninety-eight (67.1%) Staph.aureus isolates of bovine origin were pansusceptible; 39 (26.7%) isolates were resistant to a single class, and 7 (4.8%) isolates were resistant to 2 classes of antimicrobials. Two Staph. aureus (1.4%) isolates were multidrug-resistant. Resistance to penicillin was common, with 28.8% of the bovine and 75% of the human Staph. aureus isolates exhibiting resistance. A similar observation was made with the CNS, where 37.3% of the bovine and 89.5% of the human isolates were resistant to penicillin. Multidrug-resistance was common among the human CNS, with 39% of the isolates exhibiting resistance to 3 or more classes of antimicrobials. The antimicrobial susceptibility results suggest that resistance among staphylococci causing bovine intramammary infections in South Africa is uncommon and not a significant cause for concern. In contrast, antimicrobial resistance was frequently observed in staphylococcal isolates of human origin, highlighting a possible reservoir of resistance genes. Continued monitoring of staphylococcal isolates is warranted to monitor changes in the susceptibility of isolates to different classes of antimicrobials. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Can disc diffusion susceptibility tests assess the antimicrobial activity of engineered nanoparticles?

NASA Astrophysics Data System (ADS)

Kourmouli, Angeliki; Valenti, Marco; van Rijn, Erwin; Beaumont, Hubertus J. E.; Kalantzi, Olga-Ioanna; Schmidt-Ott, Andreas; Biskos, George

2018-03-01

The use of disc diffusion susceptibility tests to determine the antibacterial activity of engineered nanoparticles (ENPs) is questionable because their low diffusivity practically prevents them from penetrating through the culture media. In this study, we investigate the ability of such a test, namely the Kirby-Bauer disc diffusion test, to determine the antimicrobial activity of Au and Ag ENPs having diameters from 10 to 40 nm on Escherichia coli cultures. As anticipated, the tests did not show any antibacterial effects of Au nanoparticles (NPs) as a result of their negligible diffusivity through the culture media. Ag NPs on the other hand exhibited a strong antimicrobial activity that was independent of their size. Considering that Ag, in contrast to Au, dissolves upon oxidation and dilution in aqueous solutions, the apparent antibacterial behavior of Ag NPs is attributed to the ions they release. The Kirby-Bauer method, and other similar tests, can therefore be employed to probe the antimicrobial activity of ENPs related to their ability to release ions rather than to their unique size-dependent properties. [Figure not available: see fulltext.

SNOW LINES AS PROBES OF TURBULENT DIFFUSION IN PROTOPLANETARY DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Owen, James E.

2014-07-20

Sharp chemical discontinuities can occur in protoplanetary disks, particularly at ''snow lines'' where a gas-phase species freezes out to form ice grains. Such sharp discontinuities will diffuse out due to the turbulence suspected to drive angular momentum transport in accretion disks. We demonstrate that the concentration gradient—in the vicinity of the snow line—of a species present outside a snow line but destroyed inside is strongly sensitive to the level of turbulent diffusion (provided the chemical and transport timescales are decoupled) and provides a direct measurement of the radial ''Schmidt number'' (the ratio of the angular momentum transport to radial turbulentmore » diffusion). Taking as an example the tracer species N{sub 2}H{sup +}, which is expected to be destroyed inside the CO snow line (as recently observed in TW Hya) we show that ALMA observations possess significant angular resolution to constrain the Schmidt number. Since different turbulent driving mechanisms predict different Schmidt numbers, a direct measurement of the Schmidt number in accretion disks would allow inferences to be made about the nature of the turbulence.« less

Evaluation of different methods to detect methicillin resistance in Staphylococcus aureus (MRSA).

PubMed

Alipour, Farzad; Ahmadi, Malahat; Javadi, Shahram

2014-01-01

The studies suggest that dogs living with human are potential risk of becoming MRSA carrier and increased risk of infections caused by MRSA. Phenotypic methods to detect methicillin resistance in Staphylococcus aureus (MRSA) are inadequate. The objective of the present study was to determine methicillin resistance in S. aureus by phenotypic susceptibility test (oxacillin disk diffusion, cefoxitin disk diffusion, oxacillin screen agar) and molecular methods (PCR as a gold standard) and the latex agglutination test for the detection of PBP2a and to evaluate the results of these tests for its sensitivity and specificity. A total of 100 swab samples were taken from muzzle site, in more contact with human, of dogs and MRSA were isolated. Oxacillin (1 μg), cefoxitin (30 μg) disk diffusion and oxacillin screen agar method were used. The isolates were also subjected to latex agglutination test for detection of PBP2a and PCR to detect mecA gene. By PCR 37% of isolates show the presence of mecA. Latex agglutination was found to be the most sensitive (97.29%) and cefoxitin disk diffusion to be the most specific (96.82%) tests for detection of MRSA. Our finding showed that combining oxacillin screen agar or cefoxitin disk diffusion with latex agglutination improves sensitivity and specificity to detect methicillin resistance S. aureus (MRSA) isolates. Copyright © 2014 King Saud Bin Abdulaziz University for Health Sciences. Published by Elsevier Ltd. All rights reserved.

[Molecular study of methicillin-resistant Staphylococcus haemolyticus in a Mexican hospital].

PubMed

Castro, Natividad; Loaiza-Loeza, María Salomé; Calderón-Navarro, Amparo; Sánchez, Alejandro; Silva-Sánchez, Jesús

2006-01-01

To perform the molecular characterization of methicillin-resistant Staphylococcus haemolyticus (MRSH) clinical isolates from patients in a Mexican hospital. Sixty three Staphylococcus ssp. isolates collected from September 2000 to October 2002 were analyzed. Antimicrobial susceptibility was determined by disk diffusion method and the presence of the mecA gene was detected by PCR technique. Isolates characterization was carried out by pulsed field gel electrophoresis (PFGE). The frequency of S. haemolyticus was 25.5% (18 of 63 clinical isolates), all S. haemolyticus isolates were methicillin-resistant and they were positive for the mecA gene. A major pattern (A) with 8 subtypes was identified. This clone was distributed during the 20 months period. Most of them were isolated from the surgery (55%) and pediatric services (27.5%). The methicillin-resistant S. haemolyticus permanence as pathogen in this hospital, suggest the implementation of control programs in order to decrease the prevalence of this multiresistant pathogen.

Pyocyanine Biosynthetic Genes in Clinical and Environmental Isolates of Pseudomonas aeruginosa and Detection of Pyocyanine’s Antimicrobial Effects with or without Colloidal Silver Nanoparticles

PubMed Central

Nowroozi, Jamileh; Akhavan Sepahi, Abbas; Rashnonejad, Afrooz

2012-01-01

Objective: Pyocyanine plays an important role in the pathogenesis of Pseudomonas aeruginosa, (P. aeruginosa) and is known to have inhibitory and bactericidal effects. This study has aimed to detect the phenazine biosynthetic operon (phz ABCDEFG) and two phenazine modifying genes (phzM and phzS) by polymerase chain reaction (PCR) and detection of its possible protein bands by sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE). The antimicrobial effects of pyocyanine alone and mixed with colloidal silver nanoparticles were studied. Materials and Methods: In this descriptive study, clinical and environmental species of P. aeruginosa were isolated by thioglycollate medium culture and cetrimide agar, respectively. The existence of a phenazine biosynthetic operon and two phenazine modifying genes as well as their protein products were confirmed by PCR and SDS-PAGE, respectively. Pyocyanine was extracted with chloroform and its antimicrobial effects against bacteria such as; Escherichia coli (E. coli), P. aeruginosaand Staphylococcus aureus (S. aureus) bacteria and yeast Candida albicans (C. albicans) were tested using well, spot and disk diffusion methods. Results: In this study, 3 out of 48 clinical strains were unable to produce pyocyanine on cetrimide and Mueller Hinton (MH) agar. Two strains did not have phenazine modifying gene bands. Another strain did not have the possible protein band of the phzM gene. Pyocyanine had antimicrobial effects against the microbial strains, which increased in the presence of silver nanoparticles. Conclusion: According to the results of the present study, some P. aeruginosa strains are unable to produce pyocyanine due to the absence of the phzM or phzS genes. Therefore, these genes have an important role in pyocyanine production in P. aeruginosa. Pyocyanine shows synergistic antimicrobial effects in the presence of silver nanoparticles against microbial strains. PMID:23626932

Antimicrobial susceptibility, virulence genes, and randomly amplified polymorphic DNA analysis of Staphylococcus aureus recovered from bovine mastitis in Ningxia, China.

PubMed

Wang, Dong; Zhang, Limei; Zhou, Xuezhang; He, Yulong; Yong, Changfu; Shen, Mingliang; Szenci, Otto; Han, Bo

2016-12-01

Staphylococcus aureusis the leading pathogen involved inbovine mastitis, but knowledgeabout antimicrobial resistance, virulence factors, and genotypes of Staphylococcus aureus resulting in bovine mastitis in Ningxia, China, is limited. Therefore, antimicrobial susceptibility, virulence gene, and randomly amplified polymorphic DNA (RAPD) analyses of Staph. aureus were carried out. A total of 327 milk samples from cows with clinical and subclinical mastitis in 4 regions of Ningxia were used for the isolation and identification of pathogens according to phenotypic and molecular characteristics. Antimicrobial susceptibility against 22 antimicrobial agents was determined by disk diffusion. The presence of 8 virulence genes in Staph. aureus isolates was tested by PCR. Genotypes of isolates were investigated based on RAPD. Results showed that 35 isolates obtained from mastitis milk samples were identified as Staph. aureus. The isolates were resistant to sulfamethoxazole (100%), penicillin G (94.3%), ampicillin (94.3%), erythromycin (68.6%), azithromycin (68.6%), clindamycin (25.7%), amoxicillin (11.4%), and tetracycline (5.7%). All of the isolates contained one or more virulence genes with average (standard deviation) of 6.6±1.6. The most prevalent virulence genes were hlb (97.1%), followed by fnbpA, hla, coa (94.3% each), nuc (85.7%), fnbpB (80%), clfA (77.1%), and tsst-1 (40%). Nine different gene patterns were found and 3 of them were the dominant gene combinations (77.1%). Staphylococcus aureus isolates (n=35) were divided into 6 genotypes by RAPD tying, the genotypes III and VI were the most prevalent genotypes. There was greatvariation in genotypes of Staph. aureus isolates, not only among different farms, but also within the same herd in Ningxia province. The study showed a high incidence of Staph. aureus with genomic variation of resistance genes, which is matter of great concern in public and animal health in Ningxia province of China. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Regression analysis and categorical agreement of fluconazole disk zone diameters and minimum inhibitory concentration by broth microdilution of clinical isolates of Candida.

PubMed

Aggarwal, P; Kashyap, B

2017-06-01

Rampant use of fluconazole in Candida infections has led to predominance of less susceptible non-albicans Candida over Candida albicans. The aim of the study was to determine if zone diameters around fluconazole disk can be used to estimate the minimum inhibitory concentration (MIC) for clinical isolates of Candida species and vice versa. Categorical agreement between the Clinical & Laboratory Standards Institute (CLSI) recommended disk diffusion and CLSI broth microdilution method was sought for. Antifungal susceptibility testing by disk diffusion and Broth microdilution was done as per CLSI document M44-S3 and CLSI document M27-S4 for Candida isolates respectively. Regression analysis correlating zone diameters to MIC value was done. Pearson's correlation coefficient was calculated to determine correlation between disk zone diameters and MICs. Candida albicans (33.3%) was clearly outnumbered by other non-albicans species predominantly Candida tropicalis (42.5%) and Candida glabrata (18.4%). Ten percent of the strains were resistant to fluconazole by disk diffusion and 13% by broth microdilution. MIC range for Candida albicans and Candida tropicalis ranged from≤0.25-64μg/ml while that of Candida glabrata ranged from≤0.25-128μg/ml. Categorical agreement between disk diffusion and broth microdilution was 86.8%. Pearson's coefficient of correlation was -0.5975 indicating moderate negative correlation between the two variables. Zone sizes can be used to estimate the MIC values, although with limited accuracy. There should be a constant effort to upgrade the guidelines in view of new clinical data, and laboratories should make an active effort to incorporate them. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Inefficient volatile loss from the Moon-forming disk: Reconciling the giant impact hypothesis and a wet Moon

NASA Astrophysics Data System (ADS)

Nakajima, Miki; Stevenson, David J.

2018-04-01

The Earth's Moon is thought to have formed from a circumterrestrial disk generated by a giant impact between the proto-Earth and an impactor approximately 4.5 billion years ago. Since this impact was energetic, the disk would have been hot (4000-6000 K) and partially vaporized (20-100% by mass). This formation process is thought to be responsible for the geochemical observation that the Moon is depleted in volatiles (e.g., K and Na). To explain this volatile depletion, some studies suggest the Moon-forming disk was rich in hydrogen, which was dissociated from water, and it escaped from the disk as a hydrodynamic wind accompanying heavier volatiles (hydrodynamic escape). This model predicts that the Moon should be significantly depleted in water, but this appears to contradict some of the recently measured lunar water abundances and D/H ratios that suggest that the Moon is more water-rich than previously thought. Alternatively, the Moon could have retained its water if the upper parts (low pressure regions) of the disk were dominated by heavier species because hydrogen would have had to diffuse out from the heavy-element rich disk, and therefore the escape rate would have been limited by this slow diffusion process (diffusion-limited escape). To identify which escape the disk would have experienced and to quantify volatiles loss from the disk, we compute the thermal structure of the Moon-forming disk considering various bulk water abundances (100-1000 ppm) and mid-plane disk temperatures (2500-4000 K). Assuming that the disk consists of silicate (SiO2 or Mg2SiO4) and water and that the disk is in the chemical equilibrium, our calculations show that the upper parts of the Moon-forming disk are dominated by heavy atoms or molecules (SiO and O at Tmid > 2500- 2800 K and H2O at Tmid < 2500- 2800 K) and hydrogen is a minor species. This indicates that hydrogen escape would have been diffusion-limited, and therefore the amount of lost water and hydrogen would have been small compared to the initial abundance assumed. This result indicates that the giant impact hypothesis can be consistent with the water-rich Moon. Furthermore, since the hydrogen wind would have been weak, the other volatiles would not have escaped either. Thus, the observed volatile depletion of the Moon requires another mechanism.

[Methicillin resistance detection in Staphylococcus aureus: comparison between conventional methods and MRSA-Screen latex agglutination technique].

PubMed

Soloaga, R; Corso, A; Gagetti, P; Faccone, D; Galas, M

2004-01-01

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen that has emerged over the last four decades, causing both nosocomial and community-acquired infections. Rapid and accurate detection of methicillin resistance in S. aureus is important for the use of appropriate antimicrobial therapy and for the control of nosocomial spread of MRSA strains. We evaluated the efficiency of conventional methods for detection of methicillin resistance such as the disk diffusion, agar dilution, oxacillin agar screen test, and the latex agglutination test MRSA-Screen latex, in 100 isolates of S. aureus, 79 mecA positive and 21 mecA negative. The MRSA-Screen latex (Denka Seiken, Niigata, Japón), is a latex agglutination method that detects the presence of PLP-2a, product of mecA gene in S. aureus. The PCR of the mecA gene was used as the "gold standard" for the evaluation of the different methods tested. The percentages of sensitivity and specificity were as follows: disk difusión 97 and 100%, agar dilution 97 and 95%, oxacillin agar screen test 100 and 100%, and MRSA-Screen latex, 100 and 100 %. All methods presented high sensitivity and specificity, but MRSA-Screen latex had the advantage of giving a reliable result, equivalent to PCR, in only 15 minutes.

Diffusion of Helium Isotopes in Silicate Glasses and Minerals: Implications for Petrogenesis and Geochronology.

DTIC Science & Technology

1989-06-01

the Chemistry Department, and the WHOI Education Office for providing financial support and a nice place to work. Parts of this research was funded by...and erosion studies is unknown. c 1.5 OBJECTIVES The objectives of this research are 1) to quantify the diffusive mobility of helium isotopes in...specifically tailored for the diffusion experiments. Data is recorded on a hard disk and on paper , and is automatically backed up to floppy disks

Streptococcus suis infection: a series of 41 cases from Chiang Mai University Hospital.

PubMed

Wangkaew, Suparaporn; Chaiwarith, Romanee; Tharavichitkul, Prasit; Supparatpinyo, Khuanchai

2006-06-01

The objectives of this study were (1) to assess the clinical manifestations, treatment, and outcome of Streptococcus suis infection in adult patients in northern Thailand, (2) to evaluate the anti-microbial sensitivity pattern and (3) to determine the predicting factors of high mortality rate. A retrospective study was conducted at Chiang Mai University Hospital from May 2000 to December 2002. Anti-microbial susceptibility test was performed by agar disk diffusion and the minimal inhibitory concentration (MIC) by E-test. Forty-one patients (32 men and nine women, mean age 51 years) with S. suis infection were identified. Three patients had a history of exposure to pig or pork and one patient had a history of raw beef consumption. Clinical manifestations included infective endocarditis, meningitis, sepsis, spondylodiscitis, and endophthalmitis in 16, 13, 10, 1, and 1 patients, respectively. The overall mortality rate was 19.5%. On univariate analysis, low serum albumin, high serum total bilirubin, low platelet, and rapid onset of illness were significantly correlated with high mortality rate. All isolates were sensitive to penicillin (mean MIC90=0.027 microg/ml). S. suis infection is not uncommon in northern Thailand. High suspicion and early detection are important and could lead to the successful treatment.

Prevalence of antibiotic resistance genes in the bacterial flora of integrated fish farming environments of Pakistan and Tanzania.

PubMed

Shah, Syed Q A; Colquhoun, Duncan J; Nikuli, Hamisi L; Sørum, Henning

2012-08-21

The use of a wide variety of antimicrobials in human and veterinary medicine, including aquaculture, has led to the emergence of antibiotic resistant pathogens. In the present study, bacteria from water, sediments, and fish were collected from fish farms in Pakistan and Tanzania with no recorded history of antibiotic use. The isolates were screened for the presence of resistance genes against various antimicrobials used in aquaculture and animal husbandry. Resistant isolates selected by disk diffusion and genotyped by Southern hybridization were further screened by polymerase chain reaction (PCR) and amplicon sequencing. The prominent resistance genes identified encoded tetracycline [tetA(A) and tetA(G)], trimethoprim [dfrA1, dfrA5, dfrA7, dfrA12, and dfrA15], amoxicillin [bla(TEM)], streptomycin [strA-strB], chloramphenicol [cat-1], and erythromycin resistance [mefA]. The int1 gene was found in more than 30% of the bacterial isolates in association with gene cassettes. MAR indices ranged from 0.2 to 1. The bla(NDM-1) gene was not identified in ertapenem resistant isolates. It is hypothesized that integrated fish farming practices utilizing domestic farm and poultry waste along with antibiotic residues from animal husbandry may have contributed to a pool of resistance genes in the aquaculture systems studied.

Identification and antimicrobial suceptibility profile of bacteria causing bovine mastitis from dairy farms in Pelotas, Rio Grande do Sul.

PubMed

Freitas, C H; Mendes, J F; Villarreal, P V; Santos, P R; Gonçalves, C L; Gonzales, H L; Nascente, P S

2018-01-08

Mastitis is an inflammatory process of the udder tissue caused mainly by the bacteria Staphylococcus aureus. The indiscriminate use of antibiotics fosters conditions that favor the selection of resistant microorganisms, suppressing at the same time susceptible forms, causing a serious problem in dairy cattle. Given the importance in performing an antibiogram to select the most adequate antimicrobial therapy, the aim of this study was to identify bacteria isolated from cow's milk with mastitis, in dairy farms situated in the city of Pelotas, Rio Grande do Sul, and to determinate the susceptibility profile of these isolates against the antibiotics used to treat this illness. A total of 30 isolates of Staphylococcus spp., were selected from milk samples from the udder quarters with subclinical mastitis whose species were identified through the Vitek system. The susceptibility profile was performed by the disk diffusion assay, against: ampicillin, amoxicillin, bacitracin, cephalexin, ceftiofur, enrofloxacin, gentamicin, neomycin, norfloxacin, penicillin G, tetracycline and trimethoprim. In the antibiogram, 100.0% of the isolates were resistant to trimethoprim and 96.7% to tetracycline and neomycin, three strains of Staphylococcus spp., (10.0%) presented resistance to the 12 antibiotics tested and 24 (80.0%) to at least eight. These results showed the difficulty in treating mastitis, due to the pathogens' resistance.

Essential Oils from Different Plant Parts of Eucalyptus cinerea F. Muell. ex Benth. (Myrtaceae) as a Source of 1,8-Cineole and Their Bioactivities

PubMed Central

Silva, Sayonara Mendes; Abe, Simone Yae; Murakami, Fábio Seigi; Frensch, Gustavo; Marques, Francisco A.; Nakashima, Tomoe

2011-01-01

Eucalyptus cinerea, known as silver dollar tree, has few descriptions in traditional medicine. Chemical composition and antimicrobial properties of the essential oils of leaves, flowers and fruits, collected seasonally, were determined by GC/MS and disk diffusion/MIC, respectively. 1,8-Cineole was the main compound, particularly in fresh leaves—Spring (74.98%), dried leaves—Spring (85.32%), flowers—Winter (78.76%) and fruits—Winter (80.97%). Other compounds were found in the aerial parts in all seasons: α-pinene (2.41% to 10.13%), limonene (1.46% to 4.43%), α-terpineol (1.73% to 11.72%), and α-terpinyl acetate (3.04% to 20.44%). The essential oils showed antimicrobial activities against bacteria and yeasts, with the best results being found for the dried autumn and winter leaves oils (MIC < 0.39 mg/mL) against Streptococcus pyogenes. For the other tested microorganisms the following MIC results were found: Staphylococcus aureus— Dried leaves oil from summer (0.78 mg/mL), Pseudomonas aeruginosa—Flowers oil from autumn and fruits oil from winter (1.56 mg/mL) and Candida albicans—Flowers oil from autumn and fruits oils from winter and spring (0.78 mg/mL). PMID:26791641

Agreement Assessment of Tigecycline Susceptibilities Determined by the Disk Diffusion and Broth Microdilution Methods among Commonly Encountered Resistant Bacterial Isolates: Results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) Study, 2008 to 2010

PubMed Central

Liu, Jien-Wei; Ko, Wen-Chien; Huang, Cheng-Hua; Liao, Chun-Hsing; Lu, Chin-Te; Chuang, Yin-Ching; Tsao, Shih-Ming; Chen, Yao-Shen; Liu, Yung-Ching; Chen, Wei-Yu; Jang, Tsrang-Neng; Lin, Hsiu-Chen; Chen, Chih-Ming; Shi, Zhi-Yuan; Pan, Sung-Ching; Yang, Jia-Ling; Kung, Hsiang-Chi; Liu, Chun-Eng; Cheng, Yu-Jen; Chen, Yen-Hsu; Lu, Po-Liang; Sun, Wu; Wang, Lih-Shinn; Yu, Kwok-Woon; Chiang, Ping-Cherng; Lee, Ming-Hsun; Lee, Chun-Ming; Hsu, Gwo-Jong

2012-01-01

The Tigecycline In Vitro Surveillance in Taiwan (TIST) study, initiated in 2006, is a nationwide surveillance program designed to longitudinally monitor the in vitro activity of tigecycline against commonly encountered drug-resistant bacteria. This study compared the in vitro activity of tigecycline against 3,014 isolates of clinically important drug-resistant bacteria using the standard broth microdilution and disk diffusion methods. Species studied included methicillin-resistant Staphylococcus aureus (MRSA; n = 759), vancomycin-resistant Enterococcus faecium (VRE; n = 191), extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (n = 602), ESBL-producing Klebsiella pneumoniae (n = 736), and Acinetobacter baumannii (n = 726) that had been collected from patients treated between 2008 and 2010 at 20 hospitals in Taiwan. MICs and inhibition zone diameters were interpreted according to the currently recommended U.S. Food and Drug Administration (FDA) criteria and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. The MIC90 values of tigecycline against MRSA, VRE, ESBL-producing E. coli, ESBL-producing K. pneumoniae, and A. baumannii were 0.5, 0.125, 0.5, 2, and 8 μg/ml, respectively. The total error rates between the two methods using the FDA criteria were high: 38.4% for ESBL-producing K. pneumoniae and 33.8% for A. baumannii. Using the EUCAST criteria, the total error rate was also high (54.6%) for A. baumannii isolates. The total error rates between these two methods were <5% for MRSA, VRE, and ESBL-producing E. coli. For routine susceptibility testing of ESBL-producing K. pneumoniae and A. baumannii against tigecycline, the broth microdilution method should be used because of the poor correlation of results between these two methods. PMID:22155819

A Multiwavelength Exploration of the Grand Design Spiral M83: Diffuse X-ray Emission

NASA Astrophysics Data System (ADS)

Kuntz, K. D.; Long, K. S.; Blair, W. P.; Plucinsky, P. P.; Soria, R.; Winkler, P. F.

2013-01-01

We have obtained a series of deep X-ray images of the nearby galaxy M83, with a total exposure 729 ksec with the Chandra ACIS-S array. Since the bulk of the X-ray emitting disk falls within the BI chip, these observations allow a detailed study of the soft diffuse emission in the disk. Most of the diffuse emission is related to star-formation regions and must be powered by supernovae and stellar winds, though the amount of emission due to identifiable SNR is only a few percent. The relation between the spectral shape and surface brightness that was seen in M101 suggests that the properties of the X-ray emission in spiral disks are shaped by the local hot gas production rate (traced by the local star-formation rate) or the disk mid-plane pressure, but it is unclear which physical mechanism dominates. To illuminate this problem, we will compare M83 with the previous Chandra studies of M101 and M33.

Jet Launching in Resistive GR-MHD Black Hole–Accretion Disk Systems

NASA Astrophysics Data System (ADS)

Qian, Qian; Fendt, Christian; Vourellis, Christos

2018-05-01

We investigate the launching mechanism of relativistic jets from black hole sources, in particular the strong winds from the surrounding accretion disk. Numerical investigations of the disk wind launching—the simulation of the accretion–ejection transition—have so far almost only been done for nonrelativistic systems. From these simulations we know that resistivity, or magnetic diffusivity, plays an important role for the launching process. Here we extend this treatment to general relativistic magnetohydrodynamics (GR-MHD), applying the resistive GR-MHD code rHARM. Our model setup considers a thin accretion disk threaded by a large-scale open magnetic field. We run a series of simulations with different Kerr parameter, field strength, and diffusivity level. Indeed, we find strong disk winds with, however, mildly relativistic speed, the latter most probably due to our limited computational domain. Further, we find that magnetic diffusivity lowers the efficiency of accretion and ejection, as it weakens the efficiency of the magnetic lever arm of the disk wind. As a major driving force of the disk wind we disentangle the toroidal magnetic field pressure gradient; however, magnetocentrifugal driving may also contribute. Black hole rotation in our simulations suppresses the accretion rate owing to an enhanced toroidal magnetic field pressure that seems to be induced by frame dragging. Comparing the energy fluxes from the Blandford–Znajek-driven central spine and the surrounding disk wind, we find that the total electromagnetic energy flux is dominated by the total matter energy flux of the disk wind (by a factor of 20). The kinetic energy flux of the matter outflow is comparatively small and comparable to the Blandford–Znajek electromagnetic energy flux.

DIFFUSIVE PARTICLE ACCELERATION IN SHOCKED, VISCOUS ACCRETION DISKS: GREEN'S FUNCTION ENERGY DISTRIBUTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becker, Peter A.; Das, Santabrata; Le, Truong, E-mail: pbecker@gmu.edu, E-mail: sbdas@iitg.ernet.in, E-mail: truong.le@nhrec.org

2011-12-10

The acceleration of relativistic particles in a viscous accretion disk containing a standing shock is investigated as a possible explanation for the energetic outflows observed around radio-loud black holes. The energy/space distribution of the accelerated particles is computed by solving a transport equation that includes the effects of first-order Fermi acceleration, bulk advection, spatial diffusion, and particle escape. The velocity profile of the accreting gas is described using a model for shocked viscous disks recently developed by the authors, and the corresponding Green's function distribution for the accelerated particles in the disk and the outflow is obtained using a classicalmore » method based on eigenfunction analysis. The accretion-driven, diffusive shock acceleration scenario explored here is conceptually similar to the standard model for the acceleration of cosmic rays at supernova-driven shocks. However, in the disk application, the distribution of the accelerated particles is much harder than would be expected for a plane-parallel shock with the same compression ratio. Hence the disk environment plays a key role in enhancing the efficiency of the shock acceleration process. The presence of the shock helps to stabilize the disk by reducing the Bernoulli parameter, while channeling the excess binding energy into the escaping relativistic particles. In applications to M87 and Sgr A*, we find that the kinetic power in the jet is {approx}0.01 M-dot c{sup 2}, and the outflowing relativistic particles have a mean energy {approx}300 times larger than that of the thermal gas in the disk at the shock radius. Our results suggest that a standing shock may be an essential ingredient in accretion onto underfed black holes, helping to resolve the long-standing problem of the stability of advection-dominated accretion disks.« less

Salmonella Heidelberg: Genetic profile of its antimicrobial resistance related to extended spectrum β-lactamases (ESBLs).

PubMed

Giuriatti, Jéssica; Stefani, Lenita Moura; Brisola, Maiara Cristina; Crecencio, Regiane Boaretto; Bitner, Dinael Simão; Faria, Gláucia Amorim

2017-08-01

The objective of this study was to evaluate the phenotypic and genotypic profile of antimicrobial susceptibility and the possible involvement of extended spectrum beta-lactamases (ESBLs) in the resistance profile of Salmonella Heidelberg (SH) isolated from chicken meat. We used 18 SH isolates from chicken meat produced in 2013 in the state of Paraná, Southern Brazil. The isolates were submitted to disk-diffusion tests and from these results it was possible to determine the number of isolates considered multiresistant and the index of multiple antimicrobial resistance (IRMA) against ten antimicrobials routinely used in human and veterinary medicine. It was considered multidrug resistant the isolate that showed resistance to three or more classes of antibiotics. Another test performed was the disc-approximation in order to investigate interposed zones of inhibition, indicative of ESBLs production. In the isolates that presented multidrug resistance (18/18), a search of resistance genes involved in the production of ESBLs was performed using PCR: blaCMY-2, blaSHV-1, blaTEM-1, blaCTX-M2, blaOXA-1, blaPSE-1 and AmpC. The overall antimicrobial resistance was 80.55%. The highest levels of resistance were observed for nalidixic acid and ceftiofur (100%). The most commonly resistance pattern found (42.1%) was A (penicillin-cephalosporin-quinolone-tetracycline). The results were negative for ghost zone formation, indicative of ESBLs. However, PCR technique was able to detect resistance genes via ESBLs where the blaTEM-1 gene showed the highest amplification (83.33%), and the second most prevalent genes were blaCMY-2 (38.88%) and AmpC gene (38.88%). The blaOXA-1 and blaPSE-1 genes were not detected. These results are certainly of concern since SH is becoming more prevalent in the South of Brazil and able to cause severe disease in immune compromised individuals, showing high antimicrobial resistance to those drugs routinely used in the treatment and control of human and animal salmonellosis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Diversity and antimicrobial activity of culturable fungi from fishscale bamboo (Phyllostachys heteroclada) in China.

PubMed

Zhou, Ying-Ke; Shen, Xiao-Ye; Hou, Cheng-Lin

2017-06-01

An important and useful bamboo species, fishscale bamboo (Phyllostachys heteroclada Oliver), is broadly distributed in Southeast China and has multiple purposes, including uses in cuisine, weaving, Chinese medicine and ecological protection. However, no previous studies have focused on the endophytes of this plant. In our article, a total of 127 fungal strains were first isolated from the healthy branches and leaves of common P. heteroclada. These endophytic fungi could be directly categorized into 50 morphotypes according to their culture characteristics, and their internal transcribed spacer (ITS) regions were analyzed for molecular identification. Using the BLAST search tool of the NCBI database and phylogenetic tree analysis, these isolates were divided into two phyla, Ascomycota (95.28%) and Basidiomycota (4.72%), including at least six orders (Xylariales, Capnodiales, Pleosporales, Hypocreales, Chaetothyriales and Polyporales) and fourteen genera (Arthrinium, Pestalotiopsis, Epicoccum, Cladosporium, Nigrospora, Setophoma, Didymella, Calcarisporium, Preussia, Nemania, Creosphaeria, Ophiobolus, Phialophora and Perenniporia). It is fascinating that four genera, Calcarisporium, Preussia, Creosphaeria and Phialophora were isolated from bamboos for the first time. The inhibitory effects against clinical pathogens were also preliminarily screened, and four isolates FB43 (Calcarisporium arbuscula), FB06 (Preussia minima), FB16 (Setophoma sp.) and FB21 (Perenniporia medulla-pains) among the candidate strains displayed broad-spectrum activities according to the agar diffusion method and the disk diffusion assay. Strain FB16 (Setophoma sp.) especially indicated high bioactivity against both clinical bacteria and yeast. This study is the first report on the diversity and antimicrobial activity of the endophytic fungi associated with P. heteroclada, which could be regarded as a potential source of drug precursors and could be used in biocontrol development.

On the Grain-modified Magnetic Diffusivities in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Xu, Rui; Bai, Xue-Ning

2016-03-01

Weakly ionized protoplanetary disks (PPDs) are subject to nonideal magnetohydrodynamic (MHD) effects, including ohmic resistivity, the Hall effect, and ambipolar diffusion (AD), and the resulting magnetic diffusivities ({η }{{O}},{η }{{H}}, and {η }{{A}}) largely control the disk gas dynamics. The presence of grains not only strongly reduces the disk ionization fraction, but also modifies the scalings of {η }{{H}} and {η }{{A}} with magnetic field strength. We analytically derive asymptotic expressions of {η }{{H}} and {η }{{A}} in both the strong and weak field limits and show that toward a strong field, {η }{{H}} can change sign (at a threshold field strength {B}{{th}}), mimicking a flip of field polarity, and AD is substantially reduced. Applied to PPDs, we find that when small ˜0.1 (0.01)μm grains are sufficiently abundant (mass ratio ˜0.01 (10-4)), {η }{{H}} can change sign up to ˜2-3 scale heights above the midplane at a modest field strength (plasma β ˜ 100) over a wide range of disk radii. The reduction of AD is also substantial toward the AD-dominated outer disk and may activate the magnetorotational instability. We further perform local nonideal MHD simulations of the inner disk (within 10 au) and show that, with sufficiently abundant small grains, the magnetic field amplification due to the Hall-shear instability saturates at a very low level near the threshold field strength {B}{{th}}. Together with previous studies, we conclude by discussing the grain-abundance-dependent phenomenology of PPD gas dynamics.

Kinematics of the Diffuse Ionized Gas Disk of Andromeda

NASA Astrophysics Data System (ADS)

Thelen, Alexander; Howley, K.; Guhathakurta, P.; Dorman, C.; SPLASH Collaboration

2012-01-01

This research focuses on the flattened rotating diffuse ionized gas (DIG) disk of the Andromeda Galaxy (M31). For this we use spectra from 25 multislit masks obtained by the SPLASH collaboration using the DEIMOS spectrograph on the Keck-II 10-meter telescope. Each mask contains 200 slits covering the region around M32 (S of the center of M31), the major axis of M31, and the SE minor axis. DIG emission was serendipitously detected in the background sky of these slits. By creating a normalized "sky spectrum” to remove various other sources of emission (such as night sky lines) in the background of these slits, we have examined the rotation of the DIG disk using individual line-of-sight velocity measurements of Hα, [NII] and [SII] emission. his emission is probably the result of newly formed stars ionizing the gas in the disk. The measured IG rotation will be compared to the rotation of M31's stellar disk and HI gas disk, as well as models of an infinitely thin rotating disk, to better understand the relationship between the components of the galactic disk and its differential rotation. We wish to acknowledge the NSF for funding on this project.

Modeling the Role of Incisures in Vertebrate Phototransduction

PubMed Central

Caruso, Giovanni; Bisegna, Paolo; Shen, Lixin; Andreucci, Daniele; Hamm, Heidi E.; DiBenedetto, Emmanuele

2006-01-01

Phototransduction is mediated by a G-protein-coupled receptor-mediated cascade, activated by light and localized to rod outer segment (ROS) disk membranes, which, in turn, drives a diffusion process of the second messengers cGMP and Ca2+ in the ROS cytosol. This process is hindered by disks—which, however, bear physical cracks, known as incisures, believed to favor the longitudinal diffusion of cGMP and Ca2+. This article is aimed at highlighting the biophysical functional role and significance of incisures, and their effect on the local and global response of the photocurrent. Previous work on this topic regarded the ROS as well stirred in the radial variables, lumped the diffusion mechanism on the longitudinal axis of the ROS, and replaced the cytosolic diffusion coefficients by effective ones, accounting for incisures through their total patent area only. The fully spatially resolved model recently published by our group is a natural tool to take into account other significant details of incisures, including their geometry and distribution. Using mathematical theories of homogenization and concentrated capacity, it is shown here that the complex diffusion process undergone by the second messengers cGMP and Ca2+ in the ROS bearing incisures can be modeled by a family of two-dimensional diffusion processes on the ROS cross sections, glued together by other two-dimensional diffusion processes, accounting for diffusion in the ROS outer shell and in the bladelike regions comprised by the stack of incisures. Based on this mathematical model, a code has been written, capable of incorporating an arbitrary number of incisures and activation sites, with any given arbitrary distribution within the ROS. The code is aimed at being an operational tool to perform numerical experiments of phototransduction, in rods with incisures of different geometry and structure, under a wide spectrum of operating conditions. The simulation results show that incisures have a dual biophysical function. On the one hand, since incisures line up from disk to disk, they create vertical cytoplasmic channels crossing the disks, thus facilitating diffusion of second messengers; on the other hand, at least in those species bearing multiple incisures, they divide the disks into lobes like the petals of a flower, thus confining the diffusion of activated phosphodiesterase and localizing the photon response. Accordingly, not only the total area of incisures, but their geometrical shape and distribution as well, significantly influence the global photoresponse. PMID:16714347

Evaluating the diffusion coefficient of dopamine at the cell surface during amperometric detection: disk vs ring microelectrodes.

PubMed

Trouillon, Raphaël; Lin, Yuqing; Mellander, Lisa J; Keighron, Jacqueline D; Ewing, Andrew G

2013-07-02

During exocytosis, small quantities of neurotransmitters are released by the cell. These neurotransmitters can be detected quantitatively using electrochemical methods, principally with disk carbon fiber microelectrode amperometry. An exocytotic event then results in the recording of a current peak whose characteristic features are directly related to the mechanisms of exocytosis. We have compared two exocytotic peak populations obtained from PC12 cells with a disk carbon fiber microelectrode and with a pyrolyzed carbon ring microelectrode array, with a 500 nm ring thickness. The specific shape of the ring electrode allows for precise analysis of diffusion processes at the vicinity of the cell membrane. Peaks obtained with a ring microelectrode array show a distorted average shape, owing to increased diffusion pathways. This result has been used to evaluate the diffusion coefficient of dopamine at the surface of a cell, which is up to an order of magnitude smaller than that measured in free buffer. The lower rate of diffusion is discussed as resulting from interactions with the glycocalyx.

Isolation and characterization of Listeria species from rodents in natural environments in China.

PubMed

Wang, Yan; Lu, Liang; Lan, Ruiting; Salazar, Joelle K; Liu, Jingli; Xu, Jianguo; Ye, Changyun

2017-06-07

Listeria is ubiquitous in a variety of environments and can be isolated from a wide range of animal hosts. Rodents are capable of carrying pathogenic bacteria in their intestines, such as Listeria, and can disseminate those pathogens into the natural environment and to where human activity occurs. In this study, we investigated the occurrence and antimicrobial susceptibility of Listeria spp. isolated from wild rodents found in natural environments in China. We collected 341 intestinal fecal samples of rodents from five different regions of China, all representing different rodent habitats. The antimicrobial susceptibility of the Listeria spp. isolates obtained were firstly assessed using the Kirby-Bauer disk diffusion method. Thirty-one samples were positive for Listeria spp., of which 11 were positive for Listeria monocytogenes and seven were positive for Listeria ivanovii. Other species identified include Listeria innocua, Listeria fleischmannii and Listeria floridensis. All Listeria spp. isolates were sensitive to the majority of the antimicrobials tested, but largely resistant to oxacillin (94.1%) and cefuroxime (70.6%). All L. monocytogenes isolates were further characterized by serotyping, multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). L. monocytogenes strains were grouped into three serotypes, five sequence types and five pulsotypes (PTs) by serotyping, MLST and PFGE, respectively. Almost half of the isolates (five of 11) belonged to serotype 1/2b, ST87 and PT1. This study determined that Listeria is carried in the intestinal tracts of wild rodents from multiple regions at a low rate, filling an epidemiological data gap on Listeria in natural environments in China.

Phenotypic, antimicrobial susceptibility profile and virulence factors of Klebsiella pneumoniae isolated from buffalo and cow mastitic milk.

PubMed

Osman, Kamelia M; Hassan, Hany M; Orabi, Ahmed; Abdelhafez, Ahmed S T

2014-06-01

Studies on the prevalence and virulence genes of Klebsiella mastitis pathogens in a buffalo population are undocumented. Also, the association of rmpA kfu, uge, magA, Aerobactin, K1 and K2 virulent factors with K. pneumoniae buffalo, and cow mastitis is unreported. The virulence of K. pneumoniae was evaluated through both phenotypic and molecular assays. In vivo virulence was assessed by the Vero cell cytotoxicity, suckling mouse assay and mice lethality test. Antimicrobial susceptibility was tested by disk diffusion method. The 45 K. pneumoniae isolates from buffalo (n = 10/232) and cow (n = 35/293) milk were isolated (45/525; 8.6%) and screened via PCR for seven virulence genes encoding uridine diphosphate galactose 4 epimerase encoding gene responsible for capsule and smooth lipopolysaccharide synthesis (uge), siderophores (kfu and aerobactin), protectines or invasins (rmpA and magA), and the capsule and hypermucoviscosity (K1 and K2). The most common virulence genes were rmpA, kfu, uge, and magA (77.8% each). Aerobactin and K1 genes were found at medium rates of 66.7% each and K2 (55.6%). The Vero cell cytotoxicity and LD (50) in mice were found in 100% of isolates. A multidrug resistance pattern was observed for 40% of the antimicrobials. The distribution of virulence profiles indicate a role of rmpA, kfu, uge, magA, Aerobactin, and K1 and K2 in pathogenicity of K. pneumoniae in udder infections and invasiveness, and constitutes a threat for vulnerable animals, even more if they are in combination with antibiotic resistance.

Isolation and characterization of Listeria species from rodents in natural environments in China

PubMed Central

Wang, Yan; Lu, Liang; Lan, Ruiting; Salazar, Joelle K; Liu, Jingli; Xu, Jianguo; Ye, Changyun

2017-01-01

Listeria is ubiquitous in a variety of environments and can be isolated from a wide range of animal hosts. Rodents are capable of carrying pathogenic bacteria in their intestines, such as Listeria, and can disseminate those pathogens into the natural environment and to where human activity occurs. In this study, we investigated the occurrence and antimicrobial susceptibility of Listeria spp. isolated from wild rodents found in natural environments in China. We collected 341 intestinal fecal samples of rodents from five different regions of China, all representing different rodent habitats. The antimicrobial susceptibility of the Listeria spp. isolates obtained were firstly assessed using the Kirby–Bauer disk diffusion method. Thirty-one samples were positive for Listeria spp., of which 11 were positive for Listeria monocytogenes and seven were positive for Listeria ivanovii. Other species identified include Listeria innocua, Listeria fleischmannii and Listeria floridensis. All Listeria spp. isolates were sensitive to the majority of the antimicrobials tested, but largely resistant to oxacillin (94.1%) and cefuroxime (70.6%). All L. monocytogenes isolates were further characterized by serotyping, multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE). L. monocytogenes strains were grouped into three serotypes, five sequence types and five pulsotypes (PTs) by serotyping, MLST and PFGE, respectively. Almost half of the isolates (five of 11) belonged to serotype 1/2b, ST87 and PT1. This study determined that Listeria is carried in the intestinal tracts of wild rodents from multiple regions at a low rate, filling an epidemiological data gap on Listeria in natural environments in China. PMID:28588285

Prevalence and antimicrobial resistance of Campylobacter species isolated from raw camel, beef, lamb, and goat meat in Iran.

PubMed

Rahimi, Ebrahim; Ameri, Mehrdad; Kazemeini, Hamid Reza

2010-04-01

Campylobacter spp. are one of the most common causes of acute bacterial gastroenteritis in human beings which are transmitted mostly via food originating from animals. This study was conducted to determine the prevalence and antimicrobial resistance of Campylobacter spp. isolated from retail raw meats in Iran. From June 2008 to June 2009, a total of 722 raw meat samples from camel (n = 107), beef (n = 190), lamb (n = 225), and goat (n = 180) were purchased from randomly selected retail outlets in Isfahan and Yazd, Iran, and were evaluated for the presence of Campylobacter spp. In this study, 50 of the 722 meat samples (6.9%) were contaminated with Campylobacter spp. The highest prevalence of Campylobacter spp. was found in lamb meat (12.0%), followed by goat meat (9.4%), beef meat (2.4%), and camel meat (0.9%). The most prevalent Campylobacter spp. isolated from the meat samples was Campylobacter jejuni (84.0%); the remaining isolates were Campylobacter coli (16.0%). Susceptibilities of 50 Campylobacter isolates were determined for 10 antimicrobial drugs using the disk-diffusion assay. Resistance to tetracycline was the most common finding (68.0%), followed by resistance to ciprofloxacin (46.0%) and nalidixic acid (40.0%). All of the isolates were susceptible to erythromycin, gentamicin, and chloramphenicol. Significantly higher prevalence rates of Campylobacter spp. (p < 0.05) were found in the lamb meat samples taken in spring (20.0%) and summer (18.9%). To our knowledge, this study is the first report of the isolation of Campylobacter spp. from raw camel, lamb, and goat meat in Iran.

Characterization of Klebsiella isolates by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and determination of antimicrobial resistance with VITEK 2 advanced expert system (AES).

PubMed

Karagöz, Alper; Acar, Sümeyra; Körkoca, Hanifi

2015-01-01

The purpose of the study was to evaluate the performance of the VITEK mass spectrometry (MS) (bioMérieux, France) system for the identification of Klebsiella spp. isolated from different sources. Moreover, while assessing the ability of the VITEK 2 automated expert system (AES) to recognize antimicrobial resistance patterns, the researchers have extended the study to compare VITEK 2 with the routine antimicrobial susceptibility testing method. This study tested 51 Klebsiella spp. isolates that were isolated from environmental examples and clinical examples. Results of conventional methods and the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS were compared. Then, any differing results were compared against a reference 16S rRNA gene sequence, and when indicated, a recA sequencing analysis was done. VITEK MS correctly identified 100% of the Klebsiella spp. isolates. There were two K. oxytoca isolates incorrectly identified to the species level with conventional methods according to the 16S rRNA gene sequencing analysis. In addition, a VITEK 2 AST-N261 card was used for the detection of extended spectrum beta-lactamases (ESBL). Using the VITEK 2 AES, ESBL positivity was found at the rate of 16.3% whereas this rate was 4.08% using the disk diffusion method. MALDI-TOF MS is a rapid and accurate method for the identification of Klebsiella spp. Moreover, the bioMérieux AES provides a useful laboratory tool for the interpretation of susceptibility results.

Surveillance of bacterial contamination in small animal veterinary hospitals with special focus on antimicrobial resistance and virulence traits of enterococci.

PubMed

KuKanich, Kate S; Ghosh, Anuradha; Skarbek, Jennifer V; Lothamer, Kale M; Zurek, Ludek

2012-02-15

To determine the prevalence of bacterial contamination on 4 surfaces of 4 types of standard equipment in small animal veterinary hospitals. Surveillance study. 10 small animal veterinary hospitals. Each hospital was visited 3 times at 4-month intervals; at each visit, a cage door, stethoscope, rectal thermometer, and mouth gag were swabbed. Swab samples were each plated onto media for culture of enterococci and organisms in the family Enterobacteriaceae. Enterococci were identified via a species-specific PCR assay and sodA gene sequencing; species of Enterobacteriaceae were identified with a biochemical test kit. Antimicrobial susceptibility was assessed via the disk diffusion method. Enterococci were screened for virulence traits and genotyped to assess clonality. Among the 10 hospitals, enterococci were isolated from cage doors in 7, from stethoscopes in 7, from thermometers in 6, and from mouth gags in 1; contamination with species of Enterobacteriaceae was rare. Enterococci were mainly represented by Enterococcus faecium (35.4%), Enterococcus faecalis (33.2%), and Enterococcus hirae (28.3%). Antimicrobial resistance was common in E. faecium, whereas virulence traits were present in 99% of E. faecalis isolates but not in E. faecium isolates. Clonal multidrug-resistant E. faecium was isolated from several surfaces at 1 hospital over multiple visits, whereas sporadic nonclonal contamination was detected in other hospitals. Contamination of surfaces in small animal veterinary hospitals with multidrug-resistant enterococci is a potential concern for pets and humans contacting these surfaces. Implementing precautions to minimize enterococcal contamination on these surfaces is recommended.

Synthesis, characterization, and antimicrobial properties of novel double layer nanocomposite electrospun fibers for wound dressing applications

PubMed Central

Hassiba, Alaa J; El Zowalaty, Mohamed E; Webster, Thomas J; Abdullah, Aboubakr M; Nasrallah, Gheyath K; Khalil, Khalil Abdelrazek; Luyt, Adriaan S; Elzatahry, Ahmed A

2017-01-01

Herein, novel hybrid nanomaterials were developed for wound dressing applications with antimicrobial properties. Electrospinning was used to fabricate a double layer nanocomposite nanofibrous mat consisting of an upper layer of poly(vinyl alcohol) and chitosan loaded with silver nanoparticles (AgNPs) and a lower layer of polyethylene oxide (PEO) or polyvinylpyrrolidone (PVP) nanofibers loaded with chlorhexidine (as an antiseptic). The top layer containing AgNPs, whose purpose was to protect the wound site against environmental germ invasion, was prepared by reducing silver nitrate to its nanoparticulate form through interaction with chitosan. The lower layer, which would be in direct contact with the injured site, contained the antibiotic drug needed to avoid wound infections which would otherwise interfere with the healing process. Initially, the upper layer was electrospun, followed sequentially by electrospinning the second layer, creating a bilayer nanofibrous mat. The morphology of the nanofibrous mats was studied by scanning electron microscopy and transmission electron microscopy, showing successful nanofiber production. X-ray diffraction confirmed the reduction of silver nitrate to AgNPs. Fourier transform infrared spectroscopy showed a successful incorporation of the material used in the produced nanofibrous mats. Thermal studies carried out by thermogravimetric analysis indicated that the PVP–drug-loaded layer had the highest thermal stability in comparison to other fabricated nanofibrous mats. Antimicrobial activities of the as-synthesized nanofibrous mats against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans were determined using disk diffusion method. The results indicated that the PEO–drug-loaded mat had the highest antibacterial activity, warranting further attention for numerous wound-healing applications. PMID:28356737

Six-Year Retrospective Review of Hospital Data on Antimicrobial Resistance Profile of Staphylococcus aureus Isolated from Skin Infections from a Single Institution in Greece.

PubMed

Stefanaki, Christina; Ieronymaki, Alexandra; Matoula, Theoni; Caroni, Chrysseis; Polythodoraki, Evaggelia; Chryssou, Stella-Eugenia; Kontochristopoulos, George; Antoniou, Christina

2017-12-20

Objective: To determine the prevalence of resistant strains of Staphylococcus aureus ( S. aureus ) isolated from Skin and soft tissue infections (SSTI) to various antibiotics. Material and Methods: All culture-positive results for S. aureus from swabs taken from patients presenting at one Greek hospital with a skin infection between the years 2010-2015 were examined retrospectively. Bacterial cultures, identification of S. aureus and antimicrobial susceptibility testing were performed using the disk diffusion method according to Clinical and Laboratory Standards Institute (CLSI) guidelines and European Committee on Antimicrobial testing (EUCAST) breakpoints. EUCAST breakpoints were applied if no CLSI were available. Results: Of 2069 S. aureus isolates identified, 1845 (88%) were resistant to one or more antibiotics. The highest resistance was observed for benzylpenicillin (71.9%), followed by erythromycin (34.3%). Resistant strains to cefoxitin defined as MRSA (methicillin-resistant S. aureus ) represented 21% of total isolates. Interestingly, resistance to fusidic acid was 22.9% and to mupirocin as high as 12.7%. Low rates were observed for minocycline, rifampicin and trimethoprim/sulfamethoxazole (SXT). Resistance to antibiotics remained relatively stable throughout the six-year period, with the exception of cefoxitin, fusidic acid and SXT. A high percentage of MRSA strains were resistant to erythromycin (60%), fusidic acid (46%), clindamycin (38%) and tetracycline (35.5%). Conclusions: Special attention is required in prescribing appropriate antibiotic therapeutic regimens, particularly for MRSA. These data on the susceptibility of S. aureus may be useful for guiding antibiotic treatment.

In-vitro transdentinal diffusion of monomers from adhesives.

PubMed

Putzeys, Eveline; Duca, Radu Corneliu; Coppens, Lieve; Vanoirbeek, Jeroen; Godderis, Lode; Van Meerbeek, Bart; Van Landuyt, Kirsten L

2018-06-01

Biocompatibility of adhesives is important since adhesives may be applied on dentin near the pulp. Accurate knowledge of the quantity of monomers reaching the pulp is important to determine potential side effects. The aim of this study was to assess the transdentinal diffusion of residual monomers from dental adhesive systems using an in-vitro pulp chamber model. Dentin disks with a thickness of 300 µm were produced from human third molars. These disks were fixed between two open-ended glass tubes, representing an in-vitro pulp chamber. The etch-and-rinse adhesive OptiBond FL and the self-etch adhesive Clearfil SE Bond were applied to the dentin side of the disks, while on in the pulpal side, the glass tube was filled with 600 µL water. The transdentinal diffusion of different monomers was quantified using ultra-performance liquid chromatography-tandem mass spectrometry. The monomers HEMA, CQ, BisGMA, GPDM, 10-MDP and UDMA eluted from the dental materials and were able to diffuse through the dentin disks to a certain extent. Compounds with a lower molecular weight (uncured group: HEMA 7850 nmol and CQ 78.2 nmol) were more likely to elute and diffuse compared to monomers with a higher molecular weight (uncured group: BisGMA 0.42 nmol). When the adhesives were left uncured, diffusion was up to 10 times higher compared to the cured conditions. This in-vitro research resulted in the quantification of various monomers able to diffuse through dentin and therefore contributes to a more detailed understanding about the potential exposure of the dental pulp to monomers from dental adhesives. Biocompatibility of adhesives is important since adhesives may be applied on dentin near the pulp, where tubular density and diameter are greatest. Copyright © 2018. Published by Elsevier Ltd.

3D Radiative Hydrodynamics Simulations of Protoplanetary Disks: A Comparison Between Two Radiative Cooling Algorithms

NASA Astrophysics Data System (ADS)

Lord, Jesse W.; Boley, A. C.; Durisen, R. H.

2006-12-01

We present a comparison between two three-dimensional radiative hydrodynamics simulations of a gravitationally unstable 0.07 Msun protoplanetary disk around a 0.5 Msun star. The first simulation is the radiatively cooled disk described in Boley et al. (2006, ApJ, 651). This simulation employed an algorithm that uses 3D flux-limited diffusion wherever the vertical Rosseland optical depth is greater than 2/3, which defines the optically thick region. The optically thin atmosphere of the disk, which cools according to its emissivity, is coupled to the optically thick region through an Eddington-like boundary condition. The second simulation employed an algorithm that uses a combination of solving the radiative transfer equation along rays in the z direction and flux limited diffusion in the r and phi directions on a cylindrical grid. We compare the following characteristics of the disk simulations: the mass transport and torques induced by gravitational instabilities, the effective temperature profiles of the disks, the gravitational and Reynolds stresses measured in the disk and those expected in an alpha-disk, and the amplitudes of the Fourier modes. This work has been supported by the National Science Foundation through grant AST-0452975 (astronomy REU program to Indiana University).

Exact calculations of survival probability for diffusion on growing lines, disks, and spheres: The role of dimension.

PubMed

Simpson, Matthew J; Baker, Ruth E

2015-09-07

Unlike standard applications of transport theory, the transport of molecules and cells during embryonic development often takes place within growing multidimensional tissues. In this work, we consider a model of diffusion on uniformly growing lines, disks, and spheres. An exact solution of the partial differential equation governing the diffusion of a population of individuals on the growing domain is derived. Using this solution, we study the survival probability, S(t). For the standard non-growing case with an absorbing boundary, we observe that S(t) decays to zero in the long time limit. In contrast, when the domain grows linearly or exponentially with time, we show that S(t) decays to a constant, positive value, indicating that a proportion of the diffusing substance remains on the growing domain indefinitely. Comparing S(t) for diffusion on lines, disks, and spheres indicates that there are minimal differences in S(t) in the limit of zero growth and minimal differences in S(t) in the limit of fast growth. In contrast, for intermediate growth rates, we observe modest differences in S(t) between different geometries. These differences can be quantified by evaluating the exact expressions derived and presented here.

Ionization Chemistry and Role of Grains on Non-ideal MHD Effects in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Xu, Rui; Bai, Xue-Ning; Oberg, Karin I.

2015-01-01

Ionization in protoplanetary disks (PPDs) is one of the key elements for understanding disk chemistry. It also determines the coupling between gas and magnetic fields hence strongly affect PPD gas dynamics. We study the ionization chemistry in the presence of grains in the midplane region of PPDs and its impact on gas conductivity reflected in non-ideal MHD effects including Ohmic resistivity, Hall effect and ambipolar diffusion. We first develop a reduced chemical reaction network from the UMIST database. The reduced network contains much smaller number of species and reactions while yields reliable estimates of the disk ionization level compared with the full network. We further show that grains are likely the dominant charge carrier in the midplane regions of the inner disk, which significantly affects the gas conductivity. In particular, ambipolar diffusion is strongly reduced and the Hall coefficient changes sign in the presence of strong magnetic field. The latter provides a natural mechanism to the saturation of the Hall-shear instability.

Antimicrobial activity of ProRoot MTA in contact with blood

PubMed Central

Farrugia, C.; Baca, P.; Camilleri, J.; Arias Moliz, M. T.

2017-01-01

Dental materials based on Portland cement, which is used in the construction industry have gained popularity for clinical use due to their hydraulic properties, the interaction with tooth tissue and their antimicrobial properties. The antimicrobial properties are optimal in vitro. However in clinical use contact with blood may affect the antimicrobial properties. This study aims to assess whether antimicrobial properties of the Portland cement-based dental cements such as mineral trioxide aggregate (MTA) are also affected by contact with blood present in clinical situations. ProRoot MTA, a Portland cement-based dental cement was characterized following contact with water, or heparinized blood after 1 day and 7 days aging. The antimicrobial activity under the mentioned conditions was assessed using 3 antimicrobial tests: agar diffusion test, direct contact test and intratubular infection test. MTA in contact with blood was severely discoloured, exhibited an additional phosphorus peak in elemental analysis, no calcium hydroxide peaks and no areas of bacterial inhibition growth in the agar diffusion test were demonstrated. ProRoot MTA showed limited antimicrobial activity, in both the direct contact test and intratubular infection test. When aged in water ProRoot MTA showed higher antimicrobial activity than when aged in blood. Antimicrobial activity reduced significantly after 7 days. Further assessment is required to investigate behaviour in clinical situations. PMID:28128328

Determination of Antimicrobial Potential of Five Herbs used in Ayurveda Practices against Candida albicans, Candida parapsilosis and Methicillin Resistant Staphylococcus aureus

PubMed Central

Gunasekara, TDCP; Radhika, NDM; Ragunathan, KK; Gunathilaka, DPP; Weerasekera, MM; Hewageegana, HGSP; Arawwawala, L A D M; Fernando, SSN

2017-01-01

Background: Medicinal plants are an important source of novel antimicrobial agents. Ayurvedic treatment involves the use of a variety of medicinal plants that merit investigation. Aims: To investigate the antimicrobial activity of bark of Pongamia pinnata (L.) Pierre, stem of Rubia cordifolia Linn, leaves of Jasminum officinale Linn, stem of Berberis ceylanica C.K. Schneid. and fruit of Garcina zeylanica Roxb. Subjects and Methods: Aqueous and ethanolic extracts of dried bark of Pongamia pinnata (Magul karanda), dried stem of Rubia cordifolia Linn (Welmadata), tender leaves of Jasminum officinale Linn (Jasmine) and dried stem of Berberis ceylanica (Dāruharidrā) were prepared according to standard protocols and tested for antimicrobial activity against five clinical isolates and one standard strain each of Candida albicans (ATCC 10231), Candida parapsilosis (ATCC 22019) and six Methicillin Resistant Staphylococcus aureus (MRSA) clinical isolates using the well diffusion method. Experiments were done in triplicates using well diffusion method. The plant extracts which gave a zone of inhibition in the well diffusion assay were further tested for Minimum Inhibitory Concentrations (MIC). Results: Aqueous and ethanolic extracts of Berberis ceylanica and ethanolic extract of Rubia cordifolia had antimicrobial activity against Candida albicans and Candida parapsilosis. Aqueous and ethanolic extracts of Garcinia zeylanica, and the ethanolic extracts of Jasminum officinale, Rubia cordifolia and Pongamia pinnata had antimicrobial activity against MRSA. Conclusions: Berberis ceylanica and Rubia crodifolia had antimicrobial activity against Candida species while Garcinia zeylanica, Jasminum officinale, Rubia crodifolia and Pongamia pinnata had antimicrobial activity against MRSA. PMID:29269969

[Resistance of uropathogenic strains of Escherichia coli in pregnant women and other women in generative ages in comparison with antibiotics consumption in Zagreb].

PubMed

Culig, Josip; Mlinarić-Dzepina, Ana; Leppée, Marcel; Vranes, Jasmina

2010-02-01

To compare resistance of uropathogenic strains of Escherichia coli (UPEC) to antibiotics in women in generative ages and pregnant women during two year period (2004 and 2008) in Zagreb, and comparison of resistance and the consumption of antibiotics. The standard disk-diffusion method was used for sensitivity testing to 16 different antibiotics. Data on antibiotic utilization were used to calculate the number of defined daily doses (DDD) and DDD per 1000 inhabitants using Anatomical-Therapeutic-Chemical/DDD methodology. Data on antibiotic consumption during pregnancy were collected using a questionnaire filled in by 893 women after delivery. During 2004 resistance of UPEC to antimicrobial drugs was not different in pregnant and in non-pregnant women, with the exception of amoxicillin and nitrofurantoin, with statistically higher resistance in pregnant women (p < 0.01). Four years later the statistically higher resistance to norfloxacin was observed in non-pregnant women (p < 0.01). Comparing the resistance in 2004 and 2008, in the both groups of women a statistically significant decrease of resistance to cefalexin and nitrofurantoin was detected (p < 0.01). Outpatient utilization of antimicrobial drugs in Zagreb increased significantly, from 32 to 39 DDD/1000 inhabitants per day. The most used antibiotic was co-amoxiclav, and its utilization increased from 9.6 to 12.2 DDD/1000/day. Amoxicillin and co-amoxiclav were used during pregnancy by 9.6% interviewed women. The observed significant decrease of resistance to cefalexin makes that antibiotic the drug of choice for treatment of urinary tract infections in women in generative ages, and together with coamoxiclav can be administered in pregnancy. Constant monitoring of urinary tract pathogens resistance to antimicrobial agents ensures the effectiveness of empirical therapy, whose versatile use is limited due the potentially harmful effects of antimicrobial drugs on fetus.

The in-vitro evaluation of antibacterial, antifungal and cytotoxic properties of Marrubium vulgare L. essential oil grown in Tunisia

PubMed Central

2011-01-01

Background In order to validate its antiseptic and anticancer properties with respect to traditional uses, we have screened for the first time the antimicrobial activity of aerial parts of M. vulgare L. essential oil against different pathogenic microorganisms and the cytotoxic activity against HeLa cell lines. Methods The agar disk diffusion method was used to study the antibacterial activity of M. vulgare essential oil against 12 bacterial and 4 fungi strains. The disc diameters of zone of inhibition (DD), the minimum inhibitory concentrations (MIC) and the concentration inhibiting 50% (IC50) were investigated to characterize the antimicrobial activities of this essential oil. The in vitro cytotoxicity of M. vulgare essential oil was examined using a modified MTT assay; the viability and the IC50 were used to evaluate this test. Results The antimicrobial activity of the essential oil was investigated in order to evaluate its efficacy against the different tested microorganisms. The present results results showed a significant activity against microorganisms especially Gram (+) bacteria with inhibition zones and minimal inhibitory concentration values in the range of 6.6-25.2 mm and 1120-2600 μg/ml, respectively, whereas Gram (-) bacteria exhibited a higher resistance. As far as the antifungal activity, among four strains tested, Botrytis cinerea exhibited the strongest activity with inhibition zones of 12.6 mm. However, Fusarium solani, Penicillium digitatum and Aspergillus niger were less sensitive to M. vulgare essential oil. About the citotoxicity assay, this finding indicate the capability of this essential oil to inhibited the proliferation of HeLa cell lines under some conditions with IC50 value of 0.258 μg/ml. Conclusion This investigation showed that the M. vulgare essential oil has a potent antimicrobial activity against some Gram (+) pathogenic bacteria and Botrytis cinerea fungi. The present studies confirm the use of this essential oil as anticancer agent. Further research is required to evaluate the practical values of therapeutic applications. PMID:21936887

The in-vitro evaluation of antibacterial, antifungal and cytotoxic properties of Marrubium vulgare L. essential oil grown in Tunisia.

PubMed

Zarai, Zied; Kadri, Adel; Ben Chobba, Ines; Ben Mansour, Riadh; Bekir, Ahmed; Mejdoub, Hafedh; Gharsallah, Néji

2011-09-21

In order to validate its antiseptic and anticancer properties with respect to traditional uses, we have screened for the first time the antimicrobial activity of aerial parts of M. vulgare L. essential oil against different pathogenic microorganisms and the cytotoxic activity against HeLa cell lines. The agar disk diffusion method was used to study the antibacterial activity of M. vulgare essential oil against 12 bacterial and 4 fungi strains. The disc diameters of zone of inhibition (DD), the minimum inhibitory concentrations (MIC) and the concentration inhibiting 50% (IC50) were investigated to characterize the antimicrobial activities of this essential oil. The in vitro cytotoxicity of M. vulgare essential oil was examined using a modified MTT assay; the viability and the IC50 were used to evaluate this test. The antimicrobial activity of the essential oil was investigated in order to evaluate its efficacy against the different tested microorganisms. The present results results showed a significant activity against microorganisms especially Gram (+) bacteria with inhibition zones and minimal inhibitory concentration values in the range of 6.6-25.2 mm and 1120-2600 μg/ml, respectively, whereas Gram (-) bacteria exhibited a higher resistance. As far as the antifungal activity, among four strains tested, Botrytis cinerea exhibited the strongest activity with inhibition zones of 12.6 mm. However, Fusarium solani, Penicillium digitatum and Aspergillus niger were less sensitive to M. vulgare essential oil. About the citotoxicity assay, this finding indicate the capability of this essential oil to inhibited the proliferation of HeLa cell lines under some conditions with IC50 value of 0.258 μg/ml. This investigation showed that the M. vulgare essential oil has a potent antimicrobial activity against some Gram (+) pathogenic bacteria and Botrytis cinerea fungi. The present studies confirm the use of this essential oil as anticancer agent. Further research is required to evaluate the practical values of therapeutic applications.

Non-typhoidal Salmonella in Calabria, Italy: a laboratory and patient-based survey.

PubMed

Mascaro, Valentina; Pileggi, Claudia; Crinò, Maria; Proroga, Yolande Therese Rose; Carullo, Maria Rosaria; Graziani, Caterina; Arigoni, Fabio; Turno, Pasquale; Pavia, Maria

2017-09-11

Although there has been a decrease in the number of cases of salmonellosis in the European Union, it still represents the primary cause of foodborne outbreaks. In Calabria region, data are lacking for the incidence of human non-typhoid salmonellosis as active surveillance has never been carried out. To report the results of a laboratory and patient-based morbidity survey in Calabria to describe the incidence and distribution of Salmonella serovars isolated from humans, with a focus on antimicrobial resistance patterns. Positive cultures from human samples were collected from every laboratory participating in the surveillance, with a minimum set of information about each isolate. A questionnaire was then administered to the patients by telephone interview to assess the potential risk exposures. Salmonella isolates underwent biochemical identification, molecular analysis by PCR and antimicrobial susceptibility testing by the disk-diffusion method. During a 2-year period, 105 strains of Salmonella spp were isolated from samples of patients with diarrhoea, with the highest isolation rate for children aged 1-5 years. The standardised rate was 2.7 cases per 1 00 000 population. The most common Salmonella isolates belonged to monophasic variant of S. Typhimurium ( S. 4,[5],12:i:-) (33.3%), followed by S . Typhimurium (21.9%). 30.5% of the isolates were susceptible to all microbial agents tested and the most common pan-susceptible serotype was S. Napoli (100%). S . 4,[5],12:i:- was resistant to ampicillin, streptomycin, sulfonamides and tetracyclines in 42.9% cases, while resistance to quinolones was seen in 14.3% of the isolates. The results provide evidence that an active surveillance system effectively enhances Salmonella notifications. The high prevalence of antimicrobial resistance, including resistance to quinolones and multiresistance, enforces the need to strengthen strategies of surveillance and monitoring of antimicrobial use. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Non-typhoidal Salmonella in Calabria, Italy: a laboratory and patient-based survey

PubMed Central

Mascaro, Valentina; Pileggi, Claudia; Crinò, Maria; Proroga, Yolande Therese Rose; Carullo, Maria Rosaria; Graziani, Caterina; Arigoni, Fabio; Turno, Pasquale; Pavia, Maria

2017-01-01

Introduction Although there has been a decrease in the number of cases of salmonellosis in the European Union, it still represents the primary cause of foodborne outbreaks. In Calabria region, data are lacking for the incidence of human non-typhoid salmonellosis as active surveillance has never been carried out. Objective To report the results of a laboratory and patient-based morbidity survey in Calabria to describe the incidence and distribution of Salmonella serovars isolated from humans, with a focus on antimicrobial resistance patterns. Methods Positive cultures from human samples were collected from every laboratory participating in the surveillance, with a minimum set of information about each isolate. A questionnaire was then administered to the patients by telephone interview to assess the potential risk exposures. Salmonella isolates underwent biochemical identification, molecular analysis by PCR and antimicrobial susceptibility testing by the disk-diffusion method. Results During a 2-year period, 105 strains of Salmonella spp were isolated from samples of patients with diarrhoea, with the highest isolation rate for children aged 1–5 years. The standardised rate was 2.7 cases per 1 00 000 population. The most common Salmonella isolates belonged to monophasic variant of S. Typhimurium (S. 4,[5],12:i:-) (33.3%), followed by S. Typhimurium (21.9%). 30.5% of the isolates were susceptible to all microbial agents tested and the most common pan-susceptible serotype was S. Napoli (100%). S. 4,[5],12:i:- was resistant to ampicillin, streptomycin, sulfonamides and tetracyclines in 42.9% cases, while resistance to quinolones was seen in 14.3% of the isolates. Conclusions The results provide evidence that an active surveillance system effectively enhances Salmonella notifications. The high prevalence of antimicrobial resistance, including resistance to quinolones and multiresistance, enforces the need to strengthen strategies of surveillance and monitoring of antimicrobial use. PMID:28893751

Colonization prevalence and antibiotic susceptibility of Group B Streptococcus in pregnant women over a 6-year period in Dongguan, China

PubMed Central

Guo, Zhusheng; Xie, Shujin; Yang, Weiqing; Chen, Junjian; Wang, Jiamin; Cheng, Zhiqin; Wang, Xin; Zhu, Xuehai; Wang, Jianwen; Wang, Haiqing; Huang, Juan; Liang, Ning; McIver, David J.

2017-01-01

This study investigated the prevalence of recto-vaginal Group B Streptococcus (GBS) colonization, serotype distribution, and antimicrobial susceptibility patterns among pregnant women in Dongguan, China. Recto-vaginal swabs were collected from pregnant women at gestational age 35–37 weeks between January 1st 2009 and December 31st 2014. Isolates were serotyped by latex-agglutination and were tested against seven antimicrobials by disk diffusion. Of 7,726 pregnant women who completed GBS testing, 636 (8.2%) were GBS carriers. Of 153 GBS isolates available for typing, 6 serotypes (Ia, Ib, III, V, VI and VIII) were identified with type III being predominant, while 9 (5.9%) were non-typable isolates. All isolates were sensitive to penicillin, ceftriaxone, linezolid and vancomycin, whereas 52.4% were resistant to clindamycin, 25.9% were resistant to levofloxacin and 64.9% were resistant to erythromycin. This study showed the recto-vaginal colonization prevalence of GBS in Dongguan is significant. Due to 100% susceptibility to penicillin of all GBS samples, penicillin remains the first recommendation for treatment and prevention against GBS infection. Susceptibility testing should be performed for women allergic to penicillin in order to choose the most appropriate antibacterial agents for treatment and prevention of vertical transmission to neonates. In addition, we suggest establishing standard processes for GBS culture and identification in China as early as possible. PMID:28813477

Multisite reproducibility of the broth microdilution method for susceptibility testing of Nocardia species.

PubMed

Conville, Patricia S; Brown-Elliott, Barbara A; Wallace, Richard J; Witebsky, Frank G; Koziol, Deloris; Hall, Geraldine S; Killian, Scott B; Knapp, Cindy C; Warshauer, David; Van, Tam; Wengenack, Nancy L; Deml, Sharon; Woods, Gail L

2012-04-01

Antimicrobial susceptibility testing (AST) of clinical isolates of Nocardia is recommended to detect resistance to commonly used antimicrobial agents; such testing is complicated by difficulties in inoculum preparation and test interpretation. In this study, six laboratories performed repetitive broth microdilution testing on single strains of Nocardia brasiliensis, Nocardia cyriacigeorgica, Nocardia farcinica, Nocardia nova, and Nocardia wallacei. For each isolate, a total of 30 microdilution panels from three different lots were tested at most sites. The goal of the study was to determine the inter- and intralaboratory reproducibility of susceptibility testing of this group of isolates. Acceptable agreement (>90% agreement at ±1 dilution of the MIC mode) was found for amikacin, ciprofloxacin, clarithromycin, and moxifloxacin. After eliminating MIC values from single laboratories whose results showed the greatest deviation from those of the remaining laboratories, acceptable agreement was also found for amoxicillin-clavulanic acid, linezolid, minocycline, and tobramycin. Results showed unsatisfactory reproducibility of broth microdilution testing of ceftriaxone with N. cyriacigeorgica and N. wallacei, tigecycline with N. brasiliensis and N. cyriacigeorgica, and sulfonamides with N. farcinica and N. wallacei. N. nova ATCC BAA-2227 is proposed as a quality control organism for AST of Nocardia sp., and the use of a disk diffusion test for sulfisoxazole is proposed as a check of the adequacy of the inoculum and to confirm sulfonamide MIC results.

Microbiota and anthropic interference on antimicrobial resistance profile of bacteria isolated from Brazilian Maned-wolf (Chrysocyon brachyurus).

PubMed

Vieira-da-Motta, Olney; Eckhardt-de-Pontes, Luiz Antonio; Petrucci, Melissa Paes; dos Santos, Israel Pereira; da Cunha, Isabel Candia Nunes; Morato, Ronaldo Gonçalves

2013-12-01

Both the study of Brazilian wild mammal fauna and the conditions that foster the preservation of endangered species, such as Brazilian Maned-wolf (Chrysocyon brachyurus), in wild life are of extreme importance. In order to study the resistance profile of microbiota bacterial colonizing Brazilian Maned-wolf, this work investigated samples from eight male captive and free roaming animals originating from different Brazilian geographical regions. Samples for microbiological purposes were collected with swabs and kept in appropriate transport medium. Using routine microbiological techniques, the isolated bacteria were tested toward antimicrobial drugs by the agar disk diffusion method. Results showed that all samples from wild animals were sensitive toward all drugs tested. Conversely, the resistance profile of bacteria isolated from captive animals varied among strains and animal body site location. Escherichia coli samples from prepuce, anus and ear showed multi-resistance toward at least four drugs, especially against erythromycin and tetracycline, followed by Proteus mirabilis and P. vulgaris strains isolated from anus and ear. Among Gram-positive bacteria, strains of coagulase-negative staphylococci showed multi-resistance mainly toward erythromycin and amoxicillin. The work discusses these findings and suggests that profile of multi-resistance bacteria from captive subjects may be attributed to direct contact with human or through lifestyle factors such as feeding, predation or contact of animals with urban animals such as birds, rodents, and insects from surrounding environments.

Microbiota and anthropic interference on antimicrobial resistance profile of bacteria isolated from Brazilian maned-wolf (Chrysocyon brachyurus)

PubMed Central

Vieira-da-Motta, Olney; Eckhardt-de-Pontes, Luiz Antonio; Petrucci, Melissa Paes; dos Santos, Israel Pereira; da Cunha, Isabel Candia Nunes; Morato, Ronaldo Gonçalves

2013-01-01

Both the study of Brazilian wild mammal fauna and the conditions that foster the preservation of endangered species, such as Brazilian Maned-wolf (Chrysocyon brachyurus), in wild life are of extreme importance. In order to study the resistance profile of microbiota bacterial colonizing Brazilian Maned-wolf, this work investigated samples from eight male captive and free roaming animals originating from different Brazilian geographical regions. Samples for microbiological purposes were collected with swabs and kept in appropriate transport medium. Using routine microbiological techniques, the isolated bacteria were tested toward antimicrobial drugs by the agar disk diffusion method. Results showed that all samples from wild animals were sensitive toward all drugs tested. Conversely, the resistance profile of bacteria isolated from captive animals varied among strains and animal body site location. Escherichia coli samples from prepuce, anus and ear showed multi-resistance toward at least four drugs, especially against erythromycin and tetracycline, followed by Proteus mirabilis and P. vulgaris strains isolated from anus and ear. Among Gram-positive bacteria, strains of coagulase-negative staphylococci showed multi-resistance mainly toward erythromycin and amoxicillin. The work discusses these findings and suggests that profile of multi-resistance bacteria from captive subjects may be attributed to direct contact with human or through lifestyle factors such as feeding, predation or contact of animals with urban animals such as birds, rodents, and insects from surrounding environments. PMID:24688529

The investigation of antibacterial activity of selected native plants from North of Iran.

PubMed

Koohsari, H; Ghaemi, E A; Sadegh Sheshpoli, M; Jahedi, M; Zahiri, M

2015-01-01

Plant derived products have been used for medicinal purposes during centuries. Bacterial resistance to currently used antibiotics has become a concern to public health. The development of bacterial super resistant strains has resulted in the currently used antibiotic agents failing to end many bacterial infections. For this reason, the search is ongoing for new antimicrobial agents, both by the design and by the synthesis of new agents, or through the search of natural sources for yet undiscovered antimicrobial agents. Herbal medications in particular have seen a revival of interest due to a perception that there is a lower incidence of adverse reactions to plant preparations compared to synthetic pharmaceuticals. Coupled with the reduced costs of plant preparations, this makes the search for natural therapeutics an attractive option. This research was carried out to assess the antibacterial activity aqueous and ethanolic extracts of six Azadshahr township Native plants in north of Iran against six species of pathogen bacteria by using three methods of Disk diffusion, Well method and MBC. The results of this research indicated that the effect of ethanol extracts were more than aqueous extract and among six plants, Lippia citriodora and Plantago major ethanol extract had the most antibacterial activity in any of the three methods. Gram-positive bacteria were more sensitive than gram-negative bacteria. Staphylococcus epidermidis and Staphylococcus aureus were the most susceptible Gram-positive bacteria.

Clinico-microbiological study of Pseudomonas aeruginosa in wound infections and the detection of metallo-β-lactamase production.

PubMed

Bangera, Divya; Shenoy, Suchitra M; Saldanha, Dominic Rm

2016-12-01

Pseudomonas aeruginosa is a common opportunistic pathogen of humans among the Gram-negative bacilli. Clinically, it is associated with nosocomial infections like burns and surgical-site wound infections and remains a major health concern, especially among critically ill and immunocompromised patients. This is a prospective laboratory-based 2 year study conducted to isolate P. aeruginosa from wound specimens and the antimicrobial susceptibility pattern with reference to metallo-β-lactamase (MBL) production. Two hundred and twenty-four samples of P. aeruginosa isolated from wound specimens were included in the study. Antimicrobial susceptibility was done as per Clinical Laboratory Standard Institute (CLSI) guidelines. MBL-producing P. aeruginosa was detected using the EDTA disk diffusion synergy test. Statistical analysis was done using the SPSS 11 package (SPSS Inc., Chicago, IL). Out of the 224 P. aeruginosa isolates, 100% were susceptible to polymyxin B and colistin, 92·8% were sensitive to imipenem, 38% showed resistance to gentamicin followed by ceftazidime (31·69%) and meropenem (33·03). Sixteen (7·14%) isolates showed MBL production. Infection caused by drug-resistant P. aeruginosa is important to identify as it poses a therapeutic problem and is also a serious concern for infection control management. The acquired resistance genes can be horizontally transferred to other pathogens or commensals if aseptic procedures are not followed. © 2015 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

High prevalence of multiple resistance to antibiotics in Salmonella serovars isolated from a poultry slaughterhouse in Spain.

PubMed

Carramiñana, Juan J; Rota, Carmina; Agustín, I; Herrera, Antonio

2004-11-30

Salmonellosis is a major foodborne infection in Spain, and strains that are resistant to a great variety of antibiotics have become a major public health concern. The aim of this study was to determine the level of antibiotic resistance in 133 Salmonella isolates obtained from a poultry slaughterhouse in Zaragoza (NE Spain). Antimicrobial resistance testing was performed by disk diffusion method using 19 antibiotics. Results were interpreted following the NCCLS criteria. Overall, the highest percentage of resistance was found to the following antimicrobial agents: sulfadiazine (96.2%), neomycin (53.4%), tetracycline (21.8%), and streptomycin (11.3%). All isolates were found to be resistant to one or more of the antibiotics tested. Multiple resistance was observed in 87 strains (65.4%). We found 23 different patterns of resistance in Salmonella Enteritidis. Resistance to sulfadiazine was the most common single resistance. The most frequent patterns of multiresistant strains were neomycin+sulfadiazine and neomycin+tetracycline+sulfadiazine. S. 4,5,12:b: showed the highest percentages of resistance to the tested drugs, with five different resistance patterns found. Ampicillin+chloramphenicol+streptomycin+sulphonamides+tetracycline (ACSSuT) resistance pattern, commonly associated with S. Typhimurium DT 104, was not detected in strains of the same phage type from broilers. The appearance of substantial multiresistance in foodborne Salmonella isolates suggests the need for more prudent use of antibiotics by farmers, veterinarians, and physicians.

Essential Oil from Origanum vulgare Completely Inhibits the Growth of Multidrug-Resistant Cystic Fibrosis Pathogens.

PubMed

Pesavento, Giovanna; Maggini, Valentina; Maida, Isabel; Lo Nostro, Antonella; Calonico, Carmela; Sassoli, Chiara; Perrin, Elena; Fondi, Marco; Mengoni, Alessio; Chiellini, Carolina; Vannacci, Alfredo; Gallo, Eugenia; Gori, Luigi; Bogani, Patrizia; Bilia, Anna Rita; Campana, Silvia; Ravenni, Novella; Dolce, Daniela; Firenzuoli, Fabio; Fani, Renato

2016-06-01

Essential oils (EOs) are known to inhibit the growth of a wide range of microorganisms. Particularly interesting is the possible use of EOs to treat multidrug-resistant cystic fibrosis (CF) pathogens. We tested the essential oil (EO) from Origanum vulgare for in vitro antimicrobial activity, against three of the major human opportunistic pathogens responsible for respiratory infections in CF patients; these are methicillin-resistant Staphylococcus aureus, Stenotrophomonas maltophilia and Achromobacter xylosoxidans. Antibiotic susceptibility of each strain was previously tested by the standard disk diffusion method. Most strains were resistant to multiple antibiotics and could be defined as multi-drug-resistant (MDR). The antibacterial activity of O. vulgare EO (OEO) against a panel of 59 bacterial strains was evaluated, with MIC and MBC determined at 24, 48 and 72 hours by a microdilution method. The OEO was effective against all tested strains, although to a different extent. The MBC and MIC of OEO for S. aureus strains were either lower or equal to 0.50%, v/v, for A. xylosoxidans strains were lower or equal to 1% and 0.50%, v/v, respectively; and for S. maltophilia strains were lower or equal to 0.25%, v/v. The results from this study suggest that OEO might exert a role as an antimicrobial in the treatment of CF infections.

Antimicrobial activity of fresh garlic juice: An in vitro study

PubMed Central

Yadav, Seema; Trivedi, Niyati A.; Bhatt, Jagat D.

2015-01-01

Introduction: Antimicrobial resistance has been a global concern. Currently, interest has been focused on exploring antimicrobial properties of plants and herbs. One such botanical is Allium sativum (garlic). Aim: To evaluate the antimicrobial activity of fresh juice of garlic. Materials and Methods: Varying concentrations of fresh garlic juice (FGJ) were tested for their antimicrobial activity against common pathogenic organisms isolated at SSG Hospital, Vadodara, using well diffusion method. Moreover, minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) of FGJ were tested using broth dilution method. Sensitivity pattern of the conventional antimicrobials against common pathogenic bacteria was tested using disc diffusion method. Results: FGJ produced dose-dependent increase in the zone of inhibition at a concentration of 10% and higher. MIC of FGJ against the pathogens ranged from 4% to 16% v/v whereas MLC value ranged from 4% to 32% v/v with Escherichia coli and Staphylococcus aureus spp. showed highest sensitivity. Conclusion: FGJ has definite antimicrobial activity against common pathogenic organisms isolated at SSG Hospital, Vadodara. Further studies are needed to find out the efficacy, safety, and kinetic data of its active ingredients. PMID:27011724

Evaluation of the antimicrobial activities of chlorhexidine gluconate, sodium hypochlorite and octenidine hydrochloride in vitro.

PubMed

Tirali, Resmiye E; Bodur, Haluk; Sipahi, Bilge; Sungurtekin, Elif

2013-04-01

The objective of this study was to compare the antimicrobial activity of sodium hypochlorite (NaOCl), chlorhexidine gluconate (CHX) and octenidine hydrochloride (OCT) in different concentrations against endodontic pathogens in vitro. Agar diffusion procedure was used to determine the antimicrobial activity of the tested materials. Enterococcus faecalis, Candida albicans and the mixture of these were used for this study. In the agar diffusion test, 5.25% NaOCl exhibited better antimicrobial effect than the other concentrations of NaOCl for all strains. All concentrations of OCT were effective against C. albicans and E. faecalis. Some 0.2% CHX was ineffective on all microorganisms. Antibacterial effectiveness of all experimental solutions decreased on the mixture of all strains. Decreasing concentrations of NaOCl resulted in significantly reduced antimicrobial effect. © 2010 The Authors. Australian Endodontic Journal © 2010 Australian Society of Endodontology.

Bioactivity of Malva Sylvestris L., a Medicinal Plant from Iran

PubMed Central

Razavi, Seyed Mehdi; Zarrini, Gholamreza; Molavi, Ghader; Ghasemi, Ghader

2011-01-01

Objective(s) Malva sylvestris L. (Malvaceae), an annual plant, has been already commonly used as a medicinal plant in Iran. In the present work, we evaluate some bioactivities of the plant extracts. Materials and Methods The aired-dried plant flowers and leaves were extracted by soxhlet apparatus with n-hexane, dichloromethane and methanol. The antimicrobial, cytotoxic, and phytotoxic of the plant extracts were evaluated using disk diffusion method, MTT, and Lettuce assays, respectively. Results Both flowers and leaves of M. sylvestris methanol extracts exhibited strong antibacterial effects against Erwinia carotovora, a plant pathogen, with MIC value of 128 and 256 µg/ml, respectively. The flowers extract also showed high antibacterial effects against some human pathogen bacteria strains such as Staphylococcus aureus, Streptococcus agalactiae, Entrococcus faecalis, with MIC value of 192, 200 and 256 µg/ml, respectively. The plant methanol extracts had relatively high cytotoxic activity against MacCoy cell line. Conclusion We concluded that Malva sylvestris can be candidated as an antiseptic, a chemopreventive or a chemotherapeutic agent. PMID:23493458

Enhanced bioactivity of ZnO nanoparticles—an antimicrobial study

PubMed Central

Padmavathy, Nagarajan; Vijayaraghavan, Rajagopalan

2008-01-01

In this study, we investigate the antibacterial activity of ZnO nanoparticles with various particle sizes. ZnO was prepared by the base hydrolysis of zinc acetate in a 2-propanol medium and also by a precipitation method using Zn(NO3)2 and NaOH. The products were characterized by x-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Bacteriological tests such as minimum inhibitory concentration (MIC) and disk diffusion were performed in Luria-Bertani and nutrient agar media on solid agar plates and in liquid broth systems using different concentrations of ZnO by a standard microbial method for the first time. Our bacteriological study showed the enhanced biocidal activity of ZnO nanoparticles compared with bulk ZnO in repeated experiments. This demonstrated that the bactericidal efficacy of ZnO nanoparticles increases with decreasing particle size. It is proposed that both the abrasiveness and the surface oxygen species of ZnO nanoparticles promote the biocidal properties of ZnO nanoparticles. PMID:27878001

Enhanced bioactivity of ZnO nanoparticles—an antimicrobial study

NASA Astrophysics Data System (ADS)

Padmavathy, Nagarajan; Vijayaraghavan, Rajagopalan

2008-07-01

In this study, we investigate the antibacterial activity of ZnO nanoparticles with various particle sizes. ZnO was prepared by the base hydrolysis of zinc acetate in a 2-propanol medium and also by a precipitation method using Zn(NO3)2 and NaOH. The products were characterized by x-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Bacteriological tests such as minimum inhibitory concentration (MIC) and disk diffusion were performed in Luria-Bertani and nutrient agar media on solid agar plates and in liquid broth systems using different concentrations of ZnO by a standard microbial method for the first time. Our bacteriological study showed the enhanced biocidal activity of ZnO nanoparticles compared with bulk ZnO in repeated experiments. This demonstrated that the bactericidal efficacy of ZnO nanoparticles increases with decreasing particle size. It is proposed that both the abrasiveness and the surface oxygen species of ZnO nanoparticles promote the biocidal properties of ZnO nanoparticles.

Synthesis, characterization and biological studies of Schiff bases derived from heterocyclic moiety.

PubMed

Shanty, Angamaly Antony; Philip, Jessica Elizabeth; Sneha, Eeettinilkunnathil Jose; Prathapachandra Kurup, Maliyeckal R; Balachandran, Sreedharannair; Mohanan, Puzhavoorparambil Velayudhan

2017-02-01

Some new Schiff bases (H 1 -H 7 ) have been synthesized by the condensation of 2-aminophenol, 2-amino-4-nitrophenol, 2-amino-4-methylphenol, 2-amino benzimidazole with thiophene-2-carboxaldehyde and pyrrole-2-carboxaldehyde. The structures of newly synthesized compounds were characterized by elemental analysis, FT-IR, 1 H NMR, UV-VIS, and single crystal X-ray crystallography. The in vitro antibacterial activity of the synthesized compounds has been tested against Salmonella typhi, Bacillus coagulans, Bacillus pumills, Escherichia coli, Bacillus circulans, Pseudomonas, Clostridium and Klebsilla pneumonia by disk diffusion method. The quantitative antimicrobial activity of the test compounds was evaluated using Resazurin based Microtiter Dilution Assay. Ampicillin was used as standard antibiotics. Schiff bases individually exhibited varying degrees of inhibitory effects on the growth of the tested bacterial species. The antioxidant activity of the synthesized compounds was determined by the 1,1-diphenyl-2-picrylhydrazyl(DPPH) method. IC 50 value of synthesized Schiff bases were calculated and compared with standard BHA. Copyright © 2016 Elsevier Inc. All rights reserved.

Assessment of antimicrobial usage and residues in commercial chicken eggs from smallholder poultry keepers in Morogoro municipality, Tanzania.

PubMed

Nonga, H E; Simon, C; Karimuribo, E D; Mdegela, R H

2010-08-01

Occurrence of antimicrobial residues in commercial chicken eggs was determined in Morogoro municipality between January and February 2007. Twenty smallholder farmers were interviewed on the types of antimicrobials, reasons of use and their awareness on antimicrobial withdrawal period. Seventy egg samples were collected for qualitative antimicrobial drug residues analysis by use of agar well diffusion and Delvotest SP assays. It was found that farmers use antimicrobial drugs as prophylaxis and treatment of common chicken diseases namely fowl typhoid (85%), infectious bursa disease (Gumboro) (65%) infectious coryza (65%), collibacilosis (55%), coccidiosis (54%), Newcastle disease (50%), helminthosis (20%) and fowl pox (15%). Antimicrobials accounted for 85% of the drugs commonly used. It was also found that 65% of the farmers treat their chicken themselves. The common drugs were oxytetracycline (75%), egg booster (50%), amprolium (35%), sulphamethoxypyridazine (35%), sulphanilamide (25%), chlortetracyclines (10%), chloramphenicol (10%), sulphadiazine-trimethoprim (20%), duoxycycline (20%), sulphadiazine (25%) and flumequine (10%). Eighty per cent of the farmers had knowledge on antimicrobial withdrawal period sold eggs before withdrawal period and almost 85% were unaware of possible effects of antimicrobial residues in humans. All 70 eggs were positive to antimicrobial residues by Delvotest kit, but 21.4% positive with agar well diffusion test. It was concluded that the presence of antimicrobial residues in table eggs could be of public health significance to the egg consumers in Morogoro municipality.

Occurrence and antimicrobial resistance of pathogenic Escherichia coli and Salmonella spp. in retail raw table eggs sold for human consumption in Enugu state, Nigeria

PubMed Central

Okorie-Kanu, O. Josephine; Ezenduka, E. Vivienne; Okorie-Kanu, C. Onwuchokwe; Ugwu, L. Chinweokwu; Nnamani, U. John

2016-01-01

Aim: This study was conducted to investigate the occurrence of pathogenic Escherichia coli and Salmonella species in retail raw table eggs sold for human consumption in Enugu State and to determine the resistance of these pathogens to antimicrobials commonly used in human and veterinary practices in Nigeria. Materials and Methods: A total of 340 raw table eggs comprising 68 composite samples (5 eggs per composite sample) were collected from five selected farms (13 composite samples from the farms) and 10 retail outlets (55 composite samples from the retail outlets) in the study area over a period of 4-month (March-June, 2014). The eggs were screened for pathogenic E. coli and Salmonella species following standard procedures within 24 h of sample collection. Isolates obtained were subjected to in-vitro antimicrobial susceptibility test with 15 commonly used antimicrobials using the disk diffusion method. Results: About 37 (54.4%) and 7 (10.3%) of the 68 composite samples were positive for pathogenic E. coli and Salmonella species, respectively. The shells showed significantly higher (p<0.05) contaminations than the contents for both microorganisms. The eggs from the farms showed higher contamination with pathogenic E. coli than eggs from the retail outlets while the reverse was the case for Salmonella species even though they were not significant (p>0.05). The organisms obtained showed a multiple drug resistance. They were completely resistant to nitrofurantoin, sulfamethoxazole/trimethoprim, penicillin G and oxacillin. In addition to these, Salmonella spp. also showed 100% resistance to tetracycline. The pathogenic E. coli isolates obtained were 100% susceptible to gentamicin, neomycin, ciprofloxacin, and amoxicillin-clavulanic acid while Salmonella spp. showed 100% susceptibility to erythromycin, neomycin, and rifampicin. Both organisms showed varying degrees of resistance to streptomycin, amoxicillin, vancomycin, and doxycycline. Conclusion: From the results of the study, it can be concluded that the raw table eggs marketed for human consumption in Enugu State, Nigeria is contaminated with pathogenic E. coli and Salmonella species that showed multiple drug resistance to antimicrobial agents commonly used in veterinary and human practice. PMID:27956787

Occurrence and antimicrobial resistance of pathogenic Escherichia coli and Salmonella spp. in retail raw table eggs sold for human consumption in Enugu state, Nigeria.

PubMed

Okorie-Kanu, O Josephine; Ezenduka, E Vivienne; Okorie-Kanu, C Onwuchokwe; Ugwu, L Chinweokwu; Nnamani, U John

2016-11-01

This study was conducted to investigate the occurrence of pathogenic Escherichia coli and Salmonella species in retail raw table eggs sold for human consumption in Enugu State and to determine the resistance of these pathogens to antimicrobials commonly used in human and veterinary practices in Nigeria. A total of 340 raw table eggs comprising 68 composite samples (5 eggs per composite sample) were collected from five selected farms (13 composite samples from the farms) and 10 retail outlets (55 composite samples from the retail outlets) in the study area over a period of 4-month (March-June, 2014). The eggs were screened for pathogenic E. coli and Salmonella species following standard procedures within 24 h of sample collection. Isolates obtained were subjected to in-vitro antimicrobial susceptibility test with 15 commonly used antimicrobials using the disk diffusion method. About 37 (54.4%) and 7 (10.3%) of the 68 composite samples were positive for pathogenic E. coli and Salmonella species, respectively. The shells showed significantly higher (p<0.05) contaminations than the contents for both microorganisms. The eggs from the farms showed higher contamination with pathogenic E. coli than eggs from the retail outlets while the reverse was the case for Salmonella species even though they were not significant (p>0.05). The organisms obtained showed a multiple drug resistance. They were completely resistant to nitrofurantoin, sulfamethoxazole/trimethoprim, penicillin G and oxacillin. In addition to these, Salmonella spp. also showed 100% resistance to tetracycline. The pathogenic E. coli isolates obtained were 100% susceptible to gentamicin, neomycin, ciprofloxacin, and amoxicillin-clavulanic acid while Salmonella spp. showed 100% susceptibility to erythromycin, neomycin, and rifampicin. Both organisms showed varying degrees of resistance to streptomycin, amoxicillin, vancomycin, and doxycycline. From the results of the study, it can be concluded that the raw table eggs marketed for human consumption in Enugu State, Nigeria is contaminated with pathogenic E. coli and Salmonella species that showed multiple drug resistance to antimicrobial agents commonly used in veterinary and human practice.

Multicenter Evaluation of the Accelerate PhenoTest BC Kit for Rapid Identification and Phenotypic Antimicrobial Susceptibility Testing Using Morphokinetic Cellular Analysis

PubMed Central

2018-01-01

ABSTRACT We describe results from a multicenter study evaluating the Accelerate Pheno system, a first of its kind diagnostic system that rapidly identifies common bloodstream pathogens from positive blood cultures within 90 min and determines bacterial phenotypic antimicrobial susceptibility testing (AST) results within ∼7 h. A combination of fresh clinical and seeded blood cultures were tested, and results from the Accelerate Pheno system were compared to Vitek 2 results for identification (ID) and broth microdilution or disk diffusion for AST. The Accelerate Pheno system accurately identified 14 common bacterial pathogens and two Candida spp. with sensitivities ranging from 94.6 to 100%. Of fresh positive blood cultures, 89% received a monomicrobial call with a positive predictive value of 97.3%. Six common Gram-positive cocci were evaluated for ID. Five were tested against eight antibiotics, two resistance phenotypes (methicillin-resistant Staphylococcus aureus and Staphylococcus spp. [MRSA/MRS]), and inducible clindamycin resistance (MLSb). From the 4,142 AST results, the overall essential agreement (EA) and categorical agreement (CA) were 97.6% and 97.9%, respectively. Overall very major error (VME), major error (ME), and minor error (mE) rates were 1.0%, 0.7%, and 1.3%, respectively. Eight species of Gram-negative rods were evaluated against 15 antibiotics. From the 6,331 AST results, overall EA and CA were 95.4% and 94.3%, respectively. Overall VME, ME, and mE rates were 0.5%, 0.9%, and 4.8%, respectively. The Accelerate Pheno system has the unique ability to identify and provide phenotypic MIC and categorical AST results in a few hours directly from positive blood culture bottles and support accurate antimicrobial adjustment. PMID:29305546

Antibacterial activity and cytocompatibility of an implant coating consisting of TiO2 nanotubes combined with a GL13K antimicrobial peptide.

PubMed

Li, Tao; Wang, Na; Chen, Su; Lu, Ran; Li, Hongyi; Zhang, Zhenting

2017-01-01

Prevention of implant-associated infections at an early stage of surgery is highly desirable for the long-term efficacy of implants in dentistry and orthopedics. Infection prophylaxis using conventional antibiotics is becoming less effective due to the development of bacteria resistant to multiple antibiotics. An ideal strategy to conquer bacterial infections is the local delivery of antibacterial agents. Therefore, antimicrobial peptide (AMP) eluting coatings on implant surfaces is a promising alternative. In this study, the feasibility of utilizing TiO 2 nanotubes (TNTs), processed using anodization, as carriers to deliver a candidate AMP on titanium surfaces for the prevention of implant-associated infections is assessed. The broad-spectrum GL13K (GKIIKLKASLKLL-CONH2) AMP derived from human parotid secretory protein was selected and immobilized to TNTs using a simple soaking technique. Field emission scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and liquid chromatography-mass spectrometry analyses confirmed the successful immobilization of GL13K to anatase TNTs. The drug-loaded coatings demonstrated a sustained and slow drug release profile in vitro and eradicated the growth of Fusobacterium nucleatum and Porphyromonas gingivalis within 5 days of culture, as assessed by disk-diffusion assay. The GL13K-immobilized TNT (GL13K-TNT) coating demonstrated greater biocompatibility, compared with a coating produced by incubating TNTs with equimolar concentrations of metronidazole. GL13K-TNTs produced no observable cytotoxicity to preosteoblastic cells (MC3T3-E1). The coating may also have an immune regulatory effect, in support of rapid osseointegration around implants. Therefore, the combination of TNTs and AMP GL13K may achieve simultaneous antimicrobial and osteoconductive activities.

Microbiological Features of Upper Respiratory Tract Infections in Bulgarian Children for the Period 1998-2014.

PubMed

Gergova, Raina Tzvetanova; Petrova, Guergana; Gergov, Stefan; Minchev, Petko; Mitov, Ivan; Strateva, Tanya

2016-11-01

Across the globe, upper respiratory tract infections (URTIs) are the most prevalent cause of morbidity in childhood. The aim of our study is to analyze the incidence and etiology of bacterial URTIs in Bulgarian children, as well as the increasing antimicrobial resistance to the most common etiologic agents over a period of 17 years. Retrospective study. The study material comprised the data from 4768 patients (aged 1-16 years) with URTI during the period from 1998-2014. Specific microbiology agent detection was performed by culture examination. Susceptibilities to the investigated pathogens were determined by the disk diffusion method and minimal inhibitory concentration according to the criteria of the Clinical and Laboratory Standards Institute (CLSI). Polymerase chain reaction was used to detect the presence of β-lactam resistance genes. We identified the following as the most common URTI bacterial pathogens: Streptococcus pneumoniae (40.94%), Streptococcus pyogenes (34.16%), Haemophilus influenzae (44.23%), Moraxella catarrhalis (39.19%) and Staphylococcus aureus (23.88%). In more than 70% of cases, a polymicrobial etiology was found. The most commonly affected individuals were pre-school-aged children, which accounted for more than 36% of all patients. During the study period, a dramatic increase in resistance to antibiotic agents was observed. The most frequent types of resistance were the enzymatic inactivation of penicillins and cephalosporins (close to 100% in staphylococci and moraxellae) and inducible macrolide-lincozamide resistance (about 20% of Gram-positive cocci). Due to mandatory immunization against pneumococci and H. influenzae in Bulgaria and the vast expanding resistance to the most popular antimicrobial agents changes in the etiology of URTI have recently been noted. Regular analysis of this etiological dynamic and the antimicrobial resistance of respiratory pathogens is important for choosing the correct therapy and successful treatment.

[Phenotypic and molecular identification of extended-spectrum beta-lactamase (ESBL) TEM and SHV produced by clinical isolates Escherichia coli and Klebsiella spp. in hospitals].

PubMed

González Mesa, Leonora; Ramos Morí, Astrid; Nadal Becerra, Loreta; Morffi Figueroa, Janet; Hernández Robledo, Ernesto; Alvarez, Ana Berta; Marchena Bequer, Juan J; González Alemán, Mabel; Villain Plous, Carlos

2007-01-01

Nosocomial infections caused by gram-negative bacilli which produce extended spectrum beta-lactamase (ESBL) are associated with the increase of morbidity and mortality in hospitals. The objective of this study was to evaluate the frequency of ESBL, specifically the TEM and SHV type, produced by Escherichia coli and Klebsiella spp. strains, and also to determine the antimicrobial susceptibility of these isolates in comparison with other antibiotic families. A total of 326 strains were collected between 2002-2004 from hospitals in Havana City. The susceptibility tests were carried out according to the NCCLS guides and they were confirmed as. ESBL producers by the double disk diffusion method. The molecular characterization of these enzymes was determined by polymerase chain reaction (PCR), using two sets of oligonucleotides to amplify genes encoding TEM and SHV type beta-lactamase. The ESBL phenotype was detected in 31 (10%) Escherichia coli isolates, 19 of these strains (61%) carried the blaTEM genes, 5 (16%) blaSHV genes, 4 (12%) strains carried both genes and 11 strains (35%) carried the non-ESBL blaTEM and blaSHV genes. In Klebsiella spp. the ESBL phenotype was detected in 10 (36 %) isolates, only one strain carried the blaTEM gene. The most active antimicrobials against Escherichia coli were ciprofloxacin (64.5%) and gentamicin (58.07%); in the case of Klebsiella spp. the same antimicrobials were the most active with similar susceptibility (70%) for both. The carbapenems still remain the most active antibiotics against Escherichia coli and Klebsiella spp. strains, which are ESBL producers. However, their use should be closely controlled.

Screening of the Antimicrobial Activity against Drug Resistant Bacteria of Photorhabdus and Xenorhabdus Associated with Entomopathogenic Nematodes from Mae Wong National Park, Thailand

PubMed Central

Muangpat, Paramaporn; Yooyangket, Temsiri; Fukruksa, Chamaiporn; Suwannaroj, Manawat; Yimthin, Thatcha; Sitthisak, Sutthirat; Chantratita, Narisara; Vitta, Apichat; Tobias, Nicholas J.; Bode, Helge B.; Thanwisai, Aunchalee

2017-01-01

Photorhabdus and Xenorhabdus are symbiotic with entomopathogenic nematodes (EPNs) of the genera Heterorhabditis and Steinernema, respectively. These bacteria produce several secondary metabolites including antimicrobial compounds. The objectives of this study were to isolate and identify EPNs and their symbiotic bacteria from Mae Wong National Park, Thailand and to evaluate the antibacterial activities of symbiont extracts against drug resistant bacteria. A total of 550 soil samples from 110 sites were collected between August 2014 and July 2015. A total of EPN isolates were obtained through baiting and White trap methods, which yielded 21 Heterorhabditis and 3 Steinernema isolates. Based on molecular identification and phylogenetic analysis, the most common species found in the present study was P. luminescens subsp. akhurstii associated with H. indica. Notably, two species of EPNs, H. zealandica and S. kushidai, and two species of symbiotic bacteria, X. japonica and P. temperata subsp. temperata represented new recorded organisms in Thailand. Furthermore, the association between P. temperata subsp. temperata and H. zealandica has not previously been reported worldwide. Disk diffusion, minimal inhibitory concentration, and minimal bactericidal concentration analyses demonstrated that the crude compound extracted by ethyl acetate from P. temperata subsp. temperata could inhibit the growth of up to 10 strains of drug resistant bacteria. Based on HPLC-MS analysis, compound classes in bacterial extracts were identified as GameXPeptide, xenoamicin, xenocoumacin, mevalagmapeptide phurealipids derivatives, and isopropylstilbene. Together, the results of this study provide evidence for the diversity of EPNs and their symbiotic bacteria in Mae Wong National Park, Thailand and demonstrate their novel associations. These findings also provide an important foundation for further research regarding the antimicrobial activity of Photorhabdus bacteria. PMID:28702004

Preliminary study on the antimicrobial susceptibility pattern related to the genotype of Vibrio vulnificus strains isolated in the north-western Adriatic Sea coastal area.

PubMed

Serratore, Patrizia; Zavatta, Emanuele; Fiocchi, Eleonora; Serafini, Emanuele; Serraino, Andrea; Giacometti, Federica; Bignami, Giorgia

2017-10-20

V. vulnificus is a Gram-negative bacterium, commonly found in estuarine and coastal habitats, that can infect humans through seafood consumption or wound exposure. This study represents the first attempt to correlate the genotype of Vibrio vulnificus strains isolated in the north-western Adriatic Sea coastal area, with their antimicrobial susceptibility patterns. On the whole, 40 V. vulnificus strains, isolated from shellfish (n=20), different coastal water bodies (n=19), and the blood of a Carretta carretta turtle (n=1), were utilized. All strains were positive for the species-specific genes vvh A and hsp , with high variability for other markers: 55% (22 out of 40) resulted of the environmental (E) genotype ( vcg E, 16S rRNA type A, CPS2 or CPS0), 10% (4 out of 40) of the clinical (C) genotype ( vcg C, 16S rRNA type B, CPS1), and 35% (14 out of 40) of the mixed (M) genotype, possessing both E and C markers. The antimicrobial susceptibility was assayed by the diffusion method on agar, according to the Clinical Laboratory Standards Institute (CLSI), utilizing the following commercial disks (Oxoid): ampicillin (AMP), ampicillin- sulbactam (SAM), piperacillin (PRL), cefazolin (KZ), cefotaxime(CTX), ceftazidime (CAZ), imipenem (IPM), meropenem (MEM), amikacin (AK), gentamicin(CN), tetracycline(TE), ciprofloxacin (CIP), levofloxacin (LEV), trimethoprim-sulfamethoxazole (SXT), and chloramphenicol (C). 75% of the strains, (n=30) including all C strains, was sensitive to all the tested antibiotics, whereas E strains showed intermediate sensitivity to AK (2 strains), CIP and CAZ (1 strain), TE (1 strain) and resistance to KZ (1 strain), and 4 M strains showed I to AK.

Serotype distribution, antimicrobial resistance, and molecular characterization of invasive group B Streptococcus isolates recovered from Chinese neonates.

PubMed

Wang, Ping; Ma, Zhuoya; Tong, Jingjing; Zhao, Ruizhen; Shi, Wei; Yu, Sangjie; Yao, Kaihu; Zheng, Yuejie; Yang, Yonghong

2015-08-01

Group B Streptococcus (GBS) is an important neonatal pathogen associated with high morbidity and mortality in developed countries. However, data describing neonatal GBS disease in developing countries, particularly in Asia, are largely incomplete. The aim of this study was to determine the serotype distribution, antimicrobial resistance, and molecular characteristics of invasive GBS isolates recovered from Chinese neonates. From 2008 to 2013, 40 GBS isolates were recovered from infected neonates less than 3 months of age. All isolates were identified with the CAMP test and commercially available techniques. Serotyping was performed by latex agglutination. Antibiotic susceptibility was tested with Etest strips and the disk diffusion method. Multilocus sequence typing and erythromycin resistance gene detection (ermB and mefA) were performed by PCR. Four serotypes were identified. Serotype III (85%) was the most prevalent, followed by Ia (7.5%), Ib (5%), and V (2.5%). All isolates were sensitive to penicillin, ceftriaxone, and levofloxacin. However, resistance to erythromycin (92.5%), clindamycin (87.5%), and tetracycline (100%) was observed. Among erythromycin-resistant isolates, 73.0% carried the ermB gene alone, 5.4% carried the mefA gene alone, and 21.6% expressed both ermB and mefA genes. A total of seven sequence types (STs) were identified; the most prevalent was ST17, accounting for 80% of all isolates. Further, serotype III isolates contained ST17 (94.2%), ST19 (2.9%), and ST650 (2.9%). Serotype distribution, antimicrobial susceptibility, and sequence type characterization in Asia and in other global regions may contribute to improve the prevention and treatment of neonatal GBS infections. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Diversity of Campylobacter in retail meat and liver of lambs and goat kids.

PubMed

Lazou, Thomai; Dovas, Chrysostomos; Houf, Kurt; Soultos, Nikolaos; Iossifidou, Eleni

2014-04-01

The presence, genetic diversity, and antimicrobial susceptibility profile of Campylobacter spp. in retail lamb and goat kid carcasses were assessed. A total of 200 samples consisting of 100 meat and 100 liver surface swabs were collected from 47 lamb and 53 goat kid carcasses at 23 retail markets in Northern Greece, and 125 Campylobacter isolates were recovered from 32 meat surfaces (32%) and 44 liver surfaces (44%). Multiplex polymerase chain reaction and restriction fragment length polymorphism analysis specified Campylobacter coli as the most frequently detected species (59.2%) followed by C. jejuni (40.8%). Pulsed-field gel electrophoresis (PFGE) was applied in order to typify a subset of randomly selected isolates (n=80). SmaI-PFGE successfully clustered the 80 isolates in 38 SmaI-PFGE types, indicating high heterogeneity among the analyzed Campylobacter isolates, and provided data regarding the dissemination of Camplobacter among carcasses stored in the same retail market. Antimicrobial susceptibility profiles of Campylobacter isolates, assessed by the disk-diffusion method, indicated that 31 isolates (24.8%) were multidrug resistant, and the most common profile was the concurrent resistance to tetracycline and streptomycin. Overall, 56.8% of isolates (n=71, multidrug-resistant isolates included) exhibited resistance to at least one antimicrobial (tetracycline 34.4%, quinolones 27.2%, and streptomycin 20.8%). However, all isolates were susceptible to erythromycin and gentamicin. The findings of this study verify the contamination of retail lamb and goat kid carcasses with a heterogeneous population of thermotolerant campylobacters. These data underscore the fact that retail meat and liver of small ruminants could serve as vehicles for consumer contamination with Campylobacter and that further investigation is necessary in order to evaluate the risk imposed by such products within the epidemiology of human campylobacteriosis cases.

Comparative phenotypic and genotypic analyses of Salmonella Rissen that originated from food animals in Thailand and United States.

PubMed

Pornsukarom, S; Patchanee, P; Erdman, M; Cray, P F; Wittum, T; Lee, J; Gebreyes, W A

2015-03-01

Salmonella enterica serovar Rissen has been recognized as one of the most common serovar among humans and pork production systems in different parts of the world, especially Asia. In the United States, this serovar caused outbreaks but its epidemiologic significance remains unknown. The objectives of this study were to compare the phenotypic (antimicrobial susceptibility) and genotypic attributes of Salmonella Rissen isolated in Thailand (Thai) and the United States (US). All the Thai isolates (n = 30) were recovered from swine faecal samples. The US isolates (n = 35) were recovered from swine faecal samples (n = 29), cattle (n = 2), chicken (n = 2), dog (n = 1) and a ready-to-eat product (n = 1). The antimicrobial susceptibility of isolates was determined using the Kirby-Bauer disk diffusion method with a panel of 12 antimicrobials. Pulse-field gel electrophoresis (PFGE) was used to determine the genotypic diversity of isolates. All Thai isolates showed multidrug resistance (MDR) with the most frequent antibiotic resistance shown against ampicillin (100%), sulfisoxazole (96.7%), tetracycline (93.3%), streptomycin (90%) and chloramphenicol (30%). About half of the isolates of USA origin were pan-susceptible and roughly 30% were resistant to only tetracycline (R-type: Te). Salmonella Rissen isolated from Thailand and the USA in this study were found to be clonally unrelated. Genotypic analyses indicated that isolates were clustered primarily based on the geographic origin implying the limited clonality among the strains. Clonal relatedness among different host species within the same geography (USA) was found. We found genotypic similarity in Thai and US isolates in few instances but with no epidemiological link. Further studies to assess propensity for increased inter-regional transmission and dissemination is warranted. © 2014 Blackwell Verlag GmbH.

Longitudinal surveillance on antibiogram of important Gram-positive pathogens in Southern China, 2001 to 2015.

PubMed

Xu, Zhenbo; Xie, Jinhong; Peters, Brian M; Li, Bing; Li, Lin; Yu, Guangchao; Shirtliff, Mark E

2017-02-01

A longitudinal surveillance aimed to investigate the antibiogram of three genus of important Gram-positive pathogens in Southern China during 2001-2015. A total of 3849 Staphylococcus, Enterococcus and Streptococcus strains were isolated from Southern China during 2001-2015. Bacteria identification was performed by colony morphology, Gram staining, the API commercial kit and the Vitek 2 automated system. Antimicrobial susceptibility testing was determined by disk diffusion method and MIC method. As sampling site was concerned, 51.4% of Staphylococcus strains were isolated from sputum, whereas urinary tract remained the dominant infection site among Enterococcus and Streptococcus. According to the antimicrobial susceptibility, three genus of important Gram-positive pathogens showed high resistance against erythromycin, tetracycline, ciprofloxacin and clindamycin. Resistance rates to penicillins (penicillin, oxacillin, ampicillin) were high as well, with the exception of E. faecalis and Streptococcus. Overall, resistance rates against methicillin (oxacillin) were 63.2% in S. aureus and 76.2% in coagulase-negative Staphylococcus (CNS), along with continuous increases during the study. VRSA and vancomycin-resistant coagulase-negative Staphylococcus only appeared in 2011-2015. Sight decline was obtained for the vancomycin resistance of E. faecalis, while vancomycin-resistant E. faecium only appeared in 2011-2015, with its intermediate rate decreasing. Significant decrease in penicillin-resistant Streptococcus pneumonia (PRSP) was observed during studied period. Glycopeptide antibiotic remained highly effective to Staphylococcus, Enterococcus and Streptococcus (resistance rates <5%). Despite decline obtained for some antibiotic agents resistance during 2001-2015, antimicrobial resistance among Gram-positive pathogens still remained high in Southern China. This study may aid in the guidance for appropriate therapeutic strategy of infections caused by nosocomial pathogens. Copyright © 2016 Elsevier Ltd. All rights reserved.

Antimicrobial, antibiofilm and cytotoxic activities of Hakea sericea Schrader extracts

PubMed Central

Luís, Ângelo; Breitenfeld, Luiza; Ferreira, Susana; Duarte, Ana Paula; Domingues, Fernanda

2014-01-01

Background: Hakea sericea Schrader is an invasive shrub in Portuguese forests. Objective: The goal of this work was to evaluate the antimicrobial activity of H. sericea extracts against several strains of microorganisms, including the ability to inhibit the formation of biofilms. Additionally the cytotoxic properties of these extracts, against human cells, were assessed. Materials and Methods: The antimicrobial activity of the methanolic extracts of H. sericea was assessed by disk diffusion assay and Minimum Inhibitory Concentration (MIC) value determination. The antibiofilm activity was determined by quantification of total biofilm biomass with crystal violet. Cytotoxicity was evaluated by hemolysis assay and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test. Results: For Gram-positive bacteria, MIC values of H. sericea methanolic extracts ranged between 0.040 and 0.625 mg/mL, whereas the fruits extract yielded the lowest MIC for several strains of microorganisms, namely, S. aureus, B. cereus, L. monocytogenes and clinical methicillin-resistant S. aureus (MRSA). Stems and fruits extract at 2.5 mg/mL effectively eradicated the biofilm of S. aureus ATCC 25923, SA 01/10 and MRSA 12/10. Regarding leaves extract, hemolysis was not observed, and in the case of stems and fruits, hemolysis was verified only for higher concentrations, suggesting its low toxicity. Fruits extract presented no toxic effect to normal human dermal fibroblasts (NHDF) cells however for concentrations of 0.017 and 0.008 mg/mL this extract was able to decrease human breast adenocarcinoma cells (MCF-7) viability in about 60%, as MTT test results had confirmed. This is a clearly demonstrator of the cytotoxicity of this extract against MCF-7 cells. PMID:24914310

Prevalence, Antimicrobial Resistance, and Relatedness of Salmonella Isolated from Chickens and Pigs on Farms, Abattoirs, and Markets in Sichuan Province, China.

PubMed

Ma, Suzhen; Lei, Changwei; Kong, Linghan; Jiang, Wei; Liu, Bihui; Men, Shuai; Yang, Yanxian; Cheng, Guangyang; Chen, Yanpeng; Wang, Hongning

2017-11-01

This study aims at investigating the distribution, antimicrobial resistance, and genetic relationship of Salmonella isolated from 18 farms, their downstream abattoirs, and markets of chickens and pigs in Sichuan province, China. A total of 193 Salmonella isolates were identified from 693 samples with an isolation rate of 26.27% (88/335) in chickens and 29.33% (105/358) in pigs. Salmonella was isolated more frequently in abattoirs and markets than from farms. Serotypes were determined according to the White-Kauffmann-Le Minor scheme and 16 different serotypes were identified, with Derby being the most common, followed by Typhimurium and Meleagridis. Antimicrobial resistance phenotypes and genotypes were studied by using the disk diffusion method and polymerase chain reaction (PCR) amplification, respectively. Overall, 44.04% (n = 85) of all isolates were multidrug resistant (MDR) and resistance to nalidixic acid (51.30%) was the most frequently observed. bla CTX-M-55 was the most prevalent extended-spectrum β-lactamases gene, and polymyxin resistance gene mcr-1 was present in strains with various serotypes. Multilocus sequence typing indicated that sequence type (ST) had a close relationship with serotype, and 34.20% of all strains were ST40, which was the most prevalent. The unweighted pair group method with arithmetic means (UPGMA) dendrogram of pulsed-field gel electrophoresis showed that Salmonella isolates belonging to the same serovar from different parts of the production chain were highly genetic related, indicating that Salmonella as well as resistance genes could potentially be transmitted from farms to markets. Our study highlights the fact that Salmonella isolates from chicken and pig production chain were frequently exhibiting MDR profiles, and the dissemination of MDR Salmonella from farm to market could pose significant threats to food safety and public health.

Bacterial profile of urinary tract infection and antimicrobial susceptibility pattern among pregnant women attending at Antenatal Clinic in Dil Chora Referral Hospital, Dire Dawa, Eastern Ethiopia

PubMed Central

Derese, Behailu; Kedir, Haji; Teklemariam, Zelalem; Weldegebreal, Fitsum; Balakrishnan, Senthilkumar

2016-01-01

Purpose The aim of this study was to determine the bacterial profile of urinary tract infection (UTI) and antimicrobial susceptibility pattern among pregnant women attending at antenatal clinic in Dil Chora Referral Hospital, Dire Dawa, Eastern Ethiopia. Patients and methods An institutional-based cross-sectional study was conducted from February 18, 2015 to March 25, 2015. Clean-catch midstream urine specimens were collected from 186 pregnant women using sterile containers. Then, culture and antimicrobial susceptibility tests were performed by standard disk diffusion method. Patient information was obtained using pretested structured questionnaire. Data were entered and cleaned using EpiData Version 3 and then exported to Statistical Package for Social Science (Version 16) for further analysis. Results The prevalence of significant bacteriuria was 14%. Gram-negative bacteria were more prevalent (73%). Escherichia coli (34.6%), coagulase-negative staphylococci (19.2%), Pseudomonas aeruginosa (15.4%), and Klebsiella spp. (11.5%) were common bacterial isolates, where most of them were resistant against ampicillin, amoxicillin, tetracycline, trimethoprim–sulfamethoxazole, and chloramphenicol. Multidrug resistance (resistance in ≥2 drugs) was seen in 100% of the isolated bacteria. A majority of the bacterial isolates were sensitive to ciprofloxacin, ceftriaxone, erythromycin, and gentamicin. Conclusion This study found a number of bacterial isolates with very high resistance to the commonly prescribed drugs from pregnant women with and without symptoms of UTI. Therefore, the early routine detection of causative agents of UTI and determining their drug susceptibility pattern are important for pregnant women to avoid complications in mother and fetus. Ciprofloxacin, ceftriaxone, gentamicin, and erythromycin can be used with great care for the empirical treatment of UTI. PMID:26937197

Throat Carriage Rate and Antimicrobial Resistance of Streptococcus pyogenes In Rural Children in Argentina.

PubMed

Delpech, Gastón; Sparo, Mónica; Baldaccini, Beatriz; Pourcel, Gisela; Lissarrague, Sabina; García Allende, Leonardo

2017-03-01

The aim of this study was to determine the prevalence of asymptomatic carriers of group A β-hemolytic streptococci (GAS) in children living in a rural community and to investigate the association between episodes of acute pharyngitis and carrier status. Throat swabs were collected from September to November 2013 among children 5-13 years of age from a rural community (Maria Ignacia-Vela, Argentina). The phenotypic characterization of isolates was performed by conventional tests. Antimicrobial susceptibility was assayed for penicillin, tetracycline, chloramphenicol, erythromycin, and clindamycin (disk diffusion). The minimum inhibitory concentration was determined for penicillin, cefotaxime, tetracycline, and erythromycin. The carriage of β-hemolytic streptococci was detected in 18.1% of participants, with Streptococcus pyogenes in 18 participants followed by S. dysgalactiae ssp. equisimilis in 5. The highest proportion of GAS was found in 8 to 10-year-old children. No significant association between the number of episodes of acute pharyngitis suffered in the last year and the carrier state was detected ( p >0.05). Tetracycline resistance (55.5%) and macrolide-resistant phenotypes (11.1%) were observed. Resistance to penicillin, cefotaxime, or chloramphenicol was not expressed in any streptococcal isolate. The present study demonstrated significant throat carriage of GAS and the presence of group C streptococci ( S. dysgalactiae ssp. equisimilis ) in an Argentinian rural population. These results point out the need for continuous surveillance of GAS and non-GAS carriage as well as of antimicrobial resistance in highly susceptible populations, such as school-aged rural children. An extended surveillance program including school-aged children from different cities should be considered to estimate the prevalence of GAS carriage in Argentina.

Phytochemical profiles and antimicrobial activity of aromatic Malaysian herb extracts against food-borne pathogenic and food spoilage microorganisms.

PubMed

Aziman, Nurain; Abdullah, Noriham; Noor, Zainon Mohd; Kamarudin, Wan Saidatul Syida Wan; Zulkifli, Khairusy Syakirah

2014-04-01

Preliminary phytochemical and flavonoid compounds of aqueous and ethanolic extracts of 6 aromatic Malaysian herbs were screened and quantified using Reverse-Phase High Performance Liquid Chromatography (RP-HPLC). The herbal extracts were tested for their antimicrobial activity against 10 food-borne pathogenic and food spoilage microorganisms using disk diffusion assay. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)/minimum fungicidal concentration (MFC) of herbal extracts were determined. In the phytochemical screening process, both aqueous and ethanolic extracts of P. hydropiper exhibited presence of all 7 tested phytochemical compounds. Among all herbal extracts, the aqueous P. hydropiper and E. elatior extracts demonstrated the highest antibacterial activity against 7 tested Gram-positive and Gram-negative bacteria with diameter ranging from 7.0 to 18.5 mm and 6.5 to 19 mm, respectively. The MIC values for aqueous and ethanolic extracts ranged from 18.75 to 175 mg/mL and 0.391 to 200 mg/mL, respectively while the MBC/MFC values for aqueous and ethanolic extracts ranged from 25 to 200 mg/mL and 3.125 to 50 mg/mL, respectively. Major types of bioactive compounds in aqueous P. hydropiper and E. elatior extracts were identified using RP-HPLC instrument. Flavonoids found in these plants were epi-catechin, quercetin, and kaempferol. The ability of aqueous Persicaria hydropiper (L.) H. Gross and Etlingera elatior (Jack) R.M. Sm. extracts to inhibit the growth of bacteria is an indication of its broad spectrum antimicrobial potential. Hence these herbal extracts may be used as natural preservative to improve the safety and shelf-life of food and pharmaceutical products. © 2014 Institute of Food Technologists®

Antimicrobial Susceptibility of Udder Pathogens Isolated from Dairy Herds in the West Littoral Region of Uruguay

PubMed Central

2002-01-01

A total of 522 strains belonging to streptococci, enterococci and staphylococci isolated from sub-clinical and clinical cases of bovine mastitis from the west littoral region of Uruguay were analysed for their susceptibility to several antimicrobial agents. The susceptibility patterns were studied by agar disk diffusion methods (ADDM) and broth micro-dilution to determine the minimum inhibitory concentration (MIC). The concentration that inhibits 90% (MIC90) of the analysed strains reported in micrograms per millilitre, for Staphylococcus aureus were > 8, 8, ≤ 0.5, ≤ 4, ≤ 1, ≤ 0.5, > 64, ≤ 0.25, 0.5, ≤ 1 and ≤ 1 to penicillin, ampicillin, oxacillin, cephalotin, gentamicin, erythromycin, oxitetracycline, enrofloxacin, trimethoprim/sulfamethoxazole, neomycin, and clindamycin, respectively. Coagulase-negative staphylococci (CNS) had different values for penicillin (4) and ampicillin (2), while the other antimicrobial agents had the same MIC90 values as reported for S. aureus. The MIC90 values for streptococci were 0.12, 0.25, ≤ 4, 16, ≤ 0.25, 0.5, 0.25 for penicillin, ampicillin, cephalotin, gentamicin, erythromycin, oxytetracycline and trimethoprim-sulfamethoxazole, whereas MIC90 for enterococci were 4, 4, 4, ≤ 0.5, 2, > 8 for penicillin, ampicillin, gentamicin, erythromycin, oxytetracycline and trimethoprim-sulfamethoxazole, respectively. Of 336 strains of S. aureus, 160 (47.6%) were resistant to penicillin. For 41 CNS strains, 10 (27%) presented penicillin-resistance. All the streptococcal strains were susceptible to penicillin, while 3 (7%) of the 43 enteroccocal strains were resistant. Non significant statistical differences were found between the results obtained by ADDM and broth micro-dilution for classifying bacterial isolates as susceptible or resistant according to the National Committee of Clinical Laboratory Standards. PMID:12071114

Class 1 and class 2 integrons in avian pathogenic Escherichia coli from poultry in Italy.

PubMed

Cavicchio, Lara; Dotto, Giorgia; Giacomelli, Martina; Giovanardi, Davide; Grilli, Guido; Franciosini, Maria Pia; Trocino, Angela; Piccirillo, Alessandra

2015-06-01

The aim of this study was to investigate the occurrence of class 1 and 2 integrons in avian pathogenic Escherichia coli (APEC) from poultry in northern Italy. Strains were tested for phenotypic resistance to aminoglycosides and sulphonamides, and the association between the presence of integrons and the resistance to these antimicrobials was evaluated. A total of 299 isolates (158 from turkeys, 110 from broilers, and 31 from layer hens) were collected from 200 industrial farms. Antimicrobial susceptibility test by the disk diffusion method was performed in accordance with the Clinical and Laboratory Standards Institute (CLSI) guidelines. All strains were screened for the presence of class 1 and 2 integrons by PCR and sequencing. About 55% of APEC contained integrons (class 1, 49.8%; class 2, 10.4%). Different variants of the aadA (5 variants) and the dfrA (4 variants) genes, encoding for streptomycin and trimethoprim resistance respectively, were detected in integron-positive isolates. Less common gene cassettes, such as sat, estX, and orfF, were also identified. Fifteen and 4 gene cassette arrays were found among class 1 and 2 integrons, respectively. High levels of resistance were observed for triple sulphonamides (79.3%), streptomycin (67.2%), and sulfamethoxazole combined with trimethoprim (62.2%), whereas resistance against gentamycin (16.7%), kanamycin (14.7%), and apramycin 3.0%) was low. Integron positivity was significantly higher in isolates phenotypically resistant to aminoglycosides (63.6% vs. 37.8%, P<0.001) and sulfonamides (64.1% vs. 21.1%, P<0.001) than in susceptible ones. Integron-borne aminoglycoside and sulfonamide resistance in APEC represents a concern for the poultry industry in Italy, since they are among the most commonly used antimicrobials in poultry therapy. © 2015 Poultry Science Association Inc.

Highly diverse and antimicrobial susceptible Escherichia coli display a naïve bacterial population in fruit bats from the Republic of Congo.

PubMed

Nowak, Kathrin; Fahr, Jakob; Weber, Natalie; Lübke-Becker, Antina; Semmler, Torsten; Weiss, Sabrina; Mombouli, Jean-Vivien; Wieler, Lothar H; Guenther, Sebastian; Leendertz, Fabian H; Ewers, Christa

2017-01-01

Bats are suspected to be a reservoir of several bacterial and viral pathogens relevant to animal and human health, but studies on Escherichia coli in these animals are sparse. We investigated the presence of E. coli in tissue samples (liver, lung and intestines) collected from 50 fruit bats of five different species (Eidolon helvum, Epomops franqueti, Hypsignathus monstrosus, Myonycteris torquata, Rousettus aegyptiacus) of two different areas in the Republic of Congo between 2009 and 2010. To assess E. coli pathotypes and phylogenetic relationships, we determined the presence of 59 virulence associated genes and multilocus sequence types (STs). Isolates were further tested for their susceptibility to several antimicrobial substances by agar disk diffusion test and for the presence of an Extended-Spectrum Beta-Lactamase phenotype. E. coli was detected in 60% of the bats analysed. The diversity of E. coli strains was very high, with 37 different STs within 40 isolates. Occasionally, we detected sequence types (e.g. ST69, ST127, and ST131) and pathotypes (e.g. ExPEC, EPEC and atypical EPEC), which are known pathogens in human and/or animal infections. Although the majority of strains were assigned to phylogenetic group B2 (46.2%), which is linked with the ExPEC pathovar, occurrence of virulence-associated genes in these strains were unexpectedly low. Due to this, and as only few of the E. coli isolates showed intermediate resistance to certain antimicrobial substances, we assume a rather naïve E. coli population, lacking contact to humans or domestic animals. Future studies featuring in depth comparative whole genome sequence analyses will provide insights into the microevolution of this interesting strain collection.

Highly diverse and antimicrobial susceptible Escherichia coli display a naïve bacterial population in fruit bats from the Republic of Congo

PubMed Central

Nowak, Kathrin; Fahr, Jakob; Weber, Natalie; Lübke-Becker, Antina; Semmler, Torsten; Weiss, Sabrina; Mombouli, Jean-Vivien; Wieler, Lothar H.; Guenther, Sebastian

2017-01-01

Bats are suspected to be a reservoir of several bacterial and viral pathogens relevant to animal and human health, but studies on Escherichia coli in these animals are sparse. We investigated the presence of E. coli in tissue samples (liver, lung and intestines) collected from 50 fruit bats of five different species (Eidolon helvum, Epomops franqueti, Hypsignathus monstrosus, Myonycteris torquata, Rousettus aegyptiacus) of two different areas in the Republic of Congo between 2009 and 2010. To assess E. coli pathotypes and phylogenetic relationships, we determined the presence of 59 virulence associated genes and multilocus sequence types (STs). Isolates were further tested for their susceptibility to several antimicrobial substances by agar disk diffusion test and for the presence of an Extended-Spectrum Beta-Lactamase phenotype. E. coli was detected in 60% of the bats analysed. The diversity of E. coli strains was very high, with 37 different STs within 40 isolates. Occasionally, we detected sequence types (e.g. ST69, ST127, and ST131) and pathotypes (e.g. ExPEC, EPEC and atypical EPEC), which are known pathogens in human and/or animal infections. Although the majority of strains were assigned to phylogenetic group B2 (46.2%), which is linked with the ExPEC pathovar, occurrence of virulence-associated genes in these strains were unexpectedly low. Due to this, and as only few of the E. coli isolates showed intermediate resistance to certain antimicrobial substances, we assume a rather naïve E. coli population, lacking contact to humans or domestic animals. Future studies featuring in depth comparative whole genome sequence analyses will provide insights into the microevolution of this interesting strain collection. PMID:28700648

Synthesis and property investigation of metal-based nanomaterials for biotechnological applications

NASA Astrophysics Data System (ADS)

Darsanasiri, Nalin Dammika

Luminescent lanthanide-based materials have drawn recent interest due to their applications in in vitro cellular imaging. Sensitive biological analysis requires optical labels with high water dispersibility & stability and excellent luminescent properties. Most literature reported lanthanide complexes with high luminescence intensity are hydrophobic and unstable, limiting their biological applications. This project was designed to incorporate a highly luminescent lanthanide beta-diketonate complex in a silica nanoparticle. Eu(btfa)3dmph complex was synthesized, which exhibits red luminescence at 614 nm with a narrow (15 nm) full with half-maximum (btfa=4,4,4-trifluoro-1-phenyl-1,3-butanedione, dmph=4,7-dimethyl,1,10-phenanthroline). A synthetic procedure was optimized to incorporate the Eu-complex in a silica-based nanoparticle with an average particle diameter of 36 nm. Eu-complex based silica nanoparticles exhibit high stability and water-dispersibility with a luminescence quantum yield of 10 %. The nanoparticles showed antimicrobial activity against clinically important E.coli, S.aureus and S.epidermidis. Synthesis, materials characterization, and antimicrobial studies of the complex and the nanoparticles was discussed in the first part of this thesis. Nanotechnology is emerging as a new interdisciplinary field combining biology, chemistry, physics, and material science. Recent advances promise developments in the synthesis, modification and practical applications of polymer-coated manganese (Mn)-based zinc oxide (ZnO) nanoparticles (NPs). The size distribution, shape, and surface modification of metal-based ZnO nanoparticles are the key factors determining their specific physical properties. Due to the strong antibacterial properties and low toxicity towards mammalian cells, ZnO NPs have been successfully used in a wide range of applications including wound dressing, protective clothing, antibacterial surfaces, food preservation, and cosmetics as biocidal and disinfecting agents. In this study, cotton textiles with antimicrobial activity were developed by incorporating polymer-coated Mn-doped ZnO nanoparticles. Antimicrobial potential of synthesized Mn-doped zinc oxide (ZnO) nanoparticles against two bacteria strains ( Escherichia coli as Gram-negative bacteria, Staphylococcus aureus as Gram-positive bacteria) in liquid and solid phases was studied in this work. Polymer-coated Mn-doped ZnO nanoparticles were prepared by the modified co-precipitation method. Characterization of the nanoparticles was carried out using Ultra-violet visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The average particle size of the nanoparticles was found to be less than 15 nm. The antibacterial activity of the nanoparticles was evaluated using minimum inhibitory concentration (MIC) and agar diffusion method. Disk diffusion studies revealed that the nanoparticles have excellent antimicrobial activity against E.coli and S.aureus bacterial species. Therefore, it was concluded that the polymer-coated Mn-doped ZnO nanoparticles were excellent antibacterial agents with potential clinical applications.

Prevalence and characterization of methicillin-resistant Staphylococcus aureus carrying mecA or mecC and methicillin-susceptible Staphylococcus aureus in dairy sheep farms in central Italy.

PubMed

Giacinti, G; Carfora, V; Caprioli, A; Sagrafoli, D; Marri, N; Giangolini, G; Amoruso, R; Iurescia, M; Stravino, F; Dottarelli, S; Feltrin, F; Franco, A; Amatiste, S; Battisti, A

2017-10-01

Between January and May 2012, a total of 286 bulk tank milk samples from dairy sheep farms located in central Italy were tested for the presence of Staphylococcus aureus. One hundred fifty-three samples were positive for S. aureus (53.5%), with an average count of 2.53 log cfu/mL. A total of 679 S. aureus colonies were screened for methicillin resistance by the cefoxitin disk diffusion test, and 104 selected cefoxitin-susceptible isolates were also tested for their susceptibility to other antimicrobials representative of the most relevant classes active against Staphylococcus spp. by using the Kirby-Bauer disk diffusion method. Two methicillin-resistant Staphylococcus aureus (MRSA) isolates, carrying respectively the mecA and the mecC genes, were detected in 2 samples from 2 different farms (prevalence 0.7%). The mecA-positive MRSA isolate was blaZ positive, belonged to spa type t127, sequence type (ST)1, clonal complex (CC)1, carried a staphylococcal cassette chromosome mec (SCCmec) type IVa, and was phenotypically resistant to all the β-lactams tested and to erythromycin, streptomycin, kanamycin, and tetracycline. The mecC-positive MRSA isolate was negative for the chromosomally or plasmid-associated blaZ gene but positive for the blaZ allotype associated with SCCmec XI (blaZ-SCCmecXI), belonged to spa type 843, ST(CC)130, carried a SCCmec type XI, and was resistant only to β-lactams. Both MRSA were negative for the presence of specific immune-evasion and virulence genes such as those coding for the Panton-Valentine leucocidin, the toxic shock syndrome toxin 1, and the immune evasion cluster genes. Regarding the presence of the major S. aureus enterotoxin genes, the mecC-positive MRSA tested negative, whereas the ST (CC)1 mecA-positive MRSA harbored the seh gene. Among the 104 methicillin-susceptible S. aureus isolates examined for antimicrobial susceptibility, 63 (60.58%) were susceptible to all the antimicrobials tested, and 41 (39.42%) were resistant to at least 1 antimicrobial. In particular, 23 isolates (22.12%) were resistant to tetracycline, 16 (15.38%) to sulfonomides, 14 (13.46%) to trimethoprim and sulfamethoxazole, and 9 (8.65%) to ampicillin, whereas only 1 isolate was resistant to both fluoroquinolones and aminoglycosides. The high prevalence of S. aureus found in bulk tank milk samples and the isolation of MRSA, although at a low prevalence, underlines the importance of adopting control measures against S. aureus in dairy sheep farms to minimize the risks for animal and public health. Moreover, this study represents the first report of mecC-positive MRSA isolation in Italy and would confirm that, among livestock animals, sheep might act as a mecC-MRSA reservoir. Although this lineage seems to be rare in dairy sheep (0.35% of farms tested), because mecC-positive MRSA are difficult to detect by diagnostic routine methods employed for mecA-positive livestock-associated MRSA, diagnostic laboratories should be aware of the importance of searching for the mecC gene in all the mecA-negative S. aureus isolates displaying resistance to oxacillin, cefoxitin, or both. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Gravitational Instabilities in a Young Protoplanetary Disk with Embedded Objects

NASA Astrophysics Data System (ADS)

Desai, Karna M.

Gravitational Instabilities (GIs), a mechanism for angular momentum transport, are prominent during the early phases of protoplanetary disk evolution when the disk is relatively massive. In this dissertation, I analyze GIs by inserting different objects in a disk by employing 3D hydrodynamics simulations. GIs in a circumbinary disks are studied to determine how the presence of the companion affects the nature and strength of GIs in the disk. The circumbinary disk achieves a state of sustained marginal instability similar to an identical disk without the companion. A realistic evolution of the binary is detected. Planet and disk interactions play an important role in the evolution of planetary systems. To study this interaction during the early phases of planet formation, a migration study of Jovian planets in a GI-active disk is conducted. I find the migration timescales to be longer in a GI-active disk, when compared to laminar disks. The 3 MJupiter planet controls its own orbital evolution, while the migration of a 0.3 MJupiter planet is stochastic in nature. I define a 'critical mass' as the mass of an arm of the dominant two-armed spiral density wave within the planet's Hill diameter. Planets above this mass control their own destiny, and planets below this mass are scattered by the disk. This critical mass could provide a recipe for predicting the migration behavior of planets in GI-active disks. To understand the stochastic migration of low-mass planets, I perform a simulation of 240 zero-mass planet-tracers by inserting these at a range of locations in the disk. A Diffusion Coefficient is calculated to characterize the stochastic migration of low-mass objects. The eccentricity dispersion for the sample is also studied. I find that the diffusion of planets can be a slow process, resulting in the survival of small planetary cores.

The Large-scale Magnetic Fields of Thin Accretion Disks

NASA Astrophysics Data System (ADS)

Cao, Xinwu; Spruit, Hendrik C.

2013-03-01

Large-scale magnetic field threading an accretion disk is a key ingredient in the jet formation model. The most attractive scenario for the origin of such a large-scale field is the advection of the field by the gas in the accretion disk from the interstellar medium or a companion star. However, it is realized that outward diffusion of the accreted field is fast compared with the inward accretion velocity in a geometrically thin accretion disk if the value of the Prandtl number P m is around unity. In this work, we revisit this problem considering the angular momentum of the disk to be removed predominantly by the magnetically driven outflows. The radial velocity of the disk is significantly increased due to the presence of the outflows. Using a simplified model for the vertical disk structure, we find that even moderately weak fields can cause sufficient angular momentum loss via a magnetic wind to balance outward diffusion. There are two equilibrium points, one at low field strengths corresponding to a plasma-beta at the midplane of order several hundred, and one for strong accreted fields, β ~ 1. We surmise that the first is relevant for the accretion of weak, possibly external, fields through the outer parts of the disk, while the latter one could explain the tendency, observed in full three-dimensional numerical simulations, of strong flux bundles at the centers of disk to stay confined in spite of strong magnetororational instability turbulence surrounding them.

Multidrug-Resistant and Methicillin-Resistant Staphylococcus aureus (MRSA) in Hog Slaughter and Processing Plant Workers and Their Community in North Carolina (USA)

PubMed Central

Neyra, Ricardo Castillo; Frisancho, Jose Augusto; Rinsky, Jessica L.; Resnick, Carol; Carroll, Karen Colleen; Rule, Ana Maria; Ross, Tracy; You, Yaqi; Price, Lance B.

2014-01-01

Background: Use of antimicrobials in industrial food-animal production is associated with the presence of antimicrobial-resistant Staphylococcus aureus (S. aureus) among animals and humans. Hog slaughter/processing plants process large numbers of animals from industrial animal operations and are environments conducive to the exchange of bacteria between animals and workers. Objectives: We compared the prevalence of multidrug-resistant S. aureus (MDRSA) and methicillin-resistant S. aureus (MRSA) carriage among processing plant workers, their household members, and community residents. Methods: We conducted a cross-sectional study of hog slaughter/processing plant workers, their household members, and community residents in North Carolina. Participants responded to a questionnaire and provided a nasal swab. Swabs were tested for S. aureus, and isolates were tested for antimicrobial susceptibility and subjected to multilocus sequence typing. Results: The prevalence of S. aureus was 21.6%, 30.2%, and 22.5% among 162 workers, 63 household members, and 111 community residents, respectively. The overall prevalence of MDRSA and MRSA tested by disk diffusion was 6.9% and 4.8%, respectively. The adjusted prevalence of MDRSA among workers was 1.96 times (95% CI: 0.71, 5.45) the prevalence in community residents. The adjusted average number of antimicrobial classes to which S. aureus isolates from workers were resistant was 2.54 times (95% CI: 1.16, 5.56) the number among isolates from community residents. We identified two MDRSA isolates and one MRSA isolate from workers as sequence type 398, a type associated with exposure to livestock. Conclusions: Although the prevalence of S. aureus and MRSA was similar in hog slaughter/processing plant workers and their household and community members, S. aureus isolates from workers were resistant to a greater number of antimicrobial classes. These findings may be related to the nontherapeutic use of antimicrobials in food-animal production. Citation: Castillo Neyra R, Frisancho JA, Rinsky JL, Resnick C, Carroll KC, Rule AM, Ross T, You Y, Price LB, Silbergeld EK. 2014. Multidrug-resistant and methicillin-resistant Staphylococcus aureus (MRSA) in hog slaughter and processing plant workers and their community in North Carolina (USA). Environ Health Perspect 122:471–477; http://dx.doi.org/10.1289/ehp.1306741 PMID:24508836

Dynamics of Diffusion Flames in von Karman Swirling Flows Studied

NASA Technical Reports Server (NTRS)

Nayagam, Vedha; Williams, Forman A.

2002-01-01

Von Karman swirling flow is generated by the viscous pumping action of a solid disk spinning in a quiescent fluid media. When this spinning disk is ignited in an oxidizing environment, a flat diffusion flame is established adjacent to the disk, embedded in the boundary layer (see the preceding illustration). For this geometry, the conservation equations reduce to a system of ordinary differential equations, enabling researchers to carry out detailed theoretical models to study the effects of varying strain on the dynamics of diffusion flames. Experimentally, the spinning disk burner provides an ideal configuration to precisely control the strain rates over a wide range. Our original motivation at the NASA Glenn Research Center to study these flames arose from a need to understand the flammability characteristics of solid fuels in microgravity where slow, subbuoyant flows can exist, producing very small strain rates. In a recent work (ref. 1), we showed that the flammability boundaries are wider and the minimum oxygen index (below which flames cannot be sustained) is lower for the von Karman flow configuration in comparison to a stagnation-point flow. Adding a small forced convection to the swirling flow pushes the flame into regions of higher strain and, thereby, decreases the range of flammable strain rates. Experiments using downward facing, polymethylmethacrylate (PMMA) disks spinning in air revealed that, close to the extinction boundaries, the flat diffusion flame breaks up into rotating spiral flames (refs. 2 and 3). Remarkably, the dynamics of these spiral flame edges exhibit a number of similarities to spirals observed in biological systems, such as the electric pulses in cardiac muscles and the aggregation of slime-mold amoeba. The tail of the spiral rotates rigidly while the tip executes a compound, meandering motion sometimes observed in Belousov-Zhabotinskii reactions.

Antibiotic Resistances of Yogurt Starter Cultures Streptococcus thermophilus and Lactobacillus bulgaricus

PubMed Central

Sozzi, Tommaso; Smiley, Martin B.

1980-01-01

Twenty-nine strains of Lactobacillus bulgaricus and 15 strains of Streptococcus thermophilus were tested for resistance to 35 antimicrobial agents by using commercially available sensitivity disks. Approximately 35% of the isolates had uncharacteristic resistance patterns. PMID:16345654

The in-vitro antimicrobial activities of some medicinal plants from Cameroon.

PubMed

Gangoué-Piéboji, J; Pegnyemb, D E; Niyitegeka, D; Nsangou, A; Eze, N; Minyem, C; Mbing, J Ngo; Ngassam, P; Tih, R Ghogomu; Sodengam, B L; Bodo, B

2006-04-01

The antimicrobial activities of 10 plant species (Voacanga africana, Crepis cameroonica, Plagiostyles africana, Crotalaria retusa, Mammea africana, Lophira lanceolata, Ochna afzelii, Ouratea elongata, Ou. flava and Ou. sulcata), each of which is currently used in the traditional medicine of Cameroon, were investigated in vitro. The activities of a methanol extract of each plant were tested, in disc-diffusion assays, against 37 reference or laboratory strains of seven species of microorganism (Staphylococcus aureus, S. epidermidis, Enterococcus hirae, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Candida albicans). The minimal inhibitory concentrations of each extract were then estimated, against each of the more susceptible microorganisms (i.e. those giving an inhibition zone measuring at least 9 mm in diameter in the disc-diffusion assays), by agar dilution. Although, in the disc-diffusion assays, each of the 10 methanol extracts investigated displayed some degree of antimicrobial activity against at least one species of microorganism, no activity against the Gram-negative bacteria (Es. coli, K. pneumoniae and Ps. aeruginosa) was observed. The extract with the greatest antimicrobial activity was that of Pl. africana (Euphorbiaceae).

[Kinetics of decamethoxine, an antimicrobial agent].

PubMed

Paliĭ, G K; Nazarchuk, A A; Kulakov, A I; Nazarchuk, G G; Paliĭ, D V; Bereza, B N; Oleĭnik, D P

2014-01-01

The kinetics of decamethoxine liberation from medical antimicrobial textiles was studied. The elution of decamethoxine was shown to be a complicated diffusive-kinetic process dependent on the exposure and concentration of decamethoxine.

High accuracy diffuse horizontal irradiance measurements without a shadowband

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlemmer, J.A; Michalsky, J.J.

1995-12-31

The standard method for measuring diffuse horizontal irradiance uses a fixed shadowband to block direct solar radiation. This method requires a correction for the excess skylight blocked by the band, and this correction varies with sky conditions. Alternately, diffuse horizontal irradiance may be calculated from total horizontal and direct normal irradiance. This method is in error because of angular (cosine) response of the total horizontal pyranometer to direct beam irradiance. This paper describes an improved calculation of diffuse horizontal irradiance from total horizontal and direct normal irradiance using a predetermination of the angular response of the total horizontal pyranometer. Wemore » compare these diffuse horizontal irradiance calculations with measurements made with a shading-disk pyranometer that shields direct irradiance using a tracking disk. Results indicate significant improvement in most cases. Remaining disagreement most likely arises from undetected tracking errors and instrument leveling.« less

High accuracy diffuse horizontal irradiance measurements without a shadowband

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlemmer, J.A.; Michalsky, J.J.

1995-10-01

The standard method for measuring diffuse horizontal irradiance uses a fixed shadowband to block direct solar radiation. This method requires a correction for the excess skylight blocked by the band, and this correction varies with sky conditions. Alternately, diffuse horizontal irradiance may be calculated from the total horizontal and direct normal irradiance. This method is in error because of the angular (often referred to as cosine) response of the total horizontal pyranometer to direct beam irradiance. This paper describes an improved calculation of diffuse horizontal irradiance from total horizontal and direct normal irradiance using a predetermination of the angular responsemore » of the total horizontal pyranometer. The authors compare these diffuse horizontal irradiance calculations with measurements made with a shading-disk pyranometer that shields direct irradiance using a tracking disk. The results indicate significant improvement in most cases. The remaining disagreement most likely arises from undetected tracking errors and instrument leveling.« less

Can Ceftazidime-Avibactam and Aztreonam Overcome β-Lactam Resistance Conferred by Metallo-β-Lactamases in Enterobacteriaceae?

PubMed

Marshall, Steven; Hujer, Andrea M; Rojas, Laura J; Papp-Wallace, Krisztina M; Humphries, Romney M; Spellberg, Brad; Hujer, Kristine M; Marshall, Emma K; Rudin, Susan D; Perez, Federico; Wilson, Brigid M; Wasserman, Ronald B; Chikowski, Linda; Paterson, David L; Vila, Alejandro J; van Duin, David; Kreiswirth, Barry N; Chambers, Henry F; Fowler, Vance G; Jacobs, Michael R; Pulse, Mark E; Weiss, William J; Bonomo, Robert A

2017-04-01

Based upon knowledge of the hydrolytic profile of major β-lactamases found in Gram-negative bacteria, we tested the efficacy of the combination of ceftazidime-avibactam (CAZ-AVI) with aztreonam (ATM) against carbapenem-resistant enteric bacteria possessing metallo-β-lactamases (MBLs). Disk diffusion and agar-based antimicrobial susceptibility testing were initially performed to determine the in vitro efficacy of a unique combination of CAZ-AVI and ATM against 21 representative Enterobacteriaceae isolates with a complex molecular background that included bla IMP , bla NDM , bla OXA-48 , bla CTX-M , bla AmpC , and combinations thereof. Time-kill assays were conducted, and the in vivo efficacy of this combination was assessed in a murine neutropenic thigh infection model. By disk diffusion assay, all 21 isolates were resistant to CAZ-AVI alone, and 19/21 were resistant to ATM. The in vitro activity of CAZ-AVI in combination with ATM against diverse Enterobacteriaceae possessing MBLs was demonstrated in 17/21 isolates, where the zone of inhibition was ≥21 mm. All isolates demonstrated a reduction in CAZ-AVI agar dilution MICs with the addition of ATM. At 2 h, time-kill assays demonstrated a ≥4-log 10 -CFU decrease for all groups that had CAZ-AVI with ATM (8 μg/ml) added, compared to the group treated with CAZ-AVI alone. In the murine neutropenic thigh infection model, an almost 4-log 10 -CFU reduction was noted at 24 h for CAZ-AVI (32 mg/kg every 8 h [q8h]) plus ATM (32 mg/kg q8h) versus CAZ-AVI (32 mg/kg q8h) alone. The data presented herein require us to carefully consider this new therapeutic combination to treat infections caused by MBL-producing Enterobacteriaceae . Copyright © 2017 American Society for Microbiology.

Detection of Extraplanar Diffuse Ionized Gas in M83

NASA Astrophysics Data System (ADS)

Boettcher, Erin; Gallagher, J. S., III; Zweibel, Ellen G.

2017-08-01

We present the first kinematic study of extraplanar diffuse ionized gas (eDIG) in the nearby, face-on disk galaxy M83 using optical emission-line spectroscopy from the Robert Stobie Spectrograph on the Southern African Large Telescope. We use a Markov Chain Monte Carlo method to decompose the [N II]λ λ 6548, 6583, Hα, and [S II]λ λ 6717, 6731 emission lines into H II region and diffuse ionized gas emission. Extraplanar, diffuse gas is distinguished by its emission-line ratios ([N II]λ6583/Hα ≳ 1.0) and its rotational velocity lag with respect to the disk ({{Δ }}v=-24 km s-1 in projection). With interesting implications for isotropy, the velocity dispersion of the diffuse gas, σ =96 km s-1, is a factor of a few higher in M83 than in the Milky Way and nearby, edge-on disk galaxies. The turbulent pressure gradient is sufficient to support the eDIG layer in dynamical equilibrium at an electron scale height of {h}z=1 kpc. However, this dynamical equilibrium model must be finely tuned to reproduce the rotational velocity lag. There is evidence of local bulk flows near star-forming regions in the disk, suggesting that the dynamical state of the gas may be intermediate between a dynamical equilibrium and a galactic fountain flow. As one of the first efforts to study eDIG kinematics in a face-on galaxy, this study demonstrates the feasibility of characterizing the radial distribution, bulk velocities, and vertical velocity dispersions in low-inclination systems. Based on observations made with the Southern African Large Telescope (SALT) under program 2015-2-SCI-004 (PI: E. Boettcher).

Chemical composition and antimicrobial activity of the essential oils of Pinus peuce (Pinaceae) growing wild in R. Macedonia.

PubMed

Karapandzova, Marija; Stefkova, Gjose; Cvetkovikj, Ivana; Trajkovska-Dokik, Elena; Kaftandzieva, Ana; Kulevanova, Svetlana

2014-11-01

The chemical composition and antimicrobial activity of the essential oils isolated from twigs with needles (T+N) and from twigs without needles (T-N) from wild Pinus peuce Griseb. (Pinaceae), from three different locations in R. Macedonia, were investigated. Essential oil yields of T+N ranged from 7.5 mL/kg to 12.5 mL/kg and for T-N from 13.8 mL/kg to 17.3 mL/kg. GC/FID/MS analysis of the essential oils revealed eighty-four components, representing 93.7-95.7% and 91.2-92.0% of the T+N and T-N oils, respectively. The major components in T+N and T-N oils were monoterpenes: α-pinene (23.8-39.9%, 21.2-23.3%), camphene (2.2-5.5%, 0.7-2.0%), β-pinene (10.1-17.1%, 8.2-16.4%), myrcene (1.2-1.41%, 1.6-2.5%), limonene+β-phellandrene (6.8-14.0%, 8.8-23.6%) and bornyl acetate (2.3-6.9%, 1.1-3.4%), followed by the sesquiterpenes: trans-(E)-caryophyllene (3.6-4.3%, 3.2-7.3%), germacrene D (7.1-9.5%, 5.0-10.3%) and δ-cadinene (2.1-3.1%, 3.3-4.2%, respectively). Antimicrobial screening of the essential oils was made by disk diffusion and broth dilution methods against 13 bacterial isolates of Gram-positive and Gram-negative bacteria and one strain of Candida albicans. T-N essential oils showed antimicrobial activity toward Streptococcus pneumoniae, Staphylococcus aureus, S. epidermidis and Candida albicans as well as Streptococcus agalactiae, Acinetobacter spp. and Haemophilus influenzae. The antimicrobial activity of T+N essential oils was greater, especially against Streptococcus agalactiae, S. pyogenes, Enterococcus and Candida albicans, followed by Haemophilus influenzae, Acinetobacter spp., Escherichia coli, Salmonella enteritidis, Staphylococcus aureus and S. epidermidis. Minimal inhibitory concentrations (MICs) of all tested essential oils ranged from 15-125 μL/mL. Summarizing the obtained results, the antimicrobial activity of Pinus peuce T+N and T-N essential oils collected from different localities in R. Macedonia varied considerably. These alterations in the antimicrobial activity can be attributed to the differences in the quantitative composition and percentage amounts of the components present in the respective essential oils, although it was evident that there were no differences in the qualitative composition of the essential oils, regardless of the locality of collection, or the type of plant material (T+N or T-N).

[Comparison of microdilution and disk diffusion methods for the detection of fluconazole and voriconazole susceptibility against clinical Candida glabrata isolates and determination of changing susceptibility with new CLSI breakpoints].

PubMed

Hazırolan, Gülşen; Sarıbaş, Zeynep; Arıkan Akdağlı, Sevtap

2016-07-01

Candida albicans is the most frequently isolated species as the causative agent of Candida infections. However, in recent years, the isolation rate of non-albicans Candida species have increased. In many centers, Candida glabrata is one of the commonly isolated non-albicans species of C.glabrata infections which are difficult-to-treat due to decreased susceptibility to fluconazole and cross-resistance to other azoles. The aims of this study were to determine the in vitro susceptibility profiles of clinical C.glabrata isolates against fluconazole and voriconazole by microdilution and disk diffusion methods and to evaluate the results with both the previous (CLSI) and current species-specific CLSI (Clinical and Laboratory Standards Institute) clinical breakpoints. A total of 70 C.glabrata strains isolated from clinical samples were included in the study. The identification of the isolates was performed by morphologic examination on cornmeal Tween 80 agar and assimilation profiles obtained by using ID32C (BioMérieux, France). Broth microdilution and disk diffusion methods were performed according to CLSI M27-A3 and CLSI M44-A2 documents, respectively. The results were evaluated according to CLSI M27-A3 and M44-A2 documents and new vs. species-specific CLSI breakpoints. By using both previous and new CLSI breakpoints, broth microdilution test results showed that voriconazole has greater in vitro activity than fluconazole against C.glabrata isolates. For the two drugs tested, very major error was not observed with disk diffusion method when microdilution method was considered as the reference method. Since "susceptible" category no more exists for fluconazole vs. C.glabrata, the isolates that were interpreted as susceptible by previous breakpoints were evaluated as susceptible-dose dependent by current CLSI breakpoints. Since species-specific breakpoints remain yet undetermined for voriconazole, comparative analysis was not possible for this agent. The results obtained at 24 hours by disk diffusion method were evaluated by using both previous and current CLSI breakpoints and the agreement rates for fluconazole and voriconazole were 80% and 92.8% with previous CLSI breakpoint, 87.1% and 94.2% with new breakpoints, respectively. The high agreement rates between the two methods obtained by the new breakpoints in particular suggest that disk diffusion appears as a reliable alternative method in general for in vitro susceptibility testing of fluconazole and voriconazole against C.glabrata isolates.

Analytical Solutions for Radiative Transfer: Implications for Giant Planet Formation by Disk Instability

NASA Astrophysics Data System (ADS)

Boss, Alan P.

2009-03-01

The disk instability mechanism for giant planet formation is based on the formation of clumps in a marginally gravitationally unstable protoplanetary disk, which must lose thermal energy through a combination of convection and radiative cooling if they are to survive and contract to become giant protoplanets. While there is good observational support for forming at least some giant planets by disk instability, the mechanism has become theoretically contentious, with different three-dimensional radiative hydrodynamics codes often yielding different results. Rigorous code testing is required to make further progress. Here we present two new analytical solutions for radiative transfer in spherical coordinates, suitable for testing the code employed in all of the Boss disk instability calculations. The testing shows that the Boss code radiative transfer routines do an excellent job of relaxing to and maintaining the analytical results for the radial temperature and radiative flux profiles for a spherical cloud with high or moderate optical depths, including the transition from optically thick to optically thin regions. These radial test results are independent of whether the Eddington approximation, diffusion approximation, or flux-limited diffusion approximation routines are employed. The Boss code does an equally excellent job of relaxing to and maintaining the analytical results for the vertical (θ) temperature and radiative flux profiles for a disk with a height proportional to the radial distance. These tests strongly support the disk instability mechanism for forming giant planets.

Evolution of dynamo-generated magnetic fields in accretion disks around compact and young stars

NASA Technical Reports Server (NTRS)

Stepinski, Tomasz F.

1994-01-01

Geometrically thin, optically thick, turbulent accretion disks are believed to surround many stars. Some of them are the compact components of close binaries, while the others are throught to be T Tauri stars. These accretion disks must be magnetized objects because the accreted matter, whether it comes from the companion star (binaries) or from a collapsing molecular cloud core (single young stars), carries an embedded magnetic field. In addition, most accretion disks are hot and turbulent, thus meeting the condition for the MHD turbulent dynamo to maintain and amplify any seed field magnetic field. In fact, for a disk's magnetic field to persist long enough in comparison with the disk viscous time it must be contemporaneously regenerated because the characteristic diffusion time of a magnetic field is typically much shorter than a disk's viscous time. This is true for most thin accretion disks. Consequently, studying magentic fields in thin disks is usually synonymous with studying magnetic dynamos, a fact that is not commonly recognized in the literature. Progress in studying the structure of many accretion disks was achieved mainly because most disks can be regarded as two-dimensional flows in which vertical and radial structures are largely decoupled. By analogy, in a thin disk, one may expect that vertical and radial structures of the magnetic field are decoupled because the magnetic field diffuses more rapidly to the vertical boundary of the disk than along the radius. Thus, an asymptotic method, called an adiabatic approximation, can be applied to accretion disk dynamo. We can represent the solution to the dynamo equation in the form B = Q(r)b(r,z), where Q(r) describes the field distribution along the radius, while the field distribution across the disk is included in the vector function b, which parametrically depends on r and is normalized by the condition max (b(z)) = 1. The field distribution across the disk is established rapidly, while the radial distribution Q(r) evolves on a considerably longer timescale. It is this evolution that is the subject of this paper.

Diffusion theory of decision making in continuous report.

PubMed

Smith, Philip L

2016-07-01

I present a diffusion model for decision making in continuous report tasks, in which a continuous, circularly distributed, stimulus attribute in working memory is matched to a representation of the attribute in the stimulus display. Memory retrieval is modeled as a 2-dimensional diffusion process with vector-valued drift on a disk, whose bounding circle represents the decision criterion. The direction and magnitude of the drift vector describe the identity of the stimulus and the quality of its representation in memory, respectively. The point at which the diffusion exits the disk determines the reported value of the attribute and the time to exit the disk determines the decision time. Expressions for the joint distribution of decision times and report outcomes are obtained by means of the Girsanov change-of-measure theorem, which allows the properties of the nonzero-drift diffusion process to be characterized as a function of a Euclidian-distance Bessel process. Predicted report precision is equal to the product of the decision criterion and the drift magnitude and follows a von Mises distribution, in agreement with the treatment of precision in the working memory literature. Trial-to-trial variability in criterion and drift rate leads, respectively, to direct and inverse relationships between report accuracy and decision times, in agreement with, and generalizing, the standard diffusion model of 2-choice decisions. The 2-dimensional model provides a process account of working memory precision and its relationship with the diffusion model, and a new way to investigate the properties of working memory, via the distributions of decision times. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Comparison of real-time PCR with disk diffusion, agar screen and E-test methods for detection of methicillin-resistant Staphylococcus aureus.

PubMed

Shariati, Laleh; Validi, Majid; Tabatabaiefar, Mohammad Amin; Karimi, Ali; Nafisi, Mohammad Reza

2010-12-01

Methicillin-resistant Staphylococcus aureus (MRSA) is a nosocomial pathogen. Our main objective was to compare oxacillin disk test, oxacillin E-test, and oxacillin agar screen for detection of methicillin resistance in S. aureus, using real-time PCR for mecA as the "gold standard" comparison assay. 196 S. aureus isolates were identified out of 284 Staphylococcus isolates. These isolates were screened for MRSA with several methods: disk diffusion, agar screen (6.0 μg/ml), oxacillin E-test, and real-time PCR for detection of mecA gene. Of the 196 S. aureus isolates tested, 96 isolates (49%) were mecA-positive and 100 isolates (51%) mecA-negative. All methods tested had a statistically significant agreement with real-time PCR. E-test was 100% sensitive and specific for mecA presence. The sensitivity and specificity of oxacillin agar screen method were 98 and 99%, respectively and sensitivity and specificity of oxacillin disk diffusion method were 95 and 93%, respectively. In the present study, oxacillin E-test is proposed as the best phenotypic method. For economic reasons, the oxacillin agar screen method (6.0 μg/ml), which is suitable for the detection of MRSA, is recommended due to its accuracy and low cost.

A high spatial resolution X-ray and Hα study of hot gas in the halos of star-forming disk galaxies -- testing feedback models

NASA Astrophysics Data System (ADS)

Strickland, D. K.; Heckman, T. M.; Colbert, E. J. M.; Hoopes, C. G.; Weaver, K. A.

2002-12-01

We present arcsecond resolution Chandra X-ray and ground-based optical Hα imaging of a sample of ten edge-on star-forming disk galaxies (seven starburst and three ``normal'' spiral galaxies), a sample which covers the full range of star-formation intensity found in disk galaxies. The X-ray observations make use of the unprecented spatial resolution of the Chandra X-ray observatory to robustly remove X-ray emission from point sources, and hence obtain the X-ray properties of the diffuse thermal emission alone. This data has been combined with existing, comparable-resolution, ground-based Hα imaging. We compare these empirically-derived diffuse X-ray properties with various models for the generation of hot gas in the halos of star-forming galaxies: supernova feedback-based models (starburst-driven winds, galactic fountains), cosmologically-motivated accretion of the IGM and AGN-driven winds. SN feedback models best explain the observed diffuse X-ray emission. We then use the data to test basic, but fundamental, aspects of wind and fountain theories, e.g. the critical energy required for disk "break-out." DKS is supported by NASA through Chandra Postdoctoral Fellowship Award Number PF0-10012.

Dissemination of Multidrug-Resistant, Class I and II Integrons and Molecular Typing of CTX-M-producing Klebsiella pneumoniae.

PubMed

Akya, Alisha; Elahi, Azam; Chegenelorestani, Roya; Rezaee, Mahya

2018-01-01

Klebsiella pneumoniae ( K. pneumoniae ) is an important opportunistic pathogen causes serious community and hospital-acquired infections, which is highly resistant to antibiotics. We aimed to determine the frequency of multidrug resistant (MDR) and molecular typing of clinical isolates of K. pneumoniae . One hundred isolates of K. pneumoniae were collected from clinical samples in three general hospitals in Kermanshah. The antimicrobial susceptibility and extended-spectrum beta-lactamases (ESBL) production of isolates were determined using disk diffusion and combined disk methods, respectively. The bla CTX-M gene, class I and II integrons were detected using polymerase chain reaction. The bla CTX-M positive isolates were selected for genotyping using pulsed-field gel electrophoresis (PFGE). MDR phenotype was observed in 56% of isolates. The 40% of isolates were ESBL positive and 35 isolates contained bla CTX-M . Class I and II of integrons were detected in 50 (89.2%) and 39 (69.6%) of MDR isolates, respectively. PFGE patterns of K. pneumoniae bla CTX-M positive isolates indicated 19 clusters (X 1-19 ) with different genotype patterns. The study findings highlight the concern of circulating MDR strains of K. pneumoniae with bla CTX-M and class I and II integrons in Kermanshah hospitals. The presence of integrons among isolates may facilitate the spread of new resistance genes in this bacterium. Therefore, surveillance for the spread of MDR strains of this bacterium is recommended in hospitals.

The Relationship between the Dense Neutral and Diffuse Ionized Gas in the Thick Disks of Two Edge-on Spiral Galaxies

NASA Astrophysics Data System (ADS)

Rueff, Katherine M.; Howk, J. Christopher; Pitterle, Marissa; Hirschauer, Alec S.; Fox, Andrew J.; Savage, Blair D.

2013-03-01

We present high-resolution, optical images (BVI + Hα) of the multiphase interstellar medium (ISM) in the thick disks of the edge-on spiral galaxies NGC 4013 and NGC 4302. Our images from the Hubble Space Telescope (HST), Large Binocular Telescope, and WIYN 3.5 m telescope reveal an extensive population of filamentary dust absorption seen to z ~2-2.5 kpc. Many of these dusty thick disk structures have characteristics reminiscent of molecular clouds found in the Milky Way disk. Our Hα images show that the extraplanar diffuse ionized gas (DIG) in these galaxies is dominated by a smooth, diffuse component. The strongly filamentary morphologies of the dust absorption have no counterpart in the smoothly distributed Hα emission. We argue that the thick disk DIG and dust-bearing filaments trace physically distinct phases of the thick disk ISM, the latter tracing a dense, warm or cold neutral medium. The dense, dusty matter in the thick disks of spiral galaxies is largely tracing matter ejected from the thin disk via energetic feedback from massive stars. The high densities of the gas may be a result of converging gas flows. This dense material fuels some thick disk star formation, as evidenced by the presence of thick disk H II regions. Based on observations obtained with the NASA/ESA Hubble Space Telescope operated at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Also, based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the US, Italy, and Germany. LBT Corporation partners are the University of Arizona, on behalf of the Arizona University System; Instituto Nazionale do Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute of Potsdam, and Heidelberg University; Ohio State University, and the Research Corporation, on behalf of the University of Notre Dame, the University of Minnesota, and the University of Virginia. Also, based on observations obtained by the WIYN Observatory which is a joint facility of the University of Wisconsin-Madison, Yale University, Indiana University, and the National Optical Astronomy Observatories.

Numerical analysis of hydrodynamics in a rotor-stator reactor for biodiesel synthesis

NASA Astrophysics Data System (ADS)

Wen, Zhuqing; Petera, Jerzy

2016-06-01

A rotor-stator spinning disk reactor for intensified biodiesel synthesis is described and numerically simulated. The reactor consists of two flat disks, located coaxially and parallel to each other with a gap ranging from 0.1 mm to 0.2 mm between the disks. The upper disk is located on a rotating shaft while the lower disk is stationary. The feed liquids, triglycerides (TG) and methanol are introduced coaxially along the center line of rotating disk and stationary disk, respectively. Fluid hydrodynamics in the reactor for synthesis of biodiesel from TG and methanol in the presence of a sodium hydroxide catalyst are simulated, using convection-diffusion-reaction species transport model by the CFD software ANSYS©Fluent v. 13.0. The effects of upper disk's spinning speed, gap size and flow rates at inlets are evaluated.

Assessment of disk MHD generators for a base load powerplant

NASA Technical Reports Server (NTRS)

Chubb, D. L.; Retallick, F. D.; Lu, C. L.; Stella, M.; Teare, J. D.; Loubsky, W. J.; Louis, J. F.; Misra, B.

1981-01-01

Results from a study of the disk MHD generator are presented. Both open and closed cycle disk systems were investigated. Costing of the open cycle disk components (nozzle, channel, diffuser, radiant boiler, magnet and power management) was done. However, no detailed costing was done for the closed cycle systems. Preliminary plant design for the open cycle systems was also completed. Based on the system study results, an economic assessment of the open cycle systems is presented. Costs of the open cycle disk conponents are less than comparable linear generator components. Also, costs of electricity for the open cycle disk systems are competitive with comparable linear systems. Advantages of the disk design simplicity are considered. Improvements in the channel availability or a reduction in the channel lifetime requirement are possible as a result of the disk design.

Antimicrobial Agents Used in the Treatment of Peri-Implantitis Alter the Physicochemistry and Cytocompatibility of Titanium Surfaces.

PubMed

Kotsakis, Georgios A; Lan, Caixia; Barbosa, Joao; Lill, Krista; Chen, Ruoqiong; Rudney, Joel; Aparicio, Conrado

2016-07-01

Chemotherapeutic agents (ChAs) are considered an integral part of current treatment protocols for the decontamination of titanium implants with peri-implantitis, based on their antimicrobial effect. Despite the proven antimicrobial effect of ChAs on titanium-bound biofilms, previous studies have elucidated an unexpected disassociation between bacterial reduction and biologically acceptable treatment outcomes. In this study, the authors hypothesize that ChAs residues alter titanium physicochemistry and thus compromise cellular response to decontaminated surfaces. Grit-blasted acid-etched titanium disks were contaminated with multispecies microcosm biofilms grown from in vivo peri-implant plaque samples. To simulate implant decontamination, the contaminated disks were burnished with 0.12% chlorhexidine, 20% citric acid, 24% EDTA/1.5% NaOCl, or sterile saline and assessed surface physicochemical properties. Sterile untreated surfaces were the controls. The biologic effects of decontamination were assessed via cell proliferation and differentiation assays. Bacterial counts after decontamination confirmed that the ChAs were antimicrobial. X-ray photoelectron spectroscopy invariably detected elemental contaminants associated with each ChA molecule or salt that significantly altered wettability compared with controls. Notably, all surfaces with ChA residues showed some cytotoxic effect compared with controls (P <0.05). Increased cell counts were consistently found in the saline-treated group compared with chlorhexidine (P = 0.03). Interestingly, no association was found between antimicrobial effect and cell counts (P >0.05). ChA-specific residues left on the titanium surfaces altered titanium physical properties and adversely affected the osteoblastic response irrespective of their observed antimicrobial effect. Chlorhexidine may compromise the biocompatibility of titanium surfaces, and its use is not recommended to detoxify implants. Sterile saline, citric acid, and NaOCl-EDTA may be proposed for use in the treatment of peri-implantitis. Contrary to previous studies that recommended the selection of ChAs for the decontamination of titanium implants according to their antimicrobial effects, the present study demonstrated that the restoration of the biocompatibility of contaminated titanium surfaces is also contingent on the preservation of titanium material properties.

Dynamo magnetic field modes in thin astrophysical disks - An adiabatic computational approximation

NASA Technical Reports Server (NTRS)

Stepinski, T. F.; Levy, E. H.

1991-01-01

An adiabatic approximation is applied to the calculation of turbulent MHD dynamo magnetic fields in thin disks. The adiabatic method is employed to investigate conditions under which magnetic fields generated by disk dynamos permeate the entire disk or are localized to restricted regions of a disk. Two specific cases of Keplerian disks are considered. In the first, magnetic field diffusion is assumed to be dominated by turbulent mixing leading to a dynamo number independent of distance from the center of the disk. In the second, the dynamo number is allowed to vary with distance from the disk's center. Localization of dynamo magnetic field structures is found to be a general feature of disk dynamos, except in the special case of stationary modes in dynamos with constant dynamo number. The implications for the dynamical behavior of dynamo magnetized accretion disks are discussed and the results of these exploratory calculations are examined in the context of the protosolar nebula and accretion disks around compact objects.

High average power scaleable thin-disk laser

DOEpatents

Beach, Raymond J.; Honea, Eric C.; Bibeau, Camille; Payne, Stephen A.; Powell, Howard; Krupke, William F.; Sutton, Steven B.

2002-01-01

Using a thin disk laser gain element with an undoped cap layer enables the scaling of lasers to extremely high average output power values. Ordinarily, the power scaling of such thin disk lasers is limited by the deleterious effects of amplified spontaneous emission. By using an undoped cap layer diffusion bonded to the thin disk, the onset of amplified spontaneous emission does not occur as readily as if no cap layer is used, and much larger transverse thin disks can be effectively used as laser gain elements. This invention can be used as a high average power laser for material processing applications as well as for weapon and air defense applications.

A Low-Cost, Hands-on Module to Characterize Antimicrobial Compounds Using an Interdisciplinary, Biophysical Approach

PubMed Central

Kaushik, Karishma S.; Kessel, Ashley; Ratnayeke, Nalin; Gordon, Vernita D.

2015-01-01

We have developed a hands-on experimental module that combines biology experiments with a physics-based analytical model in order to characterize antimicrobial compounds. To understand antibiotic resistance, participants perform a disc diffusion assay to test the antimicrobial activity of different compounds and then apply a diffusion-based analytical model to gain insights into the behavior of the active antimicrobial component. In our experience, this module was robust, reproducible, and cost-effective, suggesting that it could be implemented in diverse settings such as undergraduate research, STEM (science, technology, engineering, and math) camps, school programs, and laboratory training workshops. By providing valuable interdisciplinary research experience in science outreach and education initiatives, this module addresses the paucity of structured training or education programs that integrate diverse scientific fields. Its low-cost requirements make it especially suitable for use in resource-limited settings. PMID:25602254

AMINOGLYCOSIDE RESISTANCE GENES IN Pseudomonas aeruginosa ISOLATES FROM CUMANA, VENEZUELA.

PubMed

Teixeira, Bertinellys; Rodulfo, Hectorina; Carreño, Numirin; Guzmán, Militza; Salazar, Elsa; De Donato, Marcos

2016-01-01

The enzymatic modification of aminoglycosides by aminoglycoside-acetyltransferases (AAC), aminoglycoside-adenyltransferases (AAD), and aminoglycoside-phosphotransferases (APH), is the most common resistance mechanism in P. aeruginosa and these enzymes can be coded on mobile genetic elements that contribute to their dispersion. One hundred and thirty seven P. aeruginosa isolates from the University Hospital, Cumana, Venezuela (HUAPA) were evaluated. Antimicrobial susceptibility was determined by the disk diffusion method and theaac, aadB and aph genes were detected by PCR. Most of the P. aeruginosa isolates (33/137) were identified from the Intensive Care Unit (ICU), mainly from discharges (96/137). The frequency of resistant P. aeruginosaisolates was found to be higher for the aminoglycosides tobramycin and amikacin (30.7 and 29.9%, respectively). Phenotype VI, resistant to these antibiotics, was the most frequent (14/49), followed by phenotype I, resistant to all the aminoglycosides tested (12/49). The aac(6´)-Ib,aphA1 and aadB genes were the most frequently detected, and the simultaneous presence of several resistance genes in the same isolate was demonstrated. Aminoglycoside resistance in isolates ofP. aeruginosa at the HUAPA is partly due to the presence of the aac(6´)-Ib, aphA1 andaadB genes, but the high rates of antimicrobial resistance suggest the existence of several mechanisms acting together. This is the first report of aminoglycoside resistance genes in Venezuela and one of the few in Latin America.

AMINOGLYCOSIDE RESISTANCE GENES IN Pseudomonas aeruginosa ISOLATES FROM CUMANA, VENEZUELA

PubMed Central

TEIXEIRA, Bertinellys; RODULFO, Hectorina; CARREÑO, Numirin; GUZMÁN, Militza; SALAZAR, Elsa; DONATO, Marcos DE

2016-01-01

The enzymatic modification of aminoglycosides by aminoglycoside-acetyltransferases (AAC), aminoglycoside-adenyltransferases (AAD), and aminoglycoside-phosphotransferases (APH), is the most common resistance mechanism in P. aeruginosa and these enzymes can be coded on mobile genetic elements that contribute to their dispersion. One hundred and thirty seven P. aeruginosa isolates from the University Hospital, Cumana, Venezuela (HUAPA) were evaluated. Antimicrobial susceptibility was determined by the disk diffusion method and theaac, aadB and aph genes were detected by PCR. Most of the P. aeruginosa isolates (33/137) were identified from the Intensive Care Unit (ICU), mainly from discharges (96/137). The frequency of resistant P. aeruginosaisolates was found to be higher for the aminoglycosides tobramycin and amikacin (30.7 and 29.9%, respectively). Phenotype VI, resistant to these antibiotics, was the most frequent (14/49), followed by phenotype I, resistant to all the aminoglycosides tested (12/49). The aac(6´)-Ib,aphA1 and aadB genes were the most frequently detected, and the simultaneous presence of several resistance genes in the same isolate was demonstrated. Aminoglycoside resistance in isolates ofP. aeruginosa at the HUAPA is partly due to the presence of the aac(6´)-Ib, aphA1 andaadB genes, but the high rates of antimicrobial resistance suggest the existence of several mechanisms acting together. This is the first report of aminoglycoside resistance genes in Venezuela and one of the few in Latin America. PMID:27007556

Synthesis, characterization, antimicrobial activity and carbonic anhydrase enzyme inhibitor effects of salicilaldehyde-N-methyl p-toluenesulfonylhydrazone and its Palladium(II), Cobalt(II) complexes

NASA Astrophysics Data System (ADS)

Alyar, Saliha; Adem, Şevki

2014-10-01

We report the synthesis of the ligand, salicilaldehyde-N-methyl p-toluenesulfonylhydrazone (salptsmh) derived from p-toluenesulfonicacid-1-methylhydrazide (ptsmh) and its Pd(II) and Co(II) metal complexes were synthesized for the first time. The structure of the ligand and their complexes were investigated using elemental analysis, magnetic susceptibility, molar conductance and spectral (IR, NMR and LC-MS) measurements. Salptsmh has also been characterized by single crystal X-ray diffraction. 1H and 13C shielding tensors for crystal structure were calculated with GIAO/DFT/B3LYP/6-311++G(d,p) methods in CDCl3. The complexes were found to have general composition [ML2]. The results of elemental analysis showed 1:2 (metal/ligand) stoichiometry for all the complex. Magnetic and spectral data indicate a square planar geometry for Pd(II) complex and a distorted tetrahedral geometry for Co(II) complexes. The ligand and its metal chelates have been screened for their antimicrobial activities using the disk diffusion method against the selected Gram positive bacteria: Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Enterococcus faecalis, Gram negative bacteria: Eschericha coli, Pseudomonas aeruginosa, Klebsiella pneumonia. The inhibition activities of these compounds on carbonic anhydrase II (CA II) and carbonic anhydrase I (CA I) have been investigated by comparing IC50 and Ki values and it has been found that Pd(II) complex have more enzyme inhibition efficiency than salptsmh and Co(II) complex.

Helicobacter pylori in Vegetables and Salads: Genotyping and Antimicrobial Resistance Properties

PubMed Central

Yahaghi, Emad; Khamesipour, Faham; Mashayekhi, Fatemeh; Safarpoor Dehkordi, Farhad; Sakhaei, Mohammad Hossein; Masoudimanesh, Mojtaba; Khameneie, Maryam Khayyat

2014-01-01

From a clinical and epidemiological perspective, it is important to know which genotypes and antibiotic resistance patterns are present in H. pylori strains isolated from salads and vegetables. Therefore, the present investigation was carried out to find this purpose. Three hundred eighty washed and unwashed vegetable samples and fifty commercial and traditional salad samples were collected from Isfahan, Iran. Samples were cultured and those found positive for H. pylori were analyzed using PCR. Antimicrobial susceptibility testing was performed using disk diffusion method. Seven out of 50 (14%) salad and 52 out of 380 (13.68%) vegetable samples harbored H. pylori. In addition, leek, lettuce, and cabbage were the most commonly contaminated samples (30%). The most prevalent virulence genes were oipA (86.44%) and cagA (57.625). VacA s1a (37.28%) and iceA1 (47.45%) were the most prevalent genotypes. Forty different genotypic combinations were recognized. S1a/cagA+/iceA1/oipA+ (33.89%), s1a/cagA+/iceA2/oipA (30.50%), and m1a/cagA+/iceA1/oipA+ (28.81%) were the most prevalent combined genotypes. Bacterial strains had the highest levels of resistance against metronidazole (77.96%), amoxicillin (67.79%), and ampicillin (61.01%). High similarity in the genotyping pattern of H. pylori among vegetable and salad samples and human specimens suggests that vegetable and salads may be the sources of the bacteria. PMID:25184146

Isolation and characterization of Listeria monocytogenes from the black-headed gull feces in Kunming, China.

PubMed

Cao, Xiaolong; Wang, Yi; Wang, Yan; Ye, Changyun

Listeria monocytogenes is among the most important foodborne pathogens, which can be isolated from bird feces. The aim of this study was to examine the prevalence, genotypes, virulence factors and drug-resistance characteristics of L. monocytogenes isolated from the black-headed gull in Kunming, China. Serotypes and virulence genes were identified by polymerase chain reaction. Pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST) methods were used to describe the genetic characteristics of all positive isolates. Furthermore, all L. monocytogenes isolates were tested for antimicrobial susceptibility by disk diffusion method. All isolates were positive for inlA, inlB, plcB, prfA, iap, actA and hly genes. Serotyping showed the isolates belonged to serotype 1/2b (2/9, 22%), 1/2c (3/9, 33%), and 4a (4/9, 44%). PFGE showed 4 different pulsotypes (PTs), and MLST differentiated the 9 isolates into 4 sequence types (STs), ST3 (1), ST5 (1), ST35 (3) and ST201 (4). The result of antimicrobial susceptibility revealed that all isolates were naturally sensitive to most antibiotics. The L. monocytogenes isolates had pathogenic potential. There is a potential infection risk for people who come to frequent contact with black-headed gulls in Kunming. Hence, it is necessary to conduct surveillance of L. monocytogenes in the migratory black-headed gulls, which would be valuable to prevent listeriosis in local residents and tourists. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Phenotypic and Genetic Characterization of Carbapenemase and ESBLs Producing Gram-negative Bacteria (GNB) Isolated from Patients with Cystic Fibrosis (CF) in Tehran Hospitals

PubMed Central

Vali, Parisa; Shahcheraghi, Fereshteh; Seyfipour, Maryam; Zamani, Maryam Alsadat; Allahyar, Mohammad Reza; Feizabadi, Mohammad Mehdi

2014-01-01

Background: Cystic Fibrosis (CF) is an autosomal recessive genetic disorder in white populations caused by mutation in a gene that encodes Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein. Since frequent respiratory tract infections are the major problem in patients with CF, obligation to identify the causative bacteria and determining their antibiotic resistance pattern is crucial. The purpose of this project was to detect Gram-negative bacteria (GNB) isolated from sputa of CF patients and to determine their antibiotic resistance pattern. Materials and Methods: The sputum of 52 CF patients, treated as inpatients at hospitals in Tehran, was obtained between November 2011 and June 2012. Samples cultured in selective and non-selective media and GNB recognized by biochemical tests. Antimicrobial susceptibility testing to cephalosporins, aminoglycosides and carbapenems was performed by disk diffusion method and MICs of them were measured. For phenotypic detection of carbapenemase and ESBLs production, the Modified Hodge test, double disk synergy test and the combined disk methods were performed. Subsequently, the genes encoding the extended spectrum beta-lactamases (blaPER, blaCTX-M) and carbapenemases (blaIMP-1, blaGES, blaKPC, blaNDM, blaVIM-1, blaVIM-2, blaSPM, blaSIM) in Gram negative bacteria were targeted among the resistant isolates by using PCR. PFGE was used to determine any genetic relationship among the Pseudomonas aeruginosa isolated from these patients. Results: Fifty five GNB were isolated from 52 sputum samples including Pseudomonas aeruginosa, Klebsiella ozaenae, Alcaligenes xylosoxidans, Achromobacter denitrificans, Klebsiella pneumonia and Stenotrophomonas maltophilia. The rates of resistance to different antibiotic were as follows: cefixime (%80), ceftriaxone (%43), ceftazidime (%45) and meropenem (%7). The prevalence of genes encoding the ESBLs and Carbapenemases among the the phenotypically positive strains were as follows: blaCTX-M (19), blaIMP-1 (2), blaVIM-1 (2) and blaVIM-2 (3) genes respectively. No other genes were detected. PFGE analysis revealed 8 genotypes. Six isolates had mutually 3 similar patterns. Conclusion: This study showed the existence of important ESBLs and carbapenemases genes among the GNB isolated from patients with CF. Continuous surveillance of ESBLs and Carbapenemases, also identification of their types, in bacteria isolated from these patients have an important clinical impact, since, it can often provide valuable information for effective infection control measures and for the choice of appropriate antimicrobial therapy. PMID:24596716

Modeling antimicrobial tolerance and treatment of heterogeneous biofilms.

PubMed

Zhao, Jia; Seeluangsawat, Paisa; Wang, Qi

2016-12-01

A multiphasic, hydrodynamic model for spatially heterogeneous biofilms based on the phase field formulation is developed and applied to analyze antimicrobial tolerance of biofilms by acknowledging the existence of persistent and susceptible cells in the total population of bacteria. The model implements a new conversion rate between persistent and susceptible cells and its homogeneous dynamics is bench-marked against a known experiment quantitatively. It is then discretized and solved on graphic processing units (GPUs) in 3-D space and time. With the model, biofilm development and antimicrobial treatment of biofilms in a flow cell are investigated numerically. Model predictions agree qualitatively well with available experimental observations. Specifically, numerical results demonstrate that: (i) in a flow cell, nutrient, diffused in solvent and transported by hydrodynamics, has an apparent impact on persister formation, thereby antimicrobial persistence of biofilms; (ii) dosing antimicrobial agents inside biofilms is more effective than dosing through diffusion in solvent; (iii) periodic dosing is less effective in antimicrobial treatment of biofilms in a nutrient deficient environment than in a nutrient sufficient environment. This model provides us with a simulation tool to analyze mechanisms of biofilm tolerance to antimicrobial agents and to derive potentially optimal dosing strategies for biofilm control and treatment. Copyright © 2016 Elsevier Inc. All rights reserved.

Antimicrobial effectiveness of oregano and sage essential oils incorporated into whey protein films or cellulose-based filter paper.

PubMed

Royo, Maite; Fernández-Pan, Idoya; Maté, Juan I

2010-07-01

In this study the antimicrobial effectiveness of oregano and sage essential oils (EOs) incorporated into two different matrices, whey protein isolate (WPI) and cellulose-based filter paper, was analysed. Antimicrobial properties of WPI-based films containing oregano and sage EOs were tested against Listeria innocua, Staphylococcus aureus and Salmonella enteritidis. Oregano EO showed antimicrobial activity against all three micro-organisms. The highest inhibition zones were against L. innocua. However, sage EO did not show antimicrobial activity against any of the micro-organisms. Antimicrobial activity was confirmed for both EOs using cellulose-based filter paper as supporting matrix, although it was significantly more intense for oregano EO. Inhibition surfaces were significantly greater when compared with those of the WPI films. This finding is likely due to the higher porosity and diffusivity of the active compounds in the filter paper. The interactions between the EOs and the films have a critical effect on the diffusivity of the active compounds and therefore on the final antimicrobial activity. As a result, to obtain active edible films, it is necessary to find the equilibrium point between the nature and concentration of the active compounds in the EO and the formulation of the film.

The consistency of antibiotic resistance' results in two methods of disk diffusion and MIC in isolated organisms from patients with urinary tract infections.

PubMed

Karami, A; Mazloom Zadeh, S; Rastin, A; Karami, A; Shiri, P

2015-01-01

Introduction: The urinary tract infection is the most common infection and drug resistance to it is increasing. Due to the acute infection, the prescribing of medicine is conducted before culture and antibiogram and according to the results, disk diffusion is adjusted. The aim of this study was to compare it with MIC to determine to what extent the current method could be useful. Methods: This descriptive cross-sectional investigation research regarding drug resistance was conducted with the help of two methods of disk diffusion and MIC on the isolations of patients' urine culture with UTI (midstream clean catch). Bacterial resistance was measured, and sensitivity and specificity were evaluated. Results: The MIC method was considered the gold standard and, according to the related formula, the sensitivity and specificity of disk diffusion were related to 13 antibiotics obtained as it follows: ciprofloxacin 69% and 69.1% (0.0001 > p and Kappa = .292), cotrimoxazole 50% and 77.3% (p = 0.010), nitrofurantoin 84.7% and 58.2% (0.0001 > p and Kappa = 0.44), ampicilin 83.3% and 85.3% (0.0001 > p and Kappa = 0.33), ofloxacin 65.5% and 83.9% (0.0001 > p and Kappa = 0.429), cephalexin 46.2% and 75.2% (p = 0.012 and Kappa = 0.116), gentamicin 64.2% and 66% (0.0001 > p and Kappa = 0.276), ceftriaxone 27.6% and 80.9% (p = 0.216 and Kappa = 0.074), nalidixic acid 42.1% and 89.2% (0.0001 > p and Kappa = 0.354), imipenem 63.4% and 70.4% (0.0001 > p and Kappa 0.306), co-amoxiclav 83% and 71% (0.0001 > p and Kappa = 0.412), cefixime 21% and 80.9% (0.0001 > p and Kappa = 0.412), vancomycin 55.9% and 94.7 (0.9001 > p and Kappa = 0.532). Sensitivity and specificity of this method were reported to be lower than MIC. Conclusions: Due to the low sensitivity and specificity of the disk diffusion method, antibiotic therapy should be certainly considered in clinical conditions, and risk factors for the infection and only by this approach cannot prescribe the drug.

The effects of a new therapeutic triclosan/copolymer/sodium-fluoride dentifrice on oral bacteria, including odorigenic species.

PubMed

Furgang, David; Sreenivasan, Prem K; Zhang, Yun Po; Fine, Daniel H; Cummins, Diane

2003-09-01

This investigation examined the in vitro and ex vivo antimicrobial effects of a new dentifrice, Colgate Total Advanced Fresh, formulated with triclosan/copolymer/sodium fluoride, on oral bacteria, including those odorigenic bacteria implicated in bad breath. The effects of Colgate Total Advanced Fresh were compared to commercially available fluoride dentifrices that served as controls. Three experimental approaches were undertaken for these studies. In the first approach, the dentifrice formulations were tested in vitro against 13 species of oral bacteria implicated in bad breath. The second approach examined the antimicrobial activity derived from dentifrice that was adsorbed to and released from hydroxyapatite disks. In this approach, dentifrice-treated hydroxyapatite disks were immersed in a suspension of bacteria, and reduction in bacterial viability from the release of bioactive agents from hydroxyapatite was determined. The third approach examined the effect of treating bacteria immediately after their removal from the oral cavity of 11 adult human volunteers. This ex vivo study examined the viability of cultivable oral bacteria after dentifrice treatment for 2 minutes. Antimicrobial effects were determined by plating Colgate Total Advanced Fresh and control-dentifrice-treated samples on enriched media (for all cultivable oral bacteria) and indicator media (for hydrogen-sulfide-producing organisms), respectively. Results indicated that the antimicrobial effects of Colgate Total Advanced Fresh were significantly greater than either of the other dentifrices for all 13 oral odorigenic bacterial strains tested in vitro (P < or = 0.05). In the second approach, Colgate Total Advanced Fresh-treated hydroxyapatite disks were significantly more active in reducing bacterial growth than the other dentifrices tested (P < or = 0.05). Finally, ex vivo treatment of oral bacteria with Colgate Total Advanced Fresh demonstrated a 90.9% reduction of all oral cultivable bacteria and a 91.5% reduction of oral bacteria producing hydrogen sulfide compared with the control dentifrice. In conclusion, these results, taken together with the significant reductions in clinical malodor scores by Colgate Total Advanced Fresh demonstrated in organoleptic studies, strongly suggest that this dentifrice kills the bacteria that are implicated in the cause of bad breath.

Local magnetohydrodynamic instabilities and the wave-driven dynamo in accretion disks

NASA Technical Reports Server (NTRS)

Vishniac, Ethan T.; Diamond, Patrick

1992-01-01

We consider the consequences of magnetic buoyancy and the magnetic shearing instability (MSI) on the strength and organization of the magnetic field in a thin accretion disk. We discuss a model in which the wave-driven dynamo growth rate is balanced by the dissipative effects of the MSI. As in earlier work, the net helicity is due to small advective motions driven by nonlinear interactions between internal waves. Assuming a simple model of the internal wave spectrum generated from the primary m = 1 internal waves, we find that the magnetic energy density saturates at about (H/r) exp 4/3 times the local pressure (where H is the disk thickness and r is its radius). On very small scales the shearing instability will produce an isotropic fluctuating field. For a stationary disk this is equivalent to a dimensionless 'viscosity' of about (H/r) exp 4/3. The vertical and radial diffusion coefficients will be comparable to each other. Magnetic buoyancy will be largely suppressed by the turbulence due to the MSI. We present a rough estimate of its effects and find that it removes magnetic flux from the disk at a rate comparable to that caused by turbulent diffusion.

Validation of EUCAST zone diameter breakpoints against reference broth microdilution.

PubMed

Bengtsson, S; Bjelkenbrant, C; Kahlmeter, G

2014-06-01

The European Committee on Antimicrobial Susceptibility Testing (EUCAST) began harmonizing clinical breakpoints in Europe 2002. In 2009, work to develop a disc diffusion method began and the first disc diffusion breakpoints calibrated to EUCAST clinical MIC breakpoints were published in December 2009. In this study we validated EUCAST clinical zone diameter breakpoints against the International Standard Organization (ISO) reference broth microdilution. A collection of 544 isolates (238 Gram-negative and 306 Gram-positive) were tested against a panel of antimicrobial agents. Antimicrobial susceptibility testing was performed with broth microdilution as described by ISO and disc diffusion in accordance with EUCAST methodology. Inhibition zone diameters and MIC values were interpreted and categorized (S, I and R) according to EUCAST clinical breakpoint table version 2.0. Categorical agreement (CA) as well as minor (mD), major (MD) and very major (VMD) discrepancies were determined. There was in general good correlation between susceptibility test results obtained with disc diffusion and broth microdilution. Overall CA was 97.3% for all combinations of organisms and antimicrobial agents (n = 5231) and the overall discrepancy rates were 110 (2.1%) mD, 24 (0.5%) MD and 7 (0.1%) VMD. The overall CA for Gram-positive and Gram-negative organisms were 98.7% (2346 tests) and 96.2% (2942 tests), respectively. Seven VMD were observed, five for Gram-positive organisms (coagulase negative staphylococci (n = 2) and Staphylococcus aureus (n = 3)) and two for Gram-negative organisms (Pseudomonas aeruginosa). Minor discrepancies were mainly observed in Gram-negatives and were related to different antimicrobial agents and species. © 2013 The Authors Clinical Microbiology and Infection © 2013 European Society of Clinical Microbiology and Infectious Diseases.

Antimicrobial activity of Miconia species (Melastomataceae).

PubMed

Rodrigues, Juliana; Michelin, Danielle Carvalho; Rinaldo, Daniel; Zocolo, Guilherme Julião; dos Santos, Lourdes Campaner; Vilegas, Wagner; Salgado, Hérida Regina Nunes

2008-03-01

This work evaluated the antimicrobial activity of the methanol and chloroform extracts of the leaves of Miconia cabucu, Miconia rubiginosa, and Miconia stenostachya using the disc-diffusion method. The results obtained showed that the methanol extracts of the leaves of M. rubiginosa and M. stenostachya and the chloroform extract of the leaves of M. cabucu presented antimicrobial activity against the tested microorganisms.

SATURATED TORQUE FORMULA FOR PLANETARY MIGRATION IN VISCOUS DISKS WITH THERMAL DIFFUSION: RECIPE FOR PROTOPLANET POPULATION SYNTHESIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masset, F. S.; Casoli, J., E-mail: masset@fis.unam.m, E-mail: jules.casoli@cea.f, E-mail: masset@fis.unam.m

2010-11-10

We provide torque formulae for low-mass planets undergoing type I migration in gaseous disks. These torque formulae put special emphasis on the horseshoe drag, which is prone to saturation: the asymptotic value reached by the horseshoe drag depends on a balance between coorbital dynamics (which tends to cancel out or saturate the torque) and diffusive processes (which tend to restore the unperturbed disk profiles, thereby desaturating the torque). We entertain the question of this asymptotic value and derive torque formulae that give the total torque as a function of the disk's viscosity and thermal diffusivity. The horseshoe drag features twomore » components: one that scales with the vortensity gradient and another that scales with the entropy gradient and constitutes the most promising candidate for halting inward type I migration. Our analysis, which is complemented by numerical simulations, recovers characteristics already noted by numericists, namely, that the viscous timescale across the horseshoe region must be shorter than the libration time in order to avoid saturation and that, provided this condition is satisfied, the entropy-related part of the horseshoe drag remains large if the thermal timescale is shorter than the libration time. Side results include a study of the Lindblad torque as a function of thermal diffusivity and a contribution to the corotation torque arising from vortensity viscously created at the contact discontinuities that appear at the horseshoe separatrices. For the convenience of the reader mostly interested in the torque formulae, Section 8 is self-contained.« less

In vitro evaluation of Augmentin by broth microdilution and disk diffusion susceptibility testing: regression analysis, tentative interpretive criteria, and quality control limits.

PubMed Central

Fuchs, P C; Barry, A L; Thornsberry, C; Gavan, T L; Jones, R N

1983-01-01

Augmentin (Beecham Laboratories, Bristol, Tenn.), a combination drug consisting of two parts amoxicillin to one part clavulanic acid and a potent beta-lactamase inhibitor, was evaluated in vitro in comparison with ampicillin or amoxicillin or both for its inhibitory and bactericidal activities against selected clinical isolates. Regression analysis was performed and tentative disk diffusion susceptibility breakpoints were determined. A multicenter performance study of the disk diffusion test was conducted with three quality control organisms to determine tentative quality control limits. All methicillin-susceptible staphylococci and Haemophilus influenzae isolates were susceptible to Augmentin, although the minimal inhibitory concentrations for beta-lactamase-producing strains of both groups were, on the average, fourfold higher than those for enzyme-negative strains. Among the Enterobacteriaceae, Augmentin exhibited significantly greater activity than did ampicillin against Klebsiella pneumoniae, Citrobacter diversus, Proteus vulgaris, and about one-third of the Escherichia coli strains tested. Bactericidal activity usually occurred at the minimal inhibitory concentration. There was a slight inoculum concentration effect on the Augmentin minimal inhibitory concentrations. On the basis of regression and error rate-bounded analyses, the suggested interpretive disk diffusion susceptibility breakpoints for Augmentin are: susceptible, greater than or equal to 18 mm; resistant, less than or equal to 13 mm (gram-negative bacilli); and susceptible, greater than or equal to 20 mm (staphylococci and H. influenzae). The use of a beta-lactamase-producing organism, such as E. coli Beecham 1532, is recommended for quality assurance of Augmentin susceptibility testing. PMID:6625554

Effect of Polydispersity on Diffusion in Random Obstacle Matrices

NASA Astrophysics Data System (ADS)

Cho, Hyun Woo; Kwon, Gyemin; Sung, Bong June; Yethiraj, Arun

2012-10-01

The dynamics of tracers in disordered matrices is of interest in a number of diverse areas of physics such as the biophysics of crowding in cells and cell membranes, and the diffusion of fluids in porous media. To a good approximation the matrices can be modeled as a collection of spatially frozen particles. In this Letter, we consider the effect of polydispersity (in size) of the matrix particles on the dynamics of tracers. We study a two dimensional system of hard disks diffusing in a sea of hard disk obstacles, for different values of the polydispersity of the matrix. We find that for a given average size and area fraction, the diffusion of tracers is very sensitive to the polydispersity. We calculate the pore percolation threshold using Apollonius diagrams. The diffusion constant, D, follows a scaling relation D˜(ϕc-ϕm)μ-β for all values of the polydispersity, where ϕm is the area fraction and ϕc is the value of ϕm at the percolation threshold.

Effect of polydispersity on diffusion in random obstacle matrices.

PubMed

Cho, Hyun Woo; Kwon, Gyemin; Sung, Bong June; Yethiraj, Arun

2012-10-12

The dynamics of tracers in disordered matrices is of interest in a number of diverse areas of physics such as the biophysics of crowding in cells and cell membranes, and the diffusion of fluids in porous media. To a good approximation the matrices can be modeled as a collection of spatially frozen particles. In this Letter, we consider the effect of polydispersity (in size) of the matrix particles on the dynamics of tracers. We study a two dimensional system of hard disks diffusing in a sea of hard disk obstacles, for different values of the polydispersity of the matrix. We find that for a given average size and area fraction, the diffusion of tracers is very sensitive to the polydispersity. We calculate the pore percolation threshold using Apollonius diagrams. The diffusion constant, D, follows a scaling relation D~(φ(c)-φ(m))(μ-β) for all values of the polydispersity, where φ(m) is the area fraction and φ(c) is the value of φ(m) at the percolation threshold.

Molecular serotyping and antimicrobial resistance profiles of Actinobacillus pleuropneumoniae isolated from pigs in South Korea.

PubMed

Kim, Boram; Hur, Jin; Lee, Ji Yeong; Choi, Yoonyoung; Lee, John Hwa

2016-09-01

Actinobacillus pleuropneumoniae (APP) causes porcine pleuropneumonia (PP). Serotypes and antimicrobial resistance patterns in APP isolates from pigs in Korea were examined. Sixty-five APP isolates were genetically serotyped using standard and multiplex PCR (polymerase chain reaction). Antimicrobial susceptibilities were tested using the standardized disk-agar method. PCR was used to detect β-lactam, gentamicin and tetracycline-resistance genes. The random amplified polymorphic DNA (RAPD) patterns were determined by PCR. Korean pigs predominantly carried APP serotypes 1 and 5. Among 65 isolates, one isolate was sensitive to all 12 antimicrobials tested in this study. Sixty-two isolates was resistant to tetracycline and 53 isolates carried one or five genes including tet(B), tet(A), tet(H), tet(M)/tet(O), tet(C), tet(G) and/or tet(L)-1 markers. Among 64 strains, 9% and 26.6% were resistance to 10 and three or more antimicrobials, respectively. Thirteen different antimicrobial resistance patterns were observed and RAPD analysis revealed a separation of the isolates into two clusters: cluster II (6 strains resistant to 10 antimicrobials) and cluster I (the other 59 strains). Results show that APP serotypes 1 and 5 are the most common in Korea, and multi-drug resistant strains are prevalent. RAPD analysis demonstrated that six isolates resistant to 10 antimicrobials belonged to the same cluster.

Particle trapping and snow lines in the Trappist-1 disk

NASA Astrophysics Data System (ADS)

White, Kevin; Desch, Steven; Kalyaan, Anusha

2018-01-01

The Trappist-1 system has 7 transiting planets with constrained masses and radii (Gillon et al. 2017; Wang et al. 2017), and represents a laboratory for understanding planet formation in M dwarf disks. All the planets are about 1 ME, consistent with the pebble isolation masses in M dwarf disks, in the same way ~ 30 ME Jupiter’s core matches the pebble isolation mass in the solar nebula (Ormel et al. 2017). Trappist-1 f, g, and h are apparently ice-rich (> 50%), but planets b and c are <15% ice, suggesting they formed inside the snow line in Trappist-1’s disk (Unterborn et al. 2017). Earth formed inside the snow line in the solar nebula, but is only ~ 0.1wt% water, much drier than Trappist-1 b and c. If the pebbles excluded by Jupiter were icy, this would explain the dryness of the inner solar system (Morbidelli et al. 2016). This raises the question why the Trappist-1 inner disk was not equally dry. We have calculated the efficiency by which pebbles are trapped in the pressure maxima outside of planet-opened disk gaps, comparing the rates of radial diffusion vs. radial drift (as in Desch et al. 2017). We find that while Jupiter can exclude particles mm-sized or larger, only for particles > cm-sized does radial drift act faster than radial diffusion in the Trappist-1 pressure maxima. Pressure maxima in M dwarf disks are relatively leaky particle traps, possibly admitting more icy pebbles and water into the inner disk. We predict lower emission contrast between rings and gaps in M dwarf disks observable by ALMA.

Vertical Structure of NGC 4631

NASA Astrophysics Data System (ADS)

Ann, Hong Bae; Seo, Mira Seo; Baek, Su-Ja

2011-02-01

We present a deep CCD imaging in B and V bands which allows us to analyze the vertical structure of NGC 4631. We derive the scale heights of the thin and thick disks at a variety of positions along the major axis of the disk. The scale heights of the thin disk are nearly constant while those of the thick disk tend to increase with increasing galactocentric distance. The mean scale heights of the thin disk derived from B and V images are similar to each other (˜450 pc). Instead, those of the thick disk show a strong east-west asymmetry which is caused by the diffuse stellar emission that is most prominent in the north west regions above the disk plane. The ratio of scale heights (z_{thick}/z_{thin}) is about 2.5 in the east side of the disk. However, this ratio is greater than 4 for the thick disk above the disk plane in the west side of the galaxy.

Orbital Evolution of Moons in Weakly Accreting Circumplanetary Disks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujii, Yuri I.; Gressel, Oliver; Kobayashi, Hiroshi

We investigate the formation of hot and massive circumplanetary disks (CPDs) and the orbital evolution of satellites formed in these disks. Because of the comparatively small size-scale of the sub-disk, quick magnetic diffusion prevents the magnetorotational instability (MRI) from being well developed at ionization levels that would allow MRI in the parent protoplanetary disk. In the absence of significant angular momentum transport, continuous mass supply from the parental protoplanetary disk leads to the formation of a massive CPD. We have developed an evolutionary model for this scenario and have estimated the orbital evolution of satellites within the disk. We find,more » in a certain temperature range, that inward migration of a satellite can be stopped by a change in the structure due to the opacity transitions. Moreover, by capturing second and third migrating satellites in mean motion resonances, a compact system in Laplace resonance can be formed in our disk models.« less

Rapid, specific determination of iodine and iodide by combined solid-phase extraction/diffuse reflectance spectroscopy

NASA Technical Reports Server (NTRS)

Arena, Matteo P.; Porter, Marc D.; Fritz, James S.

2002-01-01

A new, rapid methodology for trace analysis using solid-phase extraction is described. The two-step methodology is based on the concentration of an analyte onto a membrane disk and on the determination by diffuse reflectance spectroscopy of the amount of analyte extracted on the disk surface. This method, which is adaptable to a wide range of analytes, has been used for monitoring ppm levels of iodine and iodide in spacecraft water. Iodine is used as a biocide in spacecraft water. For these determinations, a water sample is passed through a membrane disk by means of a 10-mL syringe that is attached to a disk holder assembly. The disk, which is a polystyrene-divinylbenzene composite, is impregnated with poly(vinylpyrrolidone) (PVP), which exhaustively concentrates iodine as a yellow iodine-PVP complex. The amount of concentrated iodine is then determined in only 2 s by using a hand-held diffuse reflectance spectrometer by comparing the result with a calibration curve based on the Kubelka-Munk function. The same general procedure can be used to determine iodide levels after its facile and exhaustive oxidation to iodine by peroxymonosulfate (i.e., Oxone reagent). For samples containing both analytes, a two-step procedure can be used in which the iodide concentration is calculated from the difference in iodine levels before and after treatment of the sample with peroxymonosulfate. With this methodology, iodine and iodide levels in the 0.1-5.0 ppm range can be determined with a total workup time of approximately 60 s with a RSD of approximately 6%.

Nasopharyngeal carriage of Streptococcus pneumoniae in adults infected with human immunodeficiency virus in Jakarta, Indonesia.

PubMed

Harimurti, Kuntjoro; Saldi, Siti R F; Dewiasty, Esthika; Khoeri, Miftahuddin M; Yunihastuti, Evi; Putri, Tiara; Tafroji, Wisnu; Safari, Dodi

2016-01-01

This study investigated the distribution of serotype and antimicrobial susceptibility of Streptococcus pneumoniae carried by adults infected with human immunodeficiency virus (HIV) in Jakarta, Indonesia. Specimens of nasopharyngeal swab were collected from 200 HIV infected adults aged 21 to 63 years. Identification of S. pneumoniae was done by optochin susceptibility test and PCR for the presence of psaA and lytA genes. Serotyping was performed with sequential multiplex PCR and antibiotic susceptibility with the disk diffusion method. S. pneumoniae strains were carried by 10% adults with serotype 6A/B 20% was common serotype among cultured strains in 20 adults. Most of isolates were susceptible to chloramphenicol (80%) followed by clindamycin (75%), erythromycin (75%), penicillin (55%), and tetracycline (50%). This study found resistance to sulphamethoxazole/trimethoprim was most common with only 15% of strains being susceptible. High non-susceptibility to sulphamethoxazole/trimethoprim was observed in S. pneumoniae strains carried by HIV infected adults in Jakarta, Indonesia. Copyright © 2016 King Saud Bin Abdulaziz University for Health Sciences. Published by Elsevier Ltd. All rights reserved.

The inhibitory effect of natural bioactives on the growth of pathogenic bacteria

PubMed Central

Kim, Ji-Sun

2007-01-01

The objective of this study was to evaluate the inhibitory activity of natural products, against growth of Escherichia coli (ATCC 25922) and Salmonella typhimurium (KCCM 11862). Chitosan, epigallocatechin gallate (EGCG), and garlic were used as natural bioactives for antibacterial activity. The testing method was carried out according to the disk diffusion method. All of chitosan, EGCG, and garlic showed inhibitory effect against the growth of E. coli and Salmonella typhi. To evaluate the antibacterial activity of natural products during storage, chicken skins were inoculated with 106 of E. coli or Salmonella typhi. The inoculated chicken skins, treated with 0.5, 1, or 2% natural bioactives, were stored during 8 day at 4℃. The numbers of microorganisms were measured at 8 day. Both chitosan and EGCG showed significant decrease in the number of E. coli and Salmonella typhi in dose dependent manner (P < 0.05). These results suggest that natural bioactives such as chitosan, EGCG may be possible to be used as antimicrobial agents for the improvement of food safety. PMID:20368950

Activity of Aristolochia bracteolata against Moraxella catarrhalis

PubMed Central

Khedr, Amgad I. M.; Abd AlGadir, Haidar; Takeshita, Satoshi; Shah, Mohammad Monir; Ichinose, Yoshio; Maki, Toshihide

2014-01-01

A bioassay-guided fractionation of methanol extract of Aristolochia bracteolata whole plant was carried out in order to evaluate its antimicrobial activity and to identify the active compounds in this extract. Antibacterial and antifungal activities of methanol extract against gram-positive, gram-negative, and fungal strains were investigated by the agar disk diffusion method. Among the strains tested, Moraxella catarrhalis and sea urchin-derived Bacillus sp. showed the highest sensitivity towards the methanol extract and hence they are used as test organisms for the bioassay-guided fractionation. From this extract, aristolochic acid 1 (AA-1) has been isolated and has showed the greatest antibacterial activity against both standard strain and clinical isolates of Moraxella catarrhalis with equal minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 25 and 50 μg/mL. Modification of the AA-1 to AA-1 methyl ester completely abolished the antibacterial activity of the compound and the piperonylic acid moiety of AA-1 which suggested that the coexistence of phenanthrene ring and free carboxylic acid is essential for AA-1 antibacterial activity. PMID:26904734

First report of OXA-143-lactamase producing Acinetobacter baumannii in Qom, Iran.

PubMed

Sarikhani, Zohreh; Nazari, Razieh; Nateghi Rostami, Mahmoud

2017-11-01

Antibiotic resistance in Acinetobacter baumannii and outbreaks caused by this organism have been reported from several areas of the world. The present study aimed at determining the antibiotic susceptibility profiles and the distribution of OXA-type beta-lactamases among Iranian Acinetobacter baumannii isolates from Qom of Iran. For this study, 108 non-duplicate A. baumannii isolates were obtained from clinical specimens in four teaching hospitals in Qom in the central of Iran. The antimicrobial susceptibility of isolates was tested by standard disk diffusion and prevalence of bla OXA genes was investigated by PCR method. Among 97 carbapenem non-susceptible isolates of A. baumannii , 90.72% (88 isolates) isolates showed extensive drug resistance to multiple antibiotics. Among carbapenem resistant isolates, 100% carried bla OXA-51-like , 82.47% carried bla OXA-23-like , 55.67% carried bla OXA-58-like , 22.68% carried bla OXA-40-like and 14.43% had bla OXA-143-like resistance genes. This study demonstrated high genetic diversity of OXA genes among isolates of A. baumannii in Qom, Iran.

First report of OXA-143-lactamase producing Acinetobacter baumannii in Qom, Iran

PubMed Central

Sarikhani, Zohreh; Nazari, Razieh; Nateghi Rostami, Mahmoud

2017-01-01

Objective(s): Antibiotic resistance in Acinetobacter baumannii and outbreaks caused by this organism have been reported from several areas of the world. The present study aimed at determining the antibiotic susceptibility profiles and the distribution of OXA-type beta-lactamases among Iranian Acinetobacter baumannii isolates from Qom of Iran. Materials and Methods: For this study, 108 non-duplicate A. baumannii isolates were obtained from clinical specimens in four teaching hospitals in Qom in the central of Iran. The antimicrobial susceptibility of isolates was tested by standard disk diffusion and prevalence of bla OXA genes was investigated by PCR method. Results: Among 97 carbapenem non-susceptible isolates of A. baumannii, 90.72% (88 isolates) isolates showed extensive drug resistance to multiple antibiotics. Among carbapenem resistant isolates, 100% carried blaOXA-51-like, 82.47% carried blaOXA-23-like, 55.67% carried blaOXA-58-like, 22.68% carried blaOXA-40-like and 14.43% had blaOXA-143-like resistance genes. Conclusion: This study demonstrated high genetic diversity of OXA genes among isolates of A. baumannii in Qom, Iran. PMID:29299207

Shigella in Brazilian children with acute diarrhoea: prevalence, antimicrobial resistance and virulence genes.

PubMed

Sousa, Mireille Ângela Bernardes; Mendes, Edilberto Nogueira; Collares, Guilherme Birchal; Péret-Filho, Luciano Amedée; Penna, Francisco José; Magalhães, Paula Prazeres

2013-02-01

Diarrhoeal disease is still considered a major cause of morbidity and mortality among children. Among diarrhoeagenic agents, Shigella should be highlighted due to its prevalence and the severity of the associated disease. Here, we assessed Shigella prevalence, drug susceptibility and virulence factors. Faeces from 157 children with diarrhoea who sought treatment at the Children's Hospital João Paulo II, a reference children´s hospital in Belo Horizonte, state of Minas Gerais, Brazil, were cultured and drug susceptibility of the Shigella isolates was determined by the disk diffusion technique. Shigella virulence markers were identified by polymerase chain reaction. The bacterium was recovered from 10.8% of the children (88.2% Shigella sonnei). The ipaH, iuc, sen and ial genes were detected in strains isolated from all shigellosis patients; set1A was only detected in Shigella flexneri. Additionally, patients were infected by Shigella strains of different ial, sat, sen and set1A genotypes. Compared to previous studies, we observed a marked shift in the distribution of species from S. flexneri to S. sonnei and high rates of trimethoprim/sulfamethoxazole resistance.

Inhibition of Listeria monocytogenes in Fish and Meat Systems by Use of Oregano and Cranberry Phytochemical Synergies

PubMed Central

Lin, Y. T.; Labbe, R. G.; Shetty, Kalidas

2004-01-01

Optimized phenolics from oregano and cranberry extracts were evaluated for antimicrobial activity against Listeria monocytogenes in laboratory media and in beef and fish. The antimicrobial activity increased when oregano and cranberry extracts were mixed at a ratio of 75% oregano and 25% cranberry (wt/wt) with 0.1 mg of phenolic per disk or ml, and the efficacy was further enhanced by lactic acid. The inhibition by phytochemical and lactic acid synergies was most effective when beef and fish slices were stored at 4°C. PMID:15345457

Diffusion of antimicrobials in multispecies biofilms evaluated in a new biofilm model.

PubMed

van der Waal, S V; de Almeida, J; Krom, B P; de Soet, J J; Crielaard, W

2017-04-01

To describe the application of a newly-developed in vitro model in which the diffusion of antimicrobials in oral biofilms can be studied. In a flow chamber consisting of three parallel feeding channels connected with each other by eight perpendicular side channels, multispecies biofilms were grown from saliva of a single donor for 48 h. The dimensions of the side channels were 100 μm × 100 μm × 5130 μm (H × W × L). When one or more side channels were filled with biofilm, the biofilms were stained with fluorescent stains. Then, one side-channel biofilm was selected and treated with phosphate buffered saline, 2% sodium hypochlorite (NaOCl), 17% ethylenediaminetetra-acetic acid (EDTA) or modified salt solution (MSS). Diffusion of the irrigants was observed by acquiring fluorescence images at 10× objective every 15 s for 30 min. It was possible to culture biofilms in the narrow (100 μm) channels. The biofilms varied in phenotype. In this model, no diffusion of NaOCl into the biofilms was seen after its application. Seventeen-percentage EDTA only diffused into the biofilm up to 200 μm in 30 min. MSS did diffuse in the biofilm over a distance of 450 μm within 2 min after a single application. This new model enables the investigation of the diffusion of antimicrobials in biofilms. Other applications to improve our understanding of the characteristics of biofilms are now possible. © 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd.

High Rate Oxygen Reduction in Non-aqueous Electrolytes with the Addition of Perfluorinated Additives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Y.; Yang, X.; Zheng, D.

2011-08-04

The discharge rate capability of Li-air batteries is substantially increased by using perfluorinated compounds as oxygen carriers. The solubility of oxygen in a non-aqueous electrolyte can be significantly increased by the introduction of such compounds, which leads to the increase in the diffusion-limited current of oxygen reduction on the gas diffusion electrode in a Li-air battery. The perfluorinated compound is found to be stable within the electrochemical window of the electrolyte. A powder microelectrode and a rotating disk electrode were used to study the gas diffusion-limited current together with a rotating disk electrode. A 5 mA cm{sup -2} discharge ratemore » is demonstrated in a lab Li-O{sub 2} cell.« less

Prevalence of bacterial pathogens and their anti-microbial resistance in Tilapia and their pond water in Trinidad.

PubMed

Newaj-Fyzul, A; Mutani, A; Ramsubhag, A; Adesiyun, A

2008-05-01

In Trinidad, Tilapia (Oreonchromis spp.) is one of the most important fresh water food fish and the number of farms has been increasing annually. A study was conducted in the local tilapia industry to determine the microbial quality of pond water, prevalence of bacterial pathogens and their anti-microbial resistance using the disk diffusion method. Seventy-five apparently healthy fish and 15 pond water samples from three of the four commercial tilapia fish farms in the country were processed. The 202 bacterial isolates recovered from fish slurry and 88 from water, belonged to 13 and 16 genera respectively. The predominant bacteria from fish slurry were Pseudomonas spp. (60.0%), Aeromonas spp. (44.0%), Plesiomonas (41.3%) and Chromobacterium (36.0%) (P < 0.05; chi(2)) compared with isolates from pond water where Bacillus spp. (80.0%), Staphylococcus spp., Alcaligenes spp. and Aeromonas spp. (60.0%) were most prevalent (P < 0.05; chi(2)). Using eight anti-microbial agents, to test bacteria from five genera (Aeromonas, Chromobacterium, Enterobacter, Plesiomonas and Pseudomonas), 168 (97.1%) of 173 bacterial isolates from fish slurry exhibited resistance to one or more anti-microbial agents compared with 47 (90.4%) of 52 from water (P > 0.05; chi(2)). Resistance was high to ampicillin, 90.2% (158 of 173), erythromycin, 66.5% (115 of 173) and oxytetracycline, 52.6%, (91 of 173) but relatively low to chloramphenicol, 9.8% (17 of 173) and sulphamethoxazole/trimethoprim, 6.4% (11 of 173) (P < 0.05; chi(2)). For pond water isolates, the frequency of resistance across bacterial genera ranged from 75% (nine of 12) for Chromobacter spp. to 100% found amongst Enterobacter spp. (six of six), Plesiomonas spp. (nine of nine) and Pseudomonas spp. (eight of eight) (P < 0.05; chi(2)). Resistance was generally high to ampicillin, 78.8% (41 of 52), erythromycin, 51.9% (27 of 52) and oxytetracycline, 34.5% (18 of 52) but low to sulphamethoxazole/trimethoprim, 7.7% (four of 52) and norfloxacin, 3.8% (two of 52) (P < 0.05; chi(2)). It was concluded that the rather high prevalence of bacterial pathogens in tilapia along with their high prevalence of resistance to anti-microbial agents might pose therapeutic problems as well as health risk to consumers. The microbial presence and their anti-microbial resistance in the tilapia industry are being reported for the first time in the country.

Comparison between Disk Diffusion and Microdilution Methods for Determining Susceptibility of Clinical Fungal Isolates to Caspofungin▿

PubMed Central

Milici, Maria Eleonora; Maida, Carmelo Massimo; Spreghini, Elisabetta; Ravazzolo, Barbara; Oliveri, Salvatore; Scalise, Giorgio; Barchiesi, Francesco

2007-01-01

We compared the caspofungin (CAS) susceptibility testing results generated by the disk diffusion (DD) assay with the results of the Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BD) reference method for 106 yeast isolates. The isolates represented 11 different fungal species, including Candida albicans (n = 50), C. parapsilosis (n = 10), C. glabrata (n = 10), C. tropicalis (n = 10), C. guillermondii (n = 6), C. rugosa (n = 5), C. krusei (n = 5), C. kefyr (n = 2), C. pelliculosa (n = 2), Saccharomyces cerevisiae (n = 3), and Geotrichum candidum (n = 3). The DD assay was performed in supplemented Mueller-Hinton agar with CAS, which was tested at concentrations of 2, 10, and 25 μg per disk. MICs and inhibition zone diameters were evaluated at 24 and 48 h. In general, the results obtained by the DD assay correlated well with those obtained by the BD method. In particular, a significant correlation between methods was observed when CAS was used at concentration of 2 μg/disk at a reading time of either 24 or 48 h. PMID:17728477

Antimicrobial activity of isothiocyanates (ITCs) extracted from horseradish (Armoracia rusticana) root against oral microorganisms.

PubMed

Park, Ho-Won; Choi, Kyu-Duck; Shin, Il-Shik

2013-01-01

The antimicrobial activity of isothiocyanates (ITCs) extracted from horseradish root was investigated against oral microorganisms: 6 strains of facultative anaerobic bacteria, Streptococcus mutans, Streptococcus sobrinus, Lactobacillus casei, Staphylococcus aureus, Enterococcus faecalis and Aggregatibacter actinomycetemcomitans; one strain of yeast, Candida albicans, and 3 strains of anaerobic bacteria, Fusobacterium nucleatum, Prevotella nigrescens, and Clostridium perfringens. The ITCs extracted from horseradish root showed antimicrobial activity against all oral microorganisms by the paper disk method. The minimum bactericidal concentration (MBC) of the ITCs extracted from horseradish root ranged from 1.25 to 5.00 mg/ml against 6 strains of facultative anaerobic bacteria and one strain of yeast, and 4.17 to 16.67 mg/ml against 3 strains of anaerobic bacteria. The ITCs extracted from horseradish root showed the strongest antimicrobial activity, with a MBC of 1.25 mg/ml, against C. albicans among facultative microorganisms, and 4.17 mg/ml against F. nucleatum among anaerobic bacteria. These results suggest that the ITCs extracted from horseradish root may be a candidate for use as an antimicrobial agent against oral microorganisms.

Prevalence and molecular characterization of methicillin resistance among Coagulase-negative Staphylococci at a tertiary care center.

PubMed

Bhatt, Puneet; Tandel, Kundan; Singh, Alina; Kumar, M; Grover, Naveen; Sahni, A K

2016-12-01

Methicillin-resistant Coagulase-negative Staphylococci (MR-CoNS) have emerged as an important cause of nosocomial infections especially in patients with prosthetic devices and implants. This study was conducted with an aim to determine the prevalence of methicillin resistance among CoNS isolates at a tertiary care center by both phenotypic and genotypic methods. This cross sectional study was carried out from September 2011 to February 2014 in which 150 non-repetitive clinical isolates of CoNS were identified at the species level by conventional phenotypic methods. Cefoxitin disk (30 μg) diffusion testing was used to determine methicillin resistance and confirmed by detection of mec A gene by polymerase chain reaction (PCR). Out of 150 CoNS isolates, 51 were methicillin resistant by cefoxitin disk diffusion method. Out of these 51 isolates, mec A gene was detected only in 45 isolates. Moreover, mec A gene was also detected in 4 isolates, which were cefoxitin sensitive. Thus, the prevalence of methicillin resistance among CoNS was found to be 32.7% by PCR. The prevalence of methicillin resistance among Coagulase-negative Staphylococci (CoNS) was 32.7% by PCR detection of mec A gene. The sensitivity and specificity of cefoxitin disk diffusion method against mec A gene detection by PCR were found to be more than 90%. It can be concluded from this study that cefoxitin disk diffusion test can be used as a useful screening method to detect methicillin resistance among CoNS isolates. However, detection of mec A gene by PCR remains a more accurate method of detecting methicillin resistance among CoNS.

Numerical analysis of hydrodynamics in a rotor-stator reactor for biodiesel synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wen, Zhuqing; Petera, Jerzy

A rotor-stator spinning disk reactor for intensified biodiesel synthesis is described and numerically simulated. The reactor consists of two flat disks, located coaxially and parallel to each other with a gap ranging from 0.1 mm to 0.2 mm between the disks. The upper disk is located on a rotating shaft while the lower disk is stationary. The feed liquids, triglycerides (TG) and methanol are introduced coaxially along the center line of rotating disk and stationary disk, respectively. Fluid hydrodynamics in the reactor for synthesis of biodiesel from TG and methanol in the presence of a sodium hydroxide catalyst are simulated, using convection-diffusion-reactionmore » species transport model by the CFD software ANSYS©Fluent v. 13.0. The effects of upper disk’s spinning speed, gap size and flow rates at inlets are evaluated.« less

Probing for Exoplanets Hiding in Dusty Debris Disks: Disk Imaging, Characterization, and Exploration with HST-STIS Multi-roll Coronagraphy

NASA Technical Reports Server (NTRS)

Schneider, Glenn; Grady, Carol A.; Hines, Dean C.; Stark, Christopher C.; Debes, John; Carson, Joe; Kuchner, Marc J.; Perrin, Marshall; Weinberger, Alycia; Wisniewski, John P.;

Probing for exoplanets hiding in dusty debris disks: Disk imaging, characterization, and exploration with HST/STIS multi-roll coronagraphy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, Glenn; Hinz, Phillip M.; Grady, Carol A.

Spatially resolved scattered-light images of circumstellar debris in exoplanetary systems constrain the physical properties and orbits of the dust particles in these systems. They also inform on co-orbiting (but unseen) planets, the systemic architectures, and forces perturbing the starlight-scattering circumstellar material. Using Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) broadband optical coronagraphy, we have completed the observational phase of a program to study the spatial distribution of dust in a sample of 10 circumstellar debris systems and 1 'mature' protoplanetrary disk, all with HST pedigree, using point-spread-function-subtracted multi-roll coronagraphy. These observations probe stellocentric distances ≥5 AU for the nearestmore » systems, and simultaneously resolve disk substructures well beyond corresponding to the giant planet and Kuiper Belt regions within our own solar system. They also disclose diffuse very low-surface-brightness dust at larger stellocentric distances. Herein we present new results inclusive of fainter disks such as HD 92945 (F {sub disk}/F {sub star} = 5 × 10{sup –5}), confirming, and better revealing, the existence of a narrow inner debris ring within a larger diffuse dust disk. Other disks with ring-like substructures and significant asymmetries and complex morphologies include HD 181327, for which we posit a spray of ejecta from a recent massive collision in an exo-Kuiper Belt; HD 61005, suggested to be interacting with the local interstellar medium; and HD 15115 and HD 32297, also discussed in the context of putative environmental interactions. These disks and HD 15745 suggest that debris system evolution cannot be treated in isolation. For AU Mic's edge-on disk, we find out-of-plane surface brightness asymmetries at ≥5 AU that may implicate the existence of one or more planetary perturbers. Time-resolved images of the MP Mus protoplanetary disk provide spatially resolved temporal variability in the disk illumination. These and other new images from our HST/STIS GO/12228 program enable direct inter-comparison of the architectures of these exoplanetary debris systems in the context of our own solar system.« less

Marangoni convection in Casson liquid flow due to an infinite disk with exponential space dependent heat source and cross-diffusion effects

NASA Astrophysics Data System (ADS)

Mahanthesh, B.; Gireesha, B. J.; Shashikumar, N. S.; Hayat, T.; Alsaedi, A.

2018-06-01

Present work aims to investigate the features of the exponential space dependent heat source (ESHS) and cross-diffusion effects in Marangoni convective heat mass transfer flow due to an infinite disk. Flow analysis is comprised with magnetohydrodynamics (MHD). The effects of Joule heating, viscous dissipation and solar radiation are also utilized. The thermal and solute field on the disk surface varies in a quadratic manner. The ordinary differential equations have been obtained by utilizing Von Kármán transformations. The resulting problem under consideration is solved numerically via Runge-Kutta-Fehlberg based shooting scheme. The effects of involved pertinent flow parameters are explored by graphical illustrations. Results point out that the ESHS effect dominates thermal dependent heat source effect on thermal boundary layer growth. The concentration and temperature distributions and their associated layer thicknesses are enhanced by Marangoni effect.

Dusty Disks, Diffuse Clouds, and Dim Suns: Galactic Science with the Infrared Spectrograph on the Spitzer Space Telescope

NASA Technical Reports Server (NTRS)

Roellig, T. L.; Watson, D. M.; Uchida, K. I.; Forrest, W. J.; VanCleve, J. E.; Herter, T. L.; Sloan, G. C.; Furlan, E.; Wilson, J. C.; Bernard-Salas, J.

2004-01-01

The Infrared Spectrograph (IRS) on the Spitzer Space Telescope has now been in routine science operations since Dec. 14,2003. The IRS Science Team has used a portion of their guaranteed time to pursue three major science themes in galactic astronomy: the evolution of protostellar disks and debris disks; the composition and evolution of diffuse matter and clouds in the interstellar medium; and the composition and structure of brown dwarfs and low-mass main-sequence stars. We report here on the results from the first five months of IRS observations in these programs. Full IRS Spectra have already been obtained for large samples of YSO/protoplanetary disks in the Taurus and TW Hya associations, and or debris disks around main-sequence stars, in which many aspects of the evolution of planetary systems can be addressed for the first time. As anticipated, the mid-infrared IRS observations of brown dwarfs have yielded important new information about their atmospheres, including the identification of NH3 and measurements of new methane features. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA's Office of Space Science.

Dusty Disks, Diffuse Clouds, and Dim Suns - Galactic Science with the Infrared Spectrograph on the Spitzer Space Telescope

NASA Astrophysics Data System (ADS)

Roellig, T. L.; Watson, D. M.; Uchida, K. I.; Forrest, W. J.; Van Cleve, J. E.; Herter, T. L.; Sloan, G. C.; Furlan, E.; Wilson, J. C.; Bernard-Salas, J.; Saumon, D.; Leggett, S.; Chen, C.; Kemper, F.; Hartmann, L.; Marley, M.; Cushing, M.; Mainzer, A. K.; Kirkpatrick, D.; Jura, M.; Houck, J. R.

2004-05-01

The Infrared Spectrograph (IRS) on the Spitzer Space Telescope has now been in routine science operations since Dec. 14, 2003. The IRS Science Team has used a portion of their guaranteed time to pursue three major science themes in galactic astronomy: the evolution of protostellar disks and debris disks; the composition and evolution of diffuse matter and clouds in the interstellar medium; and the composition and structure of brown dwarfs and low-mass main-sequence stars. We report here on the results from the first five months of IRS observations in these programs. Full IRS Spectra have already been obtained for large samples of YSO/protoplanetary disks in the Taurus and TW Hya associations, and of debris disks around main-sequence stars, in which many aspects of the evolution of planetary systems can be addressed for the first time. As anticipated, the mid-infrared IRS observations of brown dwarfs have yielded important new information about their atmospheres, including the identification of NH3 and measurements of new methane features. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407. Support for this work was provided by NASA's Office of Space Science.

High-Velocity Microsprays Enhance Antimicrobial Activity in Streptococcus mutans Biofilms.

PubMed

Fabbri, S; Johnston, D A; Rmaile, A; Gottenbos, B; De Jager, M; Aspiras, M; Starke, E M; Ward, M T; Stoodley, P

2016-12-01

Streptococcus mutans in dental plaque biofilms play a role in caries development. The biofilm's complex structure enhances the resistance to antimicrobial agents by limiting the transport of active agents inside the biofilm. The authors assessed the ability of high-velocity water microsprays to enhance delivery of antimicrobials into 3-d-old S. mutans biofilms. Biofilms were exposed to a 90° or 30° impact, first using a 1-µm tracer bead solution (10 9 beads/mL) and, second, a 0.2% chlorhexidine (CHX) or 0.085% cetylpyridinium chloride (CPC) solution. For comparison, a 30-s diffusive transport and simulated mouthwash were also performed. Confocal microscopy was used to determine number and relative bead penetration depth into the biofilm. Assessment of antimicrobial penetration was determined by calculating the killing depth detected by live/dead viability staining. The authors first demonstrated that the microspray was able to deliver significantly more microbeads deeper in the biofilm compared with diffusion and mouthwashing exposures. Next, these experiments revealed that the microspray yielded better antimicrobial penetration evidenced by deeper killing inside the biofilm and a wider killing zone around the zone of clearance than diffusion alone. Interestingly the 30° impact in the distal position delivered approximately 16 times more microbeads and yielded approximately 20% more bacteria killing (for both CHX and CPC) than the 90° impact. These data suggest that high-velocity water microsprays can be used as an effective mechanism to deliver microparticles and antimicrobials inside S. mutans biofilms. High shear stresses generated at the biofilm-burst interface might have enhanced bead and antimicrobial delivery inside the remaining biofilm by combining forced advection into the biofilm matrix and physical restructuring of the biofilm itself. Further, the impact angle has potential to be optimized both for biofilm removal and active agents' delivery inside biofilm in those protected areas where some biofilm might remain. © International & American Associations for Dental Research 2016.

Panton-Valentine leukocidin and some exotoxins of Staphylococcus aureus and antimicrobial susceptibility profiles of staphylococci isolated from milks of small ruminants.

PubMed

Ünal, Nilgün; Askar, Şinasi; Macun, Hasan Ceyhun; Sakarya, Fatma; Altun, Belgin; Yıldırım, Murat

2012-03-01

The aims of this study were to determine the existence of pvl gene, some toxin genes, and mecA gene in Staphylococcus aureus strains isolated from sheep milk and to examine antimicrobial resistance profiles in staphylococci from sheep and goats' milk. The milk samples were collected from 13 different small ruminant farms in Kirikkale province from February to August 2009. A total of 1,604 half-udder milk samples from 857 ewes and 66 half-udder milk samples from 33 goats were collected. Staphylococcus spp. were isolated and identified from the samples. Toxin genes and mecA gene among S. aureus strains were determined by PCR. Antimicrobial susceptibility of staphylococci was examined by the disk diffusion method on Mueller-Hinton agar, and interpreted according to the Clinical Laboratory Standards Institute (CLSI) guidelines. The prevalence of subclinical intramammary infection in both ewes and goats was 5.2%. The most prevalent subclinical mastitis agents were coagulase-negative staphylococci and S. aureus with prevalences 2.8% (n:46) and 1.3% (n = 21), respectively. The prevalence of resistances in isolated Staphylococcus spp. to penicilin G, tetracycline, erythromycin, gentamicin, and enrofloxacin were found as 26.9% (18), 7.5% (5), 6.0% (4), 3.0% (2), and 1.5% (1), respectively. Only 3 of the 21 S. aureus ewe isolates (13.4%) were shown to harbor enterotoxin genes being either seh, sej or sec. However, fourteen (66.6%) of the 21 S. aureus isolates had pvl gene while none of the isolates harbored mecA gene. In conclusion, Staphylococci were shown to be the most prevalent bacteria isolated from subclinical mastitis of ewes and goats and these isolates were susceptible to most of the antibiotics. In addition, S. aureus strains isolated from ewes were harboring few staphylococcal enterotoxin genes. However, Panton-Valentine leukocidin produced by S. aureus could be an important virulence factor and contribute to subclinical mastitis pathogenicity.

Microbiological Features of Upper Respiratory Tract Infections in Bulgarian Children for the Period 1998–2014

PubMed Central

Gergova, Raina Tzvetanova; Petrova, Guergana; Gergov, Stefan; Minchev, Petko; Mitov, Ivan; Strateva, Tanya

2016-01-01

Background Across the globe, upper respiratory tract infections (URTIs) are the most prevalent cause of morbidity in childhood. Aims The aim of our study is to analyze the incidence and etiology of bacterial URTIs in Bulgarian children, as well as the increasing antimicrobial resistance to the most common etiologic agents over a period of 17 years. Study Design Retrospective study. Methods The study material comprised the data from 4768 patients (aged 1–16 years) with URTI during the period from 1998–2014. Specific microbiology agent detection was performed by culture examination. Susceptibilities to the investigated pathogens were determined by the disk diffusion method and minimal inhibitory concentration according to the criteria of the Clinical and Laboratory Standards Institute (CLSI). Polymerase chain reaction was used to detect the presence of β-lactam resistance genes. Results We identified the following as the most common URTI bacterial pathogens: Streptococcus pneumoniae (40.94%), Streptococcus pyogenes (34.16%), Haemophilus influenzae (44.23%), Moraxella catarrhalis (39.19%) and Staphylococcus aureus (23.88%). In more than 70% of cases, a polymicrobial etiology was found. The most commonly affected individuals were pre-school-aged children, which accounted for more than 36% of all patients. During the study period, a dramatic increase in resistance to antibiotic agents was observed. The most frequent types of resistance were the enzymatic inactivation of penicillins and cephalosporins (close to 100% in staphylococci and moraxellae) and inducible macrolide-lincozamide resistance (about 20% of Gram-positive cocci). Conclusion Due to mandatory immunization against pneumococci and H. influenzae in Bulgaria and the vast expanding resistance to the most popular antimicrobial agents changes in the etiology of URTI have recently been noted. Regular analysis of this etiological dynamic and the antimicrobial resistance of respiratory pathogens is important for choosing the correct therapy and successful treatment. PMID:27994923

Comparative study of the antimicrobial activity of native and exotic plants from the Caatinga and Atlantic Forest selected through an ethnobotanical survey.

PubMed

Castelo Branco Rangel de Almeida, Cecília de Fátima; de Vasconcelos Cabral, Daniela Lyra; Rangel de Almeida, Camila Castelo Branco; Cavalcanti de Amorim, Elba Lúcia; de Araújo, Janete Magali; de Albuquerque, Ulysses Paulino

2012-02-01

The idea that many commonly used medicinal plants may lead to the discovery of new drugs has encouraged the study of local knowledge of these resources. An ethnobotanical survey of species traditionally used for the treatment of infectious diseases was undertaken in two areas of northeastern Brazil: one in the Caatinga (dry forest) and another in the Atlantic Forest (humid forest). Initially, diffusion tests using paper disks and subsequently, for extracts presenting significant results (inhibition halos above 15 mm), minimum inhibitory concentrations were determined. The activity was evaluated as a percentage for each species, comparing the diameters of the inhibition halos and the number of positive results against the seven microorganisms studied. Extracts were classified into three categories: strong activity-species with halos exceeding 16 mm, moderate activity-species with halos between 13 mm and 15 mm and low activity-species with halos below 12 mm. We selected 34 species, 20 from the Caatinga and 14 from the Atlantic Forest. In the Caatinga, 50% of the 20 plant extracts studied had strong antimicrobial activity, 25% had moderate activity and 15% had low activity. In the Atlantic Forest, 28.5% of the 14 plant extracts studied showed strong activity, with 14.5% having moderate activity and 28.5% having low activity. The microorganism that was most susceptible to the extracts from the Caatinga, was Mycobacterium smegmatis; 85% of the species tested were able to inhibit its growth. The organism that was susceptible to the highest number of plant species (71%) from the Atlantic Forest was Staphylococcus aureus. Extracts from the Caatinga showed a trend of superior antimicrobial activity compared to the species from the Atlantic Forest, in terms of both inhibiting a greater variety of microorganisms and demonstrating higher activity against susceptible strains.

Staphylococcus argenteus from rabbits in Thailand.

PubMed

Indrawattana, Nitaya; Pumipuntu, Natapol; Suriyakhun, Nawarat; Jangsangthong, Arunee; Kulpeanprasit, Suphang; Chantratita, Narisara; Sookrung, Nitat; Chaicumpa, Wanpen; Buranasinsup, Shutipen

2018-06-21

Staphylococcus argenteus, a novel species of the genus Staphylococcus or a member of the S. aureus complex, is closely related to S. aureus and is usually misidentified. In this study, the presence of S. argenteus in isolated S. aureus was investigated in 67 rabbits with abscess lesions during 2014-2016. Among 19 S. aureus complex isolates, three were confirmed to be S. argenteus by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, nonribosomal peptide synthetase gene amplification, and multilocus sequence type. All S. aureus complex isolates, including the S. aureus isolates, were examined for their antimicrobial resistance phenotype by disk diffusion and for their resistance genotype by PCR assays. Among the S. argenteus isolates, one was susceptible to all antimicrobial drugs and the other two were resistant to penicillin and doxycycline. In contrast, most S. aureus isolates were resistant to penicillin (37.5%), and gentamicin (12.5%). Moreover, S. aureus isolates harbored the blaZ, mecA, aacA-aphD, and mrs(A) as well as mutations of gyrA and grlA, but S. argenteus isolates carried solely the blaZ. S. argenteus isolates were investigated for enterotoxin (sea-sed) and virulence genes by PCR. One isolate carried sea, sec, and sed, whereas the other two isolates carried only sea or sed. No isolate carried seb and see. All three S. argenteus isolates carried hla, hlb, and clfA, followed by pvl, whereas coa, spa (IgG-binding region), and spa (x region) were not detected in the three isolates. This paper presents the first identification of S. argenteus from rabbits in Thailand. S. argenteus might be pathogenic because the isolates carried virulence genes. Moreover, antimicrobial resistance was observed. Investigations of this new bacterial species should be conducted in other animal species as well as in humans. © 2018 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.

Enteric Bacterial Pathogens in Children with Diarrhea in Niger: Diversity and Antimicrobial Resistance

PubMed Central

Moumouni, Aissatou; Gouali, Malika; Mamaty, Abdoul-Aziz; Grais, Rebecca F.

2015-01-01

Background Although rotavirus is the leading cause of severe diarrhea among children in sub-Saharan Africa, better knowledge of circulating enteric pathogenic bacteria and their antimicrobial resistance is crucial for prevention and treatment strategies. Methodology/Principal Findings As a part of rotavirus gastroenteritis surveillance in Maradi, Niger, we performed stool culture on a sub-population of children under 5 with moderate-to-severe diarrhea between April 2010 and March 2012. Campylobacter, Shigella and Salmonella were sought with conventional culture and biochemical methods. Shigella and Salmonella were serotyped by slide agglutination. Enteropathogenic Escherichia coli (EPEC) were screened by slide agglutination with EPEC O-typing antisera and confirmed by detection of virulence genes. Antimicrobial susceptibility was determined by disk diffusion. We enrolled 4020 children, including 230 with bloody diarrhea. At least one pathogenic bacterium was found in 28.0% of children with watery diarrhea and 42.2% with bloody diarrhea. Mixed infections were found in 10.3% of children. EPEC, Salmonella and Campylobacter spp. were similarly frequent in children with watery diarrhea (11.1%, 9.2% and 11.4% respectively) and Shigella spp. were the most frequent among children with bloody diarrhea (22.1%). The most frequent Shigella serogroup was S. flexneri (69/122, 56.5%). The most frequent Salmonella serotypes were Typhimurimum (71/355, 20.0%), Enteritidis (56/355, 15.8%) and Corvallis (46/355, 13.0%). The majority of putative EPEC isolates was confirmed to be EPEC (90/111, 81.1%). More than half of all Enterobacteriaceae were resistant to amoxicillin and co-trimoxazole. Around 13% (46/360) Salmonella exhibited an extended-spectrum beta-lactamase phenotype. Conclusions This study provides updated information on enteric bacteria diversity and antibiotic resistance in the Sahel region, where such data are scarce. Whether they are or not the causative agent of diarrhea, bacterial infections and their antibiotic resistance profiles should be closely monitored in countries like Niger where childhood malnutrition pre-disposes to severe and invasive infections. PMID:25799400

Genetic Characterization, Antimicrobial Resistance Patterns and Virulence Determinants of Staphylococcus aureus Isolated form Bovine Mastitis.

PubMed

Awad, Amal; Ramadan, Hazem; Nasr, Sherif; Ateya, Ahmed; Atwa, Samar

2017-01-01

Staphylococcus aureus is commonly associated with mastitis in dairy herds with potential public health implications. This study was conducted to investigate the existence of S. aureus in mastitic milk and to determine the antimicrobial resistance profiles of the isolated strains as well as the resistance and virulence associated genes. Two hundred quarter milk samples were collected from 3 dairy farms at Dakahliya (n = 2) and Damietta (n = 1) Governorates, Egypt from September to December 2016. Conventional culturing and Polymerase Chain Reaction (PCR) assays targeting nuc (thermonuclease) and coa (coagulase) genes were performed. Isolates were tested for its susceptibility against 14 antimicrobial agents using disk diffusion method. All the isolates were screened for the presence of β-lactamases (blaZ, mecA) and virulence associated (pvl and tst) genes by PCR. The S. aureus was detected in 42% (84/200) of the total examined milk samples. Regarding the antibiogram results, S. aureus revealed a high resistance against ampicillin (95.2%) and penicillin (83.3%) and a lower resistance was observed against gentamicin (23.8%), amikacin (16.7%) and ciprofloxacin (14.3%). Multidrug resistances were detected in 83.3% of the isolated S. aureus. Of the 70 penicillin-resistant S. aureus isolates, blaZ gene was identified in 67 (95.7%) isolates. Fifty percent of S. aureus isolates harbored the specific amplicon of mecA gene. Markedly, all mecA positive strains displayed multidrug resistance and were also positive for blaZ gene. The virulence determinants pvl and tst were detected in 7.1 and 11.9% of the isolated S. aureus, respectively. Presence of multidrug resistant and toxin producing S. aureus in dairy farms pose a major risk to public health. Therefore, this study highlighted the importance of developing an efficient control program to inhibit the transmission of S. aureus, particularly multidrug resistant strains to humans.

Antimicrobial resistance of Campylobacter jejuni and Campylobacter coli from poultry in Italy.

PubMed

Giacomelli, Martina; Salata, Cristiano; Martini, Marco; Montesissa, Clara; Piccirillo, Alessandra

2014-04-01

This study was aimed at assessing the antimicrobial resistance (AMR) of Campylobacter isolates from broilers and turkeys reared in industrial farms in Northern Italy, given the public health concern represented by resistant campylobacters in food-producing animals and the paucity of data about this topic in our country. Thirty-six Campylobacter jejuni and 24 Campylobacter coli isolated from broilers and 68 C. jejuni and 32 C. coli from turkeys were tested by disk diffusion for their susceptibility to apramycin, gentamicin, streptomycin, cephalothin, cefotaxime, ceftiofur, cefuroxime, ampicillin, amoxicillin+clavulanic acid, nalidixic acid, flumequine, enrofloxacin, ciprofloxacin, erythromycin, tilmicosin, tylosin, tiamulin, clindamycin, tetracycline, sulfamethoxazole+trimethoprim, chloramphenicol. Depending on the drug, breakpoints provided by Comité de l'antibiogramme de la Société Française de Microbiologie, Clinical and Laboratory Standards Institute, and the manufacturer were followed. All broiler strains and 92% turkey strains were multidrug resistant. Very high resistance rates were detected for quinolones, tetracycline, and sulfamethoxazole+trimethoprim, ranging from 65% to 100% in broilers and from 74% to 96% in turkeys. Prevalence of resistance was observed also against ampicillin (97% in broilers, 88% in turkeys) and at least three cephalosporins (93-100% in broilers, 100% in turkeys). Conversely, no isolates showed resistance to chloramphenicol and tiamulin. Susceptibility prevailed for amoxicillin+clavulanic acid and aminoglycosides in both poultry species, and for macrolides and clindamycin among turkey strains and among C. jejuni from broilers, whereas most C. coli strains from broilers (87.5%) were resistant. Other differences between C. jejuni and C. coli were observed markedly in broiler isolates, with the overall predominance of resistance in C. coli compared to C. jejuni. This study provides updates and novel data on the AMR of broiler and turkey campylobacters in Italy, revealing the occurrence of high resistance to several antimicrobials, especially key drugs for the treatment of human campylobacteriosis, representing a potential risk for public health.

Alanine rich peptide from Populus trichocarpa inhibit growth of Staphylococcus aureus via targetting its extracellular domain of Sensor Histidine Kinase YycGex protein.

PubMed

Al Akeel, Raid; Mateen, Ayesha; Syed, Rabbani; Alqahtani, Mohammed S; Alqahtani, Ali S

2018-05-22

Due to growing concern towards microbial resistance, ongoing search for developing novel bioactive compounds such as peptides is on rise. The aim of this study was to evaluate antimicrobial effect of Populus trichocarpa extract, chemically identify the active peptide fraction and finds its target in Staphylococcus aureus. In this study the active fraction of P. trichocarpa crude extract was purified and characterized using MS/MS. This peptide PT13 antimicrobial activity was confirmed by in-vitro agar based disk diffusion and in-vivo infection model of G. mellonella. The proteomic expression analysis of S. aureus under influence of PT13 was studied using LTQ-Orbitrap-MS in-solution digestion and identity of target protein was acquired with their quantified expression using label-free approach of Progenesis QI software. Docking study was performed with peptide PT13 and its target YycG protein using CABS-dock. The active fraction PT13 sequence was identified as KVPVAAAAAAAAAVVASSMVVAAAK, with 25 amino acid including 13 alanine having M/Z 2194.2469. PT13 was uniformly inhibited growth S. aureus SA91 and MIC was determined 16 μg/mL for SA91 S. aureus strain. Sensor histidine kinase (YycG) was most significant target found differentially expressed under influence of PT13. G. mellonella larvae were killed rapidly due to S aureus infection, whereas death in protected group was insignificant in compare to control. The docking models showed ten docking models with RMSD value 1.89 for cluster 1 and RMSD value 3.95 for cluster 2 which is predicted to be high quality model. Alanine rich peptide could be useful in constructing as antimicrobial peptide for targeting extracellular Domain of Sensor Histidine Kinase YycG from S. aureus used in the study. Copyright © 2018 Elsevier Ltd. All rights reserved.

Identification and characterization of metallo-β-lactamases producing Pseudomonas aeruginosa clinical isolates in University Hospital from Zanjan Province, Iran.

PubMed

Doosti, Masoumeh; Ramazani, Ali; Garshasbi, Maryam

2013-01-01

Infectious by Pseudomonas aeruginosa has spread worldwide and metallo-beta-lactamases (MBL) are being reported with increasing frequency. The aim of this study was to investigate the antibiotic susceptibility and distribution of blaVIM and blaIMP genes in P. aeruginosa isolates from Zanjan Province of Iran. A total of 70 P. aeruginosa isolates were identified from patients admitted at intensive care units. The antimicrobial susceptibility was tested by disk diffusion (Kirby-Bauer) method and for production of MBL using double-disk synergy test (DDST). After DNA extraction, the presence of blaVIM and blaIMP genes and class 1 integron were detected by PCR. Most of the isolates were resistant to meropenem, cefotaxime and imipenem (IPM). Also, 44/70 (62.85%) IPM resistant isolates were confirmed by DDST. Of the 44 clinical isolates, 41 (93%) isolates showed MIC≥4 µg/ml for IPM. Based on the DDST results, 36 (87.8%) were confirmed to be MBL producers. PCR amplification showed that 23/41 (56%) carried blaVIM and 10/41 (24.3%) possessed blaIMP gene. Also, 31/44 (70.5%) isolates contained class 1 integron gene. Our results highlight that the genes for Verona integron-encoded metallo-β-lactamase, IPM β-lactamases and class 1 integrons were predominantly present among the IPM-resistant P. aeruginosa tested in our province and also the frequency of blaVIM type is higher than blaIMP. This is the first report of P. aeruginosa strains producing blaIMP with high frequency from Zanjan province of Iran.

Effects of hydroethanolic extracts of Balanites aegyptiaca (L.) Delile (Balanitaceae) on some resistant pathogens bacteria isolated from wounds.

PubMed

Anani, Kokou; Adjrah, Yao; Ameyapoh, Yaovi; Karou, Simplice Damintoti; Agbonon, Amegnona; de Souza, Comlan; Gbeassor, Messanvi

2015-04-22

The bark of Balanites aegyptiaca (L.) Delile (Balanitaceae) is widely used in the Togolese folk medicine for the treatment of wounds, malaria and skin diseases. This study aimed to evaluate the antioxidant properties and the activity of the bark extract of this plant against some resistant bacteria isolated from wounds. The antimicrobial activity was assayed using the NCCLS microdilution while the DPPH free radical scavenging and ferric reducing antioxidant power (FRAP) were used for the antioxidant activity. The susceptibility to conventional antibiotics of bacteria was assessed by an agar disk diffusion method using commercial disk. Phenolics were quantified using spectrophotometric methods. The hydroethanolic extracts of the bark inhibited in vitro the growth of Pseudomonas aeruginosa and Staphylococcus aureus in a dose-dependent manner. Bacteriostatic effects were observed on 15 (33%) and 21 (47%) strains of Staphylococcus aureus and Pseudomonas aeruginosa respectively. The MICs and MBCs against Staphylococcus aureus strains ranged respectively from 2.5 to 12.5 µg/mL and 2.5 to 50 µg/mL. Concerning Pseudomonas aeruginosa, these values were equal (12.5 µg/mL). Multidrug resistance was 95% against six antibiotics for Pseudomonas aeruginosa and 91% against five antibiotics for Staphylococcus aureus. The DPPH radical scavenging and the FRAP assays yielded weak antioxidant activity, closely linked with the total phenolic contents. This study indicated that the bark extract of Balanites aegyptiaca possess bioactive compounds implicated in the free radical scavenging and antibacterial activities, justifying the use of the plant in the traditional medicines. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Color alteration, hydrogen peroxide diffusion, and cytotoxicity caused by in-office bleaching protocols.

PubMed

de Almeida, Letícia Cunha Amaral Gonzaga; Soares, Diana Gabriela; Gallinari, Marjorie Oliveira; de Souza Costa, Carlos Alberto; Dos Santos, Paulo Henrique; Briso, André Luiz Fraga

2015-04-01

This study evaluated the color alteration, cytotoxicity, and hydrogen peroxide (HP) diffusion associated with different in-office bleaching protocols. Bovine enamel/dentin disks were subjected to three bleaching sessions with 35 % HP (three 15-min applications), 35 % HP (one 45-min application), or 20 % HP (one 45-min application). The control group was not bleached. Before bleaching, the disks were adapted to artificial pulp chambers positioned in compartments containing 1 ml of acetate buffer or medium, so that the dentin remained in contact with these substances. Immediately after bleaching, the HP that diffused through the disks was stabilized by acetate buffer and was quantified (two-way repeated measures ANOVA/Fisher's protected least significant difference (PLSD) test; α = 5 %). Cells of mouse dental papilla cell-23 (MDPC-23) were incubated in this culture media for 1 h, followed by analysis of cellular metabolism (methyl tetrazolium assay) (one-way ANOVA/Tukey test; α = 5 %) and morphology (scanning electron microscopy). The specimen color alteration (ΔE) was analyzed by reflection spectrophotometry (two-way repeated measures ANOVA/Fisher's PLSD test; α = 5 %). All protocols showed equal effectiveness at the end of the treatment. HP diffusion was significantly higher in the groups bleached with 35 % HP. Reapplication of 35 % HP resulted in increased diffusion only in the first session; however, the decrease in cell metabolism was similar for all studied protocols. Despite greater peroxide diffusion in the groups treated with 35 % HP, all protocols showed the same effectiveness and were cytotoxic to MDPC-23 cells. Bleaching protocols using high HP concentrations should be avoided because they exert aggressive actions on odontoblast-like cells.

Revised Ciprofloxacin Breakpoints for Salmonella: Is it Time to Write an Obituary?

PubMed

Girish, Revathy; Kumar, Anil; Khan, Sadia; Dinesh, Kavitha R; Karim, Shamsul

2013-11-01

To determine the minimum inhibitory concentration of ciprofloxacin among 50 blood stream isolates of Salmonella enterica. A total of 50 consecutive isolates of Salmonella enterica were tested for susceptibility to antimicrobials using the Kirby Bauer disk diffusion method. Minimum inhibitory concentrations were determined using Hi-Comb strips. All results were interpreted according to the CLSI guidelines. Of the 50 isolates 70%were Salmonella Typhi, 4% Salmonella paratyphi A, 2% Salmonella paratyphi B and the remaining 10% were identified only as Salmonella species. Using the CLSI 2011 breakpoints for disc diffusion, 86% (43/50) were resistant to nalidixic acid(NA), 22% (11/50) to ciprofloxacin, 12% to azithromycin, 6% to cotrimoxazole, 4% to ampicillin and 1% to chloramphenicol. The MIC50 and MIC90 of ciprofloxacin for S.Typhi were 0.181 μg/mL and 5.06 μg/mL respectively. While the same for S. paratyphi A was 0.212μg/mL and 0.228μg/mL respectively. None of the isolates were multi drug resistant and all were susceptible to ceftriaxone. Using the CLSI 2012 revised ciprofloxacin breakpoints for disc diffusion (>31mm) & MIC (<0.06 μg/mL), 90% (45/50) of these isolates were found to be resistant. MIC's of ciprofloxacin should be reported for all salmonella isolates and should be used to guide treatment. Blindly following western guidelines for a disease which is highly endemic in the subcontinent will spell the death knell of a cheap and effective drug in our armamentarium. Therefore it will be too premature to declare that "the concept of using ciprofloxacin in typhoid fever is dead!"

Noble metal-modified titania with visible-light activity for the decomposition of microorganisms

PubMed Central

Endo, Maya; Wei, Zhishun; Wang, Kunlei; Karabiyik, Baris; Yoshiiri, Kenta; Rokicka, Paulina; Ohtani, Bunsho

2018-01-01

Commercial titania photocatalysts were modified with silver and gold by photodeposition, and characterized by diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM). It was found that silver co-existed in zero valent (core) and oxidized (shell) forms, whereas gold was mainly zero valent. The obtained noble metal-modified samples were examined with regard to antibacterial (Escherichia coli (E. coli)) and antifungal (Aspergillus niger (A. niger), Aspergillus melleus (A. melleus), Penicillium chrysogenum (P. chrysogenum), Candida albicans (C. albicans)) activity under visible-light irradiation and in the dark using disk diffusion, suspension, colony growth (“poisoned food”) and sporulation methods. It was found that silver-modified titania, besides remarkably high antibacterial activity (inhibition of bacterial proliferation), could also decompose bacterial cells under visible-light irradiation, possibly due to an enhanced generation of reactive oxygen species and the intrinsic properties of silver. Gold-modified samples were almost inactive against bacteria in the dark, whereas significant bactericidal effect under visible-light irradiation suggested that the mechanism of bacteria inactivation was initiated by plasmonic excitation of titania by localized surface plasmon resonance of gold. The antifungal activity tests showed efficient suppression of mycelium growth by bare titania, and suppression of mycotoxin generation and sporulation by gold-modified titania. Although, the growth of fungi was hardly inhibited through disc diffusion (inhibition zones around discs), it indicates that gold does not penetrate into the media, and thus, a good stability of plasmonic photocatalysts has been confirmed. In summary, it was found that silver-modified titania showed superior antibacterial activity, whereas gold-modified samples were very active against fungi, suggesting that bimetallic photocatalysts containing both gold and silver should exhibit excellent antimicrobial properties. PMID:29600144

Antimicrobial Activity of Thin Solid Films of Silver Doped Hydroxyapatite Prepared by Sol-Gel Method

PubMed Central

Iconaru, Simona Liliana; Chapon, Patrick; Le Coustumer, Philippe; Predoi, Daniela

2014-01-01

In this work, the preparation and characterization of silver doped hydroxyapatite thin films were reported and their antimicrobial activity was characterized. Silver doped hydroxyapatite (Ag:HAp) thin films coatings substrate was prepared on commercially pure Si disks by sol-gel method. The silver doped hydroxyapatite thin films were characterized by various techniques such as Scanning electron microscopy (SEM) with energy Dispersive X-ray attachment (X-EDS), Fourier transform infrared spectroscopy (FT-IR), and glow discharge optical emission spectroscopy (GDOES). These techniques have permitted the structural and chemical characterisation of the silver doped hydroxyapatite thin films. The antimicrobial effect of the Ag:HAp thin films on Escherichia coli and Staphylococcus aureus bacteria was then investigated. This is the first study on the antimicrobial effect of Ag:HAp thin films obtained by sol-gel method. The results of this study have shown that the Ag:HAp thin films with x Ag = 0.5 are effective against E. coli and S. aureus after 24 h. PMID:24523630

Antimicrobial activity of thin solid films of silver doped hydroxyapatite prepared by sol-gel method.

PubMed

Iconaru, Simona Liliana; Chapon, Patrick; Le Coustumer, Philippe; Predoi, Daniela

2014-01-01

In this work, the preparation and characterization of silver doped hydroxyapatite thin films were reported and their antimicrobial activity was characterized. Silver doped hydroxyapatite (Ag:HAp) thin films coatings substrate was prepared on commercially pure Si disks by sol-gel method. The silver doped hydroxyapatite thin films were characterized by various techniques such as Scanning electron microscopy (SEM) with energy Dispersive X-ray attachment (X-EDS), Fourier transform infrared spectroscopy (FT-IR), and glow discharge optical emission spectroscopy (GDOES). These techniques have permitted the structural and chemical characterisation of the silver doped hydroxyapatite thin films. The antimicrobial effect of the Ag:HAp thin films on Escherichia coli and Staphylococcus aureus bacteria was then investigated. This is the first study on the antimicrobial effect of Ag:HAp thin films obtained by sol-gel method. The results of this study have shown that the Ag:HAp thin films with x(Ag) = 0.5 are effective against E. coli and S. aureus after 24 h.

Practical Disk Diffusion Test for Detecting Group B Streptococcus with Reduced Penicillin Susceptibility▿

PubMed Central

Kimura, Kouji; Wachino, Jun-ichi; Kurokawa, Hiroshi; Suzuki, Satowa; Yamane, Kunikazu; Shibata, Naohiro; Arakawa, Yoshichika

2009-01-01

Although group B streptococcus (GBS) has been considered to be uniformly susceptible to β-lactams, the presence of GBS with reduced penicillin susceptibility (PRGBS) was recently confirmed genetically. We developed a feasible and reliable method for screening PRGBS in clinical microbiology laboratories using a combination of ceftibuten, oxacillin, and ceftizoxime disks. PMID:19812274

Practical disk diffusion test for detecting group B streptococcus with reduced penicillin susceptibility.

PubMed

Kimura, Kouji; Wachino, Jun-Ichi; Kurokawa, Hiroshi; Suzuki, Satowa; Yamane, Kunikazu; Shibata, Naohiro; Arakawa, Yoshichika

2009-12-01

Although group B streptococcus (GBS) has been considered to be uniformly susceptible to beta-lactams, the presence of GBS with reduced penicillin susceptibility (PRGBS) was recently confirmed genetically. We developed a feasible and reliable method for screening PRGBS in clinical microbiology laboratories using a combination of ceftibuten, oxacillin, and ceftizoxime disks.

Anti-Inflammatory and Antimicrobial Properties of Flavonoids from Heliotropium subulatum Exudate.

PubMed

Singh, Bharat; Sharma, Ram A

2015-01-01

Heliotropium subulatum is an erect or procumbent perennial herb; leaves contain foliar trichomes and its resinous exudate is used in traditional medicine. The anti-inflammatory activity of dichloromethane fraction and isolated flavonoids was evaluated by using carrageenan and CFA-induced paw oedema models. Similarly, the disc diffusion and microdilution methods were used for the assessment of antimicrobial activity. Five isolated flavonoids were investigated for their antiinflammatory and antimicrobial activities. Eriodictyol demonstrated maximum anti-inflammatory activity (53.09%) at 30.0 mg/kg dose on 6(th) h and similarly, it inhibited the CFA-induced arthritis swelling (41.84%) with 30.0 mg/kg dose on 8(th) day respectively. As per disc diffusion and microdilution methods used for antimicrobial activity determination, the pinocembrin was found to be most active against Staphylococcus aureus (IZ=27±0.7 mm, 08 μg/ml dose) and Candida albicans (IZ=17±0.9 mm; 12 μg/ml dose). These investigated results revealed that the eriodictyol and pinocembrin showed significant anti-inflammatory and antimicrobial activities. Further studies which aimed to investigate the mechanism of action of these isolated flavonoids in the treatment of inflammations and various types of infections have been initiated.

Antioxidant and antimicrobial activity of stingless bee bread and propolis extracts

NASA Astrophysics Data System (ADS)

Akhir, Rabieatul Adawieah Md; Bakar, Mohd Fadzelly Abu; Sanusi, Shuaibu Babaji

2017-10-01

Bee bread and propolis are by-products of honey bee. The main objective of this research was to investigate the antioxidant and antimicrobial activity of stingless bee bread and propolis extracted using 70% ethanol and n-hexane. The antioxidant activity of the sample extracts were determined by spectrophotometry analysis while for the antimicrobial activity, the sample extracts were analyzed using disc diffusion and broth dilution assays. For DPPH and ABTS assays, the results showed that ethanolic extract of bee bread showed the highest free radical scavenging (%) as compared to other samples. However, FRAP values for both hexanic extracts are higher as compared to the ethanolic extracts. For disc diffusion assay, the results showed that the ethanolic extract of bee bread and propolis as well as hexanic extract of propolis were able to inhibit all tested bacteria. Meanwhile, broth dilution assay showed minimum inhibition zone (MIC) ranging from <6.67 to 33.33 µL/mL. As the conclusion, both bee bread and propolis produced by stingless bee in this study displayed antioxidant and antimicrobial effect but there are different in the degree of antioxidant and antimicrobial activity exhibited between each of the samples.

Hydrolyzable Poly[Poly(Ethylene Glycol) Methyl Ether Acrylate]-Colistin Prodrugs through Copper-Mediated Photoinduced Living Radical Polymerization.

PubMed

Zhu, Chongyu; Schneider, Elena K; Nikolaou, Vasiliki; Klein, Tobias; Li, Jian; Davis, Thomas P; Whittaker, Michael R; Wilson, Paul; Kempe, Kristian; Velkov, Tony; Haddleton, David M

2017-07-19

Through the recently developed copper-mediated photoinduced living radical polymerization (CP-LRP), a novel and well-defined polymeric prodrug of the antimicrobial lipopeptide colistin has been developed. A colistin initiator (Boc 5 -col-Br 2 ) was synthesized through the modification of colistin on both of its threonine residues using a cleavable initiator linker, 2-(2-bromo-2-methylpropanoyloxy) acetic acid (BMPAA), and used for the polymerization of acrylates via CP-LRP. Polymerization proceeds from both sites of the colistin initiator, and through the polymerization of poly(ethylene glycol) methyl ether acrylate (PEGA 480 ), three water-soluble polymer-colistin conjugates (col-PPEGA, having degrees of polymerization of 5, 10, and 20) were achieved with high yield (conversion of ≥93%) and narrow dispersities (Đ < 1.3) in 2-4 h. Little or no effect on the structure and activity of the colistin was observed during the synthesis, and most of the active colistin can be recovered from the conjugates in vitro within 2 days. Furthermore, in vitro biological analyses including disk diffusion, broth microdilution, and time-kill studies suggested that all of the conjugates have the ability to inhibit the growth of multidrug-resistant (MDR) Gram-negative bacteria, of which col-PPEGA DP5 and DP10 showed similar or better antibacterial performance compared to the clinically relevant colistin prodrug CMS, indicating their potential as an alternative antimicrobial therapy. Moreover, considering the control over the polymerization, the CP-LRP technique has the potential to provide an alternative platform for the development of polymer bioconjugates.

Chemical Composition, Antioxidant and Biological Activities of the Essential Oil and Extract of the Seeds of Glycine max (Soybean) from North Iran.

PubMed

Ghahari, Somayeh; Alinezhad, Heshmatollah; Nematzadeh, Ghorban Ali; Tajbakhsh, Mahmood; Baharfar, Robabeh

2017-04-01

Glycine max (L.) Merrill (soybean) is a major leguminous crop, cultivated globally as well as in Iran. This study examines the chemical composition of soybean essential oil, and evaluates the antioxidant and antimicrobial activities of seeds on various plant pathogens that commonly cause irreparable damages to agricultural crops. The essential oil of soybean seeds was analyzed by gas chromatography coupled to mass spectrometry. Antimicrobial activity was tested against 14 microorganisms, including three gram-positive, five gram-negative bacteria, and six fungi, using disk diffusion method and the Minimum Inhibitory Concentration technique. The soybean seeds were also subjected to screening for possible antioxidant activity by using catalase, peroxidase, superoxide dismutase, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Forty components were identified, representing 96.68% of the total oil. The major constituents of the oil were carvacrol (13.44%), (E,E)-2,4-decadienal (9.15%), p-allylanisole (5.65%), p-cymene (4.87%), and limonene (4.75%). The oil showed significant activity against Pseudomonas syringae subsp. syringae, Rathayibacter toxicus with MIC = 25 µg/mL, and Pyricularia oryzae with MIC = 12.5 µg/mL. In addition, the free radical scavenging capacity of the essential oil was determined with an IC 50 value of 162.35 µg/mL. Our results suggest that this plant may be a potential source of biocide, for economical and environmentally friendly disease control strategies. It may also be a good candidate for further biological and pharmacological investigations.

Isolation and characterization of Shiga toxin-producing Escherichia coli (STEC) in retail edible beef by-products.

PubMed

Lee, Jae-Hoon; Hyeon, Ji-Yeon; Kim, Yun-Gyeong; Chon, Jung-Whan; Park, Jun-Ho; Park, Chankyu; Choi, In-Soo; Kim, Soo-Ki; Seo, Kun-Ho

2012-02-01

The prevalence of Shiga toxin-producing Escherichia coli (STEC) was investigated in 350 edible beef intestinal samples, including omasum (n=110), abomasum (n=120), and large intestines (n=120), collected from traditional beef markets in Seoul, Korea. A total of 23 STEC strains were isolated from 15 samples (four strains from three omasa, 10 from five abomasa, and nine from seven large intestines). The O serotypes and toxin gene types of all STEC isolates were identified, and antimicrobial resistance was assessed using the disk diffusion method. The isolation rates of STEC from edible beef intestines were 2.8% in omasum, 4.2% in abomasums, and 5.9% in large intestines. All STEC isolates harbored either stx1, or both stx1 and stx2 genes simultaneously. Among the 23 isolates, 13 strains were identified as 11 different O serogroups, and 10 strains were untypable. However, enterohemorrhagic Esherichia coli O157, O26, and O111 strains were not isolated. The highest resistance rate observed was against tetracycline (39%), followed by streptomycin (35%) and ampicillin (22%). Of the 23 isolates, 12 isolates (52%) were resistant to at least one antibiotic, nine (39%) isolates were resistant to two or more antibiotics, and one isolate from an abmasum carried resistance against nine antibiotics, including beta-lactam/beta-lactamase inhibitor in combination and cephalosporins. This study shows that edible beef by-products, which are often consumed as raw food in many countries, including Korea, can be potential vehicles for transmission of antimicrobial-resistant pathogenic E. coli to humans.

Antimicrobial activity of Marcetia DC species (Melastomataceae) and analysis of its flavonoids by reverse phase-high performance liquid chromatography coupled-diode array detector.

PubMed

Leite, Tonny Cley Campos; de Sena, Amanda Reges; Dos Santos Silva, Tânia Regina; Dos Santos, Andrea Karla Almeida; Uetanabaro, Ana Paula Trovatti; Branco, Alexsandro

2012-07-01

Marcetia genera currently comprises 29 species, with approximately 90% inhabiting Bahia (Brazil), and most are endemic to the highlands of the Chapada Diamantina (Bahia). Among the species, only M. taxifolia (A.St.-Hil.) DC. populates Brazil (state of Roraima to Paraná) and also Venezuela, Colombia, and Guyana. This work evaluated the antimicrobial activity of hexane, ethyl acetate, and methanol extracts of three species of Marcetia (Marcetia canescens Naud., M. macrophylla Wurdack, and M. taxifolia A.StHil) against several microorganism. In addition, the flavonoids were analyzed in extracts by HPLC-DAD. The tests were made using Gram-positive (three strains of Staphylococcus aureus) and Gram-negative (two strains of Escherichia coli, a strain of Pseudomonas aeruginosa and another of Salmonella choleraesius) bacteria resistant and nonresistant to antibiotics and yeasts (two strains of Candida albicans and one of C. parapsilosis) by the disk diffusion method. Solid-phase extraction (SPE) was performed on the above extracts to isolate flavonoids, which were subsequently analyzed by high performance liquid chromatography coupled diode array detector (HPLC-DAD). Results showed that extracts inhibited the Gram-positive bacteria and yeast. The hexane extracts possessed the lowest activity, while the ethyl acetate and methanolic extracts were more active. Marcetia taxifolia was more effective (active against 10 microorganisms studied), and only its methanol extract inhibited Gram-negative bacteria (P. aeruginosa and S. choleraesius). SPE and HPLC-DAD analysis showed that M. canescens and M. macrophylla contain glycosylated flavonoids, while the majority of extracts from M. taxifolia were aglycone flavonoids.

Increase of β-Lactam-Resistant Invasive Haemophilus influenzae in Sweden, 1997 to 2010

PubMed Central

Resman, Fredrik; Ristovski, Mikael; Forsgren, Arne; Kaijser, Bertil; Kronvall, Göran; Medstrand, Patrik; Melander, Eva; Odenholt, Inga

2012-01-01

The proportions of Haemophilus influenzae resistant to ampicillin and other β-lactam antibiotics have been low in Sweden compared to other countries in the Western world. However, a near-doubled proportion of nasopharyngeal Swedish H. influenzae isolates with resistance to β-lactams has been observed in the last decade. In the present study, the epidemiology and mechanisms of antimicrobial resistance of H. influenzae isolates from blood and cerebrospinal fluid in southern Sweden from 1997 to 2010 (n = 465) were studied. Antimicrobial susceptibility testing was performed using disk diffusion, and isolates with resistance to any tested β-lactam were further analyzed in detail. We identified a significantly increased (P = 0.03) proportion of β-lactam-resistant invasive H. influenzae during the study period, which was mainly attributed to a significant recent increase of β-lactamase-negative β-lactam-resistant isolates (P = 0.04). Furthermore, invasive β-lactamase-negative β-lactam-resistant H. influenzae isolates from 2007 and onwards were found in higher proportions than the corresponding proportions of nasopharyngeal isolates in a national survey. Multiple-locus sequence typing (MLST) of this group of isolates did not completely separate isolates with different resistance phenotypes. However, one cluster of β-lactamase-negative ampicillin-resistant (BLNAR) isolates was identified, and it included isolates from all geographical areas. A truncated variant of a β-lactamase gene with a promoter deletion, blaTEM-1-PΔ dominated among the β-lactamase-positive H. influenzae isolates. Our results show that the proportions of β-lactam-resistant invasive H. influenzae have increased in Sweden in the last decade. PMID:22687505

Emergence of Multidrug Resistance and Metallo-beta-lactamase Producing Acinetobacter baumannii Isolated from Patients in Shiraz, Iran

PubMed Central

Moghadam, MN; Motamedifar, M; Sarvari, J; Sedigh, Ebrahim-Saraie H; Mousavi, Same M; Moghadam, FN

2016-01-01

Background: Metallo-beta-lactamase (MβL) enzymes production is one of the most important resistance mechanisms against carbapenems in some bacteria including Acinetobacter baumannii. Aims: This study was aimed to determine the antimicrobial susceptibility and the prevalence of MβL among carbapenem-resistant isolates of A. baumannii. Materials and Methods: In this cross-sectional study from October 2012 to April 2013, 98 isolates were identified as A. baumannii using Microgen™ kits and confirmed by molecular method. These isolates were tested for antimicrobial susceptibilities by disk diffusion method according to the Clinical and Laboratory Standards Institute guidelines. Carbapenem-resistant isolates were further detected phenotypically by MβL minimal inhibitory concentration (MIC)-test strips, and subsequently positive MβL isolates were confirmed by polymerase chain reaction (PCR). Results: Overall, 98% (96/98) of A. baumannii isolates were detected as carbapenem-resistant by MIC test. Highest sensitivity to the tested antibiotic with 42.9% (42/98) was observed to colistin. Of 96 carbapenem-resistant isolates, 43 were phenotypically positive for MβL; out of 43 isolates, 37 were confirmed for the presence of MβL genes by PCR. Conclusion: The frequency of drug resistance among the clinical samples of A. baumannii isolated in our study against most of the antibiotics was very high. Moreover, all MβL producing isolates were multidrug resistance. Therefore, systematic surveillance to detect MβL producing bacteria and rational prescription and use of carbapenems could be helpful to prevent the spread of carbapenem resistance. PMID:27398247

Hall Effect–Mediated Magnetic Flux Transport in Protoplanetary Disks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Xue-Ning; Stone, James M.

2017-02-10

The global evolution of protoplanetary disks (PPDs) has recently been shown to be largely controlled by the amount of poloidal magnetic flux threading the disk. The amount of magnetic flux must also coevolve with the disk, as a result of magnetic flux transport, a process that is poorly understood. In weakly ionized gas as in PPDs, magnetic flux is largely frozen in the electron fluid, except when resistivity is large. When the disk is largely laminar, we show that the relative drift between the electrons and ions (the Hall drift), and the ions and neutral fluids (ambipolar drift) can playmore » a dominant role on the transport of magnetic flux. Using two-dimensional simulations that incorporate the Hall effect and ambipolar diffusion (AD) with prescribed diffusivities, we show that when large-scale poloidal field is aligned with disk rotation, the Hall effect rapidly drags magnetic flux inward at the midplane region, while it slowly pushes flux outward above/below the midplane. This leads to a highly radially elongated field configuration as a global manifestation of the Hall-shear instability. This field configuration further promotes rapid outward flux transport by AD at the midplane, leading to instability saturation. In quasi-steady state, magnetic flux is transported outward at approximately the same rate at all heights, and the rate is comparable to the Hall-free case. For anti-aligned field polarity, the Hall effect consistently transports magnetic flux outward, leading to a largely vertical field configuration in the midplane region. The field lines in the upper layer first bend radially inward and then outward to launch a disk wind. Overall, the net rate of outward flux transport is about twice as fast as that of the aligned case. In addition, the rate of flux transport increases with increasing disk magnetization. The absolute rate of transport is sensitive to disk microphysics, which remains to be explored in future studies.« less

Antimicrobial olive leaf gelatin films for enhancing the quality of cold smoked salmon

USDA-ARS?s Scientific Manuscript database

Olive leaf products were evaluated as antimicrobial/antioxidant ingredients in edible films for smoked fish preservation. Olive leaf powder (OLP) and its water/ethanol extract (OLE) were tested against Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella enterica using agar diffusion test...

Non-typhoidal Salmonella serotypes, antimicrobial resistance and co-infection with parasites among patients with diarrhea and other gastrointestinal complaints in Addis Ababa, Ethiopia.

PubMed

Eguale, Tadesse; Gebreyes, Wondwossen A; Asrat, Daniel; Alemayehu, Haile; Gunn, John S; Engidawork, Ephrem

2015-11-04

Non-typhoidal Salmonella (NTS) is an important public health problem worldwide. Consumption of animal-derived food products and direct and/or indirect contact with animals are the major routes of acquiring infection with NTS. Published information, particularly on the serotype distribution of NTS among human patients with gastroenteritis and associated risk factors, is scarce in Ethiopia. This study investigated the prevalence, risk factors, serotype distribution and antimicrobial susceptibility of Salmonella species among diarrheic out-patients attending health centers in Addis Ababa and patients with various gastrointestinal complaints at Tikur Anbessa Specialized Hospital (TASH). Stool samples were cultured for Salmonella species according to the WHO Global Foodborne Infections Network laboratory protocol. Salmonella serotyping was conducted using slide agglutination and microplate agglutination techniques. Antibiotic susceptibility testing was performed using the disk diffusion method according to Clinical and Laboratory Standards Institute guidelines. A total of 59 (6.2 %) stool samples, out of 957 were culture positive for Salmonella species. Fifty-five (7.2 %) of 765 diarrheic patients from health centers and 4 (2.1 %) of 192 patients from TASH were culture positive for Salmonella species. Multivariable logistic regression analysis after adjusting for all other variables revealed statistically significant association of Salmonella infection with consumption of raw vegetables (OR = 1.91, 95 % CI = 1.29-2.83, χ(2) = 4.74, p = 0.025) and symptom of watery diarrhea (OR = 3.3, 95 % CI = 1.23-8.88, χ(2) = 10.54, p = 0.005). Eleven serotypes were detected, and the most prominent were S. Typhimurium (37.3 %), S. Virchow (34 %), and S. Kottbus (10.2 %). Other serotypes were S. Miami, S. Kentucky, S. Newport, S. Enteritidis, S. Braenderup, S. Saintpaul, S. Concord and S. V:ROUGH-O. Resistance to three or more antimicrobials was detected in 27 (40.3 %) of the isolates. Resistance to five or more antimicrobials was detected in 17 (25.4 %). Resistance to individual antimicrobials was found at varying proportions: streptomycin (50; 74.6 %), nitrofurantoin (27; 40.3 %), sulfisoxazole (26; 38.8 %), kanamycin (23; 34.3 %), cephalothin (12; 17.9 %), and ampicillin (11; 16.4 %) respectively. Two S. Kentucky, one S. Typhimurium and one S. Concord isolates were multi-drug resistant to more than 10 antimicrobials. The study demonstrated significant association of Salmonella infection with consumption of raw vegetables. There was no significant association of Salmonella infection with co-occurring parasites. The study also showed the dominance of S. Typhimurium and S. Virchow in primary health care units. Overall, prevalence of MDR was low compared to previous studies. Although their proportion was low, S. Kentucky and S. Concord demonstrated wider spectrum of MDR. Continuous monitoring of circulating serotypes, antimicrobial resistance profile and characterization on molecular resistance determinants is essential for proper treatment of patients and for identifying potential environmental origins of antimicrobial resistance.

Misidentification of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals in Tripoli, Libya

PubMed Central

Ahmed, Mohamed O.; Abuzweda, Abdulbaset R.; Alghazali, Mohamed H.; Elramalli, Asma K.; Amri, Samira G.; Aghila, Ezzeddin Sh.; Abouzeed, Yousef M.

2010-01-01

Background Methicillin-resistant Staphylococcus aureus (MRSA) is a nosocomial (hospital-acquired) pathogen of exceptional concern. It is responsible for life-threatening infections in both the hospital and the community. Aims To determine the frequency of MRSA misidentification in hospitals in Tripoli, Libya using current testing methods. Methods One hundred and seventy S. aureus isolates previously identified as MRSA were obtained from three hospitals in Tripoli. All isolates were reidentified by culturing on mannitol salt agar, API 20 Staph System and retested for resistance to methicillin using the cefoxitin disk diffusion susceptibility test and PBP2a. D-tests and vancomycin E-tests (Van-E-tests) were also performed for vancomycin-resistant isolates. Results Of the 170 isolates examined, 86 (51%) were confirmed as MRSA (i.e. 49% were misidentified as MRSA). Fifteen (17%) of the confirmed MRSA strains exhibited inducible clindamycin resistance. Of the 86 confirmed MRSA isolates, 13 (15%) were resistant to mupirocin, 53 (62%) were resistant to ciprofloxacin, 41 (48%) were resistant to trimethoprim-sulfamethoxazole, and none were resistant to linezolid. Although disc-diffusion testing indicated that 23 (27%) of the isolates were resistant to vancomycin, none of the isolates were vancomycin-resistant by Van-E-test. Conclusions Misidentification of nosocomial S. aureus as MRSA is a serious problem in Libyan hospitals. There is an urgent need for the proper training of microbiology laboratory technicians in standard antimicrobial susceptibility procedures and the implementation of quality control programs in microbiology laboratories of Libyan hospitals. PMID:21483574

The pulsar planet production process

NASA Technical Reports Server (NTRS)

Phinney, E. S.; Hansen, B. M. S.

1993-01-01

Most plausible scenarios for the formation of planets around pulsars end with a disk of gas around the pulsar. The supplicant author then points to the solar system to bolster faith in the miraculous transfiguration of gas into planets. We here investigate this process of transfiguration. We derive analytic sequences of quasi-static disks which give good approximations to exact solutions of the disk diffusion equation with realistic opacity tables. These allow quick and efficient surveys of parameter space. We discuss the outward transfer of mass in accretion disks and the resulting timescale constraints, the effects of illumination by the central source on the disk and dust within it, and the effects of the widely different elemental compositions of the disks in the various scenarios, and their extensions to globular clusters. We point out where significant uncertainties exist in the appropriate grain opacities, and in the effect of illumination and winds from the neutron star.

Global Evolution of an Accretion Disk with a Net Vertical Field: Coronal Accretion, Flux Transport, and Disk Winds

NASA Astrophysics Data System (ADS)

Zhu, Zhaohuan; Stone, James M.

2018-04-01

We report results from global ideal MHD simulations that study thin accretion disks (with thermal scale height H/R = 0.1 and 0.05) threaded by net vertical magnetic fields. Our computations span three orders of magnitude in radius, extend all the way to the pole, and are evolved for more than 1000 innermost orbits. We find that (1) inward accretion occurs mostly in the upper magnetically dominated regions of the disk at z ∼ R, similar to predictions from some previous analytical work and the “coronal accretion” flows found in GRMHD simulations. (2) A quasi-static global field geometry is established in which flux transport by inflows at the surface is balanced by turbulent diffusion. The resulting field is strongly pinched inwards at the surface. A steady-state advection–diffusion model, with a turbulent magnetic Prandtl number of order unity, reproduces this geometry well. (3) Weak unsteady disk winds are launched beyond the disk corona with the Alfvén radius R A /R 0 ∼ 3. Although the surface inflow is filamentary and the wind is episodic, we show that the time-averaged properties are well-described by steady-wind theory. Even with strong fields, β 0 = 103 at the midplane initially, only 5% of the angular momentum transport is driven by the wind, and the wind mass flux from the inner decade of the radius is only ∼0.4% of the mass accretion rate. (4) Within the disk, most of the accretion is driven by the Rϕ stress from the MRI and global magnetic fields. Our simulations have many applications to astrophysical accretion systems.

In vitro susceptibility of bovine mastitis pathogens to a combination of penicillin and framycetin: development of interpretive criteria for testing by broth microdilution and disk diffusion.

PubMed

Pillar, C M; Stoneburner, A; Shinabarger, D L; Abbeloos, E; Goby, L; Bradley, Andrew J

2014-10-01

Dry cow therapy is an important part of mastitis control. This therapy typically consists of an antibiotic or antibiotics administered at a single dose by intramammary infusion at dry off to treat or prevent infection by prevalent mastitis pathogens. A combination dry cow therapy consisting of the active components penicillin and framycetin is currently used in several countries. Despite its use, standardized methods for the susceptibility testing of this combination against mastitis pathogens have not been established. In this study, which used Clinical and Laboratory Standards Institute methodology, preliminary interpretive criteria for the broth microdilution minimum inhibitory concentration (MIC) testing of mastitis pathogens to penicillin combined with framycetin (2:1 wt/wt) were established based on the amount of drug achieved and maintained postadministration in the udder. Based on resulting MIC distributions of recent veterinary field isolates and a subset of isolates preselected for resistance to β-lactams or aminoglycosides and concentrations achieved postadministration, criteria for broth microdilution testing of the combination (susceptible, intermediate, resistant in micrograms per milliliter) were set as follows: Escherichia coli ≤8/4, 16/8, ≥32/16; Staphylococcus spp. ≤2/1, 4/2-8/4, >16/8; Streptococcus uberis and Streptococcus dysgalactiae <0.25/0.12, 0.5/0.25-2/1, >4/2. A disk diffusion test using disks containing 100 μg of framycetin and 10 IU of penicillin was also developed, and preliminary interpretive criteria (susceptible, intermediate, resistant in millimeters) were set based on correlation to broth MIC values and the minimization of interpretive errors between isolates tested concurrently by broth microdilution and disk diffusion as follows: E. coli ≥18, 16-17, ≤15; Staphylococcus spp. ≥21, 18-20, ≤17; Strep. uberis and Strep. dysgalactiae ≥21, 19-20, ≤18. In addition, ranges for the quality control of the testing of this combination by both broth microdilution and disk diffusion are provided. Based on these criteria and recent veterinary mastitis isolates, 96.0/96.8% of E. coli, 93.7/89.1% of Staph. aureus, 94.6/96.4% coagulase-negative staphylococci, 94.5/97.0% of Strep. uberis, and 96.7/100.0% Strep. dysgalactiae were susceptible to the combination by broth microdilution or disk diffusion, respectively. The availability of these methods will allow for the susceptibility testing of clinical isolates in the field and will also provide a way to monitor for resistance development as this combination is used going forward. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

The high diversity of MRSA clones detected in a university hospital in istanbul.

PubMed

Oksuz, Lutfiye; Dupieux, Celine; Tristan, Anne; Bes, Michele; Etienne, Jerome; Gurler, Nezahat

2013-01-01

To characterize the methicillin-resistant Staphylococcus aureus (MRSA) clones present in Istanbul, 102 MRSA isolates collected during a 5-year period at the Istanbul Medical Faculty Hospital were characterized using microarray analysis and phenotypic resistance profiles. Resistance to methicillin was detected with a cefoxitin disk diffusion assay and confirmed with a MRSA-agar and MRSA detection kit. Antimicrobial susceptibility testing was performed by a disk diffusion assay and interpreted according to the 2012 guidelines of the Antibiogram Committee of the French Society for Microbiology. Decreased susceptibility to glycopeptides was confirmed using the population analysis profile-area under the curve (PAP-AUC) method. The presence of the mecA gene was detected by polymerase chain reaction. Bacterial DNA was extracted according to the manufacturer's recommended protocol using commercial extraction kits. Strains were extensively characterized using the DNA microarray. Isolates were grouped into six clonal complexes. The most frequently detected clone was the Vienna/Hungarian/Brazilian clone (ST239-MRSA-III), which accounted for 53.9% of the isolates. These isolates were resistant to multiple antibiotics, particularly penicillin, tetracycline, rifampicin, kanamycin, tobramycin, gentamicin, levofloxacin, erythromycin, lincomycin and fosfomycin. Furthermore, three isolates were detected by population analysis profile as heterogeneous vancomycin-intermediate S. aureus (hVISA). The UK-EMRSA-15 clone (ST22-MRSA-IV PVL negative) was detected in 9.8% of the isolates and was mainly susceptible to all anti-staphylococcal antibiotics. Seven isolates (6.9%) were positive for PVL genes and were assigned to the CC80-MRSA-IV clone (European CA-MRSA clone, three isolates), ST8-MRSA-IV clone (USA300 clone, two isolates, one ACME-positive) or ST22-MRSA-IV clone ("Regensburg EMRSA" clone, two isolates). All other clones were detected in one to six isolates and corresponded to well-known clones (e.g., Pediatric clone, Dublin EMRSA clone, WA MRSA-54/63, WA MRSA-1/57). This work highlighted both the high prevalence of ST239-MRSA-III clone and the large diversity of the other MRSA clones detected in a university hospital in Istanbul.

The High Diversity of MRSA Clones Detected in a University Hospital in Istanbul

PubMed Central

Oksuz, Lutfiye; Dupieux, Celine; Tristan, Anne; Bes, Michele; Etienne, Jerome; Gurler, Nezahat

2013-01-01

Background: To characterize the methicillin-resistant Staphylococcus aureus (MRSA) clones present in Istanbul, 102 MRSA isolates collected during a 5-year period at the Istanbul Medical Faculty Hospital were characterized using microarray analysis and phenotypic resistance profiles. Methods: Resistance to methicillin was detected with a cefoxitin disk diffusion assay and confirmed with a MRSA-agar and MRSA detection kit. Antimicrobial susceptibility testing was performed by a disk diffusion assay and interpreted according to the 2012 guidelines of the Antibiogram Committee of the French Society for Microbiology. Decreased susceptibility to glycopeptides was confirmed using the population analysis profile-area under the curve (PAP-AUC) method. The presence of the mecA gene was detected by polymerase chain reaction. Bacterial DNA was extracted according to the manufacturer's recommended protocol using commercial extraction kits. Strains were extensively characterized using the DNA microarray. Results: Isolates were grouped into six clonal complexes. The most frequently detected clone was the Vienna/Hungarian/Brazilian clone (ST239-MRSA-III), which accounted for 53.9% of the isolates. These isolates were resistant to multiple antibiotics, particularly penicillin, tetracycline, rifampicin, kanamycin, tobramycin, gentamicin, levofloxacin, erythromycin, lincomycin and fosfomycin. Furthermore, three isolates were detected by population analysis profile as heterogeneous vancomycin-intermediate S. aureus (hVISA). The UK-EMRSA-15 clone (ST22-MRSA-IV PVL negative) was detected in 9.8% of the isolates and was mainly susceptible to all anti-staphylococcal antibiotics. Seven isolates (6.9%) were positive for PVL genes and were assigned to the CC80-MRSA-IV clone (European CA-MRSA clone, three isolates), ST8-MRSA-IV clone (USA300 clone, two isolates, one ACME-positive) or ST22-MRSA-IV clone (“Regensburg EMRSA” clone, two isolates). All other clones were detected in one to six isolates and corresponded to well-known clones (e.g., Pediatric clone, Dublin EMRSA clone, WA MRSA-54/63, WA MRSA-1/57). Conclusions: This work highlighted both the high prevalence of ST239-MRSA-III clone and the large diversity of the other MRSA clones detected in a university hospital in Istanbul. PMID:24151444

Dissolution kinetics of soluble nondisintegrating disks.

PubMed

de Blaey, C J; van der Graaff, H

1977-12-01

An equation describing the isotropical dissolution of soluble nondisintegrating disks was developed. It was equivalent to the cube root law only if the height and diameter of the disk were equal. The dissolution kinetics of sodium chloride disks were examined, using a beaker equipped with a centrifugal stirrer as the dissolution chamber. The fit of the experimental data to the cube root law had a coefficient of variation of about 4-5%. It was demonstrated statistically that a fit to a square root of mass versus time relation was significantly better. With increasing porosity, the dissolution process proceeded faster than predicted on the basis of the diffusion-convection model. An explanation is proposed by assuming an increased effective dissolution surface.

Survey of the galactic disk from 1 = -150 deg to 1 = 82 deg in the submillimeter range

NASA Technical Reports Server (NTRS)

Caux, Emmanuel; Serra, Guy

1987-01-01

The first almost complete survey of the galactic disk from 1 = -150 deg to 1 = 82 deg in the submillimeter range (effective wavelength = 380 microns), performed with the AGLAE balloon-borne instrument modified to include a submillimeter channel, is reported. The instrumentation and observational procedures are described, as are the signal processing and calibration. The results are presented as a profile of the submillimeter brightness of the galactic disk displayed as a function of the galactic longitude. This profile exhibits diffuse emission all along the disk with bright peaks associated with resolved sources. The averaged galactic spectrum is in agreement with a temperature distribution of the interstellar cold dust.

SURVEY AND EVALUATION OF POROUS POLYETHYLENE MEDIA FINE BUBBLE TUBE AND DISK AERATORS

EPA Science Inventory

Historically, while alternative media materials have been employed over the years with varying degrees of success, the principal fine pore diffuser medium has been porous ceramic. In the early-to-mid-1970s, diffusers with plastic porus media were installed in secondary treatment...

Evaluation of antimicrobial efficacy of Aloe vera and its effectiveness in decontaminating gutta percha cones.

PubMed

Athiban, Prakash P; Borthakur, Bikash Jyoti; Ganesan, S; Swathika, B

2012-07-01

The aim of this study was to evaluate the antimicrobial efficacy of Aloe vera and to determine its effectiveness in decontaminating gutta percha cones. A concentrated extract of Aloe vera was used to check for the antimicrobial efficacy using the agar well diffusion method. Presence of zones' of diffusion was identified against three common GP contaminants namely, E.coli, E.faecalis and Staph. aureus. New GP Cones, freshly taken out of the packet were then decontaminated for 1minute using Aloe vera gel and then placed in thioglycolate broth to check for the presence of turbidity. The zones of inhibition on the agar plate were measured as 24mm,21mm and 24mm respectively. The broth remained clear even after 48 hours of incubation. We conclude that Aloe vera is indeed effective as a GP decontaminant and it holds a promising future as a medium for storage of GP cones.

In-vitro Antimicrobial Activities of Some Iranian Conifers

PubMed Central

Afsharzadeh, Maryam; Naderinasab, Mahboobe; Tayarani Najaran, Zahra; Barzin, Mohammad; Emami, Seyed Ahmad

2013-01-01

Male and female leaves and fruits of eleven different taxons of Iranian conifers (Cupressus sempervirens var. horizontalis, C. sempervirens var. sempervirens, C. sempervirens cv. Cereifeormis, Juniperus communis subsp. hemisphaerica, J. excelsa subsp. excelsa, J. excelsa subsp. polycarpos, J. foetidissima, J. oblonga, J. sabina, Platycladus orientalis and Taxus baccata) were collected from different localities of Iran, dried and extracted with methanol. The extracts were tested for their antimicrobial activity against Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Candida albicans. The extracts were screened qualitatively using four different methods, the disc diffusion, hole plate, cylinder agar diffusion and agar dilution methods, whereas the minimum inhibitory concentrations (MIC) of each extract were determined by the agar dilution method. The best result was obtained by means of hole plate method in qualitative determination of antimicrobial activities of extracts and the greatest activity was found against S. aureus in all tested methods. PMID:24250573

Nanoscale modeling for ultrathin liquid films: Spreading and coupled layering

NASA Astrophysics Data System (ADS)

Phillips, David Michael

The hard disk drive (HDD) industry is currently experiencing a compound annual growth rate of 100% for the areal density. Current production drives have an areal density of 80 Gbit in-2, and drives with an areal density of 100 Gbit in-2 have been recently demonstrated. While much of this growth has been fueled by the development of new read/write heads, some of this gain was achieved by reducing the spacing between the heads and the magnetic media. This in turn reduces the spacing at the head-disk interface (HDI). The HDI in a HDD system consists of a slider, which contains the read/write heads, flying over the disk surface on an air bearing. The current designed separation distance, or fly height, is less than 10 nm. This spacing is expected to reduce to a mere 5 nm within the next few years. With the reduced fly height, intermittent contacts at the HDI become more probable. Only a thin lubricant film of perfluoropolyether (PFPE) and a sputtered carbon overcoat on the disk surface protect the slider and the stored data from mechanical and thermal damage. The PFPE film is quite thin, with a thickness of less than 2 nm or about a monolayer of molecules. During an HDI contact, the PFPE film is considered sacrificial and is often depleted in the contact area. In order to maintain adequate protection for the disk surface, PFPE molecules from the surrounding film must replenish the depleted area. This replenishment ability directly opposes the requirement that the PFPE film must not spin-off of the disk surface due to the disk rotation rate, which is as high as 10,000 RPM in current drives. To balance the PFPE films to sufficiently meet both requirements, HDD manufacturers functionalized the endgroups of the PFPE molecules to allow some portion of the lubricant film to reversibly bond with the disk overcoat. The result is a lubricant film that has a slower replenishment but does not spin-off. The work presented here focuses on the replenishment ability of thin films of liquid PFPE. The experimental analogue of replenishment is the one-dimensional spreading analysis. PFPEs with functional endgroups demonstrated coupled molecular layering and dewetting phenomena during the spreading analysis, while PFPEs with nonfunctional endgroups did not. All of the PFPE thin films spread via a diffusive process and had diffusion coefficients that depended on the local film thickness. A theoretical analysis is presented here for both the governing equation and the disjoining pressure driving force for the PFPE thin film spreading. For PFPEs with non-functional endgroups, a reasonable analysis is performed on the diffusion coefficient for two classes of film: submonolayer and multilayer. The diffusion coefficient of PFPEs with functional endgroups are qualitatively linked to the gradient of the film disjoining pressure. To augment this theory, both lattice-based and off-lattice Monte Carlo simulations are conducted for PFPE film models. The lattice-based model shows the existence of a critical functional endgroup interaction strength. It is also used to study the break-up of molecular layers for a spreading film via a fractal analysis. The off-lattice model is used to calculate the anisotropic pressure tensor for the model PFPE thin film and subsequently the film disjoining pressure. The model also qualitatively analyzes of the self diffusion in the film.

Growth and antimicrobial studies of γ-glycine crystal grown using CuSO4

NASA Astrophysics Data System (ADS)

Vijayalakshmi, V.; Dhanasekaran, P.

2018-05-01

In the current work single crystals of pure and 1M of CuSO4-added glycine were grown by slow evaporation method and its optical and antimicrobial properties were studied. The Polymorph of glycine transforms from a-glycine to γ-glycine due to the incorporation of CuSO4 on glycine was affirmed by the PXRD and FTIR studies. The impact of CuSO4 on the antimicrobial action of the grown samples was deliberate by utilizing the agar diffusion method.

Antimicrobial effects of Thai medicinal plants against acne-inducing bacteria.

PubMed

Chomnawang, Mullika Traidej; Surassmo, Suvimol; Nukoolkarn, Veena S; Gritsanapan, Wandee

2005-10-03

Propionibacterium acnes and Staphylococcus epidermidis have been recognized as pus-forming bacteria triggering an inflammation in acne. The present study was conducted to evaluate antimicrobial activities of Thai medicinal plants against these etiologic agents of acne vulgaris. Crude extracts were tested for antimicrobial activities by disc diffusion and broth dilution methods. The results from the disc diffusion method showed that 13 medicinal plants could inhibit the growth of Propionibacterium acnes. Among those, Senna alata, Eupatorium odoratum, Garcinia mangostana, and Barleria lupulina had strong inhibitory effects. Based on a broth dilution method, the Garcinia mangostana extract had the greatest antimicrobial effect. The MIC values were the same (0.039 mg/ml) for both bacterial species and the MBC values were 0.039 and 0.156 mg/ml against Propionibacterium acnes and Staphylococcus epidermidis, respectively. In bioautography assay, the Garcinia mangostana extract produced strong inhibition zones against Propionibacterium acnes. Antimicrobial activity from fractions of column chromatography revealed one of the active compounds in Garcinia mangostana could be mangostin, a xanthone derivative. Taken together, our data indicated that Garcinia mangostana had a strong inhibitory effect on Propionibacterium acnes and Staphylococcus epidermidis. Therefore, this plant would be an interesting topic for further study and possibly for an alternative treatment for acne.

Comparison of Anaerobic Susceptibility Results Obtained by Different Methods

PubMed Central

Rosenblatt, J. E.; Murray, P. R.; Sonnenwirth, A. C.; Joyce, J. L.

1979-01-01

Susceptibility tests using 7 antimicrobial agents (carbenicillin, chloramphenicol, clindamycin, penicillin, cephalothin, metronidazole, and tetracycline) were run against 35 anaerobes including Bacteroides fragilis (17), other gram-negative bacilli (7), clostridia (5), peptococci (4), and eubacteria (2). Results in triplicate obtained by the microbroth dilution method and the aerobic modification of the broth disk method were compared with those obtained with an agar dilution method using Wilkins-Chalgren agar. Media used in the microbroth dilution method included Wilkins-Chalgren broth, brain heart infusion broth, brucella broth, tryptic soy broth, thioglycolate broth, and Schaedler's broth. A result differing by more than one dilution from the Wilkins-Chalgren agar result was considered a discrepancy, and when there was a change in susceptibility status this was termed a significant discrepancy. The microbroth dilution method using Wilkins-Chalgren broth and thioglycolate broth produced the fewest total discrepancies (22 and 24, respectively), and Wilkins-Chalgren broth, thioglycolate, and Schaedler's broth had the fewest significant discrepancies (6, 5, and 5, respectively). With the broth disk method, there were 15 significant discrepancies, although half of these were with tetracycline, which was the antimicrobial agent associated with the highest number of significant discrepancies (33), considering all of the test methods and media. PMID:464560

Microbial response to environmental gradients in a ceramic-based diffusion system.

PubMed

Wolfaardt, G M; Hendry, M J; Birkham, T; Bressel, A; Gardner, M N; Sousa, A J; Korber, D R; Pilaski, M

2008-05-01

A solid, porous matrix was used to establish steady-state concentration profiles upon which microbial responses to concentration gradients of nutrients or antimicrobial agents could be quantified. This technique relies on the development of spatially defined concentration gradients across a ceramic plate resulting from the diffusion of solutes through the porous ceramic matrix. A two-dimensional, finite-element numerical transport model was used to predict the establishment of concentration profiles, after which concentration profiles of conservative tracers were quantified fluorometrically and chemically at the solid-liquid interface to verify the simulated profiles. Microbial growth responses to nutrient, hypochloride, and antimicrobial concentration gradients were then quantified using epifluorescent or scanning confocal laser microscopy. The observed microbial response verified the establishment and maintenance of stable concentration gradients along the solid-liquid interface. These results indicate the ceramic diffusion system has potential for the isolation of heterogeneous microbial communities as well as for testing the efficacy of antimicrobial agents. In addition, the durability of the solid matrix allowed long-term investigations, making this approach preferable to conventional gel-stabilized systems that are impeded by erosion as well as expansion or shrinkage of the gel. Copyright 2008 Wiley Periodicals, Inc.

Prevalence of multi drug antimicrobial resistance in isolated from high-risk stocker cattle at arrival and two weeks after processing.

PubMed

Snyder, E; Credille, B; Berghaus, R; Giguère, S

2017-03-01

Bovine respiratory disease (BRD) is the leading cause of morbidity and mortality in North American beef cattle. () is the bacterial pathogen most frequently isolated from cattle with BRD and the prevalence of antimicrobial resistance in this pathogen has been increasing. Administration of antimicrobials to prevent BRD is commonplace in stocker cattle, but the impact of this practice on emergence of resistance in is unknown. High risk, sale barn origin bull and steer calves ( = 169) were transported to a stocker facility in central Georgia and sampled via deep nasopharyngeal swab (NPS) at arrival processing. All calves received the macrolide antimicrobial tulathromycin (2.5 mg/kg subcutaneously) at arrival processing. A second NPS was collected from each calf 10 to 14 d after arrival. The occasional calves diagnosed and treated for BRD prior to 10 to 14 d were swabbed and cultured prior to treatment. Swabs were submitted for culture and antimicrobial susceptibility testing using the Kirby-Bauer disk diffusion method. Of the 169 cattle enrolled, 27 (16.0%) were culture positive for at arrival processing and of these, a multi-drug resistant (MDR) strain of was detected in 1 (3.7%). In contrast, 123 (72.8%) cattle were culture positive for at second sampling and of these, a MDR strain of was detected in 122 (99.2%). The proportions of cattle culture positive for and positive for MDR at arrival processing and at second sampling were significantly different ( < 0.001). At the level of the individual bacterial isolate, 366 individual isolates were collected from the calves at the time of the second sampling. Of these isolates, 361 (98.6%) were intermediate or resistant to all macrolides tested (tilmicosin, gamithromycin, tulathromycin) and the fluoroquinolone enrofloxacin. In addition, 254 isolates (69.4%) were intermediate or resistant to florfenicol and 4 (1.1%) were intermediate or resistant to ceftiofur. There was a significant difference in the proportion of isolates resistant to all of the drug classes except cephalosporins at arrival processing versus second sampling ( < 0.001). Our results show that there was an increase in the proportion of calves positive for from arrival processing to second sampling, and that there was an increase in the proportion of calves that had MDR strains of detected from arrival processing to second sampling. More research is needed to understand the role of metaphylaxis on MDR in and the impact of MDR on morbidity and mortality in stocker cattle.

Chemical epigenetics alters the secondary metabolite composition of guttate excreted by an atlantic-forest-soil-derived Penicillium citreonigrum.

PubMed

Wang, Xiaoru; Sena Filho, José G; Hoover, Ashley R; King, Jarrod B; Ellis, Trevor K; Powell, Douglas R; Cichewicz, Robert H

2010-05-28

Chemical epigenetic manipulation of Penicillium citreonigrum led to profound changes in the secondary metabolite profile of its guttate. While guttate from control cultures exhibited a relatively simple assemblage of secondary metabolites, the guttate collected from cultures treated with 50 muM 5-azacytidine (a DNA methyltransferase inhibitor) was highly enriched in compounds representing at least three distinct biosynthetic families. The metabolites obtained from the fungus included six azaphilones (sclerotiorin (1), sclerotioramine (6), ochrephilone (2), dechloroisochromophilone III (3), dechloroisochromophilone IV (4), and 6-((3E,5E)-5,7-dimethyl-2-methylenenona-3,5-dienyl)-2,4-dihydroxy-3-methylbenzaldehyde (5)), pencolide (7), and two new meroterpenes (atlantinones A and B (9 and 10, respectively)). While pencolide was detected in the exudates of both control and 5-azacytidine-treated cultures, all of the other natural products were found exclusively in the guttates of the epigenetically modified fungus. All of the metabolites from the P. citreonigrum guttate were tested for antimicrobial activity in a disk diffusion assay. Both sclerotiorin and sclerotioramine caused modest inhibition of Staphylococcus epidermidis growth; however, only sclerotioramine was active against a panel of Candida strains.

A Rapid and Efficient Screening Method for Antibacterial Compound-Producing Bacteria.

PubMed

Hettiarachchi, Sachithra; Lee, Su-Jin; Lee, Youngdeuk; Kwon, Young-Kyung; De Zoysa, Mahanama; Moon, Song; Jo, Eunyoung; Kim, Taeho; Kang, Do-Hyung; Heo, Soo-Jin; Oh, Chulhong

2017-08-28

Antibacterial compounds are widely used in the treatment of human and animal diseases. The overuse of antibiotics has led to a rapid rise in the prevalence of drug-resistant bacteria, making the development of new antibacterial compounds essential. This study focused on developing a fast and easy method for identifying marine bacteria that produce antibiotic compounds. Eight randomly selected marine target bacterial species ( Agrococcus terreus, Bacillus algicola, Mesoflavibacter zeaxanthinifaciens, Pseudoalteromonas flavipulchra, P. peptidolytica, P. piscicida, P. rubra , and Zunongwangia atlantica ) were tested for production of antibacterial compounds against four strains of test bacteria ( B. cereus, B. subtilis, Halomonas smyrnensis , and Vibrio alginolyticus ). Colony picking was used as the primary screening method. Clear zones were observed around colonies of P. flavipulchra, P. peptidolytica, P. piscicida , and P. rubra tested against B. cereus, B. subtilis , and H. smyrnensis . The efficiency of colony scraping and broth culture methods for antimicrobial compound extraction was also compared using a disk diffusion assay. P. peptidolytica, P. piscicida , and P. rubra showed antagonistic activity against H. smyrnensis, B. cereus , and B. subtilis , respectively, only in the colony scraping method. Our results show that colony picking and colony scraping are effective, quick, and easy methods of screening for antibacterial compound-producing bacteria.

Synergy of a combination of nisin and citric acid against Staphylococcus aureus and Listeria monocytogenes.

PubMed

Zhao, Xingchen; Zhen, Zhen; Wang, Xinyang; Guo, Na

2017-12-01

Food-borne diseases caused by pathogens, such as Staphylococcus aureus and Listeria monocytogenes, have long attracted attention globally from researchers, food industries, and food safety authorities. Nisin (NS) is the only bacteriocin used worldwide as a generally recognised as safe (GRAS) food preservative, while citric acid (CA) has an unrestricted use in foods since it has GRAS status. In this study, synergistic interactions of NS combined with CA against S. aureus and L. monocytogenes were studied by the chequerboard microdilution method, with fractional inhibitory concentration index values ranging from 0.25 to 0.375 and 0.19 to 0.375, respectively. The positive interactions were verified by time-kill studies in pasteurised milk and disk diffusion assays. The mechanism of the synergistic antibacterial of NS and CA is proposed following SEM analysis and the determination of release of cell constituents. These results suggest that the cell walls and membrane are the probable main targets of this antimicrobial combination. These findings indicated that the combination of NS and CA not only could be used as a new promising naturally sourced food preservative, but may also reduce the problem of bacterial resistance.

Phenotypic and genotypic profile of clinical and animal multidrug-resistant Salmonella enterica isolates from Mexico.

PubMed

Aguilar-Montes de Oca, S; Talavera-Rojas, M; Soriano-Vargas, E; Barba-León, J; Vázquez-Navarrete, J; Acosta-Dibarrat, J; Salgado-Miranda, C

2018-01-01

The objective of this study was to obtain a phenotypic and genotypic profile of Salmonella enterica including multidrug-resistant (MDR) isolates from food-producing animals and clinical isolates, as well as their genetic relatedness in two different States of Mexico (Jalisco and State of Mexico). A total of 243 isolates were evaluated in terms of antimicrobial resistance (AMR) and related genes through a disk diffusion method and PCR respectively; we found 16 MDR isolates, all of them harbouring the bla CMY gene but not qnr genes, these isolates represent less than 10% of the collection. The pulsed-field gel electrophoresis revealed a higher genotypic similitude within isolates of State of Mexico than Jalisco. A low percentage of Salmonella isolates were resistant to relevant antibiotics in human health, nevertheless, the AMR and involved genes were similar despite the different serovars and origin of the isolates. This investigation provided an insight of the current status of AMR of Salmonella isolates in two States of Mexico and pinpoint the genes involved in AMR and their epidemiological relationship, the information could help to determine an adequate therapy in human and veterinary medicine. © 2017 The Society for Applied Microbiology.

Photoionization of the diffuse interstellar medium and galactic halo by OB associtations

NASA Technical Reports Server (NTRS)

Dove, James B.; Shull, J. Michael

1994-01-01

Assuming smoothly varying H I distributions in te Galactic disk, we have calculated the geometry of diffuse II regions due to OB associations in the Galactic plane. Near the solar circle, OB associations with a Lyman continuum (Lyc) photon luminosity Psi(sub Lyc) = 3.3 x 10(exp 7) cm(exp -2) s(exp -1), produce H II regions that are density bounded in the vertical direction (H II chimneys) allowing Lyc to escape the gaseous disk and penetrate into the Galactic halo. We provide analytic formulae for the Lyc escape fraction as functions of S(sub 0) O-star catalog of Garmany and a new Lyc stellar stellar Lyc stellar flux calibration, we find a production rate of Lyc photons by OB associations within 2.5 kpc of Psi(sub Lyc) = 3.3 x 10(exp 7) cm(exp -2) s(exp -1). Integrating the fraction of Lyc photons that escape the disk over our adopted luminosity function of OB associations, we estimate that approximately 7% of the ionizing photons, or Phi(sub Lyc) = 2.3 x 10(exp 6) cm(exp -2) s(exp -1), escape each side of the H I disk layer and penetrate the diffuse ionized medium ('Reynolds layer'). This flux is sufficient to explain the potoionization of this, although we have not constructed a model for the observed H-alpha emission and pulsar dispersion measures that is fully consistent with the absorption rate of Lyc in the H II layer. Since our quiescent model does not account for the effects of dynamic chimneys and superbubbles, which should enhance Lyc escape, we conclude the O stars are the probable source of ionizing radiation for the Reynolds layer. For a random distribution of OB associations throughout the disk, the Lyc flux is nearly uniform for heights Z is greater than approximately 0.8 kpc above the midplane.

In vitro antibacterial activity of adhesive systems on Streptococcus mutans.

PubMed

Paradella, Thaís Cachuté; Koga-Ito, Cristiane Yumi; Jorge, Antonio Olavo Cardoso

2009-04-01

To evaluate the antibacterial activity of three adhesive systems -- Prime & Bond 2.1 (PB), Clearfil SE Bond (CS) and One Up Bond F (OU) -- on Streptococcus mutans in vitro. Adherence and agar disk-diffusion tests were performed. For the adherence testing, 40 human enamel specimens (4 mm2) were sterilized and the adhesive sytems were applied (n = 10). The control group did not receive the application of any adhesive system. Specimens were immersed in brain heart infusion broth (BHI) inoculated with S. mutans standardized suspension (10(6) cells/ml) for 48 h at 37 degrees C and 5% CO2. The number of S. mutans cells adhered to each specimen was evaluated by the plating method on BHI agar. For agar disk-diffusion testing, adhesive disks and disks soaked in distilled water (negative control) or 0.2% chlorexidine (positive control) were incubated with S. mutans for 48 h. The diameters of the zones of bacterial inhibition were measured. Adherence data were transformed in logarithms of base 10 (log10). Data were submitted to Kruskal-Wallis and Student-Neuman-Keuls tests at the 5% level of significance. The results of the adherence test showed that One Up Bond F (OU) and Clearfil SE Bond (CS) did not differ significantly from one another, but allowed significantly less adherence than Prime & Bond 2.1 (PB) and control [mean log10 (standard deviation) values: PB 6.10 (0.19); CS primer 4.55 (0.98); OU 4.65 (0.54); control group 6.34 (0.27)]. The disk-diffusion test showed no significant difference between OU (diameter in mm: 3.02 +/- 0.13) and CS (3.0 +/- 0.12), but both were significantly more effective in inhibiting bacterial growth than PB (1.0 +/- 0.10). The self-etching systems Clearfil SE Bond and One Up Bond F presented a greater inhibitory effect against S. mutans, also in terms of adherence, than did the conventional system, Prime & Bond 2.1.

[Effect of inoculum size on sensitivity and specificity of the double-disk synergy test for the detection of wide-spectrum beta-lactamases].

PubMed

Bedenić, B; Boras, A

2001-01-01

The plasmid-mediated extended-spectrum beta-lactamases (ESBL) confer resistance to oxymino-cephalosporins, such as cefotaxime, ceftazidime, and ceftriaxone and to monobactams such as aztreonam. It is well known fact that ESBL producing bacteria exhibit a pronounced inoculum effect against broad spectrum cephalosporins like ceftazidime, cefotaxime, ceftriaxone and cefoperazone. The aim of this investigation was to determine the effect of inoculum size on the sensitivity and specificity of double-disk synergy test (DDST) which is the test most frequently used for detection of ESBLs, in comparison with other two methods (determination of ceftazidime MIC with and without clavulanate and inhibitor potentiated disk-diffusion test) which are seldom used in clinical laboratories. The experiments were performed on a set of K. pneumoniae strains with previously characterized beta-lactamases which comprise: 10 SHV-5 beta-lactamase producing K. pneumoniae, 20 SHV-2 + 1 SHV 2a beta-lactamase producing K. pneumoniae, 7 SHV-12 beta-lactamase producing K. pneumoniae, 39 putative SHV ESBL producing K. pneumoniae and 26 K. pneumoniae isolates highly susceptible to ceftazidime according to Kirby-Bauer disk-diffusion method and thus considered to be ESBL negative. According to the results of this investigation, increase in inoculum size affected more significantly the sensitivity of DDST than of other two methods. The sensitivity of the DDST was lower when a higher inoculum size of 10(8) CFU/ml was applied, in distinction from other two methods (MIC determination and inhibitor potentiated disk-diffusion test) which retained high sensitivity regardless of the density of bacterial suspension. On the other hand, DDST displayed higher specificity compared to other two methods regardless of the inoculum size. This investigation found that DDST is a reliable method but it is important to standardize the inoculum size.

Gravitational Instabilities in a Young Protoplanetary Disk with Embedded Objects

NASA Astrophysics Data System (ADS)

Desai, Karna M.; Steiman-Cameron, Thomas Y.; Durisen, Richard H.

2018-01-01

Gravitational Instabilities (GIs), a mechanism for angular momentum transport, are more prominent during the early phases of protoplanetary disk evolution when the disk is relatively massive. In my dissertation work, I performed radiative 3D hydrodynamics simulations (by employing the code, CHYMERA) and extensively studied GIs by inserting different objects in the ‘control disk’ (a 0.14 M⊙ protoplanetary disk around a 1 M⊙ star).Studying planetary migration helps us better constrain planet formation models. To study the migration of Jovian planets, in 9 separate simulations, each of the 0.3 MJ, 1 MJ, and 3 MJ planets was inserted near the Inner and Outer Lindblad Resonances and the Corotation Radius (CR) of the dominant GI-induced two-armed spiral density wave in the disk. I found the migration timescales to be longer in a GI-active disk when compared to laminar disks. The 3 MJ planet controls its own orbital evolution, while the migration of a 0.3 MJ planet is stochastic in nature. I defined a ‘critical mass’ as the mass of an arm of the dominant two-armed spiral density wave within the planet’s Hill diameter. Planets above this mass control their own destiny, and planets below this mass are scattered by the disk. This critical mass could provide a recipe for predicting the migration behavior of planets in GI-active disks.To understand the stochastic migration of low-mass planets, I performed a simulation of 240 zero-mass planet-tracers (hereafter, planets) by inserting these at a range of locations in the control disk (an equivalent of 240 simulations of Saturn-mass or lower-mass objects). I calculated a Diffusion Coefficient (3.6 AU2/ 1000 yr) to characterize the stochastic migration of planets. I analyzed the increase in the eccentricity dispersion and compared it with the observed exoplanet eccentricities. The diffusion of planets can be a slow process, resulting in the survival of small planetary cores. Stochastic migration of planets is dynamically similar to the radial migration of stars in the Milky Way (MW). In MW, the CR of transient spiral arms can cause radial migration of stars.Also, to determine the effects of a companion, I studied GIs in a circumbinary disk with a 0.2 M⊙ brown dwarf companion.

Antibacterial Effect of Silver Diamine Fluoride on Cariogenic Organisms.

PubMed

Lou, Yali; Darvell, Brain W; Botelho, Michael G

2018-05-01

To screen the possible antimicrobial activity of a range of clinically used, silver-based compounds on cariogenic organisms: silver diamine fluoride (SDF), silver fluoride, and silver nitrate. Preliminary screening disk-diffusion susceptibility tests were conducted on Mueller-Hinton agar plates inoculated with Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces naeslundii, organisms known to be cariogenic. In order to identify which component of the silver compounds was responsible for any antibacterial (AB) effect, and to provide controls, the following were also investigated at high and low concentrations: sodium fluoride, ammonium fluoride, ammonium chloride, sodium fluoride, sodium chloride, and sodium nitrate, as well as deionized water as control. A volume of 10 pL of a test solution was dispensed onto a paper disk resting on the inoculated agar surface, and the plate incubated anaerobically at 37°C for 48 hours. The zones of inhibition were then measured. Silver diamine fluoride, silver fluoride, silver nitrate, and ammonium fluoride had significant AB effect (p < 0.05) on all three test organisms, although ammonium fluoride had no effect at low concentration; the remaining other compounds had no effect. Silver ions appear to be the principal AB agent at both high and low concentration; fluoride ions only have an AB effect at high concentration, while ammonium, nitrate, chloride and sodium ions have none. The anticaries effect of topical silver solutions appears restricted to that of the silver ions. Silver compounds, such as SDF, silver fluoride, and silver nitrate have AB effect against cariogenic organisms and these may have clinical impact in arresting or preventing dental decay. Sodium fluoride did not have AB effect under the conditions tested.

GOT C+: A Herschel Space Observatory Key Program to Study the Diffuse ISM

NASA Astrophysics Data System (ADS)

Langer, William; Velusamy, T.; Goldsmith, P. F.; Li, D.; Pineda, J.; Yorke, H.

2010-01-01

Star formation activity is regulated by pressures in the interstellar medium, which in turn depend on heating and cooling rates, modulated by the gravitational potential, and shock and turbulent pressures. To understand these processes we need information about the diffuse atomic and diffuse molecular gas cloud properties. The ionized carbon CII fine structure line at 1.9 THz is an important tracer of the atomic gas in the diffuse regions and the atomic to molecular cloud transformation. Furthermore, C+ is a major ISM coolant, the Galaxy's strongest emission line, with a total luminosity about a 1000 times that of CO J=1-0. Galactic Observations of the Terahertz C+ Line (GOT C+) is a Herschel Space Observatory Open Time Key Program to study the diffuse interstellar medium by sampling CII line emission throughout the Galactic disk. GOT C+ will obtain high spectral resolution CII using the Heterodyne Instrument for the Far Infrared (HIFI) instrument. It employees deep integrations, wide velocity coverage (350 km s-1) with 0.22 km s-1 resolution, and systematic sparse sampling of the Galactic disk together with observations of selected targets, of over 900 lines of sight. It will be a resource of the atomic gas properties, in the (a) Galactic disk, (b) Galaxy's central 300pc, (c) Galactic warp, (d) high latitude HI clouds, and (e) Photon Dominated Regions (PDRs). Along with HI, CO isotopes, and CI spectra, our C+ data will provide the astronomical community with a rich statistical database of diffuse cloud properties, for understanding the role of barometric pressure and turbulence in cloud evolution in the Galactic ISM and, by extension, other galaxies. The GOT C+ project will provide a template for future even larger-scale CII surveys. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology and is supported by a NASA grant.

GOT C+: A Herschel Space Observatory Key Program to Study the Diffuse ISM

NASA Astrophysics Data System (ADS)

Langer, William; Goldsmith, P. F.; Li, D.; Velusamy, T.; Yorke, H. W.

2009-01-01

Galactic Observations of the Terahertz C+ Line (GOT C+) is a Herschel Space Observatory (HSO) Key Program to study the diffuse interstellar medium by sampling the C+ fine structure line emission at 1.9 THz (158 microns) in the Galactic disk. Star formation activity is regulated by pressures in the interstellar medium, which in turn depend on heating and cooling rates, modulated by the gravitational potential, and shock and turbulent pressures. To understand these processes we need information about properties of the diffuse atomic and diffuse molecular gas clouds. The 158-micron CII line is an important tracer of diffuse regions, and C+ is a major ISM coolant, the Galaxy's strongest emission line virtually unobscured by dust, with a total luminosity about a 1000 times that of CO J=1-0. The GOT C+ program will obtain high spectral resolution CII spectra using the Heterodyne Instrument for the Far Infrared (HIFI) receiver. It will employ deep integrations, wide velocity coverage (350 km/s) with 0.22 km/s resolution, and systematic sparse sampling of the Galactic disk together with observations of selected targets, of over 900 lines of sight. It will be a resource to determine the properties of the atomic gas, in the (a) overall Galactic disk, (b) central 300pc of the Galactic center, (c) Galactic warp, (d) high latitude HI clouds, and (e) Photon Dominated Regions (PDRs). These spectra will provide the astronomical community with a rich statistical database of diffuse cloud properties, especially those of the atomic gas, sampled throughout the Galaxy for understanding the role of barometric pressure and turbulence in cloud evolution in the Galactic ISM and, by extension, other galaxies. The GOT C+ project will provide a template for future even larger-scale Galactic C+ surveys. This research was conducted at the Jet Propulsion Laboratory and is supported by a NASA grant.

The interstellar medium and star formation of galactic disks. I. Interstellar medium and giant molecular cloud properties with diffuse far-ultraviolet and cosmic-ray backgrounds

NASA Astrophysics Data System (ADS)

Li, Qi; Tan, Jonathan C.; Christie, Duncan; Bisbas, Thomas G.; Wu, Benjamin

2018-05-01

We present a series of adaptive mesh refinement hydrodynamic simulations of flat rotation curve galactic gas disks, with a detailed treatment of the interstellar medium (ISM) physics of the atomic to molecular phase transition under the influence of diffuse far-ultraviolet (FUV) radiation fields and cosmic-ray backgrounds. We explore the effects of different FUV intensities, including a model with a radial gradient designed to mimic the Milky Way. The effects of cosmic rays, including radial gradients in their heating and ionization rates, are also explored. The final simulations in this series achieve 4 pc resolution across the ˜20 kpc global disk diameter, with heating and cooling followed down to temperatures of ˜10 K. The disks are evolved for 300 Myr, which is enough time for the ISM to achieve a quasi-statistical equilibrium. In particular, the mass fraction of molecular gas is stabilized by ˜200 Myr. Additional global ISM properties are analyzed. Giant molecular clouds (GMCs) are also identified and the statistical properties of their populations are examined. GMCs are tracked as the disks evolve. GMC collisions, which may be a means of triggering star cluster formation, are counted and their rates are compared with analytic models. Relatively frequent GMC collision rates are seen in these simulations, and their implications for understanding GMC properties, including the driving of internal turbulence, are discussed.

Nanoscale Graphene Disk: A Natural Functionally Graded Material–How is Fourier’s Law Violated along Radius Direction of 2D Disk

PubMed Central

Yang, Nuo; Hu, Shiqian; Ma, Dengke; Lu, Tingyu; Li, Baowen

2015-01-01

In this Paper, we investigate numerically and analytically the thermal conductivity of nanoscale graphene disks (NGDs), and discussed the possibility to realize functionally graded material (FGM) with only one material, NGDs. Different from previous studies on divergence/non-diffusive of thermal conductivity in nano-structures with different size, we found a novel non-homogeneous (graded) thermal conductivity along the radius direction in a single nano-disk structure. We found that, instead of a constant value, the NGD has a graded thermal conductivity along the radius direction. That is, Fourier’s law of heat conduction is not valid in two dimensional graphene disk structures Moreover, we show the dependent of NGDs’ thermal conductivity on radius and temperature. Our study might inspire experimentalists to develop NGD based versatile FGMs, improve understanding of the heat removal of hot spots on chips, and enhance thermoelectric energy conversion efficiency by two dimensional disk with a graded thermal conductivity. PMID:26443206

Vertical Structure of Radiation-pressure-dominated Thin Disks: Link between Vertical Advection and Convective Stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Hong-Yu; Gu, Wei-Min, E-mail: guwm@xmu.edu.cn

2017-04-20

In the classic picture of standard thin accretion disks, viscous heating is balanced by radiative cooling through the diffusion process, and the radiation-pressure-dominated inner disk suffers convective instability. However, recent simulations have shown that, owing to the magnetic buoyancy, the vertical advection process can significantly contribute to energy transport. In addition, in comparing the simulation results with the local convective stability criterion, no convective instability has been found. In this work, following on from simulations, we revisit the vertical structure of radiation-pressure-dominated thin disks and include the vertical advection process. Our study indicates a link between the additional energy transportmore » and the convectively stable property. Thus, the vertical advection not only significantly contributes to the energy transport, but it also plays an important role in making the disk convectively stable. Our analyses may help to explain the discrepancy between classic theory and simulations on standard thin disks.« less

Nanoscale Graphene Disk: A Natural Functionally Graded Material-How is Fourier's Law Violated along Radius Direction of 2D Disk.

PubMed

Yang, Nuo; Hu, Shiqian; Ma, Dengke; Lu, Tingyu; Li, Baowen

2015-10-07

In this Paper, we investigate numerically and analytically the thermal conductivity of nanoscale graphene disks (NGDs), and discussed the possibility to realize functionally graded material (FGM) with only one material, NGDs. Different from previous studies on divergence/non-diffusive of thermal conductivity in nano-structures with different size, we found a novel non-homogeneous (graded) thermal conductivity along the radius direction in a single nano-disk structure. We found that, instead of a constant value, the NGD has a graded thermal conductivity along the radius direction. That is, Fourier's law of heat conduction is not valid in two dimensional graphene disk structures Moreover, we show the dependent of NGDs' thermal conductivity on radius and temperature. Our study might inspire experimentalists to develop NGD based versatile FGMs, improve understanding of the heat removal of hot spots on chips, and enhance thermoelectric energy conversion efficiency by two dimensional disk with a graded thermal conductivity.

Isolation and determination of four potential antimicrobial components from Pseudomonas aeruginosa extracts

PubMed Central

Xu, Ling-Qing; Zeng, Jian-Wen; Jiang, Chong-He; Wang, Huan; Li, Yu-Zhen; Wen, Wei-Hong; Li, Jie-Hua; Wang, Feng; Ting, Wei-Jen; Sun, Zi-Yong; Huang, Chih-Yang

2017-01-01

Background: Pseudomonas aeruginosa can cause disease and also can be isolated from the skin of healthy people. Additionally, it exhibits certain antimicrobial effects against other microorganisms. Methods: We collected 60 strains of P. aeruginosa and screened their antimicrobial effects against Staphylococcus aureus (ATCC 25923) using the filter paper-disk method, the cross-streaking method and the co-culture method and then evaluated the antimicrobial activity of the chloroform-isolated S. aureus extracts against methicillin-resistant S. aureus (MRSA, Gram-positive cocci), vancomycin intermediate-resistant S. aureus (VISA, Gram-positive cocci), Corynebacterium spp. (CS, Gram-positive bacilli), Acinetobacter baumannii (AB, Gram-negative bacilli), Moraxella catarrhalis (MC, Gram-negative diplococcus), Candida albicans (CA, fungi), Candida tropicalis (CT, fungi), Candida glabrata (CG, fungi) and Candida parapsilosis (CP, fungi). Results: The PA06 and PA46 strains have strong antimicrobial effects. High-performance liquid chromatography (HPLC) analysis revealed that the major components of PA06 and PA46 that exhibit antimicrobial activity are functionally similar to phenazine-1-carboxylic acid (PCA) and pyocyanin. Preparative HPLC was performed to separate and isolate the 4 major potential antimicrobial components: PA06ER10, PA06ER16, PA06ER23 and PA06ER31. Further, the molecular masses of PA06ER10 (260.1), PA06ER16 (274.1), PA06ER23 (286.1) and PA06ER31 (318.2) were determined by electrospray ionization (ESI) mass spectrometry. Conclusion: P. aeruginosa can produce small molecules with potential antimicrobial activities against MRSA, VISA, CS, MC, CA, CT, CG and CP but not against AB. PMID:29200950

EXor OUTBURSTS FROM DISK AMPLIFICATION OF STELLAR MAGNETIC CYCLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armitage, Philip J., E-mail: pja@jilau1.colorado.edu

EXor outbursts—moderate-amplitude disk accretion events observed in Class I and Class II protostellar sources—have timescales and amplitudes that are consistent with the viscous accumulation and release of gas in the inner disk near the dead zone boundary. We suggest that outbursts are indirectly triggered by stellar dynamo cycles, via poloidal magnetic flux that diffuses radially outward through the disk. Interior to the dead zone the strength of the net field modulates the efficiency of angular momentum transport by the magnetorotational instability. In the dead zone changes in the polarity of the net field may lead to stronger outbursts because ofmore » the dominant role of the Hall effect in this region of the disk. At the level of simple estimates we show that changes to kG-strength stellar fields could stimulate disk outbursts on 0.1 au scales, though this optimistic conclusion depends upon the uncertain efficiency of net flux transport through the inner disk. The model predicts a close association between observational tracers of stellar magnetic activity and EXor events.« less

[Characterization of isolates of carbapenemase-producing Pseudomonas aeruginosa from seven Colombian provinces].

PubMed

Saavedra, Sandra Yamile; Duarte, Carolina; González, María Nilse; Realpe, María Elena

2014-04-01

Pseudomonas aeruginosa is an opportunistic pathogen that causes multiple infections in hospitalized patients. This microorganism has developed resistance to several antimicrobial agents, including carbapenems, which are considered to be the last therapeutic option against these infections. Carbapenem resistance of P. aeruginosa is mediated by different mechanisms: Carbapenemases class B (MBL) and A, alterations in the OprD expression and overexpression of the Mex efflux pump. To describe the presence of carbapenemases in P. aeruginosa isolates from seven Colombian provinces. A total of 57 P. aeruginosa isolates were collected between September 2012 and March 2013 from national surveillance in Colombia and were sent to the Grupo de Microbiología at the Instituto Nacional de Salud (INS) for evaluation. Iidentification and antimicrobial susceptibility were confirmed through automated method (Vitek ® 2) and disk diffusion (Kirby-Bauer) according to the Clinical and Laboratory Standards Institute, CLSI, 2013. Phenotypic and genotypic confirmation was determined using the modified Hodge test (MHT), a synergism test using imipenem, EDTA-SMA and meropenem, and conventional PCR to detect the bla KPC, bla VIM, bla IMP and bla NDM genes. Of the 57 isolates, two showed sensitivity to carbapenems. Forty-three isolates were positive for carbapenemases with a high percentage of sensitivity to colistin (76.4%, n=42). The 43 isolates producing carbapenemases showed multiple drug resistance: 72.1% were positive in the MHT and 79.1% showed MBL synergism. PCR amplification confirmed that 33 isolates were positive for bla VIM, nine were positive for bla KPC and one isolate expressed both KPC and VIM carbapenemases. No isolates showed amplified products with bla IMP and bla NDM primers. The most frequent carbapenemase was VIM, followed by KPC in an approximate ratio of 3:1.

Molecular analysis and antimicrobial susceptibility of methicillin resistant Staphylococcus aureus in one of the hospitals of Tehran University of Medical Sciences: high prevalence of sequence type 239 (ST239) clone.

PubMed

Shahsavan, Shadi; Jabalameli, Leila; Maleknejad, Parviz; Aligholi, Marzieh; Imaneini, Hossein; Jabalameli, Fereshteh; Halimi, Shahnaz; Taherikalani, Morovat; Khoramian, Babak; Eslampour, Mohammad Amin; Feizabadi, Mohammad Mehdi; Emaneini, Mohammad

2011-03-01

Methicillin-resistant Staphylococcus aureus (MRSA), particularly the multidrug-resistant clones, is an increasing worldwide problem. The average incidence rate of MRSA in Tehran was found to be over 40%. A total of 140 MRSA isolates obtained from patients attending a teaching hospital in Tehran, from May 2009 to December 2009, were included in this study. The antimicrobial susceptibility profile of MRSA isolates was determined by the agar disk diffusion method. Molecular analysis of MRSA strains was accomplished by Pulsed-Field Gel Electrophoresis (PFGE) and Multi-locus sequence typing (MLST). Detection of mecA gene was used to confirm resistance to methicillin among the MRSA isolates. All the MRSA isolates were susceptible to chloramphenicol, teicoplanin, tigecycline and vancomycin. All MRSAisolates were resistant to oxacillin, whilst 139 strains showed resistance against ciprofloxacin, erythromycin, gentamicin, tetracycline and trimethoprim-sulfamethoxazole. PFGE analysis of all the 140 MRSA isolates produced five distinct pulsotypes designated as pulsotypes A-E. Most of the isolates (n=132) were clustered into pulsotype A. The most prevalent sequence type (ST) was ST 239 (pulsotype A) found in 82% (37/45) of the tested isolates. The second most prevalent type was ST 1238 (pulsotypes B, C and D) found in 15% (7/45) of the isolates. The remaining type, ST 8 (pulsotype E) was found in a single isolate. The results of this study indicated that the MRSA clone ST 239 was a major clone in the selected university hospital of Tehran and that it was widely spread among the different wards as well as all the age groups of patients.

Increasing Prevalence of Aminoglycoside-Resistant Enterococcus faecalis Isolates Due to the aac(6')-aph(2") Gene: A Therapeutic Problem in Kermanshah, Iran.

PubMed

Khani, Mitra; Fatollahzade, Mahdie; Pajavand, Hamid; Bakhtiari, Somaye; Abiri, Ramin

2016-03-01

Enterococci are important pathogens in nosocomial infections. Various types of antibiotics, such as aminoglycosides, are used for treatment of these infections. Enterococci can acquire resistant traits, which can lead to therapeutic problems with aminoglycosides. This study was designed to identify the prevalence of, and to compare, the aac(6')-aph(2") and aph(3)-IIIa genes and their antimicrobial resistance patterns among Enterococcus faecalis and E. faecium isolates from patients at Imam Reza hospital in Kermanshah in 2011 - 2012. One hundred thirty-eight clinical specimens collected from different wards of Imam Reza hospital were identified to the species level by biochemical tests. Antimicrobial susceptibility tests against kanamycin, teicoplanin, streptomycin, imipenem, ciprofloxacin, and ampicillin were performed by the disk diffusion method. The minimum inhibitory concentrations of gentamicin, streptomycin, kanamycin, and amikacin were evaluated with the microbroth dilution method. The aminoglycoside resistance genes aac(6')-aph(2") and aph(3")-IIIa were analyzed with multiplex PCR. The prevalence of isolates was 33 (24.1%) for E. faecium and 63 (46%) for E. faecalis. Eighty-nine percent of the isolates were high-level gentamicin resistant (HLGR), and 32.8% of E. faecium isolates and 67.2% of E. faecalis isolates carried aac(6')-aph(2"). The prevalence of aph(3")-IIIa among the E. faecalis and E. faecium isolates was 22.7% and 77.3%, respectively. Remarkably increased incidence of aac(6')-aph(2") among HLGR isolates explains the relationship between this gene and the high level of resistance to aminoglycosides. As the resistant gene among enterococci can be transferred, the use of new-generation antibiotics is necessary.

Characterization of Staphylococcus aureus Isolated from Food Products in Western Algeria.

PubMed

Chaalal, Wafaa; Chaalal, Nadia; Bourafa, Nadjette; Kihal, Mebrouk; Diene, Seydina M; Rolain, Jean-Marc

2018-03-15

The current study aimed to characterize Staphylococcus aureus isolates from foodstuffs collected from western Algeria. A total of 153 S. aureus isolates from various raw and processed foods were obtained and identified using matrix-assisted laser desorption and ionization time-of-flight mass spectrometry. Isolates were characterized by antimicrobial susceptibility testing and toxin gene detection. Methicillin-resistant Staphylococcus aureus (MRSA) isolates were identified by detection of the mecA gene and characterized by staphylococcal cassette chromosome mec (SCCmec) typing. We found that 30.9% (153/495) of food samples were contaminated with S. aureus. Thirty-three (21.5%) S. aureus isolates were identified as MRSA, and 16.9% (26/153) carried the mecA gene. Three SCCmec types were identified of which type IV was the most common (69.2%) followed by type V (15.3%) and type II (7.6%). Two MRSA isolates were not typable with SCCmec typing. None of the examined isolates harbored mecC. Furthermore, 14.3% (22/153) of the isolates were toxigenic S. aureus. The cytotoxin gene pvl was detected in 11.1% of the S. aureus isolates. This gene was more commonly detected (76.4%) in MRSA isolates than in methicillin-suceptible Staphylococcus aureus (MSSA) isolates. The tsst-1 gene coding for toxic shock syndrome toxin was isolated rarely (3.2%) and only in MSSA isolates. According to disk diffusion test results, 70 isolates were resistant to only one antimicrobial drug, and 51 (33.3%) isolates were multidrug resistant. Other 32 isolates were susceptible to all antibiotics. Our study highlights, for the first time, a high prevalence of multidrug-resistant S. aureus isolates carrying pvl or tsst-1 found in food products in Algeria. The risk of MRSA transmission through the food chain cannot be disregarded, particularly in uncooked foods.

Increasing Prevalence of Aminoglycoside-Resistant Enterococcus faecalis Isolates Due to the aac(6’)-aph(2”) Gene: A Therapeutic Problem in Kermanshah, Iran

PubMed Central

Khani, Mitra; Fatollahzade, Mahdie; Pajavand, Hamid; Bakhtiari, Somaye; Abiri, Ramin

2016-01-01

Background: Enterococci are important pathogens in nosocomial infections. Various types of antibiotics, such as aminoglycosides, are used for treatment of these infections. Enterococci can acquire resistant traits, which can lead to therapeutic problems with aminoglycosides. Objectives: This study was designed to identify the prevalence of, and to compare, the aac(6’)-aph(2”) and aph(3)-IIIa genes and their antimicrobial resistance patterns among Enterococcus faecalis and E. faecium isolates from patients at Imam Reza hospital in Kermanshah in 2011 - 2012. Patients and Methods: One hundred thirty-eight clinical specimens collected from different wards of Imam Reza hospital were identified to the species level by biochemical tests. Antimicrobial susceptibility tests against kanamycin, teicoplanin, streptomycin, imipenem, ciprofloxacin, and ampicillin were performed by the disk diffusion method. The minimum inhibitory concentrations of gentamicin, streptomycin, kanamycin, and amikacin were evaluated with the microbroth dilution method. The aminoglycoside resistance genes aac(6’)-aph(2”) and aph(3”)-IIIa were analyzed with multiplex PCR. Results: The prevalence of isolates was 33 (24.1%) for E. faecium and 63 (46%) for E. faecalis. Eighty-nine percent of the isolates were high-level gentamicin resistant (HLGR), and 32.8% of E. faecium isolates and 67.2% of E. faecalis isolates carried aac(6’)-aph(2”). The prevalence of aph(3”)-IIIa among the E. faecalis and E. faecium isolates was 22.7% and 77.3%, respectively. Conclusions: Remarkably increased incidence of aac(6’)-aph(2”) among HLGR isolates explains the relationship between this gene and the high level of resistance to aminoglycosides. As the resistant gene among enterococci can be transferred, the use of new-generation antibiotics is necessary. PMID:27217920

Facile microwave-assisted synthesis of Te-doped hydroxyapatite nanorods and nanosheets and their characterizations for bone cement applications.

PubMed

Yahia, I S; Shkir, Mohd; AlFaify, S; Ganesh, V; Zahran, H Y; Kilany, Mona

2017-03-01

In this work, the authors have fabricated the nanorods and nanosheets of pure and Te-doped HAp with different Te concentrations (0.04, 0.08, 0.16, 0.24wt%) by microwave-assisted technique at low temperature. The crystallite size, degree of crystallinity and lattice parameters are calculated. FE-SEM study confirms that the fabricated nanostructures are nanorods of diameter about 10nm in undoped and at low concentration of Te doping. However, at and higher concentration, it becomes nanosheets of about 5nm thickness. X-ray diffraction, FT-IR and FT-Raman studies shows that the prepared products are of HAp and Te has been successfully incorporated. From EDX the Ca/P molar ratio of the pure HAp is about 1.740, while this ratio for 0.04, 0.08, 0.16, 0.24 wt% Te doped is about 1.53, 1.678, 1.724, 1.792, respectively. Crystallite size was found to be increased with Te doping from 15nm to 62nm. The value of dielectric constant is found to be enhanced at higher concentrations of Te. The values of linear absorption coefficient were also determined and show that the prepared material with Te doping is more absorbable than pure and will be highly applicable in radiation detection applications. Furthermore, the antimicrobial potential of pure and Te doped HAp was examined against some Gram- negative and positive bacteria and fungi by agar disk diffusion method. The results demonstrated that the antimicrobial activity of Te doped HAp is stronger than that of pure HAp where it exhibited the highest activity against Bacillus subtilis>Candida albicans>Shigella dysenteriae. Copyright © 2016 Elsevier B.V. All rights reserved.

Prevalence, Molecular Characterization, and Antibiotic Susceptibility of Vibrio parahaemolyticus from Ready-to-Eat Foods in China

PubMed Central

Xie, Tengfei; Xu, Xiaoke; Wu, Qingping; Zhang, Jumei; Cheng, Jianheng

2016-01-01

Vibrio parahaemolyticus is the leading cause of foodborne outbreaks, particularly outbreaks associated with consumption of fish and shellfish, and represents a major threat to human health worldwide. This bacterium harbors two main virulence factors: the thermostable direct hemolysin (TDH) and TDH-related hemolysin (TRH). Additionally, various serotypes have been identified. The extensive use of antibiotics is a contributing factor to the increasing incidence of antimicrobial-resistant V. parahaemolyticus. In the current study, we aimed to determine the incidence and features of V. parahaemolyticus in ready-to-eat (RTE) foods in China. We found 39 V. parahaemolyticus strains on Chinese RTE foods through investigation of 511 RTE foods samples from 24 cities in China. All isolates were analyzed for the presence of tdh and trh gene by PCR, serotyping was performed using multiplex PCR, antibiotic susceptibility analysis was carried out using the disk diffusion method, and molecular typing was performed using enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR) typing and multilocus sequence typing (MLST). The results showed that none of the isolates were positive for tdh and trh. Most of the isolates (33.3%) were serotype O2. Antimicrobial susceptibility results indicated that most strains were resistant to streptomycin (89.7%), cefazolin (51.3%), and ampicillin (51.3%). The isolates were grouped into five clusters by ERIC-PCR and four clusters by MLST. We updated 10 novel loci and 33 sequence types (STs) in the MLST database. Thus, our findings demonstrated the presence of V. parahaemolyticus in Chinese RTE foods, provided insights into the dissemination of antibiotic-resistant strains, and improved our knowledge of methods of microbiological risk assessment in RTE foods. PMID:27148231

Emerging Carbapenem-Resistant Pseudomonas aeruginosa Isolates Carrying blaIMP Among Burn Patients in Isfahan, Iran.

PubMed

Radan, Mohsen; Moniri, Rezvan; Khorshidi, Ahmad; Gilasi, Hamidreza; Norouzi, Zohreh; Beigi, Fahimeh; Dasteh Goli, Yasaman

2016-09-01

Metallo-β-lactamase (MBL)-producing Pseudomonas aeruginosa is a significant pathogen in burn patients. The aim of this study was to determine the prevalence of carbapenem-resistant P. aeruginosa isolates, including those resistant to imipenemase (IMP), in a burn unit in Isfahan, Iran. One hundred and fifty P. aeruginosa isolates from burn patients were tested for antibiotic susceptibility by the disc diffusion method in accordance with CLSI guidelines. Production of MBL was identified with the EDTA disk method. DNA was purified from the MBL-positive isolates, and detection of the bla IMP gene was performed with PCR. Fifty-seven out of 150 (38%) isolates were multi-drug resistant (MDR), and 93 (62%) were extensively-drug resistant (XDR). Among all isolates, the resistance rate to ciprofloxacin, tobramycin, imipenem, meropenem, amikacin, ceftazidime, and cefepime was higher than 90%, while the resistance rates to piperacillin/tazobactam and aztreonam were 70.7% and 86%, respectively. Colistin and polymyxin B remained the most effective studied antibiotics. All of the imipenem-resistant P. aeruginosa isolates were MBL-positive, and 107 out of 144 (74.3%) of the MBL isolates were positive for the bla IMP gene. The results of this study show that the rate of P. aeruginosa -caused burn wound infections was very high, and many of the isolates were resistant to three or more classes of antimicrobials. Such extensive resistance to antimicrobial classes is important because few treatment options remain for patients with burn wound infections. bla IMP -producing P. aeruginosa isolates are a rising threat in burn-care units, and should be controlled by conducting infection-control assessments.

Induction of Efflux-Mediated Macrolide Resistance in Streptococcus pneumoniae ▿

PubMed Central

Chancey, Scott T.; Zhou, Xiaoliu; Zähner, Dorothea; Stephens, David S.

2011-01-01

The antimicrobial efflux system encoded by the operon mef(E)-mel on the mobile genetic element MEGA in Streptococcus pneumoniae and other Gram-positive bacteria is inducible by macrolide antibiotics and antimicrobial peptides. Induction may affect the clinical response to the use of macrolides. We developed mef(E) reporter constructs and a disk diffusion induction and resistance assay to determine the kinetics and basis of mef(E)-mel induction. Induction occurred rapidly, with a >15-fold increase in transcription within 1 h of exposure to subinhibitory concentrations of erythromycin. A spectrum of environmental conditions, including competence and nonmacrolide antibiotics with distinct cellular targets, did not induce mef(E). Using 16 different structurally defined macrolides, induction was correlated with the amino sugar attached to C-5 of the macrolide lactone ring, not with the size (e.g., 14-, 15- or 16-member) of the ring or with the presence of the neutral sugar cladinose at C-3. Macrolides with a monosaccharide attached to C-5, known to block exit of the nascent peptide from the ribosome after the incorporation of up to eight amino acids, induced mef(E) expression. Macrolides with a C-5 disaccharide, which extends the macrolide into the ribosomal exit tunnel, disrupting peptidyl transferase activity, did not induce it. The induction of mef(E) did not require macrolide efflux, but the affinity of macrolides for the ribosome determined the availability for efflux and pneumococcal susceptibility. The induction of mef(E)-mel expression by inducing macrolides appears to be based on specific interactions of the macrolide C-5 saccharide with the ribosome that alleviate transcriptional attenuation of mef(E)-mel. PMID:21537010

Antimicrobial activity of Marcetia DC species (Melastomataceae) and analysis of its flavonoids by reverse phase-high performance liquid chromatography coupled-diode array detector

PubMed Central

Leite, Tonny Cley Campos; de Sena, Amanda Reges; dos Santos Silva, Tânia Regina; dos Santos, Andrea Karla Almeida; Uetanabaro, Ana Paula Trovatti; Branco, Alexsandro

2012-01-01

Background: Marcetia genera currently comprises 29 species, with approximately 90% inhabiting Bahia (Brazil), and most are endemic to the highlands of the Chapada Diamantina (Bahia). Among the species, only M. taxifolia (A.St.-Hil.) DC. populates Brazil (state of Roraima to Paraná) and also Venezuela, Colombia, and Guyana. Objective: This work evaluated the antimicrobial activity of hexane, ethyl acetate, and methanol extracts of three species of Marcetia (Marcetia canescens Naud., M. macrophylla Wurdack, and M. taxifolia A.StHil) against several microorganism. In addition, the flavonoids were analyzed in extracts by HPLC-DAD. Materials and methods: The tests were made using Gram-positive (three strains of Staphylococcus aureus) and Gram-negative (two strains of Escherichia coli, a strain of Pseudomonas aeruginosa and another of Salmonella choleraesius) bacteria resistant and nonresistant to antibiotics and yeasts (two strains of Candida albicans and one of C. parapsilosis) by the disk diffusion method. Solid-phase extraction (SPE) was performed on the above extracts to isolate flavonoids, which were subsequently analyzed by high performance liquid chromatography coupled diode array detector (HPLC-DAD). Results: Results showed that extracts inhibited the Gram-positive bacteria and yeast. The hexane extracts possessed the lowest activity, while the ethyl acetate and methanolic extracts were more active. Conclusion: Marcetia taxifolia was more effective (active against 10 microorganisms studied), and only its methanol extract inhibited Gram-negative bacteria (P. aeruginosa and S. choleraesius). SPE and HPLC-DAD analysis showed that M. canescens and M. macrophylla contain glycosylated flavonoids, while the majority of extracts from M. taxifolia were aglycone flavonoids. PMID:23060695

Oliveria decumbens essential oil: Chemical compositions and antimicrobial activity against the growth of some clinical and standard strains causing infection.

PubMed

Alizadeh Behbahani, Behrooz; Tabatabaei Yazdi, Farideh; Vasiee, Alireza; Mortazavi, Seyed Ali

2018-01-01

Oliveria decumbens as a valuable medicinal plant is extensively used in traditional medicine. clinical and standard strains causing infection resistance to antimicrobial agents, is one of the important problems in medicine. The aim of this study was to investigate the antibacterial activities and phytochemical analysis of Oliveria decumbens essential oil on the growth of some clinical and standard strains causing infection (Pseudomonas aerogenes, Escherichia coli, Streptococcus pyogenes and Staphylococcus epidermidis). Oliveria decumbens essential oil composition was identified by gas chromatography/mass spectrometry. Phytochemical analysis (alkaloids, saponins, flavone and phenolic) essential oil of the Oliveria decumbens were appraised based on qualitative methods. Several methods (disk diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)) were used to appraise the antibacterial activity of the Oliveria decumbens essential oil. Thymol (28.45%) was the major compound of Oliveria decumbens essential oil. The total phenolics content (TPC) of the essential oil positively correlated with antioxidant activity (AA). The TPC and AA of Oliveria decumbens essential oil was equal to 92.45 ± 0.70 μg GAE/mg and 164.45 ± 1.20 μg/ml, respectively. The MIC of Oliveria decumbens essential oil ranged from 1 to 8 mg/ml depending on the type of bacteria (clinical and standard strains). The MBC of Oliveria decumbens essential oil varied from 1 mg/ml to 16 mg/ml. The smallest inhibition zone diameter (IZD) on different Oliveria decumbens essential oil concentrations on P. aeruginosa. Results indicate that Oliveria decumbens essential oil can prove to be an important source of AA and antibacterial and may be used for the treatment of infection diseases. Copyright © 2017 Elsevier Ltd. All rights reserved.

National Epidemiologic Surveys of Enterobacter aerogenes in Belgian Hospitals from 1996 to 1998

PubMed Central

De Gheldre, Y.; Struelens, M. J.; Glupczynski, Y.; De Mol, P.; Maes, N.; Nonhoff, C.; Chetoui, H.; Sion, C.; Ronveaux, O.; Vaneechoutte, M.

2001-01-01

Two national surveys were conducted to describe the incidence and prevalence of Enterobacter aerogenes in 21 Belgian hospitals in 1996 and 1997 and to characterize the genotypic diversity and the antimicrobial resistance profiles of clinical strains of E. aerogenes isolated from hospitalized patients in Belgium in 1997 and 1998. Twenty-nine hospitals collected 10 isolates of E. aerogenes, which were typed by arbitrarily primed PCR (AP-PCR) using two primers and pulsed-field gel electrophoresis. MICs of 10 antimicrobial agents were determined by the agar dilution method. Beta-lactamases were detected by the double-disk diffusion test and characterized by isoelectric point. The median incidence of E. aerogenes colonization or infection increased from 3.3 per 1,000 admissions in 1996 to 4.2 per 1000 admissions in the first half of 1997 (P < 0.01). E. aerogenes strains (n = 260) clustered in 25 AP-PCR types. Two major types, BE1 and BE2, included 36 and 38% of strains and were found in 21 and 25 hospitals, respectively. The BE1 type was indistinguishable from a previously described epidemic strain in France. Half of the strains produced an extended-spectrum beta-lactamase, either TEM-24 (in 86% of the strains) or TEM-3 (in 14% of the strains). Over 75% of the isolates were resistant to ceftazidime, piperacillin-tazobactam, and ciprofloxacin. Over 90% of the strains were susceptible to cefepime, carbapenems, and aminoglycosides. In conclusion, these data suggest a nationwide dissemination of two epidemic multiresistant E. aerogenes strains in Belgian hospitals. TEM-24 beta-lactamase was frequently harbored by one of these epidemic strains, which appeared to be genotypically related to a TEM-24-producing epidemic strain from France, suggesting international dissemination. PMID:11230400

Phytochemical analysis and antibacterial activities extracts of mangrove leaf against the growth of some pathogenic bacteria.

PubMed

Alizadeh Behbahani, Behrooz; Tabatabaei Yazdi, Farideh; Shahidi, Fakhri; Noorbakhsh, Hamid; Vasiee, Alireza; Alghooneh, Ali

2018-01-01

In this study, the effects of water, ethanol, methanol and glycerin at five levels (0, 31.25, 83.33, 125 and 250 ml) were investigated on the efficiency of mangrove leaf extraction using mixture optimal design. The antimicrobial effect of the extracts on Streptococcus pneumoniae, Enterococcus faecium and Klebsiella pneumoniae was evaluated using disk diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. The mangrove leaf extraction components were identified through gas chromatography/mass spectrometry (GC/MS). Phytochemical analysis (alkaloids, tannins, saponins, flavone and glycosides) were evaluated based on qualitative methods. Antioxidant activity of extracts was measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant potential (FRAP) methods. Maximum antimicrobial effect was observed in Enterococcus faecium and highest resistance against mangrove leaf extract in Enterococcus faecium and Klebsiella pneumoniae, respectively. Increasing concentration of mangrove extracts had a significant effect (p ≤ 0.05) on inhibition zone diameter. The MICs of the mangrove leaf extraction varied from 4 mg/ml to 16 mg/ml. The optimum formulation was found to contain glycerin (0 ml), water (28.22 ml), methanol (59.83 ml) and ethanol (161.95 ml). The results showed that the highest antioxidant activity was related to optimum extract of mangrove leaf and ethanolic extract respectively. The results of phytochemical screening of Avicennia marina leaves extract showed the existence of alkaloids, tannins, saponins, flavone and glycosides. 2-Propenoic acid, 3-phenyl- was the major compound of Avicennia marina. The results of non-significant lack of fit tests, and F value (14.62) indicated that the model was sufficiently accurate. In addition, the coefficient of variations (16.8%) showed an acceptable reproducibility. Copyright © 2017 Elsevier Ltd. All rights reserved.

Antimicrobial activity and physical characterization of silver nanoparticles green synthesized using nitrate reductase from Fusarium oxysporum.

PubMed

Gholami-Shabani, Mohammadhassan; Akbarzadeh, Azim; Norouzian, Dariush; Amini, Abdolhossein; Gholami-Shabani, Zeynab; Imani, Afshin; Chiani, Mohsen; Riazi, Gholamhossein; Shams-Ghahfarokhi, Masoomeh; Razzaghi-Abyaneh, Mehdi

2014-04-01

Nanostructures from natural sources have received major attention due to wide array of biological activities and less toxicity for humans, animals, and the environment. In the present study, silver nanoparticles were successfully synthesized using a fungal nitrate reductase, and their biological activity was assessed against human pathogenic fungi and bacteria. The enzyme was isolated from Fusarium oxysporum IRAN 31C after culturing on malt extract-glucose-yeast extract-peptone (MGYP) medium. The enzyme was purified by a combination of ultrafiltration and ion exchange chromatography on DEAE Sephadex and its molecular weight was estimated by gel filtration on Sephacryl S-300. The purified enzyme had a maximum yield of 50.84 % with a final purification of 70 folds. With a molecular weight of 214 KDa, it is composed of three subunits of 125, 60, and 25 KDa. The purified enzyme was successfully used for synthesis of silver nanoparticles in a way dependent upon NADPH using gelatin as a capping agent. The synthesized silver nanoparticles were characterized by X-ray diffraction, dynamic light scattering spectroscopy, and transmission and scanning electron microscopy. These stable nonaggregating nanoparticles were spherical in shape with an average size of 50 nm and a zeta potential of -34.3. Evaluation of the antimicrobial effects of synthesized nanoparticles by disk diffusion method showed strong growth inhibitory activity against all tested human pathogenic fungi and bacteria as evident from inhibition zones that ranged from 14 to 25 mm. Successful green synthesis of biologically active silver nanoparticles by a nitrate reductase from F. oxysporum in the present work not only reduces laborious downstream steps such as purification of nanoparticle from interfering cellular components, but also provides a constant source of safe biologically-active nanomaterials with potential application in agriculture and medicine.

Detection of acrA, acrB, aac(6')-Ib-cr, and qepA genes among clinical isolates of Escherichia coli and Klebsiella pneumoniae.

PubMed

Heidary, Mohsen; Bahramian, Aghil; Hashemi, Ali; Goudarzi, Mehdi; Omrani, Vahid Fallah; Eslami, Gita; Goudarzi, Hossein

2017-03-01

The distribution of drug resistance among clinical isolates of Escherichia coli and Klebsiella pneumoniae has limited the therapeutic options. The aim of this study was to report the prevalence of quinolone resistance genes among E. coli and K. pneumoniae clinical strains isolated from three educational hospitals of Tehran, Iran. A total of 100 strains of E. coli from Labbafinejad and Taleghani Hospitals and 100 strains of K. pneumoniae from Mofid Children and Taleghani Hospitals were collected between January 2013 and May 2014. Antimicrobial susceptibility tests were done by disk diffusion method based on Clinical and Laboratory Standards Institute guidelines. Detection of qepA, aac(6')-Ib-cr, acrA, and acrB genes was done by polymerase chain reaction (PCR). In this study, fosfomycin and imipenem against E. coli and fosfomycin and tigecycline against K. pneumoniae had the best effect in antimicrobial susceptibility tests. PCR assay using specific primers demonstrated that the prevalence of qepA, aac(6')-Ib-cr, acrA, and acrB genes among the 100 E. coli isolates was 0 (0%), 87 (87%), 92 (92%), and 84 (84%), respectively. The prevalence of qepA, aac(6')-Ib-cr, acrA, and acrB genes among the 100 K. pneumoniae isolates was 4 (4%), 85 (85%), 94 (94%), and 87 (87%), respectively. The distribution of qepA, aac(6')-Ib-cr, acrA, and acrB resistance determinants in E. coli and K. pneumoniae is a great concern. Therefore, infection control and prevention of spread of drug-resistant bacteria need careful management of medication and identification of resistant isolates.

Antimicrobial Resistance of Enterococcus Species Isolated from Chicken in Turkey

PubMed Central

Sanlibaba, Pınar; Tezel, Basar Uymaz; Senturk, Esra

2018-01-01

Abstract The aim of the present work was to provide information about Enterococcus strains isolated from pre-packaged chicken samples in Ankara (Turkey), focusing on their prevalence, phenotypic and genotypic characteristics, and antibiotic resistance. We report the first study on the occurrence of antibiotic resistant enterococci in pre-packaged chicken samples in Ankara. A total of 97 suspicious enterococcal isolates were identified from 122 chicken samples. All isolates were identified to species level by phenotypic and molecular methods. In the 16S rDNA sequence analysis, Enterococcus faecium (61.85%) and Enterococcus faecalis (38.15%) were found to be the most frequently detected Enterococcus spp. Of the 97 isolates tested for hemolytic activity, 12.37% enterococcal strains were β-hemolytic. β-Hemolysin was most prevalent among E. faecium (58.33%) compared to E. faecalis (41.66%). Disk diffusion method was used for determining of antibiotic resistance. The analysis of the antimicrobial resistance of the 97 Enterococcus isolates revealed that the resistance to kanamycin (98.96%), rifampicin (80.41%) and ampicillin (60.82%) was most frequent. Furthermore, resistance to erythromycin (38.14%) and ciprofloxacin (34.02%) was also observed. The frequencies of resistance to tetracycline (9.27%), penicillin G (8.24%), and chloramphenicol (3.09%), gentamicin (2.06%) and streptomycin (1.03%) were low. None of the isolates was resistant to vancomycin. Multi-drug resistance was found in 97.93% of Enterococcus strains. E. faecium strains showed a more resistant phenotype than E. faecalis strains according to the antibiotic resistance levels. The results of this study indicated that chicken meat is a potential reservoir for the transmission of antibiotic resistance from animals to humans. PMID:29805287

Crowding of Interacting Fluid Particles in Porous Media through Molecular Dynamics: Breakdown of Universality for Soft Interactions.

PubMed

Schnyder, Simon K; Horbach, Jürgen

2018-02-16

Molecular dynamics simulations of interacting soft disks confined in a heterogeneous quenched matrix of soft obstacles show dynamics which is fundamentally different from that of hard disks. The interactions between the disks can enhance transport when their density is increased, as disks cooperatively help each other over the finite energy barriers in the matrix. The system exhibits a transition from a diffusive to a localized state, but the transition is strongly rounded. Effective exponents in the mean-squared displacement can be observed over three decades in time but depend on the density of the disks and do not correspond to asymptotic behavior in the vicinity of a critical point, thus, showing that it is incorrect to relate them to the critical exponents in the Lorentz model scenario. The soft interactions are, therefore, responsible for a breakdown of the universality of the dynamics.

In Vitro Activity of Cephalothin and Three Penicillins Against Escherichia coli and Proteus Species

PubMed Central

Barry, Arthur L.; Hoeprich, Paul D.

1973-01-01

The susceptibility of clinical isolates of Escherichia coli (67) and Proteus species (58) to cephalothin, ampicillin, benzyl penicillin, and phenoxymethyl penicillin was determined in vitro by using broth dilution and disk diffusion tests. The data were correlated by using a four-category scheme for interpreting minimal inhibitory concentrations (groups 1 to 4) as recommended by a subcommittee of an international collaborative study of susceptibility testing. With cephalothin and ampicillin, groups 1 (susceptible) and 2 (moderately susceptible) were susceptible by the disk test, and with benzyl penicillin, similar results were observed when the interpretive zone standards were changed. Strains categorized as group 4 (very resistant) were resistant by the disk method, but group 3 (moderately resistant) strains were not adequately distinguished by disk testing. Group 3 susceptibility to benzyl and phenoxymethyl penicillins can be predicted by extrapolating results from tests with ampicillin disks. PMID:4202343

Crowding of Interacting Fluid Particles in Porous Media through Molecular Dynamics: Breakdown of Universality for Soft Interactions

NASA Astrophysics Data System (ADS)

Schnyder, Simon K.; Horbach, Jürgen

2018-02-01

Molecular dynamics simulations of interacting soft disks confined in a heterogeneous quenched matrix of soft obstacles show dynamics which is fundamentally different from that of hard disks. The interactions between the disks can enhance transport when their density is increased, as disks cooperatively help each other over the finite energy barriers in the matrix. The system exhibits a transition from a diffusive to a localized state, but the transition is strongly rounded. Effective exponents in the mean-squared displacement can be observed over three decades in time but depend on the density of the disks and do not correspond to asymptotic behavior in the vicinity of a critical point, thus, showing that it is incorrect to relate them to the critical exponents in the Lorentz model scenario. The soft interactions are, therefore, responsible for a breakdown of the universality of the dynamics.

Proposal for agar disk diffusion interpretive criteria for susceptibility testing of bovine mastitis pathogens using cefoperazone 30μg disks.

PubMed

Feßler, Andrea T; Kaspar, Heike; Lindeman, Cynthia J; Peters, Thomas; Watts, Jeffrey L; Schwarz, Stefan

2017-02-01

Cefoperazone is a third generation cephalosporin which is commonly used for bovine mastitis therapy. Bacterial pathogens involved in bovine mastitis are frequently tested for their susceptibility to cefoperazone. So far, the cefoperazone susceptibility testing using 30μg disks has been hampered by the lack of quality control (QC) ranges as well as the lack of interpretive criteria. In 2014, QC ranges for 30 μg cefoperazone disks have been established for Staphylococcus aureus ATCC ® 25923 and Escherichia coli ATCC ® 25922. As a next step, interpretive criteria for the susceptibility testing of bovine mastitis pathogens should be developed. For this, 637 bovine mastitis pathogens (including 112 S. aureus, 121 coagulase-negative staphylococci (CoNS), 103 E. coli, 101 Streptococcus agalactiae, 100 Streptococcus dysgalactiae and 100 Streptococcus uberis) were investigated by agar disk diffusion according to the document Vet01-A4 of the Clinical and Laboratory Standards Institute (CLSI) using 30μg cefoperazone disks and the results were compared to the corresponding MIC values as determined by broth microdilution also according to the aforementioned CLSI document. Based on the results obtained and taking into account the achievable milk concentration of cefoperazone after regular dosing, the following interpretive criteria were proposed as a guidance for mastitis diagnostic laboratories: for staphylococci and E. coli ≥23mm (susceptible), 18-22mm (intermediate) and ≤17mm (resistant) and for streptococci ≥18mm (susceptible), and ≤17mm (non-susceptible). These proposed interpretive criteria shall contribute to a harmonization of cefoperazone susceptibility testing of bovine mastitis pathogens. Copyright © 2016 Elsevier B.V. All rights reserved.

Evaluation of the Premi Test and comparison with the One-Plate Test for the detection of antimicrobials in kidney.

PubMed

Cantwell, H; O'Keeffe, M

2006-02-01

The Premi Test, a test kit designed for the rapid screening of antimicrobial residues in meat, fish and eggs, was evaluated and compared with the (modified) One-Plate Test, an agar diffusion assay. The performance characteristics described for qualitative, screening methods in Commission Decision 2002/657/EC were used for the evaluation. The Premi Test was found to detect a range of antimicrobials to MRL levels in kidney fluid but to have poorer sensitivity for some antimicrobials such as tetracyclines, sulphonamides, flumequine and streptomycin. The test was found not to be sensitive for the banned antimicrobial chloramphenicol. The One-Plate Test was found to detect most tetracyclines and flumequine to MRL levels but to be less sensitive than the Premi Test for most of the other classes of antimicrobials. Neither test alone provides a comprehensive screening test for antimicrobial residues in kidney at MRL levels. However, the Premi Test is fast, easy to use and rugged and, in combination with other antimicrobial tests, may be used to provide a comprehensive screening system for antimicrobials in tissues.

Spectral Analysis of Non-ideal MRI Modes: The Effect of Hall Diffusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohandas, Gopakumar; Pessah, Martin E., E-mail: gopakumar@nbi.ku.dk, E-mail: mpessah@nbi.ku.dk

The effect of magnetic field diffusion on the stability of accretion disks is a problem that has attracted considerable interest of late. In particular, the Hall effect has the potential to bring about remarkable changes in the dynamical behavior of disks that are without parallel. In this paper, we conduct a systematic examination of the linear eigenmodes in a weakly magnetized differentially rotating gas with a special focus on Hall diffusion. We first develop a geometrical representation of the eigenmodes and provide a detailed quantitative description of the polarization properties of the oscillatory modes under the combined influence of themore » Coriolis and Hall effects. We also analyze the effects of magnetic diffusion on the structure of the unstable modes and derive analytical expressions for the kinetic and magnetic stresses and energy densities associated with the non-ideal magnetorotational instability (MRI). Our analysis explicitly demonstrates that, if the dissipative effects are relatively weak, the kinetic stresses and energies make up the dominant contribution to the total stress and energy density when the equilibrium angular momentum and magnetic field vectors are anti-parallel. This is in sharp contrast to what is observed in the case of the ideal or dissipative MRI. We conduct shearing box simulations and find very good agreement with the results derived from linear theory. Because the modes under consideration are also exact solutions of the nonlinear equations, the unconventional nature of the kinetic and magnetic stresses may have significant implications for the nonlinear evolution in some regions of protoplanetary disks.« less

Synthesis and anti-microbial activity of hydroxylammonium ionic liquids.

PubMed

Ismail Hossain, M; El-Harbawi, Mohanad; Noaman, Yousr Abdulhadi; Bustam, Mohd Azmi B; Alitheen, Noorjahan Banu Mohamed; Affandi, Nor Azrin; Hefter, Glenn; Yin, Chun-Yang

2011-06-01

Eight hydroxylammonium-based room temperature ionic liquids (ILs) have been synthesized by acid-base neutralization of ethanolamines with organic acids. The ILs were characterized by infrared and nuclear magnetic resonance spectroscopies and elemental analysis. Their anti-microbial activities were determined using the well-diffusion method. All eight ILs were toxic to Staphylococcus aureus, while 2-hydroxyethylammonium lactate and 2-hydroxy-N-(2-hydroxyethyl)-N-methylethanaminium acetate showed high anti-microbial activity against a wide range of human pathogens. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Dynamical simulations of the interacting galaxies in the NGC 520/UGC 957 system

NASA Technical Reports Server (NTRS)

Stanford, S. A.; Balcells, Marc

1991-01-01

Numerical simulations of the interacting galaxies in the NGC 520/UGC 957 system are presented. Two sets of models were produced to investigate the postulated three-galaxy system of two colliding disk galaxies within NGC 520 and the dwarf galaxy UGC 957. The first set of models simulated a dwarf perturbing one-disk galaxy, which tested the possibility that NGC 520 contains only one galaxy disturbed by the passage of UGC 957. The resulting morphology of the perturbed single disk in the simulation fails to reproduce the observed tidal tails and northwest mass condensation of NGC 520. A second set of models simulated two colliding disks, which tested the hypothesis that NGC 520 itself contains two galaxies in a strong collision and UGC 957 is unimportant to the interaction. These disk-disk models produced a good match to the morphology of the present NGC 520. It is concluded that (1) NGC 520 contains two colliding disk galaxies which have produced the brighter southern half of the long tidal tail and (2) UGC 957, which may originally have been a satellite of one of the disk galaxies, formed the diffuse northern tail as it orbited NGC 520.

Antimicrobial Wound Dressing. Phase 1

DTIC Science & Technology

1987-06-11

12 a. Antimicrobial Sensitivity Tests 12 b. Anin.il Model 13 5. Preparatiua of Microcapsules 14 B. Results 15 1. AIn Vit Diffusion 15 a. PVA... Microcapsules 35 Table 5 Tetracycline Hydrochloride Cellulose 36 Triacetate Microcapsules Table 6 Polyethylene Oxide Hydrogels 37 Table 7 Swelling of...Water and Crosslinking Effect Figure 24 In Vi trq Chlorhexidine Release 70 Polyacrylamide Hydrogel - Microcapsules Figure 25 In _Vitro Tetracycline

Detection of antimicrobial resistance genes associated with the International Space Station environmental surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urbaniak, C.; Sielaff, A. Checinska; Frey, K. G.

Antimicrobial resistance (AMR) is a global health issue. In an effort to minimize this threat to astronauts, who may be immunocompromised and thus at a greater risk of infection from antimicrobial resistant pathogens, a comprehensive study of the ISS “resistome’ was conducted. Using whole genome sequencing (WGS) and disc diffusion antibiotic resistance assays, 9 biosafety level 2 organisms isolated from the ISS were assessed for their antibiotic resistance. Molecular analysis of AMR genes from 24 surface samples collected from the ISS during 3 different sampling events over a span of a year were analyzed with Ion AmpliSeq™ and metagenomics. Discmore » diffusion assays showed that Enterobacter bugandensis strains were resistant to all 9 antibiotics tested and Staphylococcus haemolyticus being resistant to none. Ion AmpliSeq™ revealed that 123 AMR genes were found, with those responsible for beta-lactam and trimethoprim resistance being the most abundant and widespread. Using a variety of methods, the genes involved in antimicrobial resistance have been examined for the first time from the ISS. Lastly, this information could lead to mitigation strategies to maintain astronaut health during long duration space missions when return to Earth for treatment is not possible.« less

Detection of antimicrobial resistance genes associated with the International Space Station environmental surfaces

DOE PAGES

Urbaniak, C.; Sielaff, A. Checinska; Frey, K. G.; ...

2018-01-16

Antimicrobial resistance (AMR) is a global health issue. In an effort to minimize this threat to astronauts, who may be immunocompromised and thus at a greater risk of infection from antimicrobial resistant pathogens, a comprehensive study of the ISS “resistome’ was conducted. Using whole genome sequencing (WGS) and disc diffusion antibiotic resistance assays, 9 biosafety level 2 organisms isolated from the ISS were assessed for their antibiotic resistance. Molecular analysis of AMR genes from 24 surface samples collected from the ISS during 3 different sampling events over a span of a year were analyzed with Ion AmpliSeq™ and metagenomics. Discmore » diffusion assays showed that Enterobacter bugandensis strains were resistant to all 9 antibiotics tested and Staphylococcus haemolyticus being resistant to none. Ion AmpliSeq™ revealed that 123 AMR genes were found, with those responsible for beta-lactam and trimethoprim resistance being the most abundant and widespread. Using a variety of methods, the genes involved in antimicrobial resistance have been examined for the first time from the ISS. Lastly, this information could lead to mitigation strategies to maintain astronaut health during long duration space missions when return to Earth for treatment is not possible.« less

Hybrid Nanoscale Architecture of Wound Dressing with Super Hydrophilic, Antimicrobial, and Ultralow Fouling Attributes.

PubMed

Depan, D; Misra, R D K

2015-02-01

Currently available wound dressings to heal thermal and chronic wounds are unable to respond to the challenges of resistance to bacterial infection, protein adsorption, and increased levels of wound exudates. To this end, we have conceived the fabrication of a new and ideal wound dressing with a number of key attributes. They include effective antimicrobial activity in a controlled manner, ultralow fouling property that provides resistance to protein adsorption and bacterial adhesion, maintain a moist but not saturated environment to promote healing, and is non-adherent and effective in the presence of heavy wound exudate. The novel approach to reduce infection and bacterial colonization involves incorporation of a unique silver-clay nanohybrid architecture in zwitterionic polymer, poly(sulfobetaine). The innovative concept of silver-clay hybrid structure enables us to obtain high, sustained, and diffusion-controlled antimicrobial activity of silver eluting polymer. The sustained and diffusion-controlled high antimicrobial efficiency is obtained through a process involving in situ precipitation of silver nanoparticles with large surface area on the surface of clay platelets. Furthermore, the use of recently developed zwitterionic polymer, poly(sulfobetaine) [poly(SB)] for wound dressing, provides antifouling property, which resists protein adsorption.

Detection of antimicrobial resistance genes associated with the International Space Station environmental surfaces.

PubMed

Urbaniak, C; Sielaff, A Checinska; Frey, K G; Allen, J E; Singh, N; Jaing, C; Wheeler, K; Venkateswaran, K

2018-01-16

Antimicrobial resistance (AMR) is a global health issue. In an effort to minimize this threat to astronauts, who may be immunocompromised and thus at a greater risk of infection from antimicrobial resistant pathogens, a comprehensive study of the ISS "resistome' was conducted. Using whole genome sequencing (WGS) and disc diffusion antibiotic resistance assays, 9 biosafety level 2 organisms isolated from the ISS were assessed for their antibiotic resistance. Molecular analysis of AMR genes from 24 surface samples collected from the ISS during 3 different sampling events over a span of a year were analyzed with Ion AmpliSeq ™ and metagenomics. Disc diffusion assays showed that Enterobacter bugandensis strains were resistant to all 9 antibiotics tested and Staphylococcus haemolyticus being resistant to none. Ion AmpliSeq ™ revealed that 123 AMR genes were found, with those responsible for beta-lactam and trimethoprim resistance being the most abundant and widespread. Using a variety of methods, the genes involved in antimicrobial resistance have been examined for the first time from the ISS. This information could lead to mitigation strategies to maintain astronaut health during long duration space missions when return to Earth for treatment is not possible.

Antimicrobial susceptibility of Streptococcus suis isolated from clinically healthy swine in Brazil

PubMed Central

Soares, Taíssa Cook Siqueira; Paes, Antonio Carlos; Megid, Jane; Ribolla, Paulo Eduardo Martins; Paduan, Karina dos Santos; Gottschalk, Marcelo

2014-01-01

Streptococcus suis is an important pathogen in the swine industry. This study is the first to report on the antimicrobial susceptibility of S. suis isolated from clinically healthy pigs in Brazil; the fourth major pork producer in the world. The antimicrobial susceptibility of 260 strains was determined by disc diffusion method. Strains were commonly susceptible to ceftiofur, cephalexin, chloramphenicol, and florfenicol, with more than 80% of the strains being susceptible to these antimicrobials. A high frequency of resistance to some of the antimicrobial agents was demonstrated, with resistance being most common to sulfa-trimethoprim (100%), tetracycline (97.69%), clindamycin (84.61%), norfloxacin (76.92%), and ciprofloxacin (61.15%). A high percentage of multidrug resistant strains (99.61%) were also found. The results of this study indicate that ceftiofur, cephalexin, and florfenicol are the antimicrobials of choice for empirical control of the infections caused by S. suis. PMID:24688177

Antimicrobial agent-free hybrid cationic starch/sodium alginate polyelectrolyte films for food packaging materials.

PubMed

Şen, Ferhat; Uzunsoy, İrem; Baştürk, Emre; Kahraman, Memet Vezir

2017-08-15

This study aimed to develop polyelectrolyte structured antimicrobial food packaging materials that do not contain any antimicrobial agents. Cationic starch was synthesized and characterized by FT-IR spectroscopy and 1 H NMR spectroscopy. Its nitrogen content was determined by Kjeldahl method. Polyelectrolyte structured antimicrobial food packaging materials were prepared using starch, cationic starch and sodium alginate. Antimicrobial activity of materials was defined by inhibition zone method (disc diffusion method). Thermal stability of samples was evaluated by TGA and DSC. Hydrophobicity of samples was determined by contact angle measurements. Surface morphology of samples was investigated by SEM. Moreover, gel contents of samples were determined. The obtained results prove that produced food packaging materials have good thermal, antimicrobial and surface properties, and they can be used as food packaging material in many industries. Copyright © 2017 Elsevier Ltd. All rights reserved.

DEAD, UNDEAD, AND ZOMBIE ZONES IN PROTOSTELLAR DISKS AS A FUNCTION OF STELLAR MASS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohanty, Subhanjoy; Ercolano, Barbara; Turner, Neal J., E-mail: s.mohanty@imperial.ac.uk, E-mail: ercolano@usm.lmu.de, E-mail: neal.turner@jpl.nasa.gov

We investigate the viability of the magnetorotational instability (MRI) in X-ray ionized viscous accretion disks around both solar-type stars and very low mass stars. In particular, we determine the disk regions where the MRI can be shut off either by Ohmic resistivity (the so-called dead and undead zones) or by ambipolar diffusion (a region we term the zombie zone). We consider two stellar masses: M {sub *} = 0.7 M {sub Sun} and 0.1 M {sub Sun }. In each case, we assume that: the disk surface density profile is that of a scaled Minimum Mass Solar Nebula, with Mmore » {sub disk}/M {sub *} = 0.01 as suggested by current data; disk ionization is driven primarily by stellar X-rays, complemented by cosmic rays and radionuclides; and the stellar X-ray luminosity scales with bolometric luminosity as L{sub X} /L {sub *} Almost-Equal-To 10{sup -3.5}, as observed. Ionization rates are calculated with the MOCCASIN Monte Carlo X-ray transport code, and ionization balance determined using a simplified chemical network, including well-mixed 0.1 {mu}m grains at various levels of depletion. We find that (1) ambipolar diffusion is the primary factor controlling MRI activity in disks around both solar-type and very low mass classical T Tauri stars. Assuming that the MRI yields the maximum possible field strength at each radius, we further find that: (2) the MRI-active layer constitutes only {approx}5%-10% of the total disk mass; (3) the accretion rate ( M-dot ) varies radially in both magnitude and sign (inward or outward), implying time-variable accretion as well as the creation of disk gaps and overdensities, with consequences for planet formation and migration; (4) achieving the empirical accretion rates in solar-type and very low mass stars requires a depletion of well-mixed small grains (via grain growth and/or settling) by a factor of 10-1000 relative to the standard dust-to-gas mass ratio of 10{sup -2}; and (5) the current non-detection of polarized emission from field-aligned grains in the outer disk regions is consistent with active MRI at those radii.« less

Rotating disk electrode system for elevated pressures and temperatures.

PubMed

Fleige, M J; Wiberg, G K H; Arenz, M

2015-06-01

We describe the development and test of an elevated pressure and temperature rotating disk electrode (RDE) system that allows measurements under well-defined mass transport conditions. As demonstrated for the oxygen reduction reaction on polycrystalline platinum (Pt) in 0.5M H2SO4, the setup can easily be operated in a pressure range of 1-101 bar oxygen, and temperature of 140 °C. Under such conditions, diffusion limited current densities increase by almost two orders of magnitude as compared to conventional RDE setups allowing, for example, fuel cell catalyst studies under more realistic conditions. Levich plots demonstrate that the mass transport is indeed well-defined, i.e., at low electrode potentials, the measured current densities are fully diffusion controlled, while at higher potentials, a mixed kinetic-diffusion controlled regime is observed. Therefore, the setup opens up a new field for RDE investigations under temperature and current density conditions relevant for low and high temperature proton exchange membrane fuel cells.

Rotating disk electrode system for elevated pressures and temperatures

NASA Astrophysics Data System (ADS)

Fleige, M. J.; Wiberg, G. K. H.; Arenz, M.

2015-06-01

We describe the development and test of an elevated pressure and temperature rotating disk electrode (RDE) system that allows measurements under well-defined mass transport conditions. As demonstrated for the oxygen reduction reaction on polycrystalline platinum (Pt) in 0.5M H2SO4, the setup can easily be operated in a pressure range of 1-101 bar oxygen, and temperature of 140 °C. Under such conditions, diffusion limited current densities increase by almost two orders of magnitude as compared to conventional RDE setups allowing, for example, fuel cell catalyst studies under more realistic conditions. Levich plots demonstrate that the mass transport is indeed well-defined, i.e., at low electrode potentials, the measured current densities are fully diffusion controlled, while at higher potentials, a mixed kinetic-diffusion controlled regime is observed. Therefore, the setup opens up a new field for RDE investigations under temperature and current density conditions relevant for low and high temperature proton exchange membrane fuel cells.

A new effective assay to detect antimicrobial activity of filamentous fungi.

PubMed

Pereira, Eric; Santos, Ana; Reis, Francisca; Tavares, Rui M; Baptista, Paula; Lino-Neto, Teresa; Almeida-Aguiar, Cristina

2013-01-15

The search for new antimicrobial compounds and the optimization of production methods turn the use of antimicrobial susceptibility tests a routine. The most frequently used methods are based on agar diffusion assays or on dilution in agar or broth. For filamentous fungi, the most common antimicrobial activity detection methods comprise the co-culture of two filamentous fungal strains or the use of fungal extracts to test against single-cell microorganisms. Here we report a rapid, effective and reproducible assay to detect fungal antimicrobial activity against single-cell microorganisms. This method allows an easy way of performing a fast antimicrobial screening of actively growing fungi directly against yeast. Because it makes use of an actively growing mycelium, this bioassay also provides a way for studying the production dynamics of antimicrobial compounds by filamentous fungi. The proposed assay is less time consuming and introduces the innovation of allowing the direct detection of fungal antimicrobial properties against single cell microorganisms without the prior isolation of the active substance(s). This is particularly useful when performing large screenings for fungal antimicrobial activity. With this bioassay, antimicrobial activity of Hypholoma fasciculare against yeast species was observed for the first time. Copyright © 2012 Elsevier GmbH. All rights reserved.

The Cosmic Battery in Astrophysical Accretion Disks

NASA Astrophysics Data System (ADS)

Contopoulos, Ioannis; Nathanail, Antonios; Katsanikas, Matthaios

2015-06-01

The aberrated radiation pressure at the inner edge of the accretion disk around an astrophysical black hole imparts a relative azimuthal velocity on the electrons with respect to the ions which gives rise to a ring electric current that generates large-scale poloidal magnetic field loops. This is the Cosmic Battery established by Contopoulos and Kazanas in 1998. In the present work we perform realistic numerical simulations of this important astrophysical mechanism in advection-dominated accretion flows, ADAFs. We confirm the original prediction that the inner parts of the loops are continuously advected toward the central black hole and contribute to the growth of the large-scale magnetic field, whereas the outer parts of the loops are continuously diffusing outward through the turbulent accretion flow. This process of inward advection of the axial field and outward diffusion of the return field proceeds all the way to equipartition, thus generating astrophysically significant magnetic fields on astrophysically relevant timescales. We confirm that there exists a critical value of the magnetic Prandtl number between unity and 10 in the outer disk above which the Cosmic Battery mechanism is suppressed.

Evaluation of antimicrobial efficacy of Aloe vera and its effectiveness in decontaminating gutta percha cones

PubMed Central

Athiban, Prakash P; Borthakur, Bikash Jyoti; Ganesan, S; Swathika, B

2012-01-01

Aim: The aim of this study was to evaluate the antimicrobial efficacy of Aloe vera and to determine its effectiveness in decontaminating gutta percha cones. Materials and Methods: A concentrated extract of Aloe vera was used to check for the antimicrobial efficacy using the agar well diffusion method. Presence of zones’ of diffusion was identified against three common GP contaminants namely, E.coli, E.faecalis and Staph. aureus. New GP Cones, freshly taken out of the packet were then decontaminated for 1minute using Aloe vera gel and then placed in thioglycolate broth to check for the presence of turbidity. Results: The zones of inhibition on the agar plate were measured as 24mm,21mm and 24mm respectively. The broth remained clear even after 48 hours of incubation. Conclusion: We conclude that Aloe vera is indeed effective as a GP decontaminant and it holds a promising future as a medium for storage of GP cones. PMID:22876011

In vitro sensitivity of Hungarian Actinobaculum suis strains to selected antimicrobials.

PubMed

Biksi, I; Major, Andrea; Fodor, L; Szenci, O; Vetési, F

2003-01-01

In vitro antimicrobial sensitivity of 12 Hungarian isolates and the type strain ATCC 33144 of Actinobaculum suis to different antimicrobial compounds was determined both by the agar dilution and by the disc diffusion method. By agar dilution, MIC50 values in the range of 0.05-3.125 micrograms/ml were determined for penicillin, ampicillin, ceftiofur, doxycycline, tylosin, pleuromutilins, chloramphenicol, florfenicol, enrofloxacin and lincomycin. The MIC50 value of oxytetracycline and spectinomycin was 6.25 and 12.5 micrograms/ml, respectively. For ofloxacin, flumequine, neomycin, streptomycin, gentamicin, nalidixic acid, nitrofurantoin and sulphamethoxazole + trimethoprim MIC50 values were in the range of 25-100 micrograms/ml. With the disc diffusion method, all strains were sensitive to penicillin, cephalosporins examined, chloramphenicol and florfenicol, tetracyclines examined, pleuromutilins, lincomycin and tylosin. Variable sensitivity was observed for fluoroquinolones (flumequine, enrofloxacin, ofloxacin), most of the strains were susceptible to marbofloxacin. Almost all strains were resistant to aminoglycosides but most of them were sensitive to spectinomycin. A strong correlation was determined for disc diffusion and MIC results (Spearman's rho 0.789, p < 0001). MIC values of the type strain and MIC50 values of other tested strains did not differ significantly. Few strains showed a partially distinct resistance pattern for erythromycin, lincomycin and ampicillin in both methods.

LUNAR ACCRETION FROM A ROCHE-INTERIOR FLUID DISK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salmon, Julien; Canup, Robin M., E-mail: julien@boulder.swri.edu, E-mail: robin@boulder.swri.edu

2012-11-20

We use a hybrid numerical approach to simulate the formation of the Moon from an impact-generated disk, consisting of a fluid model for the disk inside the Roche limit and an N-body code to describe accretion outside the Roche limit. As the inner disk spreads due to a thermally regulated viscosity, material is delivered across the Roche limit and accretes into moonlets that are added to the N-body simulation. Contrary to an accretion timescale of a few months obtained with prior pure N-body codes, here the final stage of the Moon's growth is controlled by the slow spreading of themore » inner disk, resulting in a total lunar accretion timescale of {approx}10{sup 2} years. It has been proposed that the inner disk may compositionally equilibrate with the Earth through diffusive mixing, which offers a potential explanation for the identical oxygen isotope compositions of the Earth and Moon. However, the mass fraction of the final Moon that is derived from the inner disk is limited by resonant torques between the disk and exterior growing moons. For initial disks containing <2.5 lunar masses (M{sub Last-Quarter-Moon }), we find that a final Moon with mass > 0.8 M{sub Last-Quarter-Moon} contains {<=}60% material derived from the inner disk, with this material preferentially delivered to the Moon at the end of its accretion.« less

Antioxidative, antimicrobial and cytotoxic effects of the phenolics of Leea indica leaf extract

PubMed Central

Rahman, Md. Atiar; Imran, Talha bin; Islam, Shahidul

2012-01-01

This study investigated the phytochemical, antioxidative, antimicrobial and cytotoxic effects of Leea indica leaf ethanol extract. Phytochemical values namely total phenolic and flavonoid contents, total antioxidant capacity, DPPH radical scavenging effect, FeCl3 reducing power, DMSO superoxide scavenging effect and Iron chelating effects were studied by established methods. Antibacterial, antifungal and cytotoxic effects were screened by disk diffusion technique, food poison technique and brine shrimp bioassay, respectively. Results showed the total phenolic content 24.00 ± 0.81 g GAE/100 g, total flavonoid content 194.68 ± 2.43 g quercetin/100 g and total antioxidant capacity 106.61 ± 1.84 g AA/100 g dry extract. Significant (P < 0.05) IC50 values compared to respective standards were recorded in DPPH radical scavenging (139.83 ± 1.40 μg/ml), FeCl3 reduction (16.48 ± 0.64 μg/ml), DMSO superoxide scavenging (676.08 ± 5.80 μg/ml) and Iron chelating (519.33 ± 16.96 μg/ml) methods. In antibacterial screening, the extract showed significant (P < 0.05) zone of inhibitions compared to positive controls Ampicillin and Tetracycline against Gram positive Bacillus subtilis, Bacillus cereus, Bacillus megaterium, and Staphylococcus aureus and Gram negative Salmonella typhi, Salmonella paratyphi, Pseudomonas aeroginosa, Shigella dysenteriae, Vibrio cholerae, and Escherichia coli. Significant minimum inhibitory concentrations compared to tetracycline were obtained against the above organisms. In antifungal assay, the extract inhibited the growth of Aspergillus flavus, Candida albicans and Fusarium equisetii by 38.09 ± 0.59, 22.58 ± 2.22, and 22.58 ± 2.22%, respectively. The extract showed a significant LC50 value compared to vincristine sulfate in cytotoxic assay. The results evidenced the potential antioxidative, antimicrobial and cytotoxic capacities of Leea inidica leaf extract to be processed for pharmaceutical use. PMID:23961238

Frequency of antimicrobial resistance and integron gene cassettes in Escherichia coli isolated from giant pandas (Ailuropoda melanoleuca) in China.

PubMed

Zou, Wencheng; Li, Caiwu; Yang, Xin; Wang, Yongxiang; Cheng, Guangyang; Zeng, Jinxin; Zhang, Xiuzhong; Chen, Yanpeng; Cai, Run; Huang, Qianru; Feng, Lan; Wang, Hongning; Li, Desheng; Zhang, Guiquan; Chen, Yanxi; Zhang, Zhizhong; Zhang, Heming

2018-03-01

Escherichia coli (E. coli) is considered as a common opportunistic pathogen, which causes seriously intestinal infections to giant pandas (Ailuropoda melanoleuca) and other animals. The aim of this investigation was to characterize the antimicrobial resistance and integron gene cassettes in E. coli isolated from the faeces of giant pandas in China. A total of 89 E. coli were isolated, after diagnosis of isolates and genomes were extracted. All the isolates were screened for the presence of related drug-resistance genes and integron gene cassettes through the Polymerase Chain Reaction (PCR) and sequencing. In addition, antimicrobial resistance testing was performed according to the standard disk diffusion method (CLSI 2013). The results demonstrated that all the isolates were multi-drug resistance (MDR). High resistance proportions of the E. coli isolates were to streptomycin (93%), cefazolin (90%), amikacin (75%), tetracycline (65%), ampicillin (62%), cefotaxime and trimethoprim-sulfamethoxazole (54%, each). With respect to the various resistance genes; bla CTX-M , sul1, ant (3')-Ia, tetA, qnrB, tetE, floR, aac (6')-Ib, sul2, rmtA, cmlA, rmtB and tetC were identified with the respective frequencies of 44%, 45%, 38%, 37%, 35%, 27%, 26%, 20%, 18%, 15%, 10%, 7% and 4%. None of the isolates was positive for qnrA and cfr genes. Moreover, a further investigation of integron revealed that the emergence of class 1 and 2 integrons were in 47% and 8% isolates, respectively. While class 3 integron was not screened. Six types of containing in class 1 integron specific gene cassettes (dfrA12-orfF-aadA2, dfrA17-aadA5, aadA1, aadA5, dfrA1 and dfrA7) were identified. However, only one gene cassette (dfrA1-sat2-aadA1) was detected in class 2 integron. These finding emphasize that a high level of E. coli isolates harbored antibiotics resistance and integron gene cassettes, which may bring so many potential threats to the health of giant pandas. Copyright © 2018 Elsevier Ltd. All rights reserved.

Origanum vulgare mediated green synthesis of biocompatible gold nanoparticles simultaneously possessing plasmonic, antioxidant and antimicrobial properties

PubMed Central

Cuibus, Flavia; Sevastre, Bogdan; Stiufiuc, Gabriela; Duma, Mihaela; Hanganu, Daniela; Iacovita, Cristian; Stiufiuc, Rares; Lucaciu, Constantin Mihai

2018-01-01

Purpose The leaves and flowering stem of Origanum vulgare contain essential oils, flavonoids, phenolic acids and anthocyanins. We propose a new, simple, one-pot, O. vulgare extract (OVE) mediated green synthesis method of biocompatible gold nanoparticles (AuNPs) possessing improved antioxidant, antimicrobial and plasmonic properties. Materials and methods Different concentrations of OVEs were used to reduce gold ions and to synthetize biocompatible spherical AuNPs. Their morphology and physical properties have been investigated by means of transmission electron microscopy, ultraviolet–visible absorption spectroscopy, photon correlation spectroscopy and Fourier transform infrared spectroscopy, whereas their plasmonic properties have been tested using surface-enhanced Raman spectroscopy (SERS). The antioxidant properties of nanoparticles (NPs) have been evaluated by 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay, and the antimicrobial tests were performed using the disk diffusion assay. Their cytotoxicity has been assessed by means of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Results The experimental results confirmed the successful synthesis of biocompatible, spherical, plasmonic NPs having a mean diameter of ~40 nm and an outstanding aqueous stability. This new class of NPs exhibits a very good antioxidant activity and presents interesting inhibitory effects against Staphylococcus aureus and Candida albicans. Due to their plasmonic properties, AuNPs are used as SERS substrates for the detection of a test molecule (methylene blue) up to a concentration of 10−7 M and a pharmaceutical compound (propranolol) in solution. Cytotoxicity assays revealed that AuNPs are better tolerated by normal human dermal fibroblast cells, while the melanoma cancer cells are more sensitive. Conclusion The biocompatible AuNPs synthetized using OVEs showed significant bactericidal and antimycotic activities, the most sensitive microorganisms being S. aureus and C. albicans, both commonly involved in various dermatological infections. Moreover, the significant antioxidant effect might recommend their use for protective and/or preventive effect in various skin inflammatory conditions, including the reduction in side effects in dermatological infections. Meanwhile, the as-synthesized biocompatible AuNPs can be successfully used as SERS substrates for the detection of pharmaceutical compounds in aqueous solutions. PMID:29503540

Comparison of antimicrobial effects of titanium tetrafluoride, chlorhexidine, xylitol and sodium fluoride on streptococcus mutans: An in-vitro study.

PubMed

Eskandarian, Tahereh; Motamedifar, Mohammad; Arasteh, Peyman; Eghbali, Seyed Sajad; Adib, Ali; Abdoli, Zahra

2017-03-01

No studies have yet documented the bactericidal effects of TiF4, and its role in the treatment of dental caries, and no definite protocol has been introduced to regulate its use. The aim of this study was to determine the antimicrobial/bactericidal effects of TiF4 on Streptococcus Mutans ( S. Mutans ) and to compare it with chlorhexidine (Chx), sodium fluoride (NaF) and xylitol. This study was conducted at the Shiraz University of Medical Sciences microbiology laboratory during March 2015 to September 2015. In this in-vitro study, first a bacterial suspension was prepared and adjusted to a 0.5 McFarland standard (equivalent to 1×10 8 CFU/ml). The minimal inhibitory concentration (MIC) and minimal bactericidal concentrations (MBC) of TiF4, Chx, NaF and xylitol were assessed using broth microdilution assay and disk diffusion methods. In order to neutralize the acidic nature of TiF4, we used a sodium hydroxide preparation to obtain a pH of 7.2 and repeated all of the previous tests with the neutralized TiF4 solution. We reported the final results as percentages where appropriate. The MIC of TiF4, NaF and Chx for S. Mutans were 12.5%, 12.5% and 6.25%, respectively. At a concentration of 12.5% the inhibition zone diameters were 9 mm, 15mm and 14mm for TiF4, NaF and Chx, respectively. The MBC was 25%, 12.5% and 12.5% for TiF4, NaF and Chx, respectively. Xylitol failed to show any bactericidal or growth inhibitory effect in all of its concentrations. When we repeated the tests with an adjusted pH, identical results were obtained. TiF4 solutions have anti-growth and bactericidal effects on S. Mutans at a concentration of 12.5% which is comparable with chlorhexidine and NaF, indicating the possible use of this solution in dental practice as an anti-cariogenic agent, furthermore the antimicrobial activity is unaffected by pH of the environment.

Comparison of antimicrobial effects of titanium tetrafluoride, chlorhexidine, xylitol and sodium fluoride on streptococcus mutans: An in-vitro study

PubMed Central

Eskandarian, Tahereh; Motamedifar, Mohammad; Arasteh, Peyman; Eghbali, Seyed Sajad; Adib, Ali; Abdoli, Zahra

2017-01-01

Introduction No studies have yet documented the bactericidal effects of TiF4, and its role in the treatment of dental caries, and no definite protocol has been introduced to regulate its use. The aim of this study was to determine the antimicrobial/bactericidal effects of TiF4 on Streptococcus Mutans (S. Mutans) and to compare it with chlorhexidine (Chx), sodium fluoride (NaF) and xylitol. Methods This study was conducted at the Shiraz University of Medical Sciences microbiology laboratory during March 2015 to September 2015. In this in-vitro study, first a bacterial suspension was prepared and adjusted to a 0.5 McFarland standard (equivalent to 1×108 CFU/ml). The minimal inhibitory concentration (MIC) and minimal bactericidal concentrations (MBC) of TiF4, Chx, NaF and xylitol were assessed using broth microdilution assay and disk diffusion methods. In order to neutralize the acidic nature of TiF4, we used a sodium hydroxide preparation to obtain a pH of 7.2 and repeated all of the previous tests with the neutralized TiF4 solution. We reported the final results as percentages where appropriate. Results The MIC of TiF4, NaF and Chx for S. Mutans were 12.5%, 12.5% and 6.25%, respectively. At a concentration of 12.5% the inhibition zone diameters were 9 mm, 15mm and 14mm for TiF4, NaF and Chx, respectively. The MBC was 25%, 12.5% and 12.5% for TiF4, NaF and Chx, respectively. Xylitol failed to show any bactericidal or growth inhibitory effect in all of its concentrations. When we repeated the tests with an adjusted pH, identical results were obtained. Conclusion TiF4 solutions have anti-growth and bactericidal effects on S. Mutans at a concentration of 12.5% which is comparable with chlorhexidine and NaF, indicating the possible use of this solution in dental practice as an anti-cariogenic agent, furthermore the antimicrobial activity is unaffected by pH of the environment. PMID:28461883

Pattern formations and optimal packing.

PubMed

Mityushev, Vladimir

2016-04-01

Patterns of different symmetries may arise after solution to reaction-diffusion equations. Hexagonal arrays, layers and their perturbations are observed in different models after numerical solution to the corresponding initial-boundary value problems. We demonstrate an intimate connection between pattern formations and optimal random packing on the plane. The main study is based on the following two points. First, the diffusive flux in reaction-diffusion systems is approximated by piecewise linear functions in the framework of structural approximations. This leads to a discrete network approximation of the considered continuous problem. Second, the discrete energy minimization yields optimal random packing of the domains (disks) in the representative cell. Therefore, the general problem of pattern formations based on the reaction-diffusion equations is reduced to the geometric problem of random packing. It is demonstrated that all random packings can be divided onto classes associated with classes of isomorphic graphs obtained from the Delaunay triangulation. The unique optimal solution is constructed in each class of the random packings. If the number of disks per representative cell is finite, the number of classes of isomorphic graphs, hence, the number of optimal packings is also finite. Copyright © 2016 Elsevier Inc. All rights reserved.

Antimicrobial Activity Evaluation on Silver Doped Hydroxyapatite/Polydimethylsiloxane Composite Layer.

PubMed

Ciobanu, C S; Groza, A; Iconaru, S L; Popa, C L; Chapon, P; Chifiriuc, M C; Hristu, R; Stanciu, G A; Negrila, C C; Ghita, R V; Ganciu, M; Predoi, D

2015-01-01

The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag:HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC-American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag:HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells.

Antimicrobial Activity Evaluation on Silver Doped Hydroxyapatite/Polydimethylsiloxane Composite Layer

PubMed Central

Ciobanu, C. S.; Groza, A.; Iconaru, S. L.; Popa, C. L.; Chapon, P.; Chifiriuc, M. C.; Hristu, R.; Stanciu, G. A.; Negrila, C. C.; Ghita, R. V.; Ganciu, M.; Predoi, D.

2015-01-01

The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pressure corona discharges. Finally, the new silver doped hydroxyapatite/polydimethylsiloxane composite layer has been obtained by the thermal evaporation technique. The Ag:HAp-PDMS composite layers were characterized by various techniques, such as Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity of the Ag:HAp-PDMS composite layer was assessed against Candida albicans ATCC 10231 (ATCC—American Type Culture Collection) by culture based and confirmed by SEM and Confocal Laser Scanning Microscopy (CLSM) methods. This is the first study reporting the antimicrobial effect of the Ag:HAp-PDMS composite layer, which proved to be active against Candida albicans biofilm embedded cells. PMID:26504849

Antimicrobial resistance and beta-lactamase production of clinical isolates of prevotella and porphyromonas species.

PubMed

Bahar, Hrisi; Torun, Muzeyyen Mamal; Demirci, Mehmet; Kocazeybek, Bekir

2005-03-01

This study determined the beta-lactamase production and the antimicrobial resistance of 72 Prevotella species and 48 Porphyromonas species isolated from different clinical specimens. All strains were identified using API 32 ID. The beta-lactamase production was determined by nitrocefin disks. E test strips of benzylpenicillin, ampicillin + sulbactam, cefoxitin, clindamycin, metronidazole and imipenem were tested for each strain. Nineteen Prevotella melaninogenica, 18 Prevotella intermedia, 16 Prevotella denticola, 11 Prevotella loescheii and 8 Prevotella bivia strains were identified. Four were clindamycin resistant. The highest beta-lactamase production was found at a rate of 68.4% in P. melaninogenica species. Additionally, 33 Porphyromonas asaccharolytica and 15 Porphyromonas gingivalis strains were identified. None of them produced beta-lactamase. In view of the emerging antibiotic resistance among anaerobes, the current local susceptibility profile of our Prevotella and Porphyromonas species will establish the basis for additional surveys tracing significant changes in the antimicrobial resistance of our clinical isolates. Copyright 2005 S. Karger AG, Basel.

Accretion Disk Reverberation with Hubble Space Telescope Observations of NGC 4593: Evidence for Diffuse Continuum Lags

NASA Astrophysics Data System (ADS)

Cackett, Edward M.; Chiang, Chia-Ying; McHardy, Ian; Edelson, Rick; Goad, Michael R.; Horne, Keith; Korista, Kirk T.

2018-04-01

The Seyfert 1 galaxy NGC 4593 was monitored spectroscopically with the Hubble Space Telescope as part of a reverberation mapping campaign that also included Swift, Kepler, and ground-based photometric monitoring. During 2016 July 12–August 6, we obtained 26 spectra across a nearly continuous wavelength range of ∼1150–10000 Å. These were combined with Swift data to produce a UV/optical “lag spectrum,” which shows the interband lag relative to the Swift UVW2 band as a function of wavelength. The broad shape of the lag spectrum appears to follow the τ ∝ λ 4/3 relation seen previously in photometric interband lag measurements of other active galactic nuclei (AGNs). This shape is consistent with the standard thin disk model, but the magnitude of the lags implies a disk that is a factor of ∼3 larger than predicted, again consistent with what has been previously seen in other AGNs. In all cases these large disk sizes, which are also implied by independent gravitational microlensing of higher-mass AGNs, cannot be simply reconciled with the standard model. However, the most striking feature in this higher-resolution lag spectrum is a clear excess around the 3646 Å Balmer jump. This strongly suggests that diffuse emission from gas in the much larger broad-line region (BLR) must also contribute significantly to the interband lags. While the relative contributions of the disk and BLR cannot be uniquely determined in these initial measurements, it is clear that both will need to be considered to comprehensively model and understand AGN lag spectra.

Magnetic Field Transport in Accretion Disks

NASA Astrophysics Data System (ADS)

Jafari, Amir; Vishniac, Ethan T.

2018-02-01

The leading models for launching astrophysical jets rely on strong poloidal magnetic fields threading the central parts of their host accretion disks. Numerical simulations of magneto-rotationally turbulent disks suggest that such fields are actually advected from the environment by the accreting matter rather than generated by internal dynamos. This is puzzling from a theoretical point of view, since the reconnection of the radial field across the midplane should cause an outward drift on timescales much shorter than the accretion time. We suggest that a combination of effects are responsible for reducing the radial field near the midplane, causing efficient inward advection of the poloidal field. Magnetic buoyancy in subsonic turbulence pushes the field lines away from the midplane, decreasing the large-scale radial field in the main body of the disk. In magneto-rotationally driven turbulence, magnetic buoyancy dominates over the effects of turbulent pumping, which works against it, and turbulent diamagnetism, which works with it, in determining the vertical drift of the magnetic field. Balancing buoyancy with diffusion implies that the bending angle of the large-scale poloidal field can be very large near the surface, as required for outflows, but vanishes near the midplane, which impedes turbulent reconnection and outward diffusion. This effect becomes less efficient as the poloidal flux increases. This suggests that accretion disks are less likely to form jets if they have a modest ratio of outer to inner radii or if the ambient field is very weak. The former effect is probably responsible for the scarcity of jets in cataclysmic variable systems.

Modeling MHD accretion-ejection: episodic ejections of jets triggered by a mean-field disk dynamo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stepanovs, Deniss; Fendt, Christian; Sheikhnezami, Somayeh, E-mail: deniss@stepanovs.org, E-mail: fendt@mpia.de

2014-11-20

We present MHD simulations exploring the launching, acceleration, and collimation of jets and disk winds. The evolution of the disk structure is consistently taken into account. Extending our earlier studies, we now consider the self-generation of the magnetic field by an α{sup 2}Ω mean-field dynamo. The disk magnetization remains on a rather low level, which helps to evolve the simulations for T > 10, 000 dynamical time steps on a domain extending 1500 inner disk radii. We find the magnetic field of the inner disk to be similar to the commonly found open field structure, favoring magneto-centrifugal launching. The outermore » disk field is highly inclined and predominantly radial. Here, differential rotation induces a strong toroidal component, which plays a key role in outflow launching. These outflows from the outer disk are slower, denser, and less collimated. If the dynamo action is not quenched, magnetic flux is continuously generated, diffuses outward through the disk, and fills the entire disk. We have invented a toy model triggering a time-dependent mean-field dynamo. The duty cycles of this dynamo lead to episodic ejections on similar timescales. When the dynamo is suppressed as the magnetization falls below a critical value, the generation of the outflows and also accretion is inhibited. The general result is that we can steer episodic ejection and large-scale jet knots by a disk-intrinsic dynamo that is time-dependent and regenerates the jet-launching magnetic field.« less

Stability of a chemically active floating disk

NASA Astrophysics Data System (ADS)

Vandadi, Vahid; Jafari Kang, Saeed; Rothstein, Jonathan; Masoud, Hassan

2017-11-01

We theoretically study the translational stability of a chemically active disk located at a flat liquid-gas interface. The initially immobile circular disk uniformly releases an interface-active agent that locally changes the surface tension and is insoluble in the bulk. If left unperturbed, the stationary disk remains motionless as the agent is discharged. Neglecting the inertial effects, we numerically test whether a perturbation in the translational velocity of the disk can lead to its spontaneous and self-sustained motion. Such a perturbation gives rise to an asymmetric distribution of the released factor that could trigger and sustain the Marangoni propulsion of the disk. An implicit Fourier-Chebyshev spectral method is employed to solve the advection-diffusion equation for the concentration of the active agent. The solution, given a linear equation of state for the surface tension, provides the shear stress distribution at the interface. This and the no-slip condition on the wetted surface of the disk are then used at each time step to semi-analytically determine the Stokes flow in the semi-infinite liquid layer. Overall, the findings of our investigation pave the way for pinpointing the conditions under which interface-bound active particles become dynamically unstable.

THE PDS 66 CIRCUMSTELLAR DISK AS SEEN IN POLARIZED LIGHT WITH THE GEMINI PLANET IMAGER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolff, Schuyler G.; Greenbaum, Alexandra Z.; Perrin, Marshall

2016-02-10

We present H- and K-band imaging polarimetry for the PDS 66 circumstellar disk obtained during the commissioning of the Gemini Planet Imager (GPI). Polarization images reveal a clear detection of the disk in to the 0.″12 inner working angle (IWA) in the H band, almost three times closer to the star than the previous Hubble Space Telescope (HST) observations with NICMOS and STIS (0.″35 effective IWA). The centro-symmetric polarization vectors confirm that the bright inner disk detection is due to circumstellar scattered light. A more diffuse disk extends to a bright outer ring centered at 80 AU. We discuss several physicalmore » mechanisms capable of producing the observed ring + gap structure. GPI data confirm enhanced scattering on the east side of the disk that is inferred to be nearer to us. We also detect a lateral asymmetry in the south possibly due to shadowing from material within the IWA. This likely corresponds to a temporally variable azimuthal asymmetry observed in HST/STIS coronagraphic imaging.« less

Large-scale Density Structures in Magneto-rotational Disk Turbulence

NASA Astrophysics Data System (ADS)

Youdin, Andrew; Johansen, A.; Klahr, H.

2009-01-01

Turbulence generated by the magneto-rotational instability (MRI) is a strong candidate to drive accretion flows in disks, including sufficiently ionized regions of protoplanetary disks. The MRI is often studied in local shearing boxes, which model a small section of the disk at high resolution. I will present simulations of large, stratified shearing boxes which extend up to 10 gas scale-heights across. These simulations are a useful bridge to fully global disk simulations. We find that MRI turbulence produces large-scale, axisymmetric density perturbations . These structures are part of a zonal flow --- analogous to the banded flow in Jupiter's atmosphere --- which survives in near geostrophic balance for tens of orbits. The launching mechanism is large-scale magnetic tension generated by an inverse cascade. We demonstrate the robustness of these results by careful study of various box sizes, grid resolutions, and microscopic diffusion parameterizations. These gas structures can trap solid material (in the form of large dust or ice particles) with important implications for planet formation. Resolved disk images at mm-wavelengths (e.g. from ALMA) will verify or constrain the existence of these structures.

Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

NASA Astrophysics Data System (ADS)

Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.; Medina, A. N.; Baesso, M. L.; Astrath, N. G. C.; Astrath, F. B. G.; Santos, A. D.; Moraes, J. C. S.; Bento, A. C.

2013-11-01

The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (˜7 min) and with similar thermal expansion (˜12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its application in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10-3 cm2/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s0.5/cm2 K and volume heat capacity (5.2 ± 0.7) J/cm3 K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water).

Magnetic flux concentration and zonal flows in magnetorotational instability turbulence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Xue-Ning; Stone, James M., E-mail: xbai@cfa.harvard.edu

2014-11-20

Accretion disks are likely threaded by external vertical magnetic flux, which enhances the level of turbulence via the magnetorotational instability (MRI). Using shearing-box simulations, we find that such external magnetic flux also strongly enhances the amplitude of banded radial density variations known as zonal flows. Moreover, we report that vertical magnetic flux is strongly concentrated toward low-density regions of the zonal flow. Mean vertical magnetic field can be more than doubled in low-density regions, and reduced to nearly zero in high-density regions in some cases. In ideal MHD, the scale on which magnetic flux concentrates can reach a few diskmore » scale heights. In the non-ideal MHD regime with strong ambipolar diffusion, magnetic flux is concentrated into thin axisymmetric shells at some enhanced level, whose size is typically less than half a scale height. We show that magnetic flux concentration is closely related to the fact that the turbulent diffusivity of the MRI turbulence is anisotropic. In addition to a conventional Ohmic-like turbulent resistivity, we find that there is a correlation between the vertical velocity and horizontal magnetic field fluctuations that produces a mean electric field that acts to anti-diffuse the vertical magnetic flux. The anisotropic turbulent diffusivity has analogies to the Hall effect, and may have important implications for magnetic flux transport in accretion disks. The physical origin of magnetic flux concentration may be related to the development of channel flows followed by magnetic reconnection, which acts to decrease the mass-to-flux ratio in localized regions. The association of enhanced zonal flows with magnetic flux concentration may lead to global pressure bumps in protoplanetary disks that helps trap dust particles and facilitates planet formation.« less

Non-destructive thermal wave method applied to study thermal properties of fast setting time endodontic cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Picolloto, A. M.; Mariucci, V. V. G.; Szpak, W.

The thermal wave method is applied for thermal properties measurement in fast endodontic cement (CER). This new formula is developed upon using Portland cement in gel and it was successfully tested in mice with good biocompatibility and stimulated mineralization. Recently, thermal expansion and setting time were measured, conferring to this material twice faster hardening than the well known Angelus Mineral trioxide aggregate (MTA) the feature of fast hardening (∼7 min) and with similar thermal expansion (∼12 μstrain/ °C). Therefore, it is important the knowledge of thermal properties like thermal diffusivity, conductivity, effusivity in order to match thermally the tissue environment upon its applicationmore » in filling cavities of teeth. Photothermal radiometry technique based on Xe illumination was applied in CER disks 600 μm thick for heating, with prepared in four particle sizes (25, 38, 45, and 53) μm, which were added microemulsion gel with variation volumes (140, 150, 160, and 170) μl. The behavior of the thermal diffusivity CER disks shows linear decay for increase emulsion volume, and in contrast, thermal diffusivity increases with particles sizes. Aiming to compare to MTA, thermal properties of CER were averaged to get the figure of merit for thermal diffusivity as (44.2 ± 3.6) × 10{sup −3} cm{sup 2}/s, for thermal conductivity (228 ± 32) mW/cm K, the thermal effusivity (1.09 ± 0.06) W s{sup 0.5}/cm{sup 2} K and volume heat capacity (5.2 ± 0.7) J/cm{sup 3} K, which are in excellent agreement with results of a disk prepared from commercial MTA-Angelus (grain size < 10 μm using 57 μl of distilled water)« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shahamat, Narjes; Abbassi, Shahram, E-mail: abbassi@um.ac.ir

In the present work we study self-gravity effects on the vertical structure of a magnetized neutrino-dominated accretion disk as a central engine for gamma-ray bursts (GRBs). Some of the disk physical timescales that are supposed to play a pivotal role in the late-time evolutions of the disk, such as viscous, cooling, and diffusion timescales, have been studied. We are interested in investigating the possibility of the occurrence of X-ray flares, observed in late-time GRBs’ extended emission through the “magnetic barrier” and “fragmentation” processes in our model. The results lead us to interpret self-gravity as an amplifier for Blandford–Payne luminosity (BPmore » power) and the generated magnetic field, but a suppressor for neutrino luminosity and magnetic barrier processes via highlighting the fragmentation mechanism in the outer disk, especially for the higher mass accretion rates.« less

Three-Dimensional Radiative Hydrodynamics for Disk Stability Simulations: A Proposed Testing Standard and New Results

NASA Astrophysics Data System (ADS)

Boley, Aaron C.; Durisen, Richard H.; Nordlund, Åke; Lord, Jesse

2007-08-01

Recent three-dimensional radiative hydrodynamics simulations of protoplanetary disks report disparate disk behaviors, and these differences involve the importance of convection to disk cooling, the dependence of disk cooling on metallicity, and the stability of disks against fragmentation and clump formation. To guarantee trustworthy results, a radiative physics algorithm must demonstrate the capability to handle both the high and low optical depth regimes. We develop a test suite that can be used to demonstrate an algorithm's ability to relax to known analytic flux and temperature distributions, to follow a contracting slab, and to inhibit or permit convection appropriately. We then show that the radiative algorithm employed by Mejía and Boley et al. and the algorithm employed by Cai et al. pass these tests with reasonable accuracy. In addition, we discuss a new algorithm that couples flux-limited diffusion with vertical rays, we apply the test suite, and we discuss the results of evolving the Boley et al. disk with this new routine. Although the outcome is significantly different in detail with the new algorithm, we obtain the same qualitative answers. Our disk does not cool fast due to convection, and it is stable to fragmentation. We find an effective α~10-2. In addition, transport is dominated by low-order modes.

[In vitro studies on antioxidant and antimicrobial activities of polysaccharide from Lycoris aurea].

PubMed

Ru, Qiao-Mei; Pei, Zhen-Ming; Zheng, Hai-Lei

2008-10-01

To study the preliminary antioxidant and antimicrobial activities of polysaccharide extracted from Lycoris aurea. The scavenging activities of the polysaccharide in vitro on superoxide radical (O2-*), hydroxyl radical (*OH), alkyl radical (R*) and hydrogen peroxide (H2O2) were investigated by modified chemical systems. Meanwhile, the antimicrobial activities were tested using paper-discagar diffusion method. In general, the antioxidant activities of the polysaccharide were lower compared with Vc. However, the scavenging effects to *OH and H2O2 were parallel to Vc. Meanwhile, polysaccharide from Lycoris aurea had strong antimicrobial activities against Micrococcus luteus, Bacillus pumilus and Staphylococcus aureus. The polysaccharide extracted from L. aurea can scavenge *OH and H2O2 effectively and inhibit Gram-positive bacterias.

Radiative heating of interstellar grains falling toward the solar nebula: 1-D diffusion calculations

NASA Technical Reports Server (NTRS)

Simonelli, D. P.; Pollack, J. B.; McKay, C. P.

1997-01-01

As the dense molecular cloud that was the precursor of our Solar System was collapsing to form a protosun and the surrounding solar-nebula accretion disk, infalling interstellar grains were heated much more effectively by radiation from the forming protosun than by radiation from the disk's accretion shock. Accordingly, we have estimated the temperatures experienced by these infalling grains using radiative diffusion calculations whose sole energy source is radiation from the protosun. Although the calculations are 1-dimensional, they make use of 2-D, cylindrically symmetric models of the density structure of a collapsing, rotating cloud. The temperature calculations also utilize recent models for the composition and radiative properties of interstellar grains (Pollack et al. 1994. Astrophys. J. 421, 615-639), thereby allowing us to estimate which grain species might have survived, intact, to the disk accretion shock and what accretion rates and molecular-cloud rotation rates aid that survival. Not surprisingly, we find that the large uncertainties in the free parameter values allow a wide range of grain-survival results: (1) For physically plausible high accretion rates or low rotation rates (which produce small accretion disks), all of the infalling grain species, even the refractory silicates and iron, will vaporize in the protosun's radiation field before reaching the disk accretion shock. (2) For equally plausible low accretion rates or high rotation rates (which produce large accretion disks), all non-ice species, even volatile organics, will survive intact to the disk accretion shock. These grain-survival conclusions are subject to several limitations which need to be addressed by future, more sophisticated radiative-transfer models. Nevertheless, our results can serve as useful inputs to models of the processing that interstellar grains undergo at the solar nebula's accretion shock, and thus help address the broader question of interstellar inheritance in the solar nebula and present Solar System. These results may also help constrain the size of the accretion disk: for example, if we require that the calculations produce partial survival of organic grains into the solar nebula, we infer that some material entered the disk intact at distances comparable to or greater than a few AU. Intriguingly, this is comparable to the heliocentric distance that separates the C-rich outer parts of the current Solar System from the C-poor inner regions.

Radiative heating of interstellar grains falling toward the solar nebula: 1-D diffusion calculations.

PubMed

Simonelli, D P; Pollack, J B; McKay, C P

1997-02-01

As the dense molecular cloud that was the precursor of our Solar System was collapsing to form a protosun and the surrounding solar-nebula accretion disk, infalling interstellar grains were heated much more effectively by radiation from the forming protosun than by radiation from the disk's accretion shock. Accordingly, we have estimated the temperatures experienced by these infalling grains using radiative diffusion calculations whose sole energy source is radiation from the protosun. Although the calculations are 1-dimensional, they make use of 2-D, cylindrically symmetric models of the density structure of a collapsing, rotating cloud. The temperature calculations also utilize recent models for the composition and radiative properties of interstellar grains (Pollack et al. 1994. Astrophys. J. 421, 615-639), thereby allowing us to estimate which grain species might have survived, intact, to the disk accretion shock and what accretion rates and molecular-cloud rotation rates aid that survival. Not surprisingly, we find that the large uncertainties in the free parameter values allow a wide range of grain-survival results: (1) For physically plausible high accretion rates or low rotation rates (which produce small accretion disks), all of the infalling grain species, even the refractory silicates and iron, will vaporize in the protosun's radiation field before reaching the disk accretion shock. (2) For equally plausible low accretion rates or high rotation rates (which produce large accretion disks), all non-ice species, even volatile organics, will survive intact to the disk accretion shock. These grain-survival conclusions are subject to several limitations which need to be addressed by future, more sophisticated radiative-transfer models. Nevertheless, our results can serve as useful inputs to models of the processing that interstellar grains undergo at the solar nebula's accretion shock, and thus help address the broader question of interstellar inheritance in the solar nebula and present Solar System. These results may also help constrain the size of the accretion disk: for example, if we require that the calculations produce partial survival of organic grains into the solar nebula, we infer that some material entered the disk intact at distances comparable to or greater than a few AU. Intriguingly, this is comparable to the heliocentric distance that separates the C-rich outer parts of the current Solar System from the C-poor inner regions.

Pharmacological and phytochemical screening of Palestinian traditional medicinal plants Erodium laciniatum and Lactuca orientalis.

PubMed

Jaradat, Nidal; AlMasri, Motasem; Zaid, Abdel Naser; Othman, Dua'a Ghazi

2017-09-01

Various epidemiological studies showed that herbal remedies containing polyphenols may protect against various diseases such as cancers, vascular diseases and inflammatory pathologies. Currently, such groups of bioactive compounds have become a subject of many antimicrobials and antioxidant investigations. Accordingly, the current study aimed to conduct biological and phytochemical screening for two Palestinian traditional medicinal plants, Erodium laciniatum and Lactuca orientalis. Current plants phytoconstituents and their antioxidant activities were evaluated by using standard phytochemical methods; meanwhile, antimicrobial activities were estimated by using several types of American Type Culture Collection and multidrug resistant clinical isolates by using agar diffusion well-variant, agar diffusion disc-variant and broth microdilution methods. Phytochemical screenings showed that L. orientalis and E. laciniatum contain mixtures of secondary and primary metabolites Moreover, total flavonoid, tannins and phenols content in E. laciniatum extract were higher than the L. orientalis extracts with almost the same antioxidant potentials. Additionally, both plants organic and aqueous extracts showed various potentials of antimicrobial activity Conclusions: Overall, the studied species have a mixture of phytochemicals, flavonoids, phenols and tannins also have antioxidant and antimicrobial activities which approved their folk uses in treatments of infectious and Alzheimer diseases and simultaneously can be used as therapeutic agents in the pharmaceutical industries.

Prunus mume extract exhibits antimicrobial activity against pathogenic oral bacteria.

PubMed

Seneviratne, Chamida J; Wong, Ricky W K; Hägg, Urban; Chen, Yong; Herath, Thanuja D K; Samaranayake, P Lakshman; Kao, Richard

2011-07-01

Prunus mume is a common fruit in Asia, which has been used in traditional Chinese medicine. In this study, we focused on the antimicrobial properties of Prunus mume extract against oral pathogens related to dental caries and periodontal diseases. A total of 15 oral pathogens including Streptococcus mutans, S. sobrinus, S. mitis, S. sanguinis, Lactobacillus acidophilus, P. gingivalis, Aggregatibacter actinomycetemcomitans, and Candida species were included in the study. Initially, agar diffusion assay was performed to screen the antimicrobial activities of Prunus mume extract. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were then determined for sensitive species. Effect of Prunus mume extract on human oral keratinocytes (HOK) viability was also tested. In the agar diffusion assay, drug suspension of 2 g/mL was able to inhibit all the bacterial species tested, but not the fungal species. MIC and MBC range of Prunus mume extract against the oral bacteria was 0.15625-0.0003 g/mL and P. gingivalis being the most susceptible species. Prune extract did not cause any detrimental effect on HOK. Prunus mume extract may be a potential candidate for developing an oral antimicrobial agent to control or prevent dental diseases associated with oral pathogenic bacteria. © 2011 The Authors. International Journal of Paediatric Dentistry © 2011 BSPD, IAPD and Blackwell Publishing Ltd.

Normal versus anomalous self-diffusion in two-dimensional fluids: memory function approach and generalized asymptotic Einstein relation.

PubMed

Shin, Hyun Kyung; Choi, Bongsik; Talkner, Peter; Lee, Eok Kyun

2014-12-07

Based on the generalized Langevin equation for the momentum of a Brownian particle a generalized asymptotic Einstein relation is derived. It agrees with the well-known Einstein relation in the case of normal diffusion but continues to hold for sub- and super-diffusive spreading of the Brownian particle's mean square displacement. The generalized asymptotic Einstein relation is used to analyze data obtained from molecular dynamics simulations of a two-dimensional soft disk fluid. We mainly concentrated on medium densities for which we found super-diffusive behavior of a tagged fluid particle. At higher densities a range of normal diffusion can be identified. The motion presumably changes to sub-diffusion for even higher densities.

Normal versus anomalous self-diffusion in two-dimensional fluids: Memory function approach and generalized asymptotic Einstein relation

NASA Astrophysics Data System (ADS)

Shin, Hyun Kyung; Choi, Bongsik; Talkner, Peter; Lee, Eok Kyun

2014-12-01

Based on the generalized Langevin equation for the momentum of a Brownian particle a generalized asymptotic Einstein relation is derived. It agrees with the well-known Einstein relation in the case of normal diffusion but continues to hold for sub- and super-diffusive spreading of the Brownian particle's mean square displacement. The generalized asymptotic Einstein relation is used to analyze data obtained from molecular dynamics simulations of a two-dimensional soft disk fluid. We mainly concentrated on medium densities for which we found super-diffusive behavior of a tagged fluid particle. At higher densities a range of normal diffusion can be identified. The motion presumably changes to sub-diffusion for even higher densities.

Photon Bubbles and the Vertical Structure of Accretion Disks

NASA Astrophysics Data System (ADS)

Begelman, Mitchell C.

2006-06-01

We consider the effects of ``photon bubble'' shock trains on the vertical structure of radiation pressure-dominated accretion disks. These density inhomogeneities are expected to develop spontaneously in radiation-dominated accretion disks where magnetic pressure exceeds gas pressure, even in the presence of magnetorotational instability (MRI). They increase the rate at which radiation escapes from the disk and may allow disks to exceed the Eddington limit by a substantial factor without blowing themselves apart. To refine our earlier analysis of photon bubble transport in accretion disks, we generalize the theory of photon bubbles to include the effects of finite optical depths and radiation damping. Modifications to the diffusion law at low τ tend to ``fill in'' the low-density regions of photon bubbles, while radiation damping inhibits the formation of photon bubbles at large radii, small accretion rates, and small heights above the equatorial plane. Accretion disks dominated by photon bubble transport may reach luminosities from 10 to >100 times the Eddington limit (LEdd), depending on the mass of the central object, while remaining geometrically thin. However, photon bubble-dominated disks with α-viscosity are subject to the same thermal and viscous instabilities that plague standard radiation pressure-dominated disks, suggesting that they may be intrinsically unsteady. Photon bubbles can lead to a ``core-halo'' vertical disk structure. In super-Eddington disks the halo forms the base of a wind, which carries away substantial energy and mass, but not enough to prevent the luminosity from exceeding LEdd. Photon bubble-dominated disks may have smaller color corrections than standard accretion disks of the same luminosity. They remain viable contenders for some ultraluminous X-ray sources and may play a role in the rapid growth of supermassive black holes at high redshift.

Limiting diffusion current at rotating disk electrode with dense particle layer.

PubMed

Weroński, P; Nosek, M; Batys, P

2013-09-28

Exploiting the concept of diffusion permeability of multilayer gel membrane and porous multilayer we have derived a simple analytical equation for the limiting diffusion current at rotating disk electrode (RDE) covered by a thin layer with variable tortuosity and porosity, under the assumption of negligible convection in the porous film. The variation of limiting diffusion current with the porosity and tortuosity of the film can be described in terms of the equivalent thickness of stagnant solution layer, i.e., the average ratio of squared tortuosity to porosity. In case of monolayer of monodisperse spherical particles, the equivalent layer thickness is an algebraic function of the surface coverage. Thus, by means of cyclic voltammetry of RDE with a deposited particle monolayer we can determine the monolayer surface coverage. The effect of particle layer adsorbed on the surface of RDE increases non-linearly with surface coverage. We have tested our theoretical results experimentally by means of cyclic voltammetry measurements of limiting diffusion current at the glassy carbon RDE covered with a monolayer of 3 μm silica particles. The theoretical and experimental results are in a good agreement at the surface coverage higher than 0.7. This result suggests that convection in a monolayer of 3 μm monodisperse spherical particles is negligibly small, in the context of the coverage determination, in the range of very dense particle layers.

Genomic Characteristics of Bifidobacterium thermacidophilum Pig Isolates and Wild Boar Isolates Reveal the Unique Presence of a Putative Mobile Genetic Element with tetW for Pig Farm Isolates

PubMed Central

Tsuchida, Sayaka; Maruyama, Fumito; Ogura, Yoshitoshi; Toyoda, Atsushi; Hayashi, Tetsuya; Okuma, Moriya; Ushida, Kazunari

2017-01-01

Genomic analysis was performed on seven strains of Bifidobacterium thermacidophilum, a Sus-associated Bifidobacterium. Three strains from the feces of domestic pigs (Sus scrofa domesticus) and four strains from the rectal feces of free-range Japanese wild boars (S. s. scrofa) were compared. The phylogenetic position of these isolates suggested by genomic analyses were not concordant with that suggested by 16S rRNA sequence. There was biased distribution of genes for virulence, phage, metabolism of aromatic compounds, iron acquisition, cell division, and DNA metabolism. In particular four wild boar isolates harbored fiber-degrading enzymes, such as endoglucanase, while two of the pig isolates obtained from those grown under an intensive feeding practice with routine use of antimicrobials, particularly tetracycline harbored a tetracycline resistance gene, which was further proved functional by disk diffusion test. The tetW gene is associated with a serine recombinase of an apparently non-bifidobacterial origin. The insertion site of the tetW cassette was precisely defined by analyzing the corresponding genomic regions in the other tetracycline-susceptible isolates. The cassette may have been transferred from some other bacteria in the pig gut. PMID:28861055

Bioactive Secondary Metabolites from Schizogyne sericea (Asteraceae) Endemic to Canary Islands.

PubMed

Venditti, Alessandro; Bianco, Armandodoriano; Muscolo, Camilla; Zorzetto, Christian; Sánchez-Mateo, Candelaria C; Rabanal, Rosa M; Quassinti, Luana; Bramucci, Massimo; Damiano, Silvia; Iannarelli, Romilde; Lupidi, Giulio; Papa, Fabrizio; Petrelli, Dezemona; Vitali, Luca A; Vittori, Sauro; Maggi, Filippo

2016-07-01

Schizogyne sericea (Asteraceae) is a halophytic shrub endemic to the Canary Islands and traditionally employed as analgesic, astringent, anti-inflammatory, and vulnerary. A comprehensive phytochemical investigation was conducted on the flowering aerial parts by analyzing both essential oil constituents and polar compounds. The essential oil was dominated by p-cymene, with the noteworthy occurrence of β-pinene and thymol esters. From the EtOH extract, eight compounds were isolated and structurally elucidated. Essential oil, polar fractions, and isolates (2), (4), and (5) were separately in vitro assayed for antiproliferative activity on human tumor cell lines (A375, MDA-MB 231, and HCT116) by MTT assay, for antioxidant potential by DPPH, ABTS, and FRAP assays, and for antimicrobial activity by the agar disk diffusion method. Results revealed that essential oil and compounds 1 and 2 exert a strong inhibition on tumor cells, and in some cases, higher than that of cisplatin. Fractions containing thymol derivatives (1 and 2) and caffeoylquinic acid derivatives 4 and 5 displayed antioxidant activity comparable to that of Trolox, making S. sericea extract an interesting natural product with potential applications as preservative or in the treatment of diseases in which oxidative stress plays an important role. © 2016 Wiley-VHCA AG, Zürich.

Comparative in vitro activity of tigecycline against bacteria recovered from clinical specimens in Latin America.

PubMed

Bantar, C; Curcio, D; Fernandez Canigia, L; García, P; Guzmán Blanco, M; Leal, A L

2009-04-01

The present study was performed to evaluate the in vitro activity of tigecycline in comparison to other agents against isolates recovered from patients hospitalized in latin American. Organisms were collected in 47 clinical laboratories from 4 countries of latin America between November 2005 and October 2006 and were tested by using disk diffusion method as described by the CLSI. A total of 7966 isolates were assessed. Tigecycline proved highly active against staphylococci and enterococci (>99% susceptibility). Imipenem was the most active agent against Escherichia coli (100% susceptibility), followed by tigecycline, 98.6% susceptibility. Resistance to cefotaxime in this species was 15.3%. Global tigecycline susceptibility of Klebsiella species was 90.2%, but the susceptibility rate was significantly slower in Venezuela (82%) than in Argentina, Colombia and Chile (93%) (p<0.01). Global cefotaxime resistance to Klebsiella spp. was 32.2% and carbapenem resistance was detected in all countries. By adopting a susceptible breakpoint >or =16mm, 91.3% of the Acinetobacter isolates proved susceptible to tigecycline. Results from the present study suggest that tigecycline may be a suitable option in latin America, a region where multidrug resistance seems to be a dramatic, increasing problem and new antimicrobial choices are urgently needed.

Performance of the Chromogenic Medium CHROMagar Staph Aureus and the Staphychrom Coagulase Test in the Detection and Identification of Staphylococcus aureus in Clinical Specimens

PubMed Central

Carricajo, Anne; Treny, Axel; Fonsale, Nathalie; Bes, Michele; Reverdy, Marie Elisabeth; Gille, Yves; Aubert, Gerald; Freydiere, Anne Marie

2001-01-01

CHROMagar Staph aureus (CSAM) (CHROMagar Microbiology, Paris, France) is a new chromogenic medium designed to enable detection of colonies of Staphylococcus aureus by their pink color. A total of 775 specimens were cultured in parallel on CHROMagar Staph aureus and conventional media. Among the 267 S. aureus strains recovered on at least one medium, 263 were isolated on CSAM medium (sensitivity, 98.5%), and 245 (sensitivity, 91.8%) were isolated on conventional media. The specificity of presumptive identification of S. aureus on the basis of pink colony color on CSAM medium was 97% (493 of 508). This specificity increased to 100% when coagulase detection with the Staphychrom coagulase test was added and to 98.8% when S. aureus surface components were detected by agglutination in the Pastorex Staph Plus test. Susceptibility testing of 67 S. aureus strains, performed in parallel on pink CSAM colonies and on colonies grown on blood agar, gave similar results. Thus, rapid and accurate recognition and identification of S. aureus isolates were achieved with CSAM as the primary isolation medium, followed by the staphylocoagulase Staphychrom test. Antimicrobial susceptibility testing (disk-diffusion method or ATB STAPH System) can be performed directly on pink CSAM colonies. PMID:11427572