Schreckenberger, Paul C.; Binnicker, Matthew J.
A meeting of clinical microbiologists, representing a diverse group of practice settings, together with representatives from industry partners, discussed the pitfalls of current practices for testing and reporting antimicrobial susceptibility test results. The participants in this session identified several needs. Regarding what antibiotics to test, the discussants noted that the CLSI M100 documents must be readily accessible to all those who need them and presented in a way that is easily understood. Engineering controls (e.g., software programs) are needed that incorporate intrinsic resistance and susceptibility information and contain pathways that would allow the reporting of antibiotics for only those body locations where the antibiotic reaches therapeutic concentrations. These programs should be linked with the patient electronic medical record (EMR) and flag the physician or clinical pharmacist using an active alert messenger when testing reveals that the antibiotic(s) that the patient is receiving may not be optimal or de-escalation of the antibiotic treatment regimen is indicated. Guidelines for the practice of cascade reporting are needed and should be developed to assist laboratories in the identification and reporting of therapeutic and cost-effective antimicrobials. Personalized antibiotic reporting (PAR) software programs are needed that would deduce the optimal antibiotic for each individual patient based on a number of clinical and laboratory features. These would include the following: (i) organism identification; (ii) MIC; (iii) patient-specific factors such as weight, immune status, allergies, creatinine clearance, and albumin level; (iv) site of infection; (v) desired method of dosing (bolus versus continuous infusion); (vi) patient convenience (oral versus intravenous); (vii) drug interactions; and (viii) cost.
Felmingham, D; Brown, D F
Studies in the 1960s demonstrated the problems of variability in susceptibility testing methods, especially those affecting the performance of disc diffusion procedures. These studies made apparent the need for standardization and resulted in more clearly defined performance limits for growth medium, incubation conditions, inoculum concentration, disc content for diffusion methods, the setting of interpretative MIC breakpoints and the establishment of quality control parameters. More recently, there has been a growing interest in the use of instrumentation for reading disc diffusion tests and the endpoints of agar or broth dilution MIC determinations. Instrumentation ranges in complexity from the simple optical reading of zones of inhibition or growth endpoints, requiring operator interpretation, to more sophisticated devices for reading, recording and 'expert system' analysis of results with interfacing of instruments to laboratory information management systems. Some of the more developed systems are fully automated and can also identify the organisms tested. The pressure to reduce labour costs and provide results earlier favours the use of more automated systems whilst the requirement for resistance surveillance provides impetus for the use of systems that provide quantitative results and electronic data handling.
Wexler, Hannah M.; Goldstein, Ellie J. C.
SUMMARY Susceptibility testing of anaerobic bacteria recovered from selected cases can influence the choice of antimicrobial therapy. The Clinical and Laboratory Standards Institute (CLSI) has standardized many laboratory procedures, including anaerobic susceptibility testing (AST), and has published documents for AST. The standardization of testing methods by the CLSI allows comparisons of resistance trends among various laboratories. Susceptibility testing should be performed on organisms recovered from sterile body sites, those that are isolated in pure culture, or those that are clinically important and have variable or unique susceptibility patterns. Organisms that should be considered for individual isolate testing include highly virulent pathogens for which susceptibility cannot be predicted, such as Bacteroides, Prevotella, Fusobacterium, and Clostridium spp.; Bilophila wadsworthia; and Sutterella wadsworthensis. This review describes the current methods for AST in research and reference laboratories. These methods include the use of agar dilution, broth microdilution, Etest, and the spiral gradient endpoint system. The antimicrobials potentially effective against anaerobic bacteria include beta-lactams, combinations of beta-lactams and beta-lactamase inhibitors, metronidazole, chloramphenicol, clindamycin, macrolides, tetracyclines, and fluoroquinolones. The spectrum of efficacy, antimicrobial resistance mechanisms, and resistance patterns against these agents are described. PMID:23824372
Andersen, Klaus R.; Jørgensen, Erik; Droce, Aida; Olesen, Tom; Jensen, Bent B.; Rosenvinge, Flemming S.; Sondergaard, Teis E.
Rapid antibiotic susceptibility testing is in high demand in health care fields as antimicrobial-resistant bacterial strains emerge and spread. Here, we describe an optical screening system (oCelloScope) which, based on time-lapse imaging of 96 bacteria-antibiotic combinations at a time, introduces real-time detection of bacterial growth and antimicrobial susceptibility with imaging material to support the automatically generated graphs. Automated antibiotic susceptibility tests of a monoculture showed statistically significant antibiotic effects within 6 min and within 30 min in complex samples from pigs suffering from catheter-associated urinary tract infections. The oCelloScope system provides a fast high-throughput screening method for detecting bacterial susceptibility that might entail an earlier diagnosis and introduction of appropriate targeted therapy and thus combat the threat from multidrug-resistant pathogenic bacteria. The oCelloScope system can be employed for a broad range of applications within bacteriology and might present new vistas as a point-of-care instrument in clinical and veterinary settings. PMID:23596243
Bygdeman, S M; Mårdh, P A
The determination of the minimal growth-inhibiting concentration (MIC), the minimal metabolism-inhibiting concentration (MMC), and the minimal mycoplasmacidal concentration (MCC) of various antimicrobial compounds for Mycoplasma hominis is influenced by the pH of the test media, the inoculum size, and the incubation time, although each of these factors generally do not affect the minimal concentration more than fourfold. M. hominis is resistant to beta-lactam antibiotics, vancomycin, sulfonamides, trimethoprim, and polymyxin B. There are great differences in the susceptibility of M. hominis to various macrolide antibiotics. Thus the organism is resistant to erythromycin and oleandomycin, moderately resistant to tylosin and spiramycin, susceptible to josamycin as well as to another macrolide drug, labelled M-4365G. M. hominis is also highly susceptible to the macrolide-like compound rosaramicin and to the tetracyclines (although resistant strains occur). It is susceptible to lincomycin and clindamycin, and moderately susceptible to chloramphenicol and rifampicin. The aminoglycosides have limited activity against M. hominis.
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Antimicrobial susceptibility test disc. 866.1620 Section 866.1620 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... to determine the antimicrobial agent of choice in the treatment of bacterial diseases....
... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Antimicrobial susceptibility test powder. 866.1640 Section 866.1640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Diagnostic Devices § 866.1640 Antimicrobial...
... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Antimicrobial susceptibility test powder. 866.1640 Section 866.1640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Diagnostic Devices § 866.1640 Antimicrobial...
... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Antimicrobial susceptibility test powder. 866.1640 Section 866.1640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Diagnostic Devices § 866.1640 Antimicrobial...
... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Antimicrobial susceptibility test powder. 866.1640 Section 866.1640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Diagnostic Devices § 866.1640 Antimicrobial...
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Antimicrobial susceptibility test powder. 866.1640 Section 866.1640 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Diagnostic Devices § 866.1640 Antimicrobial...
Clinton, Lani K.; Hewitt, Carolyn; Koyamatsu, Terri; Sun, Yilun; Jamison, Ginger; Perkins, Rosalie; Tang, Li; Pounds, Stanley; Bankowski, Matthew J.
The delayed reporting of antimicrobial susceptibility testing remains a limiting factor in clinical decision-making in the treatment of bacterial infection. This study evaluates the use of forward laser light scatter (FLLS) to measure bacterial growth for the early determination of antimicrobial susceptibility. Three isolates each (two clinical isolates and one reference strain) of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were tested in triplicate using two commercial antimicrobial testing systems, the Vitek2 and the MicroScan MIC panel, to challenge the BacterioScan FLLS. The BacterioScan FLLS showed a high degree of categorical concordance with the commercial methods. Pairwise comparison with each commercial system serving as a reference standard showed 88.9% agreement with MicroScan (two minor errors) and 72.2% agreement with Vitek (five minor errors). FLLS using the BacterioScan system shows promise as a novel method for the rapid and accurate determination of antimicrobial susceptibility. PMID:27558176
Ge, Beilei; Wang, Fei; Sjölund-Karlsson, Maria; McDermott, Patrick F
Most Campylobacter infections are self-limiting but antimicrobial treatment (e.g., macrolides, fluoroquinolones) is necessary in severe or prolonged cases. Susceptibility testing continues to play a critical role in guiding therapy and epidemiological monitoring of resistance. The methods of choice for Campylobacter recommended by the Clinical and Laboratory Standards Institute (CLSI) are agar dilution and broth microdilution, while a disk diffusion method was recently standardized by the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Macrolides, quinolones, and tetracyclines are among the common antimicrobials recommended for testing. Molecular determination of Campylobacter resistance via DNA sequencing or PCR-based methods has been performed. High levels of resistance to tetracycline and ciprofloxacin are frequently reported by many national surveillance programs, but resistance to erythromycin and gentamicin in Campylobacter jejuni remains low. Nonetheless, variations in susceptibility observed over time underscore the need for continued public health monitoring of Campylobacter resistance from humans, animals, and food.
Legionella pneumophila is a Gram-negative opportunistic human pathogen that causes a severe pneumonia known as Legionnaires' disease. Notably, in the human host, the organism is believed to replicate solely within an intracellular compartment, predominantly within pulmonary macrophages. Consequently, successful therapy is predicated on antimicrobials penetrating into this intracellular growth niche. However, standard antimicrobial susceptibility testing methods test solely for extracellular growth inhibition. Here, we make use of a high-throughput assay to characterize intracellular growth inhibition activity of known antimicrobials. For select antimicrobials, high-resolution dose-response analysis was then performed to characterize and compare activity levels in both macrophage infection and axenic growth assays. Results support the superiority of several classes of nonpolar antimicrobials in abrogating intracellular growth. Importantly, our assay results show excellent correlations with prior clinical observations of antimicrobial efficacy. Furthermore, we also show the applicability of high-throughput automation to two- and three-dimensional synergy testing. High-resolution isocontour isobolograms provide in vitro support for specific combination antimicrobial therapy. Taken together, findings suggest that high-throughput screening technology may be successfully applied to identify and characterize antimicrobials that target bacterial pathogens that make use of an intracellular growth niche. PMID:26392509
Weigel, Linda M.; Sue, David; Michel, Pierre A.; Kitchel, Brandon; Pillai, Segaran P.
An effective public health response to a deliberate release of Bacillus anthracis will require a rapid distribution of antimicrobial agents for postexposure prophylaxis and treatment. However, conventional antimicrobial susceptibility testing for B. anthracis requires a 16- to 20-h incubation period. To reduce this time, we have combined a modified broth microdilution (BMD) susceptibility testing method with real-time quantitative PCR (qPCR). The growth or inhibition of growth of B. anthracis cells incubated in 2-fold dilutions of ciprofloxacin (CIP) (0.015 to 16 μg/ml) or doxycycline (DOX) (0.06 to 64 μg/ml) was determined by comparing the fluorescence threshold cycle (CT) generated by target amplification from cells incubated with each drug concentration with the CT of the no-drug (positive growth) control. This ΔCT readily differentiated susceptible and nonsusceptible strains. Among susceptible strains, the median ΔCT values were ≥7.51 cycles for CIP and ≥7.08 cycles for DOX when drug concentrations were at or above the CLSI breakpoint for susceptibility. For CIP- and DOX-nonsusceptible strains, the ΔCT was <1.0 cycle at the breakpoint for susceptibility. When evaluated with 14 genetically and geographically diverse strains of B. anthracis, the rapid method provided the same susceptibility results as conventional methods but required less than 6 h, significantly decreasing the time required for the selection and distribution of appropriate medical countermeasures. PMID:20439614
García-Sánchez, José E; García-Sánchez, Enrique; García-García, María Inmaculada
The anaerobic bacteria resistance to antibiotics is increasing, and even has appeared against the most active of those, like metronidazol and carbapenems. This fact forces to make and periodical sensibility tests -at least in the most aggressive and virulent species, in cases that they are isolated from life locations and in the absence of therapeutic response- to check the local sensibility and to establish suitable empiric therapies, all based on multicentric studies carried out in order to this or well to check the activity of new antibiotics. For the laboratory routine, the easiest sensibility method is the E-test/MIC evaluator. Another alternative is microdilution, that's only normalized for Bacteroides. There are preliminary facts that allow the use of disc diffusion method in some species of Bacteroides and Clostridium. For the temporal and multicentric studies, the procedure is dilution in agar plate, the reference method. Copyright © 2014 Elsevier España, S.L. All rights reserved.
Jorgensen, J H; Redding, J S; Maher, L A; Howell, A W
The need for complex growth media has complicated routine susceptibility testing of Haemophilus influenzae because of antagonism of certain antimicrobial agents by the medium or because of difficulties in interpretation of growth endpoints. Haemophilus test medium (HTM) is a simple, transparent medium for broth- or agar-based tests with H. influenzae. HTM incorporates Mueller-Hinton medium with additions of 15 micrograms of hematin per ml, 15 micrograms of NAD per ml, and 5 mg of yeast extract per ml as growth-promoting additives. Agar or broth microdilution MICs of 10 antimicrobial agents for a collection of 179 H. influenzae isolates determined by using HTM compared favorably with MICs determined by the conventional agar or broth dilution methods recommended by the National Committee for Clinical Laboratory Standards. Disk diffusion tests performed with HTM allowed accurate categorization of susceptible and resistant strains and were easier to interpret than tests performed with Mueller-Hinton chocolate agar. A particular advantage of HTM was the reliability of broth- or agar-based test results with trimethoprim-sulfamethoxazole. The results of the study suggest modification of current National Committee for Clinical Laboratory Standards MIC-interpretive criteria for H. influenzae with amoxicillin-clavulanate, chloramphenicol, and trimethoprim-sulfamethoxazole. Error rate-bounded analysis of MICs and disk diffusion zone sizes also suggest modified zone-interpretive criteria for ampicillin, amoxicillin-clavulanate, chloramphenicol, and tetracycline with HTM or conventional media. Interpretive zone sizes are newly proposed for cefaclor and rifampin disk diffusion tests. PMID:3500965
Chiang, Ya-Ling; Lin, Chi-Hung; Yen, Muh-Yong; Su, Yuan-Deng; Chen, Shean-Jen; Chen, How-Foo
Utilizing the ultra sensitivity of surface plasmon resonance (SPR) biosensor to examine drug resistance of bacteria was studied in this research. Susceptible and resistant strains of Escherichia coli JM109 to ampicillin and those of Staphylococcus epidermidis to tetracycline, served as a blind test, were examined. The bacteria adhered on the Au thin film was treated by the injection of antibiotic flow. The optical property change of the bacteria responded to antibiotics were recorded through SPR mechanism. As a result, the susceptible strain of E. coli generally revealed more than three times of SPR angle shift when compared to the resistant one; the susceptible strain of S. epidermidis revealed irregular SPR angle shift while the resistant strain kept the SPR angle almost unchanged. The new SPR method took less than 2h of antibiotic treatment time to complete the antimicrobial susceptibility test. Different from conventional applications of SPR, specific antibodies is not required in this method. As compared to the conventional assays, Kirby-Bauer disk diffusion and variations of broth microdilution usually take 1 day to weeks to issue the report. Using this SPR assay can greatly reduce the waiting period for laboratory tests, and can therefore benefit patients who need proper antibiotic treatments to control bacterial infections. The sensitivity of the SPR biosensor built for the application is around 1.4 x 10(-4) on the refractive index.
... of antimicrobic-impregnated paper discs used to measure by a disc-agar diffusion technique or a disc... antimicrobial agents. In the disc-agar diffusion technique, bacterial susceptibility is ascertained by directly...
... of antimicrobic-impregnated paper discs used to measure by a disc-agar diffusion technique or a disc... antimicrobial agents. In the disc-agar diffusion technique, bacterial susceptibility is ascertained by directly...
... of antimicrobic-impregnated paper discs used to measure by a disc-agar diffusion technique or a disc... antimicrobial agents. In the disc-agar diffusion technique, bacterial susceptibility is ascertained by directly...
Jorgensen, J H; Lee, J C; Jones, P M
A chemically defined growth medium containing physiological concentrations of magnesium and calcium ions was utilized in a microdilution procedure for antimicrobial drug susceptibility testing of Pseudomonas aeruginosa. Determinations of growth end points were simplified by use of sodium citrate as a sole carbon source and bromothymol blue as a pH indicator. Growth of the test organisms was detectable by a change in the indicator color from green to blue after alkalinization of the medium due to citrate utilization. Minimal inhibitory concentrations of amikacin, carbenicillin, gentamicin, and tobramycin were determined on 100 recent clinical isolates of Pseudomonas. Parallel determinations using the microdilution procedure and a conventional tube-broth dilution technique incorporating Mueller-Hinton broth with identical magnesium and calcium content generally agreed within one twofold dilution. Modal minimal inhibitory concentrations for susceptible strains using the microdilution method were: amikacin, 6 mug/ml; carbenicillin, 50 mug/ml; gentamicin, 1.5 mug/ml; tobramycin, 1.5 mug/ml. This modified microdilution technique allowed rapid, definitive minimal inhibitory concentration determinations, using growth end points defined by a color indicator change.
Macià, M D; Rojo-Molinero, E; Oliver, A
Biofilms are organized bacterial communities embedded in an extracellular polymeric matrix attached to living or abiotic surfaces. The development of biofilms is currently recognized as one of the most relevant drivers of persistent infections. Among them, chronic respiratory infection by Pseudomonas aeruginosa in cystic fibrosis patients is probably the most intensively studied. The lack of correlation between conventional susceptibility test results and therapeutic success in chronic infections is probably a consequence of the use of planktonically growing instead of biofilm-growing bacteria. Therefore, several in vitro models to evaluate antimicrobial activity on biofilms have been implemented over the last decade. Microtitre plate-based assays, the Calgary device, substratum suspending reactors and the flow cell system are some of the most used in vitro biofilm models for susceptibility studies. Likewise, new pharmacodynamic parameters, including minimal biofilm inhibitory concentration, minimal biofilm-eradication concentration, biofilm bactericidal concentration, and biofilm-prevention concentration, have been defined in recent years to quantify antibiotic activity in biofilms. Using these parameters, several studies have shown very significant quantitative and qualitative differences for the effects of most antibiotics when acting on planktonic or biofilm bacteria. Nevertheless, standardization of the procedures, parameters and breakpoints, by official agencies, is needed before they are implemented in clinical microbiology laboratories for routine susceptibility testing. Research efforts should also be directed to obtaining a deeper understanding of biofilm resistance mechanisms, the evaluation of optimal pharmacokinetic/pharmacodynamic models for biofilm growth, and correlation with clinical outcome. © 2014 The Authors Clinical Microbiology and Infection © 2014 European Society of Clinical Microbiology and Infectious Diseases.
... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Culture medium for antimicrobial susceptibility tests. 866.1700 Section 866.1700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND....1700 Culture medium for antimicrobial susceptibility tests. (a) Identification. A culture medium...
... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Culture medium for antimicrobial susceptibility tests. 866.1700 Section 866.1700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND....1700 Culture medium for antimicrobial susceptibility tests. (a) Identification. A culture medium...
... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Culture medium for antimicrobial susceptibility tests. 866.1700 Section 866.1700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND....1700 Culture medium for antimicrobial susceptibility tests. (a) Identification. A culture medium...
Hidalgo, A; Carvajal, A; García-Feliz, C; Osorio, J; Rubio, P
This study is the first conducted in Spain to evaluate antimicrobial susceptibility of field isolates of Brachyspira hyodysenteriae. One hundred and eight isolates of the bacterium, recovered from different Spanish swine farms between 2000 and 2007, were investigated. The minimum inhibitory concentrations (MIC) of erythromycin, tylosin, tiamulin, valnemulin, clindamycin and lincomycin were determined using a broth microdilution technique. Most of the isolates showed poor susceptibility to erythromycin (MIC(90)>256 microg/ml), tylosin (MIC(90)>256 microg/ml), clindamycin (MIC(90)>4 microg/ml) and lincomycin (MIC(90)=128 microg/ml). Reduced susceptibility to tiamulin and valnemulin was observed with a MIC>2 microg/ml in 17.6% and 7.41% of the B. hyodysenteriae isolates, respectively. Moreover, a survival analysis permitted the detection of an increasing trend in the MIC values for almost all the antimicrobials used in the treatment of swine dysentery when comparing recent isolates (from 2006 to 2007) with those recovered in earlier years (between 2000 and 2004).
Waters, Valerie; Ratjen, Felix
Antibiotic therapy for acute pulmonary exacerbations in people with cystic fibrosis (CF) is usually chosen based on the results of antimicrobial susceptibility testing of individual drugs. Combination antimicrobial susceptibility testing assesses the efficacy of drug combinations including two or three antibiotics in vitro and can often demonstrate antimicrobial efficacy against bacterial isolates even when individual antibiotics have little or no effect. Therefore, choosing antibiotics based on combination antimicrobial susceptibility testing could potentially improve response to treatment in people with CF with acute exacerbations. To compare antibiotic therapy based on conventional antimicrobial susceptibility testing to antibiotic therapy based on combination antimicrobial susceptibility testing in the treatment of acute pulmonary exacerbations in people with CF and chronic infection with P. aeruginosa. We identified relevant trials from the Group's Cystic Fibrosis Trials Register. Most recent search: November 2007. Randomised and quasi-randomised controlled trials of antibiotic therapy based on conventional antimicrobial susceptibility testing compared to antibiotic therapy based on combination antimicrobial susceptibility testing in the treatment of acute pulmonary exacerbations in CF due to chronic infection with P. aeruginosa. Both authors independently selected trials, assessed their quality and extracted data from eligible studies. Additionally, the authors contacted the study investigators to obtain further information. The search identified one study eligible for inclusion in the review. This study prospectively assessed whether the use of multiple combination bactericidal antibiotic testing (MCBT) improved clinical outcomes in participants with acute pulmonary exacerbations of CF who were infected with multiresistant bacteria. 132 participants were randomised in the study. The study investigators provided data specific to the participants who were only
Lubbers, Brian V; Turnidge, John
Bovine respiratory disease (BRD) is one of the most common diseases of cattle worldwide. Given the significant bacterial component of this disease, antimicrobial agents remain one of the mainstays of therapy. However, the potential welfare and economic impact resulting from the selection of inappropriate antimicrobial therapy for BRD poses significant risks to both animal and animal owner. To determine the 'best' antimicrobial agent for a specific case, the decision-making process needs to incorporate all available evidence, often including the results of bacterial culture and antimicrobial susceptibility testing. While antimicrobial susceptibility testing can be a valuable diagnostic tool, integrating the test results into the clinical decision making process can be a challenging experience. This review details the process by which interpretive criteria for susceptibility tests are developed. Principles for how to best integrate antimicrobial susceptibility testing, both at the individual animal test and aggregate test levels, into the clinical decision making process are discussed. Non-traditional testing methodologies and how they may improve susceptibility testing in the future are also reviewed. Copyright © 2014 Elsevier Ltd. All rights reserved.
Papich, Mark G
Veterinarians are quick to attribute an unsuccessful antimicrobial treatment to a failure of the culture and susceptibility test. There are many reasons why antimicrobial treatment fails. When evaluating a patient that has failed to respond to therapy, one must consider any of the many factors that contribute to antibiotic failure.
Waters, Valerie; Ratjen, Felix
The antibiotics used to treat pulmonary infections in people with cystic fibrosis are typically chosen based on the results of antimicrobial susceptibility testing performed on bacteria traditionally grown in a planktonic mode (grown in a liquid). However, there is considerable evidence to suggest that Pseudomonas aeruginosa actually grows in a biofilm (or slime layer) in the airways of cystic fibrosis patients with chronic pulmonary infections. Therefore, choosing antibiotics based on biofilm rather than conventional antimicrobial susceptibility testing could potentially improve response to treatment of Pseudomonas aeruginosa in people with cystic fibrosis. To compare biofilm antimicrobial susceptibility testing-driven therapy to conventional antimicrobial susceptibility testing-driven therapy in the treatment of Pseudomonas aeruginosa infection in people with cystic fibrosis. We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched a registry of ongoing trials and the reference lists of relevant articles and reviews.Most recent search: 02 August 2012. Randomized controlled trials of antibiotic therapy based on biofilm antimicrobial susceptibility testing compared to antibiotic therapy based on conventional antimicrobial susceptibility testing in the treatment of Pseudomonas aeruginosa pulmonary infection in individuals with cystic fibrosis. Both authors independently selected trials, assessed their risk of bias and extracted data from eligible trials. Additionally, the authors contacted the trial investigators to obtain further information. The search identified one multicentre, randomized, double-blind controlled clinical trial eligible for inclusion in the review (39 participants). This trial prospectively assessed whether the use of biofilm antimicrobial susceptibility testing improved microbiological and clinical outcomes in participants
Mach, Kathleen E.; Mohan, Ruchika; Baron, Ellen Jo; Shih, Mei-Chiung; Gau, Vincent; Wong, Pak Kin; Liao, Joseph C.
Purpose A significant barrier to efficient antibiotic management of infection is that the standard diagnostic methodologies do not provide results at the point of care. The delays between sample collection and bacterial culture and antibiotic susceptibility reporting have led to empirical use of antibiotics, contributing to the emergence of drug resistant pathogens. As a key step toward the development of a point of care device for determining the antibiotic susceptibility of urinary tract pathogens, we report on a biosensor based antimicrobial susceptibility test. Materials and Methods For assay development bacteria were cultured with or without antibiotics, and growth was quantitated by determining viable counts and electrochemical biosensor measurement of bacterial 16S rRNA. To determine antibiotic susceptibility directly from patient samples, urine was cultured on antibiotic plates for 2.5 hours and growth was determined by electrochemical measurement of bacterial 16S rRNA. For assay validation 252 urine samples were collected from patients at the Spinal Cord Injury Service at Veterans Affairs Palo Alto Health Care System. The biosensor based antimicrobial susceptibility test was completed for samples containing gram-negative organisms. Pathogen identification and antibiotic susceptibility results were compared between our assay and standard microbiological analysis. Results A direct biosensor quantitation of bacterial 16S rRNA can be used to monitor bacterial growth for a biosensor based antimicrobial susceptibility test. Clinical validation of a biosensor based antimicrobial susceptibility test with patient urine samples demonstrated that this test was 94% accurate in 368 pathogen-antibiotic tests compared to standard microbiological analysis. Conclusions This biosensor based antimicrobial susceptibility test, in concert with our previously described pathogen identification assay, can provide culture and susceptibility information directly from a urine sample
[Consensus for antimicrobial susceptibility testing for Enterobacteriaceae. Subcommittee on Antimicrobials, SADEBAC (Argentinian Society of Clinical Bacteriology), Argentinian Association of Microbiology].
Famiglietti, A; Quinteros, M; Vázquez, M; Marín, M; Nicola, F; Radice, M; Galas, M; Pasterán, F; Bantar, C; Casellas, J M; Kovensky Pupko, J; Couto, E; Goldberg, M; Lopardo, H; Gutkind, G; Soloaga, R
Taking into account previous recommendations from the National Committee for Clinical Laboratory Standards (NCCLS), the Antimicrobial Committee, Sociedad Argentina de Bacteriología Clínica (SADEBAC), Asociación Argentina de Microbiología (AAM), and the experience from its members and some invited microbiologists, a consensus was obtained for antimicrobial susceptibility testing and interpretation in most frequent enterobacterial species isolated from clinical samples in our region. This document describes the natural antimicrobial resistance of some Enterobacteriaceae family members, including the resistance profiles due to their own chromosomal encoded beta-lactamases. A list of the antimicrobial agents that should be tested, their position on the agar plates, in order to detect the most frequent antimicrobial resistance mechanisms, and considerations on which antimicrobial agents should be reported regarding to the infection site and patient characteristics are included. Also, a description on appropriate phenotypic screening and confirmatory test for detection of prevalent extended spectrum beta-lactamases in our region are presented. Finally, a summary on frequent antimicrobial susceptibility profiles and their probably associated resistance mechanisms, and some infrequent antimicrobial resistance profiles that deserve confirmation are outlined.
Brooks, Matthew B; Morley, Paul S; Dargatz, David A; Hyatt, Doreene R; Salman, M D; Akey, Bruce L
To describe antimicrobial susceptibility testing practices of veterinary diagnostic laboratories in the United States and evaluate the feasibility of collating this information for the purpose of monitoring antimicrobial resistance in bacterial isolates from animals. Cross-sectional study. A questionnaire was mailed to veterinary diagnostic laboratories throughout the United States to identify those laboratories that conduct susceptibility testing. Nonrespondent laboratories were followed up through telephone contact and additional mailings. Data were gathered regarding methods of susceptibility testing, standardization of methods, data management, and types of isolates tested. Eighty-six of 113 (76%) laboratories responded to the survey, and 64 of the 86 (74%) routinely performed susceptibility testing on bacterial isolates from animals. Thirty-four of the 36 (94%) laboratories accredited by the American Association of Veterinary Laboratory Diagnosticians responded to the survey. Laboratories reported testing > 160,000 bacterial isolates/y. Fifty-one (88%) laboratories reported using the Kirby-Bauer disk diffusion test to evaluate antimicrobial susceptibility; this accounted for 65% of the isolates tested. Most (87%) laboratories used the NCCLS (National Committee for Clinical Laboratory Standards) documents for test interpretation. Seventy-five percent of the laboratories performed susceptibility testing on bacterial isolates only when they were potential pathogens. The veterinary diagnostic laboratories represent a comprehensive source of data that is not easily accessible in the United States. Variability in testing methods and data storage would present challenges for data aggregation, summary, and interpretation.
Canut-Blasco, Andrés; Calvo, Jorge; Rodríguez-Díaz, Juan Carlos; Martínez-Martínez, Luis
Cumulative reports on antimicrobial susceptibility tests data are important for selecting empirical treatments, as an educational tool in programs on antimicrobial use, and for establishing breakpoints defining clinical categories. These reports should be based on data validated by clinical microbiologists using diagnostic samples (not surveillance samples). In order to avoid a bias derived from including several isolates obtained from the same patient, it is recommended that, for a defined period, only the first isolate is counted. A minimal number of isolates per species should be presented: a figure of >=30 isolates is statistically acceptable. The report is usually presented in a table format where, for each cell, information on clinically relevant microorganisms-antimicrobial agents is presented. Depending on particular needs, multiple tables showing data related to patients, samples, services or special pathogens can be prepared.
Waters, Valerie; Ratjen, Felix
The antibiotics used to treat pulmonary infections in people with cystic fibrosis are typically chosen based on the results of antimicrobial susceptibility testing performed on bacteria traditionally grown in a planktonic mode (grown in a liquid). However, there is considerable evidence to suggest that Pseudomonas aeruginosa actually grows in a biofilm (or slime layer) in the airways of people with cystic fibrosis with chronic pulmonary infections. Therefore, choosing antibiotics based on biofilm rather than conventional antimicrobial susceptibility testing could potentially improve response to treatment of Pseudomonas aeruginosa in people with cystic fibrosis. This is an update of a previously published Cochrane Review. To compare biofilm antimicrobial susceptibility testing-driven therapy to conventional antimicrobial susceptibility testing-driven therapy in the treatment of Pseudomonas aeruginosa infection in people with cystic fibrosis. We searched the Cochrane Cystic Fibrosis Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books. We also searched a registry of ongoing trials and the reference lists of relevant articles and reviews.Most recent search: 19 November 2014. Randomized controlled trials of antibiotic therapy based on biofilm antimicrobial susceptibility testing compared to antibiotic therapy based on conventional antimicrobial susceptibility testing in the treatment of Pseudomonas aeruginosa pulmonary infection in people with cystic fibrosis. Both authors independently selected trials, assessed their risk of bias and extracted data from eligible trials. Additionally, the review authors contacted the trial investigators to obtain further information. The searches identified two multicentre, randomized, double-blind controlled clinical trials eligible for inclusion in the review with a total of 78 participants; one trial was done in people who were clinically stable, the other in people
Kulathunga, Dharmasiri G R S; Rubin, Joseph E
The re-emergence of swine dysentery (Brachyspira-associated muco-haemorrhagic colitis) since the late 2000's has illuminated diagnostic challenges associated with this genus. The methods used to detect, identify and characterize Brachyspira from clinical samples have not been standardized and laboratories frequently rely heavily on in-house techniques. Particularly concerning is the lack of standardized methods for determining and interpreting the antimicrobial susceptibility of Brachyspira spp. The integration of laboratory data into a treatment plan is a critical component of prudent antimicrobial usage, the lack of standardized methods is therefore an important limitation to the evidence based use of antimicrobials. This review will focus on describing the methodological limitations and inconsistencies between current susceptibility testing schemes employed for Brachyspira, provide an overview of what we do know about the susceptibility of these organisms and suggest future directions to improve and standardize diagnostic strategies.
Dayao, Denise Ann E; Kienzle, Marco; Gibson, Justine S; Blackall, Patrick J; Turni, Conny
The aim of this study was to examine the antimicrobial susceptibility of 97 Haemophilus parasuis cultured from Australian pigs. As there is no existing standard antimicrobial susceptibility technique available for H. parasuis, methods utilising the supplemented media, BA/SN for disc diffusion and test medium broth (TMB) for a microdilution technique, were initially evaluated with the reference strains recommended by the Clinical and Laboratory Standards Institute. The results of the media evaluation suggested that BA/SN and TMB can be used as suitable media for susceptibility testing of H. parasuis. The proposed microdilution technique was then used with 97 H. parasuis isolates and nine antimicrobial agents. The study found that Australian isolates showed elevated minimum inhibitory concentrations (MICs) for ampicillin (1%), penicillin (2%), erythromycin (7%), tulathromycin (9%), tilmicosin (22%), tetracycline (31%) and trimethoprim-sulfamethoxazole (40%). This study has described potential antimicrobial susceptibility methods for H. parasuis and has detected a low percentage of Australian H. parasuis isolates with elevated antimicrobial MICs.
Nash, Kevin A.; Wallace, Richard J.
Summary: Within the past 10 years, treatment and diagnostic guidelines for nontuberculous mycobacteria have been recommended by the American Thoracic Society (ATS) and the Infectious Diseases Society of America (IDSA). Moreover, the Clinical and Laboratory Standards Institute (CLSI) has published and recently (in 2011) updated recommendations including suggested antimicrobial and susceptibility breakpoints. The CLSI has also recommended the broth microdilution method as the gold standard for laboratories performing antimicrobial susceptibility testing of nontuberculous mycobacteria. This article reviews the laboratory, diagnostic, and treatment guidelines together with established and probable drug resistance mechanisms of the nontuberculous mycobacteria. PMID:22763637
Waters, Valerie; Ratjen, Felix
Antibiotic therapy for acute pulmonary exacerbations in people with cystic fibrosis (CF) is usually chosen based on the results of antimicrobial susceptibility testing of individual drugs. Combination antimicrobial susceptibility testing assesses the efficacy of drug combinations including two or three antibiotics in vitro and can often demonstrate antimicrobial efficacy against bacterial isolates even when individual antibiotics have little or no effect. Therefore, choosing antibiotics based on combination antimicrobial susceptibility testing could potentially improve response to treatment in people with CF with acute exacerbations. This is an updated version of a previously published review. To compare antibiotic therapy based on conventional antimicrobial susceptibility testing to antibiotic therapy based on combination antimicrobial susceptibility testing in the treatment of acute pulmonary exacerbations in people with CF and chronic infection with P. aeruginosa. We identified relevant trials from the Group's Cystic Fibrosis Trials Register.Latest search: 27 July 2015. Randomised and quasi-randomised controlled trials of antibiotic therapy based on conventional antimicrobial susceptibility testing compared to antibiotic therapy based on combination antimicrobial susceptibility testing in the treatment of acute pulmonary exacerbations in CF due to chronic infection with P. aeruginosa. Both authors independently selected trials, assessed their quality and extracted data from eligible studies. Additionally, the authors contacted the study investigators to obtain further information. The search identified one study eligible for inclusion in the review. This study prospectively assessed whether the use of multiple combination bactericidal antibiotic testing (MCBT) improved clinical outcomes in participants with acute pulmonary exacerbations of CF who were infected with multiresistant bacteria. A total of 132 participants were randomised in the study. The study
Chung, Chih-Yao; Wang, Jhih-Cheng; Chuang, Han-Sheng
This study combined optical diffusometry and bead-based immunoassays to develop a novel technique for quantifying the growth of specific microorganisms and achieving rapid AST. Diffusivity rises when live bacteria attach to particles, resulting in additional energy from motile microorganisms. However, when UV-sterilized (dead) bacteria attach to particles, diffusivity declines. The experimental data are consistent with the theoretical model predicted according to the equivalent volume diameter. Using this diffusometric platform, the susceptibility of Pseudomonas aeruginosa to the antibiotic gentamicin was tested. The result suggests that the proliferation of bacteria is effectively controlled by gentamicin. This study demonstrated a sensitive (one bacterium on single particles) and time-saving (within 2 h) platform with a small sample volume (~0.5 μL) and a low initial bacteria count (50 CFU per droplet ~ 105 CFU/mL) for quantifying the growth of microorganisms depending on Brownian motion. The technique can be applied further to other bacterial strains and increase the success of treatments against infectious diseases in the near future. PMID:26863001
Smith, Kenneth P; Richmond, David L; Brennan-Krohn, Thea; Elliott, Hunter L; Kirby, James E
Antibiotic resistance is compromising our ability to treat bacterial infections. Clinical microbiology laboratories guide appropriate treatment through antimicrobial susceptibility testing (AST) of patient bacterial isolates. However, increasingly, pathogens are developing resistance to a broad range of antimicrobials, requiring AST of alternative agents for which no commercially available testing methods are available. Therefore, there exists a significant AST testing gap in which current methodologies cannot adequately address the need for rapid results in the face of unpredictable susceptibility profiles. To address this gap, we developed a multicomponent, microscopy-based AST (MAST) platform capable of AST determinations after only a 2 h incubation. MAST consists of a solid-phase microwell growth surface in a 384-well plate format, inkjet printing-based application of both antimicrobials and bacteria at any desired concentrations, automated microscopic imaging of bacterial replication, and a deep learning approach for automated image classification and determination of antimicrobial minimal inhibitory concentrations (MICs). In evaluating a susceptible strain set, 95.8% were within ±1 and 99.4% were within ±2, twofold dilutions, respectively, of reference broth microdilution MIC values. Most (98.3%) of the results were in categorical agreement. We conclude that MAST offers promise for rapid, accurate, and flexible AST to help address the antimicrobial testing gap.
Sharma, Meenu; Thibert, Louise; Chedore, Pamela; Shandro, Cary; Jamieson, Frances; Tyrrell, Gregory; Christianson, Sara; Soualhine, Hafid; Wolfe, Joyce
The purpose of this study was to establish a standardized protocol for second-line antimicrobial susceptibility testing of Mycobacterium tuberculosis using the Bactec MGIT 960 system in Canadian laboratories. Four Canadian public health laboratories compared the susceptibility testing results of 9 second-line antimicrobials between the Bactec 460 and Bactec MGIT 960 systems. Based on the data generated, we have established that the Bactec MGIT 960 system provides results comparable to those obtained with the previous Bactec 460 method. The critical concentrations established for the testing of the antimicrobials used are as follows: amikacin, 1 μg/ml; capreomycin, 2.5 μg/ml; ethionamide, 5 μg/ml; kanamycin, 2.5 μg/ml; linezolid, 1 μg/ml; moxifloxacin, 0.25 μg/ml; ofloxacin, 2 μg/ml; p-aminosalicylic acid, 4 μg/ml; rifabutin, 0.5 μg/ml. PMID:21998413
Sharma, Meenu; Thibert, Louise; Chedore, Pamela; Shandro, Cary; Jamieson, Frances; Tyrrell, Gregory; Christianson, Sara; Soualhine, Hafid; Wolfe, Joyce
The purpose of this study was to establish a standardized protocol for second-line antimicrobial susceptibility testing of Mycobacterium tuberculosis using the Bactec MGIT 960 system in Canadian laboratories. Four Canadian public health laboratories compared the susceptibility testing results of 9 second-line antimicrobials between the Bactec 460 and Bactec MGIT 960 systems. Based on the data generated, we have established that the Bactec MGIT 960 system provides results comparable to those obtained with the previous Bactec 460 method. The critical concentrations established for the testing of the antimicrobials used are as follows: amikacin, 1 μg/ml; capreomycin, 2.5 μg/ml; ethionamide, 5 μg/ml; kanamycin, 2.5 μg/ml; linezolid, 1 μg/ml; moxifloxacin, 0.25 μg/ml; ofloxacin, 2 μg/ml; p-aminosalicylic acid, 4 μg/ml; rifabutin, 0.5 μg/ml.
... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Culture medium for antimicrobial susceptibility tests. 866.1700 Section 866.1700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Diagnostic Devices § 866...
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Culture medium for antimicrobial susceptibility tests. 866.1700 Section 866.1700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Diagnostic Devices § 866...
García-Agudo, Lidia; García-Martos, Pedro; Jesús, Iría; Rodríguez-Iglesias, Manuel
Rapidly growing mycobacteria (RGM) are considered opportunistic pathogens. An increasing number of post traumatic or surgical infections are caused by these microorganisms. To determine the antimicrobial susceptibility of RGM using the E-test method. A total of 54 isolates of RGM was obtained from several clinical samples and selected for this study Strains were identified to the species level by phenotypic and biochemical characteristics, PCR-restriction enzyme analysis of the hsp65 gene (PRA) and sequencing of the 16S rRNA. Susceptibility was investigated by E-test to amikacin, cefoxitin, ciprofioxacin, clarithromycin, imipenem, quinupristin/dalfopristin, linezolid and tigecycline. Twelve different species of RGM were identified: Mycobacterium fortuitum (23 strains), M chelonae (11), M abscessus (10), Msenegalense (2), Malvei (1), Mbrumae (1), Mmageritense (1), mucogenicum (1), M neoaurum (1), Mperegrinum (1), M septicum (1) y M smegmatis (1). All the strains were inhibited by low concentrations of amikacin and tigecycline. Susceptibility to cefoxitin, fluoroquinolones, clarithromycin, imipenem and linezolid was variable. All but two strains were resistant to quinupristin/ dalfopristin. Due to the uneven antimicrobial susceptibility of different species of RGM, an antimicrobial susceptibility test is mandatory for these microorganisms. The E-test method is well suited to determine minimum inhibitory concentrations.
Waters, Valerie; Ratjen, Felix
Antibiotic therapy for acute pulmonary exacerbations in people with cystic fibrosis is usually chosen based on the results of antimicrobial susceptibility testing of individual drugs. Combination antimicrobial susceptibility testing assesses the efficacy of drug combinations including two or three antibiotics in vitro and can often demonstrate antimicrobial efficacy against bacterial isolates even when individual antibiotics have little or no effect. Therefore, choosing antibiotics based on combination antimicrobial susceptibility testing could potentially improve response to treatment in people with cystic fibrosis with acute exacerbations. This is an updated version of a previously published review. To compare antibiotic therapy based on conventional antimicrobial susceptibility testing to antibiotic therapy based on combination antimicrobial susceptibility testing in the treatment of acute pulmonary exacerbations in people with cystic fibrosis and chronic infection with Pseudomonas aeruginosa. We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Cystic Fibrosis Trials Register which comprises of references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. Date of latest search: 19 December 2016.We also searched ongoing trials registries. Date of latest search: 08 March 2017. Randomised and quasi-randomised controlled studies of antibiotic therapy based on conventional antimicrobial susceptibility testing compared to antibiotic therapy based on combination antimicrobial susceptibility testing in the treatment of acute pulmonary exacerbations in cystic fibrosis due to chronic infection with Pseudomonas aeruginosa. Both authors independently selected studies, assessed their quality and extracted data from eligible studies. Additionally, the authors contacted the study investigators to obtain further information. The search identified one multicentre study
Ballestero-Téllez, Mónica; Recacha, Esther; de Cueto, Marina; Pascual, Álvaro
Mass spectrometry Matrix-Assisted Laser Desorption-Ionization Time-of-Flight (MALDI-TOF) helps in the rapid identification of microorganisms causing blood stream infection. Rapid and reliable methods are required to decrease the turnaround time for reporting antimicrobial susceptibility results from blood culture isolates. An evaluation was performed on the reliability of a method for antimicrobial susceptibility testing of positive blood culture isolates from briefly incubated solid medium cultures. The agreement between the evaluated and standard methods was 99.3%. The major and minor error rates were 0.4% and 0.3%, respectively, and no very major errors were observed. The inoculation of briefly incubated solid medium cultures into antimicrobial susceptibility testing panels is an easy and reliable technique, and helps to decrease the turnaround time for reporting antimicrobial susceptibility results of positive blood cultures. Copyright © 2016 Elsevier España, S.L.U. y Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.
Quach, D.T.; Sakoulas, G.; Nizet, V.; Pogliano, J.; Pogliano, K.
Successful treatment of bacterial infections requires the timely administration of appropriate antimicrobial therapy. The failure to initiate the correct therapy in a timely fashion results in poor clinical outcomes, longer hospital stays, and higher medical costs. Current approaches to antibiotic susceptibility testing of cultured pathogens have key limitations ranging from long run times to dependence on prior knowledge of genetic mechanisms of resistance. We have developed a rapid antimicrobial susceptibility assay for Staphylococcus aureus based on bacterial cytological profiling (BCP), which uses quantitative fluorescence microscopy to measure antibiotic induced changes in cellular architecture. BCP discriminated between methicillin-susceptible (MSSA) and -resistant (MRSA) clinical isolates of S. aureus (n = 71) within 1–2 h with 100% accuracy. Similarly, BCP correctly distinguished daptomycin susceptible (DS) from daptomycin non-susceptible (DNS) S. aureus strains (n = 20) within 30 min. Among MRSA isolates, BCP further identified two classes of strains that differ in their susceptibility to specific combinations of beta-lactam antibiotics. BCP provides a rapid and flexible alternative to gene-based susceptibility testing methods for S. aureus, and should be readily adaptable to different antibiotics and bacterial species as new mechanisms of resistance or multidrug-resistant pathogens evolve and appear in mainstream clinical practice. PMID:26981574
Gülmez, Dolunay; Hasçelik, Gülşen
Enterococcus spp. are important pathogens which are intrinsically resistant to most of the commonly used antimicrobial agents such as aminoglycosides and cephalosporins. Accurate determination of resistance is important to ensure appropriate antimicrobial therapy. This study was undertaken to compare the susceptibility results obtained by Phoenix system (Becton Dickinson, USA) with reference microdilution method. We included 1248 Enterococcus spp. (903 Enterococcus faecalis, 345 Enterococcus faecium) strains isolated from clinical samples between 2005-2007 in routine microbiology laboratory of Hacettepe University Hospital. The strains were identified and the antimicrobial susceptibilities were determined by the Phoenix system. Antimicrobial susceptibilities to ampicillin, teicoplanin, vancomycin, gentamicin and streptomycin were also studied by microdilution method according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Evaluation revealed excellent agreement for all of the antibiotics with category agreement rates of > 97%. Among 1248 strains, 76 revealed discordant results. Very major error rates were 1.5% for ampicillin, 1.3% for gentamicin, and 0.9% for streptomycin. Major error rates were 1.4% for streptomycin, 0.6% for ampicillin and vancomycin and 0.3% for gentamicin. Minor error rates were found as 0.2% for vancomycin, and 0.1% for teicoplanin. Resistance rates obtained by microdilution were as follows; high level streptomycin 44%, high level gentamicin 29.7%, ampicillin 25.6%, vancomycin 2.2% and teicoplanin 2.2%. Resistance rates were higher in E.faecium than E.faecalis and 96.4% of the vancomycin resistant enterococcus isolates were identified as E.faecium. In conclusion, based on the data obtained, Phoenix system is reliable for testing susceptibilities of Enterococcus spp. to these antimicrobials. Since isolation of vancomycin resistant enterococci has an important impact in terms of hospital infection control, vancomycin
Lee, Wen-Bin; Fu, Chien-Yu; Chang, Wen-Hsin; You, Huey-Ling; Wang, Chih-Hung; Lee, Mel S; Lee, Gwo-Bin
Bacterial resistance to antimicrobial compounds is increasing at a faster rate than the development of new antibiotics; this represents a critical challenge for clinicians worldwide. Normally, the minimum inhibitory concentration of an antibiotic, the dosage at which bacterial growth is thwarted, provides an effective quantitative measure for antimicrobial susceptibility testing, and determination of minimum inhibitory concentration is conventionally performed by either a serial broth dilution method or with the commercially available Etest(®) (Biomerieux, France) kit. However, these techniques are relatively labor-intensive and require a significant amount of training. In order to reduce human error and increase operation simplicity, a simple microfluidic device that can perform antimicrobial susceptibility testing automatically via a broth dilution method to accurately determine the minimum inhibitory concentration was developed herein. As a proof of concept, wild-type (ATCC 29212) and vancomycin-resistant Enterococcus cells were incubated at five different vancomycin concentrations on-chip, and the sample injection, transport, and mixing processes occurred within five reaction chambers and three reagent chambers via the chip's automatic dispensation and dilution functions within nine minutes. The minimum inhibitory concentration values measured after 24h of antibiotic incubation were similar to those calculated using Etest(®). With its high flexibility, reliability, and portability, the developed microfluidic device provides a simple method for antimicrobial susceptibility testing in an automated format that could be implemented for clinical and point-of-care applications.
Blondeau, Joseph M
Current measurements of antimicrobial susceptibility or resistance utilize a standardized bacterial inoculum (10(5) cfu/mL) exposed to varying drug concentrations in a test tube. Following incubation under ideal conditions, the lowest drug concentration inhibiting growth is the minimum inhibitory concentration (MIC). When the MIC exceeds the amount of drug that can be safely achieved in the body, we call these microorganisms resistant; established breakpoints for various 'bug-drug' combinations are used to categorize microorganisms as susceptible, intermediate or resistant. MIC testing has been used for decades to guide antimicrobial therapy and remains an important measurement for infectious diseases. More recently, the mutant prevention concentration (MPC) has been described as a novel measurement of in vitro susceptibility or resistance and is based on the testing of larger bacterial inocula, i.e. > or =10(9) cfu/mL - such as those associated with some infections in humans and animals. MPC defines the lowest drug concentration required to block the growth of the least susceptible cell present in high density bacterial populations. MPC testing applies to microorganisms considered susceptible to the drug by MIC testing. The mutant selection window (MSW) defines the 'danger zone' for therapeutic drug concentrations. Minimizing the length of time the drug concentration remains in the MSW may reduce the likelihood for resistance selection during therapy. The MSW is bordered by the MIC and MPC values and the drug concentration range between the measured MIC and MPC values defines the MSW. MPC values, when considered with drug pharmacology, may allow prediction on the probability of resistance selection when bacteria are exposed to antimicrobial agents during therapy for infectious diseases. In today's environment, resistance prevention should be a goal of antimicrobial therapy.
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...
Mayrhofer, Sigrid; Zitz, Ulrike; Birru, Firew H; Gollan, Dagmar; Gołoś, Aleksandra K; Kneifel, Wolfgang; Domig, Konrad J
Lactobacilli play a crucial role as probiotics and as starter cultures in the production of fermented foods. Although lactobacilli are a technologically useful and beneficial group of bacteria, a few members of them have been rarely correlated with bacterial infections. Correspondingly, clinicians are interested in the antimicrobial susceptibility of lactobacilli. In addition, antimicrobial susceptibility testing (AST) is also relevant for commercially applied lactobacilli as bacterial strains harboring transferable antibiotic resistance genes should not be used in fermented and probiotic foods. Therefore, two methods were developed by different organizations, which were compared within this study. For this purpose, 22 Lactobacillus-type strains were tested for their antimicrobial susceptibility to 16 antibiotics following the procedures of the Clinical and Laboratory Standards Institute (CLSI) and the International Organization of Standardization (ISO)/International Dairy Federation (IDF). Crucial discrepancies between both procedures were detected mainly due to the different AST media. Hence, half of the strains tested did not consistently grow in the CLSI medium, whereas all showed evaluable growth in the ISO/IDF medium. However, some antibiotics were influenced by the latter medium. In particular, low levels of essential agreement between both methods were obtained with seven antibiotics. Accordingly, different interpretative criteria are needed for both procedures to distinguish resistant from susceptible strains.
Abbott, Felicity K; Milne, Kathleen E N; Stead, David A; Gould, Ian M
The Burkholderia cepacia complex (Bcc) is notorious for the life-threatening pulmonary infections it causes in patients with cystic fibrosis. The multidrug-resistant nature of Bcc and differing infective Bcc species make the design of appropriate treatment regimens challenging. Previous synergy studies have failed to take account of the species of Bcc isolates. Etest methodology was used to facilitate minimum inhibitory concentration (MIC) and antimicrobial combination testing on 258 isolates of Bcc, identified to species level by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). The most active antimicrobials were trimethoprim/sulphamethoxazole, doxycycline and minocycline (52.5%, 46.4% and 45.9% of isolates susceptible, respectively). Synergy was observed in 9.2% of the 1799 combinations tested; the most common synergistic combinations were tobramycin + ceftazidime, meropenem + tobramycin and levofloxacin + piperacillin/tazobactam (35.4%, 32.3% and 22.2% synergy, respectively). Antimicrobial susceptibility analysis revealed differences between Burkholderia cenocepacia and Burkholderia multivorans. Disparity in clinical outcome during infection with these two micro-organisms necessitates further investigation into the clinical outcomes of treatment regimens in light of species identification and in vitro antimicrobial susceptibility studies.
Sifré, Elodie; Salha, Ben Amor; Ducournau, Astrid; Floch, Pauline; Chardon, Hubert; Mégraud, Francis; Lehours, Philippe
Antimicrobial susceptibility testing of Campylobacter isolates is of great importance for treatment options especially in systemic diseases. The European Committee for Antimicrobial Susceptibility Testing (EUCAST) recently proposed epidemiological cut-offs (ECOFFs) for a limited number of antimicrobial compounds and for Campylobacter jejuni and Campylobacter coli only. In the present study, the EUCAST method was used after minor modifications to define antimicrobial susceptibility patterns for, 1997 C. jejuni, 419 C. coli and 100 Campylobacter fetus strains received at the French National Reference Center for Campylobacters and Helicobacters. Our results show that the ECOFFs defined by EUCAST for tetracycline and ciprofloxacin can be used for C. jejuni and C. coli. The same ECOFF can be used for erythromycin for the three species. The C. jejuni and C. coli ECOFFs for ciprofloxacin however cannot be applied to C. fetus. We also provide data to categorise two 2 β-lactams of interest for systemic diseases, ampicillin and amoxicillin+clavulanate, for the three species. Copyright © 2015 Elsevier B.V. All rights reserved.
Bacteria in the Staphylococcus intermedius group, including Staphylococcus pseudintermedius, often encode mecA-mediated methicillin resistance. Reliable detection of this phenotype for proper treatment and infection control decisions requires that these coagulase-positive staphylococci are accurately identified and specifically that they are not misidentified as S. aureus. As correct species level bacterial identification becomes more commonplace in clinical laboratories, one can expect to see changes in guidance for antimicrobial susceptibility testing and interpretation. The study by Wu et al. in this issue (M. T. Wu, C.-A. D. Burnham, L. F. Westblade, J. Dien Bard, S. D. Lawhon, M. A. Wallace, T. Stanley, E. Burd, J. Hindler, R. M. Humphries, J Clin Microbiol 54:535–542, 2016, http://dx.doi.org/10.1128/JCM.02864-15) highlights the impact of robust identification of S. intermedius group organisms on the selection of appropriate antimicrobial susceptibility testing methods and interpretation. PMID:26763965
Choi, Jungil; Yoo, Jungheon; Lee, Mincheol; Kim, Eun-Geun; Lee, Ji Soo; Lee, Seungok; Joo, Seik; Song, Sang Hoon; Kim, Eui-Chong; Lee, Jung Chan; Kim, Hee Chan; Jung, Yong-Gyun; Kwon, Sunghoon
A rapid antibiotic susceptibility test (AST) is desperately needed in clinical settings for fast and appropriate antibiotic administration. Traditional ASTs, which rely on cell culture, are not suitable for urgent cases of bacterial infection and antibiotic resistance owing to their relatively long test times. We describe a novel AST called single-cell morphological analysis (SCMA) that can determine antimicrobial susceptibility by automatically analyzing and categorizing morphological changes in single bacterial cells under various antimicrobial conditions. The SCMA was tested with four Clinical and Laboratory Standards Institute standard bacterial strains and 189 clinical samples, including extended-spectrum β-lactamase-positive Escherichia coli and Klebsiella pneumoniae, imipenem-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and vancomycin-resistant Enterococci from hospitals. The results were compared with the gold standard broth microdilution test. The SCMA results were obtained in less than 4 hours, with 91.5% categorical agreement and 6.51% minor, 2.56% major, and 1.49% very major discrepancies. Thus, SCMA provides rapid and accurate antimicrobial susceptibility data that satisfy the recommended performance of the U.S. Food and Drug Administration. Copyright © 2014, American Association for the Advancement of Science.
Rosser, S. J.; Alfa, M. J.; Hoban, S.; Kennedy, J.; Harding, G. K.
Viridans group streptococci (VGS) are commonly isolated from the blood of hospitalized patients. The E test represents a convenient method for determining the MICs for VGS, but for this purpose it has not been well validated against reference methods. In this study, 180 unselected VGS isolates were identified to a species level, and the MICs of penicillin, cefuroxime, cefotaxime, and vancomycin were determined by both agar dilution and the E test. Available data regarding demographic and laboratory variables for each VGS bacteremic episode were collected, the significance of each VGS isolate was assessed, and the associations between and among laboratory and clinical variables were investigated. Among all VGS isolates, 68.3% (median of three runs) were found to be fully susceptible to penicillin by agar dilution. The E test and agar dilution showed average agreements (within ±1 dilution) of 92.2% for penicillin, 95.7% for cefuroxime 91.3% for cefotaxime, and 86.7% for vancomycin. Agreements over serial E tests and serial agar dilutions were excellent for β-lactam agents (intraclass correlation coefficients, >0.9) but less impressive for vancomycin. Very major error rates for the E test were ≤0.7%, and combined major and minor error rates were within acceptable limits for all antimicrobial agents tested. Lysis-centrifugation culture methods were more often associated with clinically insignificant VGS isolates; otherwise, no associations between clinical and laboratory variables were noted. PMID:9854058
Foerster, Sunniva; Desilvestro, Valentino; Hathaway, Lucy J; Althaus, Christian L; Unemo, Magnus
Rapid, cost-effective and objective methods for antimicrobial susceptibility testing of Neisseria gonorrhoeae would greatly enhance surveillance of antimicrobial resistance. Etest, disc diffusion and agar dilution methods are subjective, mostly laborious for large-scale testing and take ∼24 h. We aimed to develop a rapid broth microdilution assay using resazurin (blue), which is converted into resorufin (pink fluorescence) in the presence of viable bacteria. The resazurin-based broth microdilution assay was established using 132 N. gonorrhoeae strains and the antimicrobials ceftriaxone, cefixime, azithromycin, spectinomycin, ciprofloxacin, tetracycline and penicillin. A regression model was used to estimate the MICs. Assay results were obtained in ∼7.5 h. The EC 50 of the dose-response curves correlated well with Etest MIC values (Pearson's r = 0.93). Minor errors resulting from misclassifications of intermediate strains were found for 9% of the samples. Major errors (susceptible strains misclassified as resistant) occurred for ceftriaxone (4.6%), cefixime (3.3%), azithromycin (0.6%) and tetracycline (0.2%). Only one very major error was found (a ceftriaxone-resistant strain misclassified as susceptible). Overall the sensitivity of the assay was 97.1% (95% CI 95.2-98.4) and the specificity 78.5% (95% CI 74.5-82.9). A rapid, objective, high-throughput, quantitative and cost-effective broth microdilution assay was established for gonococci. For use in routine diagnostics without confirmatory testing, the specificity might remain suboptimal for ceftriaxone and cefixime. However, the assay is an effective low-cost method to evaluate novel antimicrobials and for high-throughput screening, and expands the currently available methodologies for surveillance of antimicrobial resistance in gonococci.
Kadlec, Meichei Wang; You, David; Liao, Joseph C; Wong, Pak Kin
This study demonstrates a low-cost, portable diagnostic system for rapid antimicrobial susceptibility testing in resource-limited settings. To determine the antimicrobial resistance phenotypically, the growth of pathogens in microwell arrays is detected under different antibiotic conditions. The use of a colorimetric cell viability reagent is shown to significantly improve the sensitivity of the assay compared with standard absorbance spectroscopy. Gas-permeable microwell arrays are incorporated for facilitating rapid bacterial growth and eliminating the requirement of bulky supporting equipment. Antibiotics can also be precoated in the microwell array to simplify the assay protocol toward point-of-care applications. Furthermore, a low-cost cell phone-based microphotometric system is developed for detecting the bacterial growth in the microwell array. By optimizing the operating conditions, the system allows antimicrobial susceptibility testing for samples with initial concentrations from 10(1) to 10(6) cfu/mL. Using urinary tract infection as the model system, we demonstrate rapid antimicrobial resistance profiling for uropathogens in both culture media and urine. With its simplicity and cost-effectiveness, the cell phone-based microphotometric system is anticipated to have broad applicability in resource-limited settings toward the management of infectious diseases caused by multidrug-resistant pathogens. © 2013 Society for Laboratory Automation and Screening.
Sutter, Vera L.; Kwok, Yung-Yuan; Finegold, Sydney M.
A modified Bauer-Kirby-Sherris-Turck method for disc susceptibility testing of anaerobic bacteria is presented. When tetracycline was used against 100 strains of Bacteroides fragilis as a model, reasonably reproducible results were obtained after overnight incubation in both the GasPak atmosphere and an atmosphere achieved by adding 10% CO2 to a mixture of 10% H2 and 90% N2. The minimal inhibitory concentration for the strains determined by the agar dilution technique correlated well with the results of disc tests performed in the GasPak atmosphere with 30-μg tetracycline discs. Among 63 strains isolated from 1970 to the present, only 24 (38.1%) were found to be susceptible to tetracycline. PMID:5017675
Evans, N J; Brown, J M; Hartley, C; Smith, R F; Carter, S D
Digital dermatitis (DD) is a major infectious lameness of dairy cattle and sheep considered to be caused by treponemes. The aim of this study was to identify antibiotics effective against DD treponemes that might be useful in the treatment of ruminant DD in the future or to identify antibiotics useful in isolation studies. Here, a microdilution method was used to identify in vitro antimicrobial susceptibility of treponemes cultured from DD lesions to eight relevant antibiotics. DD treponemes exhibited highest susceptibility to amoxicillin, azithromycin and gamithromycin. Unfortunately, amoxicillin whilst having potential for DD treatment in other animals (e.g. sheep) would require milk withhold periods in dairy cattle. DD treponemes were not particularly susceptible to two cephalosporins: cefalexin and ceftiofur, which do not require milk withhold. The bacteria demonstrated low susceptibility to trimethoprim and especially colistin suggesting these antimicrobials may be particularly useful in isolation of DD treponemes. The most promising high susceptibility results for macrolides indicate a rationale to consider veterinary licensed macrolides as DD treatments. Furthermore, given the DD treponeme antibiotic susceptibility similarities to established treatments for human treponematoses, identification of treponemacidal, long acting β-lactam analogues not requiring milk withhold may allow for development of a successful treatment for dairy cattle DD.
Smith, Stella; Braun, Sascha; Akintimehin, Faith; Fesobi, Toun; Bamidele, Moses; Coker, Akitoye; Monecke, Stefan; Ehricht, Ralf
Microarray-based serogenotyping, antimicrobial susceptibility tests and the detection of relevant resistance genes were performed on isolates of Salmonella spp. from retail meat samples obtained in Lagos, Nigeria. Out of 151 meat samples, 33 Salmonella isolates were obtained. Nine different Salmonella serovars (S. Amoutive, S. Bargny, S. Drac, S. Ealing, S. Urbana, S. Hadar, S. Nyborg, S. Anatum and S. Havana) were identified by microarray-based serogenotyping and confirmed afterwards using classical serotyping. Antibiotic susceptibility tests with 17 antibiotics showed that almost all isolates were fully susceptible to this panel. The results of this study indicated a high prevalence of Salmonella in retail meat, the presence of some previously rather rarely described Serovars in retail meat samples from Lagos, and a need to monitor for Salmonella and their antibiotic resistance determinants. The microarray-based system used herein proved to be perfectly suited as epidemiological tool to replace classical serotyping. Copyright © 2016 Elsevier Ltd. All rights reserved.
Boyle, V J; Fancher, M E; Ross, R W
A rapid (6-7 hr), modified Kirby-Bauer disk-susceptibility method, by which derivatives of tetrazolium dyes are used to enhance delineation between areas of growth and zones of inhibition, has been developed. Inoculated petri plates, prepared by the Kirby-Bauer method, were sprayed, after 6 to 7 hr of incubation (37 C), with aqueous solutions of MTT-tetrazolium or INT-tetrazolium resulting in readily detectable zones of inhibition. Excellent correlation was obtained between the modified test and the standard Kirby-Bauer test when challenged with a variety of gram-negative bacteria and Staphylococcus aureus strains. Additionally, the modified test has demonstrated reproducibility comparable to the standard Kirby-Bauer test. It is demonstrated that the modified test is applicable to susceptibility determinations with representative, commercially available antimicrobial disks. This applicability indicates that the modified method could provide rapid in vitro guidelines for in vivo therapy.
Garcia-Garrote, Fernando; Cercenado, Emilia; Bouza, Emilio
We evaluated the new automated VITEK 2 system (bioMérieux) for the identification and antimicrobial susceptibility testing of enterococci. The results obtained with the VITEK 2 system were compared to those obtained by reference methods: standard identification by the scheme of Facklam and Sahm [R. R. Facklam and D. F. Sahm, p. 308–314, in P. R. Murray et al., ed., Manual of Clinical Microbiology, 6th ed., 1995] and with the API 20 STREP system and, for antimicrobial susceptibility testing, broth microdilution and agar dilution methods by the procedures of the National Committee for Clinical Laboratory Standards. The presence of vanA and vanB genes was determined by PCR. A total of 150 clinical isolates were studied, corresponding to 60 Enterococcus faecalis, 55 Enterococcus faecium, 26 Enterococcus gallinarum, 5 Enterococcus avium, 2 Enterococcus durans, and 2 Enterococcus raffinosus isolates. Among those isolates, 131 (87%) were correctly identified to the species level with the VITEK 2 system. Approximately half of the misidentifications were for E. faecium with low-level resistance to vancomycin, identified as E. gallinarum or E. casseliflavus; however, a motility test solved the discrepancies and increased the agreement to 94%. Among the strains studied, 66% were vancomycin resistant (57 VanA, 16 VanB, and 26 VanC strains), 23% were ampicillin resistant (MICs, ≥16 μg/ml), 31% were high-level gentamicin resistant, and 45% were high-level streptomycin resistant. Percentages of agreement for susceptibility and resistance to ampicillin, vancomycin, and teicoplanin and for high-level gentamicin resistance and high-level streptomycin resistance were 93, 95, 97, 97, and 96%, respectively. The accuracy of identification and antimicrobial susceptibility testing of enterococci with the VITEK 2 system, together with the significant reduction in handling time, will have a positive impact on the work flow of the clinical microbiology laboratory. PMID:10834961
Garcia-Garrote, F; Cercenado, E; Bouza, E
We evaluated the new automated VITEK 2 system (bioMérieux) for the identification and antimicrobial susceptibility testing of enterococci. The results obtained with the VITEK 2 system were compared to those obtained by reference methods: standard identification by the scheme of Facklam and Sahm [R. R. Facklam and D. F. Sahm, p. 308-314, in P. R. Murray et al., ed., Manual of Clinical Microbiology, 6th ed., 1995] and with the API 20 STREP system and, for antimicrobial susceptibility testing, broth microdilution and agar dilution methods by the procedures of the National Committee for Clinical Laboratory Standards. The presence of vanA and vanB genes was determined by PCR. A total of 150 clinical isolates were studied, corresponding to 60 Enterococcus faecalis, 55 Enterococcus faecium, 26 Enterococcus gallinarum, 5 Enterococcus avium, 2 Enterococcus durans, and 2 Enterococcus raffinosus isolates. Among those isolates, 131 (87%) were correctly identified to the species level with the VITEK 2 system. Approximately half of the misidentifications were for E. faecium with low-level resistance to vancomycin, identified as E. gallinarum or E. casseliflavus; however, a motility test solved the discrepancies and increased the agreement to 94%. Among the strains studied, 66% were vancomycin resistant (57 VanA, 16 VanB, and 26 VanC strains), 23% were ampicillin resistant (MICs, >/=16 microgram/ml), 31% were high-level gentamicin resistant, and 45% were high-level streptomycin resistant. Percentages of agreement for susceptibility and resistance to ampicillin, vancomycin, and teicoplanin and for high-level gentamicin resistance and high-level streptomycin resistance were 93, 95, 97, 97, and 96%, respectively. The accuracy of identification and antimicrobial susceptibility testing of enterococci with the VITEK 2 system, together with the significant reduction in handling time, will have a positive impact on the work flow of the clinical microbiology laboratory.
Smith, Sinéad M; O'Morain, Colm; McNamara, Deirdre
The gram-negative bacterium Helicobacter pylori (H. pylori) causes chronic gastritis, gastric and duodenal ulcers, gastric cancer and mucosa-associated lymphoid tissue lymphoma. Treatment is recommended in all symptomatic patients. The current treatment options for H. pylori infection are outlined in this review in light of the recent challenges in eradication success, largely due to the rapid emergence of antibiotic resistant strains of H. pylori. Antibiotic resistance is a constantly evolving process and numerous studies have shown that the prevalence of H. pylori antibiotic resistance varies significantly from country to country, and even between regions within the same country. In addition, recent data has shown that previous antibiotic use is associated with harbouring antibiotic resistant H. pylori. Local surveillance of antibiotic resistance is warranted to guide clinicians in their choice of therapy. Antimicrobial resistance is assessed by H. pylori culture and antimicrobial susceptibility testing. Recently developed molecular tests offer an attractive alternative to culture and allow for the rapid molecular genetic identification of H. pylori and resistance-associated mutations directly from biopsy samples or bacterial culture material. Accumulating evidence indicates that surveillance of antimicrobial resistance by susceptibility testing is feasible and necessary to inform clinicians in their choice of therapy for management of H. pylori infection.
Cirković, Ivana; Hauschild, Tomasz; Jezek, Petr; Dimitrijević, Vladimir; Vuković, Dragana; Stepanović, Srdjan
This study evaluated the performance of the BD Phoenix system for the identification (ID) and antimicrobial susceptibility testing (AST) of Staphylococcus vitulinus. Of the 10 S. vitulinus isolates included in the study, 2 were obtained from the Czech Collection of Microorganisms, 5 from the environment, 2 from human clinical samples, and 1 from an animal source. The results of conventional biochemical and molecular tests were used for the reference method for ID, while antimicrobial susceptibility testing performed in accordance with Clinical and Laboratory Standards Institute recommendations and PCR for the mecA gene were the reference for AST. Three isolates were incorrectly identified by the BD Phoenix system; one of these was incorrectly identified to the genus level, and two to the species level. The results of AST by the BD Phoenix system were in agreement with those by the reference method used. While the results of susceptibility testing compared favorably, the 70% accuracy of the Phoenix system for identification of this unusual staphylococcal species was not fully satisfactory.
Kinnunen, Paivo; McNaughton, Brandon H; Albertson, Theodore; Sinn, Irene; Mofakham, Sima; Elbez, Remy; Newton, Duane W; Hunt, Alan; Kopelman, Raoul
Bacterial antibiotic resistance is one of the major concerns of modern healthcare worldwide, and the development of rapid, growth-based, antimicrobial susceptibility tests is key for addressing it. The cover image shows a self-assembled asynchronous magnetic bead rotation (AMBR) biosensor developed for rapid detection of bacterial growth. Using the biosensors, the minimum inhibitory concentration of a clinical E. coli isolate can be measured within two hours, where currently tests take 6-24 hours. A 16-well prototype is also constructed for simple and robust observation of the self-assembled AMBR biosensors.
Bobenchik, April M.; Hindler, Janet A.; Giltner, Carmen L.; Saeki, Sandra
Vitek 2 (bioMérieux, Inc., Durham, NC) is a widely used commercial antimicrobial susceptibility testing system. We compared MIC results obtained by Vitek 2 to those obtained by the Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BMD) reference method for 134 staphylococcal and 84 enterococcal clinical isolates. Nineteen agents were evaluated, including all those available on Vitek 2 for testing staphylococci and enterococci. The resistance phenotypes tested included methicillin-resistant Staphylococcus aureus (MRSA) (n = 58), S. aureus with inducible clindamycin resistance (ICR) (n = 30), trimethoprim-sulfamethoxazole-resistant MRSA (n = 10), vancomycin-resistant Enterococcus (n = 37), high-level gentamicin-resistant Enterococcus (n = 15), linezolid-resistant Enterococcus (n = 5), and daptomycin-nonsusceptible Enterococcus faecalis (n = 6). For the staphylococci, there was 98.9% categorical agreement (CA). There was one very major error (VME) for gentamicin in a Staphylococcus hominis isolate, six VMEs for inducible clindamycin in S. aureus isolates, and two major errors (ME) for daptomycin in an S. aureus and a Staphylococcus epidermidis isolate. For enterococci, there was 97.3% CA. Two VMEs were observed for daptomycin in isolates of E. faecalis and 2 ME, 1 for high-level gentamicin resistance and 1 for nitrofurantoin, in E. faecium isolates. Overall, there was 98.3% CA and 99% essential agreement for the testing of staphylococci and enterococci by the Vitek 2. With the exception of detecting ICR in S. aureus, Vitek 2 performed reliably for antimicrobial susceptibility testing of staphylococci and enterococci. PMID:24478467
Bobenchik, April M; Hindler, Janet A; Giltner, Carmen L; Saeki, Sandra; Humphries, Romney M
Vitek 2 (bioMérieux, Inc., Durham, NC) is a widely used commercial antimicrobial susceptibility testing system. We compared MIC results obtained by Vitek 2 to those obtained by the Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BMD) reference method for 134 staphylococcal and 84 enterococcal clinical isolates. Nineteen agents were evaluated, including all those available on Vitek 2 for testing staphylococci and enterococci. The resistance phenotypes tested included methicillin-resistant Staphylococcus aureus (MRSA) (n = 58), S. aureus with inducible clindamycin resistance (ICR) (n = 30), trimethoprim-sulfamethoxazole-resistant MRSA (n = 10), vancomycin-resistant Enterococcus (n = 37), high-level gentamicin-resistant Enterococcus (n = 15), linezolid-resistant Enterococcus (n = 5), and daptomycin-nonsusceptible Enterococcus faecalis (n = 6). For the staphylococci, there was 98.9% categorical agreement (CA). There was one very major error (VME) for gentamicin in a Staphylococcus hominis isolate, six VMEs for inducible clindamycin in S. aureus isolates, and two major errors (ME) for daptomycin in an S. aureus and a Staphylococcus epidermidis isolate. For enterococci, there was 97.3% CA. Two VMEs were observed for daptomycin in isolates of E. faecalis and 2 ME, 1 for high-level gentamicin resistance and 1 for nitrofurantoin, in E. faecium isolates. Overall, there was 98.3% CA and 99% essential agreement for the testing of staphylococci and enterococci by the Vitek 2. With the exception of detecting ICR in S. aureus, Vitek 2 performed reliably for antimicrobial susceptibility testing of staphylococci and enterococci.
Jorgensen, James H; Crawford, Sharon A; Fulcher, Letitia C; Glennen, Anita; Harrington, Susan M; Swenson, Jana; Lynfield, Ruth; Murray, Patrick R; Tenover, Fred C
In 2005, the Clinical and Laboratory Standards Institute published MIC interpretive criteria for 13 antimicrobial agents used for either therapy or prophylaxis of Neisseria meningitidis infections. The MIC method includes the use of lysed horse blood-supplemented Mueller-Hinton broth with incubation in 5% CO2 for 20 to 24 h. Since some clinical laboratories might prefer the option of disk diffusion testing for infrequently encountered isolates a multicenter collaborative study was conducted to evaluate the reproducibility of a disk diffusion method for testing isolates of N. meningitidis. Interpretive criteria were developed for 12 antimicrobial agents. Four laboratories tested a common collection of 50 meningococcal strains and then tested 25 unique isolates per laboratory. Isolates were tested using Mueller-Hinton sheep blood agar plates incubated for 20 to 24 h in 5% CO2; they were also tested by the reference broth microdilution method in parallel. Pooling of the MIC and disk diffusion data from the common and unique isolates provided a sufficient sample size to develop susceptible, intermediate, and resistant zone diameter interpretive criteria using the error rate-bounded method for the following agents: chloramphenicol, trimethoprim-sulfamethoxazole, ciprofloxacin, and rifampin. Due to the lack of resistant strains at the present time, "susceptible only" interpretive criteria were proposed for cefotaxime, ceftriaxone, meropenem, azithromycin, and minocycline. The numbers of minor interpretive errors with penicillin and ampicillin disk tests were unacceptably high and precluded recommended testing of those agents by the disk method. However, amdinocillin, an agent that preferentially binds to the altered penicillin binding protein responsible for diminished penicillin susceptibility, has potential utility as a surrogate screening reagent for ampicillin resistance. A disk diffusion breakpoint was derived for nalidixic acid to serve as a surrogate marker for
Moellering, Robert C.; Mercier, Bettie A.; Kunz, Lawrence J.; Poitras, James W.
A computer-associated electronic zone analyzer was evaluated for use in measuring zones of inhibition for single-disc antimicrobial susceptibility testing. This unit gave measurements which were reproducible and comparable to those obtained by the standard manual technique. By feeding results directly into the computer, this system eliminates errors in interpretation of zone sizes and in transcription of results to clinical reports. It has also been shown to eliminate possible sources of observer bias. In routine high-volume use, this system has resulted in a substantial saving of man-hours of work. Images PMID:4670493
Huang, Ay Huey; Wu, Jiunn Jong; Weng, Yu Mei; Ding, Hwia Cheng; Chang, Tsung Chain
Nonfastidious aerobic gram-negative bacilli (GNB) are commonly isolated from blood cultures. The feasibility of using an electrochemical method for direct antimicrobial susceptibility testing of GNB in positive blood cultures was evaluated. An aliquot (10 μl) of 1:10-diluted positive blood cultures containing GNB was inoculated into the Bactometer module well (bioMérieux Vitek, Hazelwood, Mo.) containing 1 ml of Mueller-Hinton broth supplemented with an antibiotic. Susceptibility tests were performed in a breakpoint broth dilution format, with the results being categorized as resistant, intermediate, or susceptible. Seven antibiotics (ampicillin, cephalothin, gentamicin, amikacin, cefamandole, cefotaxime, and ciprofloxacin) were used in this study, with each agent being tested at the two interpretive breakpoint concentrations. The inoculated modules were incubated at 35°C, and the change in impedance in each well was continuously monitored for 24 h by the Bactometer. The MICs of the seven antibiotics for each blood isolate were also determined by the standardized broth microdilution method. Of 146 positive blood cultures (1,022 microorganism-antibiotic combinations) containing GNB tested by the direct method, the rates of very major, major, and minor errors were 0, 1.1, and 2.5%, respectively. The impedance method was simple; no centrifugation, preincubation, or standardization of the inocula was required, and the susceptibility results were normally available within 3 to 6 h after inoculation. The rapid method may allow proper antimicrobial treatment almost 30 to 40 h before the results of the standard methods are available. PMID:9738038
Wicks, J H; Nelson, R L; Krejcarek, G E
A rapid inoculum standardization system for antimicrobial susceptibility testing without incubation or the conventional turbidity adjustment has been developed. The rapid inoculum standardization system consists of a plastic rod with cross-hatched grooves on one end and a specific nutrient medium in a vial. The crosshatched grooves are designed to pick up and release a known number of viable microorganisms. In use, the end of the rod is touched to five colonies 1 to 2 mm in diameter from a primary agar plate, thus filling the grooves with bacteria. The rod is placed into the vial, and the bacteria are suspended in the medium by agitation with a Vortex Genie Mixer. The resulting suspension contains 5 X 10(7) to 5 X 10(8) CFU/ml for most gram-negative bacilli and gram-positive cocci. Microorganisms such as streptococci that have colonies less than 1 mm in diameter require as many as 10 colonies for an adequate inoculum suspension. Ninety-five commonly encountered bacterial isolates were tested in triplicate by agar plate counts. The resulting overall geometric mean of the agar plate counts was 1.52 X 10(8) CFU/ml for the species tested. We have found that the rapid inoculum standardization system provides a consistent and reproducible method for the standardization of inoculum for antimicrobial susceptibility testing without the incubation period and turbidity adjustment. Images PMID:6874902
Hampson, D J; Stephens, C P; Oxberry, S L
Susceptibilities of predominantly Australian isolates of the pathogenic intestinal spirochaetes Brachyspira intermedia (n = 25) and Brachyspira pilosicoli (n = 17) from chickens were tested in agar dilution against four concentrations each of the antimicrobials tiamulin, lincomycin, tylosin, metronidazole, tetracycline and ampicillin. Based on available minimum inhibitory concentration (MIC) breakpoint values for Brachyspira hyodysenteriae or other Gram-negative enteric veterinary pathogens, isolates of both species generally were susceptible to tiamulin, lincomycin, metronidazole and tetracycline. Although not classed as resistant, four isolates of B. intermedia had an elevated MIC range for tiamulin (1 to 4 mg/l), 11 isolates of B. intermedia and five of B. pilosicoli had an elevated MIC range for lincomycin (10 to 50 mg/l), one isolate of B. pilosicoli had an elevated MIC range for tetracycline (10 to 20 mg/l), and one isolate of B. intermedia and five of B. pilosicoli had an elevated MIC range for ampicillin (10 to 50 mg/l). A clear lack of susceptibility to tylosin (MIC > 4 mg/l) was seen in 11 isolates each of B. intermedia and B. pilosicoli, and to ampicillin (MIC > 32 mg/l) in two isolates of B. pilosicoli. These data suggest that some resistance to common antimicrobials exists among intestinal spirochetes obtained from laying hens and supports the need of MIC data for clinical isolates before any treatment is considered.
Liu, Tingting; Lu, Yi; Gau, Vincent; Liao, Joseph C; Wong, Pak Kin
Rapid pathogen detection and antimicrobial susceptibility testing (AST) are required in diagnosis of acute bacterial infections to determine the appropriate antibiotic treatment. Molecular approaches for AST are often based on the detection of known antibiotic resistance genes. Phenotypic culture analysis requires several days from sample collection to result reporting. Toward rapid diagnosis of bacterial infection in non-traditional healthcare settings, we have developed a rapid AST approach that combines phenotypic culture of bacterial pathogens in physiological samples and electrochemical sensing of bacterial 16S rRNA. The assay determines the susceptibility of pathogens by detecting bacterial growth under various antibiotic conditions. AC electrokinetic fluid motion and Joule heating induced temperature elevation are optimized to enhance the sensor signal and minimize the matrix effect, which improve the overall sensitivity of the assay. The electrokinetics enhanced biosensor directly detects the bacterial pathogens in blood culture without prior purification. Rapid determination of the antibiotic resistance profile of Escherichia coli clinical isolates is demonstrated.
Brazelton de Cárdenas, J N; Su, Y; Rodriguez, A; Hewitt, C; Tang, L; Garner, C D; Hayden, R T
Identification (ID) and antimicrobial susceptibility testing (AST) remain rate limiting steps in producing actionable data for clinical care of bloodstream infections. Rapid, automated phenotypic ID and AST by fluorescent in situ hybridization and automated microscopy were used to characterize blood stream infections in a predominantly pediatric oncology patient population. Results were compared to standard of care (SOC) phenotypic methods. The Accelerate Pheno System (AXDX) had a sensitivity of 91.2% and an accuracy of 100% to the genus level for identification, and an overall categorical agreement 91.2-91.8% for susceptibility, depending on the breakpoints used. The AXDX required a mean time of 1.4hours for identification and 6.6hours for susceptibility testing compared to SOC, requiring 32.5 and 46.7hours, respectively. Identification and susceptibility by rapid phenotypic methods shows a high degree of accuracy; the marked reduction in time to results may have significant implications for patient care. Copyright © 2017 Elsevier Inc. All rights reserved.
Zankari, Ea; Hasman, Henrik; Kaas, Rolf Sommer; Seyfarth, Anne Mette; Agersø, Yvonne; Lund, Ole; Larsen, Mette Voldby; Aarestrup, Frank M
Antimicrobial susceptibility testing of bacterial isolates is essential for clinical diagnosis, to detect emerging problems and to guide empirical treatment. Current phenotypic procedures are sometimes associated with mistakes and may require further genetic testing. Whole-genome sequencing (WGS) may soon be within reach even for routine surveillance and clinical diagnostics. The aim of this study was to evaluate WGS as a routine tool for surveillance of antimicrobial resistance compared with current phenotypic procedures. Antimicrobial susceptibility tests were performed on 200 isolates originating from Danish pigs, covering four bacterial species. Genomic DNA was purified from all isolates and sequenced as paired-end reads on the Illumina platform. The web servers ResFinder and MLST (www.genomicepidemiology.org) were used to identify acquired antimicrobial resistance genes and MLST types (where MLST stands for multilocus sequence typing). ResFinder results were compared with phenotypic antimicrobial susceptibility testing results using EUCAST epidemiological cut-off values and MLST types. A total of 3051 different phenotypic tests were performed; 482 led to the categorizing of isolates as resistant and 2569 as susceptible. Seven cases of disagreement between tested and predicted susceptibility were observed, six of which were related to spectinomycin resistance in Escherichia coli. Correlation between MLST type and resistance profiles was only observed in Salmonella Typhimurium, where isolates belonging to sequence type (ST) 34 were more resistant than ST19 isolates. High concordance (99.74%) between phenotypic and predicted antimicrobial susceptibility was observed. Thus, antimicrobial resistance testing based on WGS is an alternative to conventional phenotypic methods.
Glupczynski, Y; Berhin, C; Nizet, H
The objective was to collect recent data on the antibiotic susceptibility of clinically significant anaerobes in Belgium. A total of 333 anaerobic clinical isolates from various body sites were prospectively collected between 2005 and 2007 at two tertiary care hospitals in Belgium. The minimal inhibitory concentrations (MICs) were determined using the E-test method for nine anti-anaerobic antibiotics. Sixty-one percent of the isolates were beta-lactamase producers, which explains the poor activity of penicillin. Amoxicillin/clavulanic acid, piperacillin/tazobactam, metronidazole and meropenem were very active against most anaerobes, but around 10% of the Bacteroides fragilis group strains were non-susceptible to the two beta-lactam/beta-lactamase inhibitors. No resistance was observed to metronidazole, while 3% of the Bacteroides spp. had decreased susceptibility to meropenem (MIC > or = 4 mg/L). Cefoxitin, clindamycin and moxifloxacin were less active, with 33%, 52% and 57% of the B. fragilis group being non-susceptible respectively. Tigecycline showed consistently good activity against most anaerobes with MIC(50) and MIC(90) of 0.25 and 2 mg/L. Metronidazole, amoxicillin/clavulanate, piperacillin/tazobactam and meropenem remain good empirical choices when anaerobes are expected in our setting. Because of the occurrence of resistance to most classes of current anti-anaerobic antibiotics, it is recommended that the antimicrobial resistance patterns be monitored regularly in order to guide empirical therapy.
Richter, Sandra S; Howard, Wanita J; Weinstein, Melvin P; Bruckner, David A; Hindler, Janet F; Saubolle, Michael; Doern, Gary V
This multicenter study evaluated the BD Phoenix Automated Microbiology System STREP panel (BD Diagnostic Systems). Antimicrobial susceptibility testing (AST) with 13 agents was performed on 2,013 streptococci (938 Streptococcus pneumoniae isolates; 396 group B streptococci [GBS]; 369 viridans group streptococci [VGS]; 290 beta-hemolytic streptococcus groups A, C, and G; and 20 other streptococci) with the Phoenix system and a broth microdilution reference method. Clinical and challenge isolates were tested against cefepime, cefotaxime (CTX), ceftriaxone (CTR), clindamycin (CLI), erythromycin (ERY), gatifloxacin, levofloxacin, linezolid, meropenem, penicillin (PEN), tetracycline (TET), trimethoprim-sulfamethoxazole, and vancomycin. Clinical isolates with major errors or very major errors (VMEs) were retested in duplicate by both methods. The final results for clinical isolates showed the following trends. For all of the organism-antimicrobial agent combinations tested, categorical agreement (CA) was 92 to 100%, with one exception-VGS-PEN (87% CA; all errors were minor). For S. pneumoniae, there was one major error with CLI (0.1%) and one or two VMEs with CTX (4%), CTR (4.5%), ERY (0.9%), and TET (0.7%). For groups A, C, and G, the CA was 97 to 100% and the only VMEs were resolved by additional reference laboratory testing. For GBS, there was only one VME (TET, 0.3%) and D-zone testing of 23 isolates with CLI major errors (one isolate unavailable) revealed inducible CLI resistance. For VGS, the major error rates were 0 to 3% and VMEs occurred with seven agents (3.5 to 7.1%). The mean times required for organism groups to generate results ranged from 8.4 to 9.4 h. The Phoenix system provided reliable and rapid AST results for most of the organism-antimicrobial agent combinations tested.
Heliopoulos, Nikolaos S; Galeou, Angeliki; Papageorgiou, Sergios K; Favvas, Evangelos P; Katsaros, Fotios K; Stamatakis, Kostas
Up to now antimicrobial susceptibility testing (AST) methods are indirect and generally involve the manual counting of bacterial colonies following the extraction of microorganisms from the surface under study and their inoculation in a separate procedure. In this work, an in situ, direct and instrumental method for the evaluation and assessment of antibacterial properties of materials and surfaces is proposed. Instead of indirectly determining antibacterial activity using the typical gram(-) test organisms with the subsequent manual colony count or inhibition zone measurement, the proposed procedure, employs photosynthetic gram(-) cyanobacteria deposited directly onto the surface under study and assesses cell proliferation and viability by a quick, accurate and reproducible instrumental chlorophyll fluorescence spectrophotometric technique. In contrast with existing methods of determination of antibacterial properties, it produces high resolution and quantitative results and is so versatile that it could be used to evaluate the antibacterial properties of any compound (organic, inorganic, natural or man-made) under any experimental conditions, depending on the targeted application.
Desmet, S; Verhaegen, J; Glupzcynski, Y; Van Eldere, J; Melin, P; Goossens, H; Piérard, D; Declercq, P; Lagrou, K; Boel, A; Cartuyvels, R; Denis, O; Vandewal, W; Saegeman, V
A challenge panel of bacterial strains useful for clinical laboratories to validate their European Committee on Antimicrobial Susceptibility Testing (EUCAST) antimicrobial susceptibility test (AST) system was established. A total of 117 strains, obtained from Belgian Reference Centres (n = 57) and from routine clinical samples (n = 60) was selected based on resistance pattern. These strains were analysed in seven different laboratories by three different automated AST systems (Vitek (n = 2), Phoenix (n = 2) and Microscan (n = 2)) and by disc diffusion from five different manufacturers (Rosco (n = 2), Becton-Dickinson (n = 2), Biomérieux (n = 1), Bio-rad (n = 1) and i2a (n = 1)). To select the challenge panel, selection criteria were set for categorical agreement between the different systems and the number of very major errors, major errors and minor errors. Very major and major errors for at least two antibiotics were observed in 43% of all strains, leading to the exclusion of these strains from the selected panel. In only 10% of all tested strains was there 100% categorical agreement for all antibiotics. Finally, 28 strains (14 Gram-positive and 14 Gram-negative) covering a wide spectrum of resistance mechanisms were selected. Pilot-testing of this challenge panel in 20 laboratories mainly confirmed the results of the validation study. Only six strains withheld for the pilot study could not be used as challenge strain due to an overall (very) major error rate of >5% for a particular antibiotic (n = 5) or for two antibiotics (n = 1). To conclude, this challenge panel should facilitate the implementation and use of EUCAST breakpoints in laboratories.
Dowling, J N; McDevitt, D A; Pasculle, A W
Disk diffusion antimicrobial susceptibility testing of members of the family Legionellaceae was accomplished on buffered charcoal yeast extract agar by allowing the bacteria to grow for 6 h before placement of the disks, followed by an additional 42-h incubation period before the inhibitory zones were measured. This system was standardized by comparing the zone sizes with the MICs for 20 antimicrobial agents of nine bacterial strains in five Legionella species and of 19 laboratory-derived, erythromycin-resistant variants of Legionella micdadei. A high, linear correlation between zone size and MIC was found for erythromycin, trimethoprim, penicillin, ampicillin, carbenicillin, cephalothin, cefamandole, cefoxitin, moxalactam, chloramphenicol, vancomycin, and clindamycin. Disk susceptibility testing could be employed to screen Legionella isolates for resistance to any of these antimicrobial agents, of which only erythromycin is known to be efficacious in the treatment of legionellosis. With selected antibiotics, disk susceptibility patterns also appeared to accurately identify to the species level the legionellae. The range of the MICs of the legionellae for rifampin and the aminoglycosides was too small to determine whether the correlation of zone size with MIC was linear. However, laboratory-derived, high-level rifampin-resistant variants of L. micdadei demonstrated no inhibition zone around the rifampin disk, indicating that disk susceptibility testing would likely identify a rifampin-resistant clinical isolate. Of the antimicrobial agents tested, the only agents for which disk susceptibility testing was definitely not possible on buffered charcoal yeast extract agar were oxacillin, the tetracyclines, and the sulfonamides. PMID:6565706
Coenzyme Q1 is herein proposed as the best catalyst among coenzymes Q and vitamins K for quinone-catalyzed luminol chemiluminescent assays applied to rapid determination of viability or rapid antimicrobial susceptibility tests of Mycobacterium bovis. Luminol chemiluminescence intensity (LCI) was determined 10 min after the incubation of M. bovis with coenzyme Q1, and was proportional to CFU (colony-forming unit)/ml in the range of 9,000 to 2,250,000. LCI depended on the the production of the superoxide anion (O2-) rather than H2O2 during a 10-min incubation of M. bovis with coenzyme Q1, as superoxide dismutase reduced LCI more effectively than catalase. The minimal inhibitory concentrations (MICs) of 10 kinds of antituberculous agents estimated on the basis of decrease in LCI after one or two days' cultivation were in good agreement with MICs determined by turbidity analysis, which requires upwards of 1 week to complete.
Heliopoulos, Nikolaos S; Galeou, Angeliki; Papageorgiou, Sergios K; Favvas, Evangelos P; Katsaros, Fotios K; Stamatakis, Kostas
The chlorophyll a fluorescence based antimicrobial susceptibility testing (AST) method presented in a previous work was based on the measurement of Chl a fluorescence of the gram(-) cyanobacterium Synechococcus sp. PCC 7942. Synechococcus sp. PCC 7942 as a gram(-) bacterium is affected by antibacterial agents via mechanisms affecting all gram(-) bacteria, however, as an exclusively phototrophic organism it would also be affected by photosynthesis inhibitory action of an agent that otherwise has no antibacterial properties. In this report, the method is modified by replacing the exclusively phototrophic Synechococcus sp. PCC 7942 with the Synechocystis sp. PCC 6714, capable of both phototrophic and heterotrophic growth in order to add versatility and better reflect the antibacterial effects of surfaces under study towards nonphotosynthetic bacteria. Copyright © 2015 Elsevier B.V. All rights reserved.
Dekter, H E; Orelio, C C; Morsink, M C; Tektas, S; Vis, B; Te Witt, R; van Leeuwen, W B
Patients suffering from bacterial bloodstream infections have an increased risk of developing systematic inflammatory response syndrome (SIRS), which can result in rapid deterioration of the patients' health. Diagnostic methods for bacterial identification and antimicrobial susceptibility tests are time-consuming. The aim of this study was to investigate whether Raman spectroscopy would be able to rapidly provide an antimicrobial susceptibility profile from bacteria isolated directly from positive blood cultures. First, bacterial strains (n = 133) were inoculated in tryptic soy broth and incubated in the presence or absence of antibiotics for 5 h. Antimicrobial susceptibility profiles were analyzed by Raman spectroscopy. Subsequently, a selection of strains was isolated from blood cultures and analyzed similarly. VITEK®2 technology and broth dilution were used as the reference methods. Raman spectra from 67 antibiotic-susceptible strains showed discriminatory spectra in the absence or at low concentrations of antibiotics as compared to high antibiotic concentrations. For 66 antibiotic-resistant strains, no antimicrobial effect was observed on the bacterial Raman spectra. Full concordance with VITEK®2 data and broth dilution was obtained for the antibiotic-susceptible strains, 68 % and 98 %, respectively, for the resistant strains. Discriminative antimicrobial susceptibility testing (AST) profiles were obtained for all bacterial strains isolated from blood cultures, resulting in full concordance with the VITEK®2 data. It can be concluded that Raman spectroscopy is able to detect the antimicrobial susceptibility of bacterial species isolated from a positive blood culture bottle within 5 h. Although Raman spectroscopy is cheap and rapid, further optimization is required, to fulfill a great promise for future AST profiling technology development.
Safavieh, Mohammadali; Pandya, Hardik J; Venkataraman, Maanasa; Thirumalaraju, Prudhvi; Kanakasabapathy, Manoj Kumar; Singh, Anupriya; Prabhakar, Devbalaji; Chug, Manjyot Kaur; Shafiee, Hadi
Rapid antimicrobial susceptibility testing is important for efficient and timely therapeutic decision making. Due to globally spread bacterial resistance, the efficacy of antibiotics is increasingly being impeded. Conventional antibiotic tests rely on bacterial culture, which is time-consuming and can lead to potentially inappropriate antibiotic prescription and up-front broad range of antibiotic use. There is an urgent need to develop point-of-care platform technologies to rapidly detect pathogens, identify the right antibiotics, and monitor mutations to help adjust therapy. Here, we report a biosensor for rapid (<90 min), real time, and label-free bacteria isolation from whole blood and antibiotic susceptibility testing. Target bacteria are captured on flexible plastic-based microchips with printed electrodes using antibodies (30 min), and its electrical response is monitored in the presence and absence of antibiotics over an hour of incubation time. We evaluated the microchip with Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) as clinical models with ampicillin, ciprofloxacin, erythromycin, daptomycin, gentamicin, and methicillin antibiotics. The results are compared with the current standard methods, i.e. bacteria viability and conventional antibiogram assays. The technology presented here has the potential to provide precise and rapid bacteria screening and guidance in clinical therapies by identifying the correct antibiotics for pathogens.
Van den Bulck, K; Decostere, A; Gruntar, I; Baele, M; Krt, B; Ducatelle, R; Haesebrouck, F
The susceptibilities of Helicobacter felis (15 strains), H. bizzozeronii (7 strains), and H. salomonis (3 strains) to 10 antimicrobial agents were investigated by determination of the MIC using the agar dilution method. No consistent differences were noticed between the different Helicobacter species, which were all highly susceptible to ampicillin, clarithromycin, tetracycline, tylosin, enrofloxacin, gentamicin, and neomycin, as demonstrated by low MICs. Higher MICs were obtained for lincomycin (up to 8 microg/ml) and spectinomycin (up to 4 microg/ml). Two H. felis strains showed a MIC of 16 microg/ml for metronidazole, suggesting acquired resistance to this antimicrobial agent.
Jorgensen, J H; Skweres, J A; Mishra, S K; McElmeel, M L; Maher, L A; Mulder, R; Lancaster, M V; Pierson, D L
Very little is known regarding the effects of the microgravity environment of space flight upon the action of antimicrobial agents on bacterial pathogens. This study was undertaken to develop a simple method for conducting antibacterial susceptibility tests during a space shuttle mission. Specially prepared susceptibility test research cards (bioMérieux Vitek, Hazelwood, Mo.) were designed to include 6 to 11 serial twofold dilutions of 14 antimicrobial agents, including penicillins, cephalosporins, a beta-lactamase inhibitor, vancomycin, erythromycin, tetracycline, gentamicin, ciprofloxacin, and trimethoprim-sulfamethoxazole. MICs of the drugs were determined by visual reading of color end points in the Vitek research cards made possible by incorporation of a colorimetric growth indicator (alamarBlue; Accumed International, Westlake, Ohio). This study has demonstrated reproducible susceptibility results in the testing of isolates of Staphylococcus aureus, group A Streptococcus species, Enterococcus faecalis, Escherichia coli (beta-lactamase-positive and -negative strains), Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa. In some instances, the MICs were comparable to those determined by a standard broth microdilution method, while in some cases the unique test media and format yielded slightly different values that were themselves reproducible. The proposed in-flight experiment will include inoculation of the Vitek cards on the ground prior to launch of the space shuttle, storage of inoculated cards at refrigeration temperature aboard the space shuttle until experiment initiation, and then incubation of the cards for 18 to 48 h prior to visual interpretation of MICs by the mission's astronauts. Ground-based studies have shown reproducible MICs following storage of inoculated cards for 7 days at 4 to 8 degrees C to accommodate the mission's time schedule and the astronaut's activities. For comparison, ground-based control (normal gravity
Jorgensen, James H.; Skweres, Joyce A.; Mishra S. K.; McElmeel, M. Letticia; Maher, Louise A.; Mulder, Ross; Lancaster, Michael V.; Pierson, Duane L.
Very little is known regarding the affects of the microgravity environment of space flight upon the action of antimicrobial agents on bacterial pathogens. This study was undertaken to develop a simple method for conducting antibacterial susceptibility tests during a Space Shuttle mission. Specially prepared susceptibility test research cards (bioMerieux Vitek, Hazelwood, MO) were designed to include 6-11 serial two-fold dilutions of 14 antimicrobial agents, including penicillins, cephalosporins, a Beta-lactamase inhibitor, vancomycin, erythromycin, tetracycline, gentamicin, ciprofloxacin, and trimethoprim/sulfamethoxazole. Minimal inhibitory concentrations (MICS) of the drugs were determined by visual reading of color endpoints in the Vitek research cards made possible by incorporation of a colorimetric growth indicator (alamarBlue(Trademark), Accumed International, Westlake, OH). This study has demonstrated reproducible susceptibility results when testing isolates of Staphylococcus aurezis, Group A Streptococcus, Enterococcusfaecalis, Escherichia coli (beta-lactamase positive and negative strains), Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomoiias aeruginosa. In some instances, the MICs were comparable to those determined using a standard broth microdilution method, while in some cases the unique test media and format yielded slightly different values, that were themselves reproducible. The proposed in-flight experiment will include inoculation of the Vitek cards on the ground prior to launch of the Space Shuttle, storage of inoculated cards at refrigeration temperature aboard the Space Shuttle until experiment initiation, then incubation of the cards for 18-48 h prior to visual interpretation of MICs by the mission's astronauts. Ground-based studies have shown reproducible MICs following storage of inoculated cards for 7 days at 4-8 C to accommodate the mission's time schedule and the astronauts' activities. For comparison, ground-based control
Liu, Hsi; Taylor, Thomas H; Pettus, Kevin; Trees, David
We studied whether the Etest can be used as an alternative to agar dilution to determine antimicrobial susceptibilities of ceftriaxone, cefixime, and cefpodoxime in Neisseria gonorrhoeae surveillance. One hundred fifteen clinical and laboratory isolates of N. gonorrhoeae were tested following the Clinical Laboratory Improvement Amendments (CLIA)-approved CLSI standard agar dilution method and, separately, by the Etest according to the manufacturer's recommendations. The MICs were determined and compared. Ten laboratory-generated mutants were used to simulate substantially nonsusceptible specimens. The Etest and agar dilution methods were well correlated. Statistical tests produced regression R2 values of 88%, 82%, and 85% and Pearson correlation coefficients of 92%, 91%, and 92% for ceftriaxone, cefixime, and cefpodoxime, respectively. When paired comparisons were made, the two tests were 88.7%, 80%, and 87% within 1 log2 dilution from each other for ceftriaxone, cefixime, and cefpodoxime, respectively. The within-2-log2 agreements were 99.1%, 98.3%, and 94.8% for ceftriaxone, cefixime, and cefpodoxime, respectively. Notwithstanding the good correlations and the within-2-log2 general agreement, the Etest results produced slightly lower MICs than the agar dilution results. In conclusion, we found that the Etest can be effectively used as an alternative to agar dilution testing to determine the susceptibility of N. gonorrhoeae to ceftriaxone, cefixime, and cefpodoxime, although we recommend further research into extremely resistant isolates. For isolates within the typical range of clinical MICs, reexamination of the Etest interpretation of susceptible and nonsusceptible categories would likely allow for successful transition from agar dilution to the Etest.
Taylor, Thomas H.; Pettus, Kevin; Trees, David
We studied whether the Etest can be used as an alternative to agar dilution to determine antimicrobial susceptibilities of ceftriaxone, cefixime, and cefpodoxime in Neisseria gonorrhoeae surveillance. One hundred fifteen clinical and laboratory isolates of N. gonorrhoeae were tested following the Clinical Laboratory Improvement Amendments (CLIA)-approved CLSI standard agar dilution method and, separately, by the Etest according to the manufacturer's recommendations. The MICs were determined and compared. Ten laboratory-generated mutants were used to simulate substantially nonsusceptible specimens. The Etest and agar dilution methods were well correlated. Statistical tests produced regression R2 values of 88%, 82%, and 85% and Pearson correlation coefficients of 92%, 91%, and 92% for ceftriaxone, cefixime, and cefpodoxime, respectively. When paired comparisons were made, the two tests were 88.7%, 80%, and 87% within 1 log2 dilution from each other for ceftriaxone, cefixime, and cefpodoxime, respectively. The within-2-log2 agreements were 99.1%, 98.3%, and 94.8% for ceftriaxone, cefixime, and cefpodoxime, respectively. Notwithstanding the good correlations and the within-2-log2 general agreement, the Etest results produced slightly lower MICs than the agar dilution results. In conclusion, we found that the Etest can be effectively used as an alternative to agar dilution testing to determine the susceptibility of N. gonorrhoeae to ceftriaxone, cefixime, and cefpodoxime, although we recommend further research into extremely resistant isolates. For isolates within the typical range of clinical MICs, reexamination of the Etest interpretation of susceptible and nonsusceptible categories would likely allow for successful transition from agar dilution to the Etest. PMID:24554750
Ter Laak, E A; Pijpers, A; Noordergraaf, J H; Schoevers, E C; Verheijden, J H
The MICs of 18 antimicrobial agents used against strains of three porcine Mycoplasma species were determined by a serial broth dilution method. Twenty field strains of M. hyorhinis, ten field strains of M. hyopneumoniae, six field strains of M. flocculare, and the type strains of these species were tested. Twelve field strains and the type strain of M. hyorhinis were also tested by an agar dilution method. Tests were read at various time points. When the broth dilution method was used, the final MIC had to be read 2 days after color changes had stopped. MICs of tetracycline, oxytetracycline, doxycycline, and minocycline were low for the three Mycoplasma species tested. MICs of chlortetracycline were 8 to 16 times higher than MICs of the other tetracyclines. Spiramycin, tylosin, kitasamycin, spectinomycin, tiamulin, lincomycin, and clindamycin were effective against all strains of M. hyorhinis and M. hyopneumoniae. The quinolones were highly effective against M. hyopneumoniae but less effective against M. hyorhinis. The susceptibility patterns for M. hyopneumoniae and M. flocculare were similar. PMID:2024954
Ter Laak, E A; Pijpers, A; Noordergraaf, J H; Schoevers, E C; Verheijden, J H
The MICs of 18 antimicrobial agents used against strains of three porcine Mycoplasma species were determined by a serial broth dilution method. Twenty field strains of M. hyorhinis, ten field strains of M. hyopneumoniae, six field strains of M. flocculare, and the type strains of these species were tested. Twelve field strains and the type strain of M. hyorhinis were also tested by an agar dilution method. Tests were read at various time points. When the broth dilution method was used, the final MIC had to be read 2 days after color changes had stopped. MICs of tetracycline, oxytetracycline, doxycycline, and minocycline were low for the three Mycoplasma species tested. MICs of chlortetracycline were 8 to 16 times higher than MICs of the other tetracyclines. Spiramycin, tylosin, kitasamycin, spectinomycin, tiamulin, lincomycin, and clindamycin were effective against all strains of M. hyorhinis and M. hyopneumoniae. The quinolones were highly effective against M. hyopneumoniae but less effective against M. hyorhinis. The susceptibility patterns for M. hyopneumoniae and M. flocculare were similar.
Kim, Samuel C.; Cestellos-Blanco, Stefano; Inoue, Keisuke; Zare, Richard N.
Effective treatment of bacterial infection relies on timely diagnosis and proper prescription of antibiotic drugs. The antimicrobial susceptibility test (AST) is one of the most crucial experimental procedures, providing the baseline information for choosing effective antibiotic agents and their dosages. Conventional methods, however, require long incubation times or significant instrumentation costs to obtain test results. We propose a lab-on-a-chip approach to perform AST in a simple, economic, and rapid manner. Our assay platform miniaturizes the standard broth microdilution method on a microfluidic device (20 × 20 mm) that generates an antibiotic concentration gradient and delivers antibiotic-containing culture media to eight 30-nL chambers for cell culture. When tested with 20 μL samples of a model bacterial strain (E. coli ATCC 25922) treated with ampicillin or streptomycin, our method allows for the determination of minimum inhibitory concentrations consistent with the microdilution test in three hours, which is almost a factor of ten more rapid than the standard method. PMID:27025635
Al-Othrubi, Saleh M; Hanafiah, Alfizah; Radu, Son; Neoh, Humin; Jamal, Rahaman
To find out the prevalence and antimicrobial susceptibility of Vibrio parahaemolyticus in seafoods and environmental sources. The study was carried out at the Center of Excellence for Food Safety Research, University Putra Malaysia; Universiti Kebangsaan Malaysia; Medical Molecular Biology Institute; and University Kebansaan Malaysia Hospital, Malaysia between January 2006 and August 2008. One hundred and forty-four isolates from 400 samples of seafood (122 isolates) and seawater sources (22 isolates) were investigated for the presence of thermostable direct hemolysin (tdh+) and TDH-related hemolysin (trh+) genes using the standard methods. The E-test method was used to test the antimicrobial susceptibility. The study indicates low occurrence of tdh+ (0.69%) and trh+ isolates (8.3%). None of the isolates tested posses both virulence genes. High sensitivity was observed against tetracycline (98%). The mean minimum inhibitory concentration (MIC) of the isolates toward ampicillin increased from 4 ug/ml in 2004 to 24 ug/ml in 2007. The current study demonstrates a low occurrence of pathogenic Vibrio parahaemolyticus in the marine environment and seafood. Nonetheless, the potential risk of vibrio infection due to consumption of Vibrio parahaemolyticus contaminated seafood in Malaysia should not be neglected.
Jacobs, M R; Mithal, Y; Robins-Browne, R M; Gaspar, M N; Koornhof, H J
Antimicrobial susceptibility testing of pneumococci is now essential to monitor for the presence of resistance to agents such as the penicillins, macrolides, lincomycins, chloramphenicol, and tetracycline. In this study, clinical isolates of a selection of resistant South African strains were tested for antimicrobial susceptibility by minimal inhibitory concentration (MIC) determination and by a modified Kirby-Bauer disk diffusion technique, using Mueller-Hinton medium supplemented with 5% horse blood. Disk diffusion breakpoints were determined for penicillin G, erythromycin, clindamycin, tetracycline, chloramphenicol, and rifampin. Reliable results were obtained on disk diffusion for all these agents except for penicillin G. With 6-mug penicillin G disks, zones of strains with intermediate penicillin susceptibility overlapped those of sensitive and resistant strains. With 5-mug methicillin disks, clearer separation of strains based on susceptibility to penicillin G occurred. Strains with zones of <35 mm around penicillin G disks and <25 mm around methicillin disks should have penicillin G MICs determined to confirm their resistance to penicillin G. In view of the potential for pneumococci to be resistant to the agents used in this study, antimicrobial susceptibility of all clinically significant isolates should be determined.
Cifuentes-D, Marcela; Silva, Francisco; García, Patricia; Bello, Helia; Briceño, Isabel; Calvo-A, Mario; Labarca, Jaime
Bacteria antimicrobial resistance is an uncontrolled public health problem that progressively increases its magnitude and complexity. The Grupo Colaborativo de Resistencia, formed by a join of experts that represent 39 Chilean health institutions has been concerned with bacteria antimicrobial susceptibility in our country since 2008. In this document we present in vitro bacterial susceptibility accumulated during year 2012 belonging to 28 national health institutions that represent about 36% of hospital discharges in Chile. We consider of major importance to report periodically bacteria susceptibility so to keep the medical community updated to achieve target the empirical antimicrobial therapies and the control measures and prevention of the dissemination of multiresistant strains.
Nakasone, Isamu; Kisanuki, Kyoko; Higa, Miyako; Kinjo, Tohru; Yamane, Nobuhisa
We evaluated the usefulness of an early-harvested bacterial cell suspension to the fully automated RAISUS (Nissui Pharmaceuticals Co., Ltd., Tokyo) to provide the results of species-identification and antimicrobial susceptibility testings within a day after overnight-incubation of the primary cultures. A single, well-separated colony appeared on the primary culture plate was transferred onto a blood agar or chocolate agar plates, then incubated for 3 to 6 hours. The cell suspension to the RAISUS was properly prepared to the McFarland 0.5 turbidity from the early-harvested bacterial cells. When the five ATCC reference strains, consisting of Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Streptococcus pneumoniae ATCC 49619, Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853, were repeatedly tested for the species-identification, all the identification results were acceptable. Antimicrobial susceptibility tests were evaluated with the above five strains and Haemophilus influenzae ATCC 49247. The results obtained indicated that the most susceptibility test results were comparable to those MICs obtained by the standard test procedure, but some strains, in particular, H. influenzae and P. aeruginosa gave significantly discrepant MICs for certain antimicrobial agents. The significant discrepancy in MIC determinations regarded the difference of viable cell concentrations in the cell suspension prepared respectively. Through the analysis of laboratory workflow, it became to apparent that 18S to 20S of the tests were completed by 5:00 p.m., and it required to wait until 3:00 a.m. to complete 90S of the tests. With these results, the early-harvested bacterial cell suspension is applicable to species-identification by RAISUS, but it is necessary to adjust viable cell concentrations to antimicrobial susceptibility test. Also, it is urgent to reconstitute a daily workflow to improve the rapidity of RAISUS test function.
Mazzariol, Annarita; Aldegheri, Marco; Ligozzi, Marco; Lo Cascio, Giuliana; Koncan, Raffaella; Fontana, Roberta
A total of 78 isolates of Pseudomonas aeruginosa grouped according to the phenotype for ceftazidime and imipenem susceptibility/resistance were used to assess the accuracy of the Vitek 2 system in antimicrobial susceptibility testing. Comparisons were made with a MIC gradient test for piperacillin-tazobactam, ceftazidime, aztreonam, imipenem, meropenem, gentamicin, and ciprofloxacin. For the total of 546 isolate-antimicrobial combinations tested, the category agreement was 83.6%, with 2.0, 1.6, and 12.8% very major, major, and minor errors, respectively. Vitek 2 accuracy was influenced differently by the mechanism responsible for resistance, and interpretation of the results in relation to phenotype could improve the performance of the system. PMID:18434562
Wang, Xin; Meng, Jianghong; Zhou, Ting; Zhang, Yanming; Yang, Baowei; Xi, Meili; Sheng, Jinling; Zhi, Shuai; Xia, Xiaodong
Staphylococcus aureus is commonly present in humans and animals. The aim of this study was to investigate antimicrobial resistance and genetic characteristics of S. aureus from food and food animals in Shaanxi Province in China. A total of 332 nasal swabs, breast skin swabs, raw milk, and pork samples were collected from local pig, dairy farms, or local grocery stores and screened for the presence of S. aureus. S. aureus isolates were characterized using antimicrobial susceptibility, pulsed-field gel electrophoresis (PFGE) analysis, and polymerase chain reaction for detecting pvl and mecA genes. Methicillin-resistant S. aureus (MRSA) strains were additionally tested for SCCmec type and exfoliative toxin genes. The prevalence of S. aureus was 30.6% in pig nasal swabs, 32.5% in pork, 25.7% in cow nasal swabs, 30.8% in cow breast skin swabs, and 29.3% in milk samples. Resistances were common among isolates tested against erythromycin (65.7%), tetracycline (65.7%), ciprofloxacin (52.7%), followed by gentamicin (36.7%), chloramphenicol (23.1%), cefoxitin (8.3%), and oxacillin (7.7%), but no isolate was resistant to vancomycin, amikacin, or cefoperazone. pvl gene was found in the isolates from all types of samples except from cow nasal swabs. Fourteen isolates from pig nasal swabs contained mecA gene and were considered as MRSA. PFGE analysis showed that nasal isolates differed from food isolates, but isolates from the same animal source appeared to cluster closely. The PFGE patterns of MRSA isolates were different from other S. aureus isolates from pig nasal cavity even though they were from the same source. All the MRSA isolates belonged to SCCmec type IV(b). No isolates contained exfoliative toxin genes. These findings indicated that S. aureus, including multidrug-resistant S. aureus, are widely spread in food animals and animal-derived foods in Shaanxi Province, China. MRSA isolates from pigs may pose potential health risks for workers in swine farms and the
Kommedal, Øyvind; Aasen, Johanne Lind; Lindemann, Paul Christoffer
Diagnostic testing of positive blood cultures is among the most critical tasks performed by clinical microbiology laboratories, and the total analysis time from sampling to results should be kept as short as possible. By providing identification of pelleted bacteria directly from positive blood-cultures, MALDI-TOF MS opens for relatively low-complex species-adjusted genetic susceptibility testing from the same bacterial pellet. In our lab routine, we prospectively evaluated a rapid in-house real-time PCR targeting the most common aminoglycoside and cephalosporin resistance genes in Escherichia coli and Klebsiella pneumoniae and measured time to preliminary susceptibility reporting for 138 samples. The results were compared to direct phenotypic susceptibility testing with interpretation after 6 h and overnight incubation respectively. Results from the genetic susceptibility testing were available for 69.5% (96/138) of the positive blood cultures within 24 h after sample collection. No phenotypic susceptibility results were available at this time. Compared to overnight direct susceptibility testing, the average time from sample collection to preliminary susceptibility reporting was reduced with 43%, from 45 h and 5 min to 25 h and 44 min, providing an earlier adjustment of antimicrobial therapy for 12 patients. Minor logistic adjustments have the potential to save yet another 4 h.
Kärpänoja, Pauliina; Nissinen, Antti; Huovinen, Pentti; Sarkkinen, Hannu
Knowledge of the quality and conformity of antimicrobial resistance data is important for comparing resistance rates regionally and over time. In this study, we have evaluated these features of the Finnish national susceptibility surveillance data for two respiratory tract pathogens, Streptococcus pneumoniae and Haemophilus influenzae. For this purpose internal quality control results for two isolates (S. pneumoniae ATCC 49619 and H. influenzae ATCC 49247) were analyzed from 21 clinical microbiology laboratories over a 3-year period. The results show that standardization of the susceptibility testing methods has proceeded well. The number of protocols used for susceptibility testing has declined (from seventeen methods to two with S. pneumoniae and from eleven to three with H. influenzae) and the reproducibility is good. Nevertheless, we noticed that a few laboratories test and report susceptibility results without defined break-points and even include antimicrobials with questionable therapeutic effect. Another non-compliance with the standard was a lack of a regular control system to verify the attainment of the intended quality of results in some laboratories. Interlaboratory analysis of quality control results is a good way to evaluate the quality and conformity of national resistance data. Finnish laboratories have produced very reproducible and accurate susceptibility results in the pre-EUCAST period, which ended in 2011.
Dargatz, David A; Erdman, Matthew M; Harris, Beth
Antimicrobial resistance is a serious threat to animal and human health worldwide, requiring a collaborative, holistic approach. The U.S. Government has developed a national strategy to address antimicrobial resistance, with one component being to monitor antimicrobial resistance in agricultural settings. We developed a survey to collect information about antimicrobial susceptibility testing (AST) from the veterinary diagnostic laboratory community in the United States, assessing current practices and technologies and determining how AST information is shared. Of the 132 surveys administered, 52 (39%) were returned. Overall, responding laboratories conducted susceptibility tests on 98,788 bacterial isolates in 2014, with Escherichia coli being the most common pathogen tested across all animal species. The 2 most common AST methods employed were the disk diffusion method (71%) and the Sensititre platform broth microdilution system (59%). Laboratories primarily used the Clinical Laboratory Standards Institute (CLSI) VET-01 standard (69%) and the automatically calculated interpretations provided by the commercial AST systems (61%) for interpreting their AST data. Only 22% of laboratories published AST data on a periodic basis, usually via annual reports published on the laboratory's website or through peer-reviewed journals for specific pathogens. Our results confirm that disk diffusion and broth microdilution remain the standard AST methods employed by U.S. veterinary diagnostic laboratories, and that CLSI standards are commonly used for interpreting AST results. This information will help determine the most efficient standardized methodology for future surveillance. Furthermore, the current infrastructure within laboratories, once harmonized, will help provide a mechanism for conducting national surveillance programs.
Lascols, Christine; Sue, David; Weigel, Linda M.
Rapid methods to determine antimicrobial susceptibility would assist in the timely distribution of effective treatment or postexposure prophylaxis in the aftermath of the release of bacterial biothreat agents such as Bacillus anthracis, Yersinia pestis, or Burkholderia pseudomallei. Conventional susceptibility tests require 16 to 48 h of incubation, depending on the bacterial species. We evaluated a method that is based on laser light scattering technology that measures cell density in real time. We determined that it has the ability to rapidly differentiate between growth (resistant) and no growth (susceptible) of several bacterial threat agents in the presence of clinically relevant antimicrobials. Results were available in <4 h for B. anthracis and <6 h for Y. pestis and B. pseudomallei. One exception was B. pseudomallei in the presence of ceftazidime, which required >10 h of incubation. Use of laser scattering technology decreased the time required to determine antimicrobial susceptibility by 50% to 75% for B. anthracis, Y. pestis, and B. pseudomallei compared to conventional methods. PMID:26984973
Xu, Jin; Liu, Xiumei; Yang, Baolan; Li, Zhigang
The aim of our study was to analyse the antibiotic susceptibility of 31 probiotics strains, including 9 Bifidobacterium and 22 Lactobacillus used for the manufacture of various fermented foods in China. Probiotics are tested for minimum inhibitory concentrations (MIC) of 24 kinds of antibiotics by broth dilution method on cation-adjusted Mueller-Hinton broth with lysed horse blood. 31 strains of probiotics were sensitive to ampicillin, penicillin, imipenem, gentamicine, amoxicillin, amoxicillin/clavulanic acid, gatifloxacin, erythromycin, clindamycin, and resistant to nalidixic acid, vancomycine, fosfomycin.
Farmer, James J.; O'Donnell, Edward D.
A computerized system is described which is used to store, manipulate and retrieve antimicrobial susceptibility data in the clinical microbiology lab. Features include facilitated input of susceptibility data, rapid generation of reports, realtime access to data, and enhanced retrieval of information for Infection Control.
Cercenado, Emilia; Cercenado, Sonia; Marín, Mercedes; Rico, María-Victoria; Vicente, Teresa; Bouza, Emilio
We compared the direct E-test susceptibility testing (DET) on respiratory samples with a standard microbroth dilution method (MBD) after quantitative cultures. A total of 152 samples from intensive care unit patients were processed by DET onto Mueller-Hinton agar. Oxacillin, piperacillin/tazobactam, cefepime, imipenem, ciprofloxacin, and amikacin were the antimicrobials evaluated. Cultures were 102 monomicrobials and 50 polymicrobials. Overall, 93.8% of the isolates were recovered by the DET. Among the 772 microorganism-antibiotic combinations evaluated, there was a total agreement with the MBD in 96.1%. There were 8 very major errors (1.03%), 15 major (1.94%), and 7 minor (0.91%). All discrepancies but one corresponded to polymicrobial cultures, and most occurred with cefepime (8 cases, 7.07%) and imipenem (7 cases, 6.18%). Readings of DET were easy to interpret and improved with transmitted light. DET on respiratory samples is a rapid technique that provides susceptibility results in 18 to 24 h comparable with these obtained by MBD.
Feng, Steve W.; Tseng, Derek; Di Carlo, Dino; Garner, Omai B.; Ozcan, Aydogan
Antimicrobial susceptibility testing (AST) is commonly used for determining microbial drug resistance, but routine testing, which can significantly reduce the spread of multi-drug resistant organisms, is not regularly performed in resource-limited and field-settings due to technological challenges and lack of trained diagnosticians. We developed a portable cost-effective smartphone-based colorimetric 96-well microtiter plate (MTP) reader capable of automated AST without the need for a trained diagnostician. This system is composed of a smartphone used in conjunction with a 3D-printed opto-mechanical attachment, which holds a set of inexpensive light-emitting-diodes and fiber-optic cables coupled to the 96-well MTP for enabling the capture of the transmitted light through each well by the smartphone camera. Images of the MTP plate are captured at multiple exposures and uploaded to a local or remote server (e.g., a laptop) for automated processing/analysis of the results using a custom-designed smartphone application. Each set of images are combined to generate a high dynamic-range image and analyzed for well turbidity (indicative of bacterial growth), followed by interpretative analysis per plate to determine minimum inhibitory concentration (MIC) and drug susceptibility for the specific bacterium. Results are returned to the originating device within 1 minute and shown to the user in tabular form. We demonstrated the capability of this platform using MTPs prepared with 17 antibiotic drugs targeting Gram-negative bacteria and tested 82 patient isolate MTPs of Klebsiella pneumoniae, achieving well turbidity accuracy of 98.19%, MIC accuracy of 95.15%, and drug susceptibility interpretation accuracy of 99.06%, meeting the FDA defined criteria for AST.
Dupont, Chloé; Jumas-Bilak, Estelle; Michon, Anne-Laure; Chiron, Raphaël; Marchandin, Hélène
Chronic colonization by opportunistic environmental bacteria is frequent in the airways of cystic fibrosis (CF) patients. Studies of Pseudomonas aeruginosa evolution during persistence have highlighted the emergence of pathoadaptive genotypes and phenotypes, leading to complex and diversified inpatient colonizing populations also observed at the intraspecimen level. Such diversity, including heterogeneity in resistance profiles, has been considered an adaptive strategy devoted to host persistence. Longitudinal genomic diversity has been shown for the emergent opportunistic pathogen Achromobacter, but phenotypic and genomic diversity has not yet been studied within a simple CF sputum sample. Here, we studied the genomic diversity and antimicrobial resistance heterogeneity of 132 Achromobacter species strains (8 to 27 strains of identical or distinct colonial morphotypes per specimen) recovered from the sputum samples of 9 chronically colonized CF patients. We highlighted the high within-sample and within-morphotype diversity of antimicrobial resistance (disk diffusion) and genomic (pulsed-field gel electrophoresis) profiles. No sputum sample included strains with identical pulsotypes or antibiotic susceptibility patterns. Differences in clinical categorization were observed for the 9 patients and concerned 3 to 11 antibiotics, including antibiotics recommended for use against Achromobacter Within-sample antimicrobial resistance heterogeneity, not predictable from colonial morphology, suggested that it may represent a selective advantage against antibiotics in an Achromobacter persisting population and potentially compromise the antibiotic management of CF airway infections. Copyright © 2016 American Society for Microbiology.
Dupont, Chloé; Jumas-Bilak, Estelle; Michon, Anne-Laure; Chiron, Raphaël
ABSTRACT Chronic colonization by opportunistic environmental bacteria is frequent in the airways of cystic fibrosis (CF) patients. Studies of Pseudomonas aeruginosa evolution during persistence have highlighted the emergence of pathoadaptive genotypes and phenotypes, leading to complex and diversified inpatient colonizing populations also observed at the intraspecimen level. Such diversity, including heterogeneity in resistance profiles, has been considered an adaptive strategy devoted to host persistence. Longitudinal genomic diversity has been shown for the emergent opportunistic pathogen Achromobacter, but phenotypic and genomic diversity has not yet been studied within a simple CF sputum sample. Here, we studied the genomic diversity and antimicrobial resistance heterogeneity of 132 Achromobacter species strains (8 to 27 strains of identical or distinct colonial morphotypes per specimen) recovered from the sputum samples of 9 chronically colonized CF patients. We highlighted the high within-sample and within-morphotype diversity of antimicrobial resistance (disk diffusion) and genomic (pulsed-field gel electrophoresis) profiles. No sputum sample included strains with identical pulsotypes or antibiotic susceptibility patterns. Differences in clinical categorization were observed for the 9 patients and concerned 3 to 11 antibiotics, including antibiotics recommended for use against Achromobacter. Within-sample antimicrobial resistance heterogeneity, not predictable from colonial morphology, suggested that it may represent a selective advantage against antibiotics in an Achromobacter persisting population and potentially compromise the antibiotic management of CF airway infections. PMID:27807149
Sun, Wei; Weingarten, Rebecca A; Xu, Miao; Southall, Noel; Dai, Sheng; Shinn, Paul; Sanderson, Philip E; Williamson, Peter R; Frank, Karen M; Zheng, Wei
Current antimicrobial susceptibility testing has limited screening capability for identifying empirical antibiotic combinations to treat severe bacterial infections with multidrug-resistant (MDR) organisms. We developed a new antimicrobial susceptibility assay using automated ultra-high-throughput screen technology in combination with a simple bacterial growth assay. A rapid screening of 5170 approved drugs and other compounds identified 25 compounds with activities against MDR Klebsiella pneumoniae. To further improve the efficacy and reduce the effective drug concentrations, we applied a targeted drug combination approach that integrates drugs' clinical antimicrobial susceptibility breakpoints, achievable plasma concentrations, clinical toxicities and mechanisms of action to identify optimal drug combinations. Three sets of three-drug combinations were identified with broad-spectrum activities against 10 MDR clinical isolates including K. pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Citrobacter freundii, Enterobacter cloacae and Escherichia coli. Colistin–auranofin–ceftazidime and colistin–auranofin–rifabutin suppressed >80% growth of all 10 MDR strains; while rifabutin–colistin–imipenem inhibited >75% of these strains except two Acinetobacter baumannii isolates. The results demonstrate this new assay has potential as a real-time method to identify new drugs and effective drug combinations to combat severe clinical infections with MDR organisms. PMID:27826141
Sun, Wei; Weingarten, Rebecca A; Xu, Miao; Southall, Noel; Dai, Sheng; Shinn, Paul; Sanderson, Philip E; Williamson, Peter R; Frank, Karen M; Zheng, Wei
Current antimicrobial susceptibility testing has limited screening capability for identifying empirical antibiotic combinations to treat severe bacterial infections with multidrug-resistant (MDR) organisms. We developed a new antimicrobial susceptibility assay using automated ultra-high-throughput screen technology in combination with a simple bacterial growth assay. A rapid screening of 5170 approved drugs and other compounds identified 25 compounds with activities against MDR Klebsiella pneumoniae. To further improve the efficacy and reduce the effective drug concentrations, we applied a targeted drug combination approach that integrates drugs' clinical antimicrobial susceptibility breakpoints, achievable plasma concentrations, clinical toxicities and mechanisms of action to identify optimal drug combinations. Three sets of three-drug combinations were identified with broad-spectrum activities against 10 MDR clinical isolates including K. pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Citrobacter freundii, Enterobacter cloacae and Escherichia coli. Colistin-auranofin-ceftazidime and colistin-auranofin-rifabutin suppressed >80% growth of all 10 MDR strains; while rifabutin-colistin-imipenem inhibited >75% of these strains except two Acinetobacter baumannii isolates. The results demonstrate this new assay has potential as a real-time method to identify new drugs and effective drug combinations to combat severe clinical infections with MDR organisms.
Smith, Kenneth P; Kirby, James E
With rapid emergence of multidrug-resistant bacteria, there is often a need to perform susceptibility testing for less commonly used or newer antimicrobial agents. Such testing can often be performed only by using labor-intensive, manual dilution methods and lies outside the capacity of most clinical labs, necessitating reference laboratory testing and thereby delaying the availability of susceptibility data. To address the compelling clinical need for microbiology laboratories to perform such testing in-house, we explored a novel, automated, at-will broth microdilution-based susceptibility testing platform. Specifically, we used the modified inkjet printer technology in the HP D300 digital dispensing system to dispense, directly from stock solutions into a 384-well plate, the 2-fold serial dilution series required for broth microdilution testing. This technology was combined with automated absorbance readings and data analysis to determine MICs. Performance was verified by testing members of the Enterobacteriaceae for susceptibility to ampicillin, cefazolin, ciprofloxacin, colistin, gentamicin, meropenem, and tetracycline in comparison to the results obtained with a broth microdilution reference standard. In precision studies, essential and categorical agreement levels were 96.8% and 98.3%, respectively. Furthermore, significantly fewer D300-based measurements were outside ±1 dilution from the modal MIC, suggesting enhanced reproducibility. In accuracy studies performed using a panel of 80 curated clinical isolates, rates of essential and categorical agreement and very major, major, and minor errors were 94%, 96.6%, 0%, 0%, and 3.4%, respectively. Based on these promising initial results, it is anticipated that the D300-based methodology will enable hospital-based clinical microbiology laboratories to perform at-will broth microdilution testing of antimicrobials and to address a critical testing gap.
Smith, Kenneth P.
With rapid emergence of multidrug-resistant bacteria, there is often a need to perform susceptibility testing for less commonly used or newer antimicrobial agents. Such testing can often be performed only by using labor-intensive, manual dilution methods and lies outside the capacity of most clinical labs, necessitating reference laboratory testing and thereby delaying the availability of susceptibility data. To address the compelling clinical need for microbiology laboratories to perform such testing in-house, we explored a novel, automated, at-will broth microdilution-based susceptibility testing platform. Specifically, we used the modified inkjet printer technology in the HP D300 digital dispensing system to dispense, directly from stock solutions into a 384-well plate, the 2-fold serial dilution series required for broth microdilution testing. This technology was combined with automated absorbance readings and data analysis to determine MICs. Performance was verified by testing members of the Enterobacteriaceae for susceptibility to ampicillin, cefazolin, ciprofloxacin, colistin, gentamicin, meropenem, and tetracycline in comparison to the results obtained with a broth microdilution reference standard. In precision studies, essential and categorical agreement levels were 96.8% and 98.3%, respectively. Furthermore, significantly fewer D300-based measurements were outside ±1 dilution from the modal MIC, suggesting enhanced reproducibility. In accuracy studies performed using a panel of 80 curated clinical isolates, rates of essential and categorical agreement and very major, major, and minor errors were 94%, 96.6%, 0%, 0%, and 3.4%, respectively. Based on these promising initial results, it is anticipated that the D300-based methodology will enable hospital-based clinical microbiology laboratories to perform at-will broth microdilution testing of antimicrobials and to address a critical testing gap. PMID:27335151
Khalili, Hossein; Soltani, Rasool; Negahban, Sorrosh; Abdollahi, Alireza; Gholami, Keirollah
Disk diffusion test is the usual applicable method for assessing the antimicrobial susceptibility pattern in most institutions and hospitals. The aim of this study was to determine the reliability of resistant-reported results of disk diffusion test for 6 routinely used antibiotics against Gram-positive microorganisms of nosocomial origin, using E-test method. Over a 1-year period, clinical specimens (e.g. blood, tracheal secretions, wound secretions, urine, etc.) were obtained from hospitalized patients with defined nosocomial infection and were cultured. Isolated Gram-positive bacteria underwent disk diffusion test for cephalothin, oxacillin, clindamycin, ciprofloxacin, vancomycin, teicoplanin (only for Enterococci), and meropenem antibiotics. E-test method was performed for all isolates resistant or intermediately sensitive to the disks of any mentioned antibiotics. Data showed compatible results of disk diffusion test with the results of E-test method for cephalothin, oxacillin, ciprofloxacin, vancomycin, and teicoplanin. None of ciprofloxacin- and vancomycin-resistant isolates in disk diffusion test showed sensitivity in E-test method. Significant differences between the results of disk diffusion and E-test methods were observed for clindamycin and meropenem against S.aureus (p = 0.01 and 0.04, respectively) and Enterococcus spp (p = 0.03 and 0.02, respectively). In order to increase the reliability of antimicrobial susceptibility results, it is recommended to perform E-test for nosocomial Gram-positive microorganisms that show antibiotic resistance by disk diffusion test and it is more important for clindamycin and meropenem. PMID:24250479
Khalili, Hossein; Soltani, Rasool; Negahban, Sorrosh; Abdollahi, Alireza; Gholami, Keirollah
Disk diffusion test is the usual applicable method for assessing the antimicrobial susceptibility pattern in most institutions and hospitals. The aim of this study was to determine the reliability of resistant-reported results of disk diffusion test for 6 routinely used antibiotics against Gram-positive microorganisms of nosocomial origin, using E-test method. Over a 1-year period, clinical specimens (e.g. blood, tracheal secretions, wound secretions, urine, etc.) were obtained from hospitalized patients with defined nosocomial infection and were cultured. Isolated Gram-positive bacteria underwent disk diffusion test for cephalothin, oxacillin, clindamycin, ciprofloxacin, vancomycin, teicoplanin (only for Enterococci), and meropenem antibiotics. E-test method was performed for all isolates resistant or intermediately sensitive to the disks of any mentioned antibiotics. Data showed compatible results of disk diffusion test with the results of E-test method for cephalothin, oxacillin, ciprofloxacin, vancomycin, and teicoplanin. None of ciprofloxacin- and vancomycin-resistant isolates in disk diffusion test showed sensitivity in E-test method. Significant differences between the results of disk diffusion and E-test methods were observed for clindamycin and meropenem against S.aureus (p = 0.01 and 0.04, respectively) and Enterococcus spp (p = 0.03 and 0.02, respectively). In order to increase the reliability of antimicrobial susceptibility results, it is recommended to perform E-test for nosocomial Gram-positive microorganisms that show antibiotic resistance by disk diffusion test and it is more important for clindamycin and meropenem.
Jorgensen, James H.; Barry, Arthur L.; Traczewski, M. M.; Sahm, Daniel F.; McElmeel, M. Leticia; Crawford, Sharon A.
The VITEK 2 is a new automated instrument for rapid organism identification and susceptibility testing. It has the capability of performing rapid susceptibility testing of Streptococcus pneumoniae with specially configured cards that contain enriched growth medium and antimicrobial agents relevant for this organism. The present study compared the results of testing of a group of 53 challenge strains of pneumococci with known resistance properties and a collection of clinical isolates examined in two study phases with a total of 402 and 416 isolates, respectively, with a prototype of the VITEK 2. Testing was conducted in three geographically separate laboratories; the challenge collection was tested by all three laboratories, and the unique clinical isolates were tested separately by the individual laboratories. The VITEK 2 results of tests with 10 antimicrobial agents were compared to the results generated by the National Committee for Clinical Laboratory Standards reference broth microdilution MIC test method. Excellent interlaboratory agreement was observed with the challenge strains. The overall agreement within a single twofold dilution of MICs defined by the VITEK 2 and reference method with the clinical isolates was 96.3%, although there were a number of off-scale MICs that could not be compared. The best agreement with the clinical isolates was achieved with ofloxacin and chloramphenicol (100%), and the lowest level of agreement among those drugs with sufficient on-scale MICs occurred with trimethoprim-sulfamethoxazole (89.7%). Overall there were 1.3% very major, 6.6% minor, and no major interpretive category errors encountered with the clinical isolates, although >80% of the minor interpretive errors involved only a single log2 dilution difference. The mean time for generation of susceptibility results with the clinical isolates was 8.1 h. The VITEK 2 provided rapid, reliable susceptibility category determinations with both the challenge and clinical
Ligozzi, Marco; Bernini, Cinzia; Bonora, Maria Grazia; de Fatima, Maria; Zuliani, Jessica; Fontana, Roberta
A study was conducted to evaluate the new VITEK 2 system (bioMérieux) for identification and antibiotic susceptibility testing of gram-positive cocci. Clinical isolates of Staphylococcus aureus (n = 100), coagulase-negative staphylococci (CNS) (n = 100), Enterococcus spp. (n = 89), Streptococcus agalactiae (n = 29), and Streptococcus pneumoniae (n = 66) were examined with the ID-GPC identification card and with the AST-P515 (for staphylococci), AST-P516 (for enterococci and S. agalactiae) and AST-P506 (for pneumococci) susceptibility cards. The identification comparison methods were the API Staph for staphylococci and the API 20 Strep for streptococci and enterococci; for antimicrobial susceptibility testing, the agar dilution method according to the procedure of the National Committee for Clinical Laboratory Standards (NCCLS) was used. The VITEK 2 system correctly identified to the species level (only one choice or after simple supplementary tests) 99% of S. aureus, 96.5% of S. agalactiae, 96.9% of S. pneumoniae, 92.7% of Enterococcus faecalis, 91.3% of Staphylococcus haemolyticus, and 88% of Staphylococcus epidermidis but was least able to identify Enterococcus faecium (71.4% correct). More than 90% of gram-positive cocci were identified within 3 h. According to the NCCLS breakpoints, antimicrobial susceptibility testing with the VITEK 2 system gave 96% correct category agreement, 0.82% very major errors, 0.17% major errors, and 2.7% minor errors. Antimicrobial susceptibility testing showed category agreement from 94 to 100% for S. aureus, from 90 to 100% for CNS, from 91 to 100% for enterococci, from 96 to 100% for S. agalactiae, and from 91 to 100% for S. pneumoniae. Microorganism-antibiotic combinations that gave very major errors were CNS-erythromycin, CNS-oxacillin, enterococci-teicoplanin, and enterococci-high-concentration gentamicin. Major errors were observed for CNS-oxacillin and S. agalactiae-tetracycline combinations. In conclusion the results of
McGill, K; Kelly, L; Madden, R H; Moran, L; Carroll, C; O'Leary, A; Moore, J E; McNamara, E; O'Mahony, M; Fanning, S; Whyte, P
The antibiotic resistance profiles of 75 Campylobacter isolates of food and human clinical origin was determined by two agar diffusion susceptibility methods; disc diffusion and epsilometer-test (E-test). The most common therapeutic antimicrobials, erythromycin, ciprofloxacin and tetracycline were studied, along with chloramphenicol, ampicillin and naladixic acid. The resistance observed for each antimicrobial, as determined by both of methods, were statistically compared using Fisher two-tailed analysis. Of the six antimicrobials studied only two were shown to have statistically different patterns when resistance was compared by disc diffusion and E-test. The percentage of isolates resistant to clinically relevant antimicrobials using both techniques ranged from 6.6 to 21.3% for erythromycin, 25.3-26.6% for tetracycline and 33.3-36.0% for ciprofloxacin. The prevalence of multi-drug resistant (MDR) campylobacters (isolates resistant to 2 or more antimicrobials) for both disc diffusion and E-test was 44%. It can be concluded that, for four of the six antimicrobials assessed, antimicrobial resistance prevalences could be equally determined by either of the methods studied.
Mégraud, Francis; Lehn, Norbert; Lind, Tore; Bayerdörffer, Ekkehard; O’Morain, Colm; Spiller, Robin; Unge, Peter; van Zanten, Sander Veldhuyzen; Wrangstadh, Michael; Burman, Carl Fredrik
Culture and susceptibility testing of Helicobacter pylori strains was performed in a large multinational, multicenter randomized clinical trial. Culture was carried out on gastric biopsy samples obtained from 516 patients at entry and had a sensitivity of 99% when the [13C]urea breath test was used as a reference. Susceptibility testing was performed for clarithromycin and metronidazole on 485 strains by an agar dilution method and the epsilometer test (Etest) and for amoxicillin by an agar dilution method only. Resistance to clarithromycin (>1 μg/ml) was found in 3% of the H. pylori strains, with a perfect correlation between Etest and agar dilution methods. Resistance to metronidazole (>8 μl/ml) was found in 27% of the strains by agar dilution, but there were important discrepancies between it and the Etest method. No resistance to amoxicillin was found. The logarithms of the MICs of the three antibiotics against susceptible strains had a distribution close to normal. The impact of resistance was tested in the four arms of the trial. There were not enough clarithromycin-resistant strains to evaluate the impact of resistance on the cure rate of clarithromycin-based regimens. For metronidazole-resistant strains, the impact noted in the clarithromycin-metronidazole arm was partially overcome when omeprazole was added (76% eradication for resistant strains versus 95% for susceptible strains). Secondary resistance to clarithromycin occurred in strains from 12 of 105 patients (11.4%) after the failure of a clarithromycin-based regimen to effect eradication. The detection of point mutations in clarithromycin-resistant strains was performed by a combination of PCR and restriction fragment length polymorphism. Mutations (A2142G and 2143G) were found in all strains tested except one. This study stresses the importance of performing susceptibility tests in clinical trials in order to explain the results of different treatments. PMID:10543758
Stone, Nimalie D.; O'Hara, Caroline M.; Williams, Portia P.; McGowan, John E.; Tenover, Fred C.
We compared the antimicrobial susceptibility testing results generated by disk diffusion and the VITEK 2 automated system with the results of the Clinical and Laboratory Standards Institute (CLSI) broth microdilution (BMD) reference method for 61 isolates of unusual species of Enterobacteriaceae. The isolates represented 15 genera and 26 different species, including Buttiauxella, Cedecea, Kluyvera, Leminorella, and Yokenella. Antimicrobial agents included aminoglycosides, carbapenems, cephalosporins, fluoroquinolones, penicillins, and trimethoprim-sulfamethoxazole. CLSI interpretative criteria for Enterobacteriaceae were used. Of the 12 drugs tested by BMD and disk diffusion, 10 showed >95% categorical agreement (CA). CA was lower for ampicillin (80.3%) and cefazolin (77.0%). There were 3 very major errors (all with cefazolin), 1 major error (also with cefazolin), and 26 minor errors. Of the 40 isolates (representing 12 species) that could be identified with the VITEK 2 database, 36 were identified correctly to species level, 1 was identified to genus level only, and 3 were reported as unidentified. VITEK 2 generated MIC results for 42 (68.8%) of 61 isolates, but categorical interpretations (susceptible, intermediate, and resistant) were provided for only 22. For the 17 drugs tested by both BMD and VITEK 2, essential agreement ranged from 80.9 to 100% and CA ranged from 68.2% (ampicillin) to 100%; thirteen drugs exhibited 100% CA. In summary, disk diffusion provides a reliable alternative to BMD for testing of unusual Enterobacteriaceae, some of which cannot be tested, or produce incorrect results, by automated methods. PMID:17135429
Venditti, M; Gelfusa, V; Tarasi, A; Brandimarte, C; Serra, P
The in vitro susceptibilities of 10 isolates of Erysipelothrix rhusiopathiae to 16 antimicrobial agents were determined. Penicillin and imipenem were the most active agents, followed by piperacillin, cefotaxime, ciprofloxacin, pefloxacin, and clindamycin. Some resistance was observed with erythromycin, tetracycline, and chloramphenicol. Activity was poor or absent with vancomycin, teicoplanin, daptomycin, trimethoprim-sulfamethoxazole, gentamicin, and netilmicin. PMID:2291674
Multicenter laboratory evaluation of the bioMérieux Vitek antimicrobial susceptibility testing system with 11 antimicrobial agents versus members of the family Enterobacteriaceae and Pseudomonas aeruginosa.
Doern, G V; Brueggemann, A B; Perla, R; Daly, J; Halkias, D; Jones, R N; Saubolle, M A
A four-center study in which a total of 1,082 recent clinical isolates of members of the family Enterobacteriaceae and Pseudomonas aeruginosa were examined versus 11 antimicrobial agents with the bioMérieux Vitek susceptibility test system (Hazelwood, Mo.) and the GNS-F6 card was conducted. In addition, a challenge set consisting of the same 200 organisms was examined in each of the four participating laboratories. Results obtained with the Vitek system were compared to MICs determined by a standardized broth microdilution method. For purposes of comparison, susceptibility categories (susceptible, intermediate, or resistant) were assigned on the basis of the results of both methods. The result of the broth microdilution test was considered definitive. The total category error rate with the Vitek system and the recent clinical isolates (11,902 organism-antimicrobial comparisons) was 4.5%, i.e., 1.7% very major errors, 0.9% major errors, and 1.9% minor errors. The total category error rate calculated from tests performed with the challenge set (i.e., 8,800 organism-antimicrobial comparisons) was 5.9%, i.e., 2.2% very major errors, 1.1% major errors, and 2.6% minor errors. Very major error rates higher than the totals were noted with Enterobacter cloacae versus ampicillin-sulbactam, aztreonam, ticarcillin, and ticarcillin-clavulanate and with P. aeruginosa versus mezlocillin, ticarcillin, and ticarcillin-clavulanate. Major error rates higher than the averages were observed with Proteus mirabilis versus imipenem and with Klebsiella pneumoniae versus ofloxacin. Excellent overall interlaboratory reproducibility was observed with the Vitek system. The importance of inoculum size as a primary determinant in the accuracy of susceptibility test results with the Vitek system was clearly demonstrated in this study. Specifically, when an inoculum density fourfold higher than that recommended by the manufacturer was used, high rates of false resistance results were obtained
Comparison of agar dilution, broth microdilution, disk diffusion, E-test, and BACTEC radiometric methods for antimicrobial susceptibility testing of clinical isolates of the Nocardia asteroides complex.
Ambaye, A; Kohner, P C; Wollan, P C; Roberts, K L; Roberts, G D; Cockerill, F R
An evaluation was undertaken to determine the optimal method for the in vitro susceptibility testing of 26 Nocardia asteroides complex isolates to the following antimicrobial agents: amikacin, ampicillin, amoxicillin-clavulanate, ceftriaxone, ciprofloxacin, erythromycin, imipenem, minocycline, and trimethoprim-sulfamethoxazole. Five testing methods were studied including the agar dilution, broth microdilution, and disk diffusion methods, the epsilometer test (E-test), and the BACTEC radiometric method. Results for each antimicrobial agent and each testing method were interpreted as indicating susceptibility, intermediate susceptibility, or resistance according to current guidelines of the National Committee for Clinical Laboratory Standards (NCCLS) for bacteria that grow aerobically and were then compared to a "gold standard" susceptibility test result. The gold standard result for each Nocardia isolate was established by a consensus of the results of the majority of testing methods used in the study. When the results were combined for all antimicrobial agents tested against all Nocardia isolates by all methods, the BACTEC radiometric method produced the highest level of agreement (97.9%) with the consensus results and had the fewest very major (n = 1), major (n = 2), and minor (n = 2) errors. In contrast, the results of the agar dilution method were in least agreement (93.2%) with the consensus results, and this method also produced the most very major (n = 8), major (n = 4), and, along with the disk diffusion method, minor (n = 6) errors. For all test methods, interpretive errors were most frequent when testing ampicillin or amoxicillin-clavulanate. Moreover, for all Nocardia nova isolates tested, ampicillin susceptibility results by any of the testing methods were not in agreement with the results of testing for beta-lactamase by the nitrocefin (Cefinase) disk method. We conclude that among the methods evaluated, the BACTEC radiometric method appeared to be the
Cosme, Angel; Montes, Milagrosa; Ibarra, Begoña; Tamayo, Esther; Alonso, Horacio; Mendarte, Usua; Lizasoan, Jacobo; Herreros-Villanueva, Marta; Bujanda, Luis
AIM To evaluate the efficacy of antimicrobial susceptibility-guided therapy before first-line treatment for infection in patients with dual or triple antibiotic resistance. METHODS A total of 1034 patients infected by Helicobacter pylori (H. pylori) during 2013-2014 were tested for antimicrobial susceptibility. 157 of 1034 (15%) patients showed resistance to two (127/1034; 12%) and to three (30/1034; 3%) antibiotics. Sixty-eight patients with dual H. pylori-resistance (clarithromycin, metronidazole or levofloxacin) were treated for 10 d with triple therapies: OAL (omeprazole 20 mg b.i.d., amoxicillin 1 g b.i.d., and levofloxacin 500 mg b.i.d.) 43 cases, OAM (omeprazole 20 mg b.i.d., amoxicillin 1 g b.i.d., and metronidazole 500 mg b.i.d.) 12 cases and OAC (omeprazole 20 mg b.id., amoxicillin 1 g b.i.d., and clarithromycin 500 mg b.i.d.) 13 cases based on the antimicrobial susceptibility testing. Twelve patients showed triple H. pylori-resistance (clarithromycin, metronidazole and levofloxacin) and received for 10 d triple therapy with OAR (omeprazole 20 mg b.id., amoxicillin 1 g b.i.d., and rifabutin 150 mg b.i.d.). Eradication was confirmed by 13C-urea breath test. Adverse effects and compliance were assessed by a questionnaire. RESULTS Intention-to-treat eradication rates were: OAL (97.6%), OAM (91.6%), OAC (92.3%) and OAR (58.3%). Cure rate was significantly higher in naïve patients treated with OAR-10 compared to patients who had two or three previous treatment failures (83% vs 33%). Adverse events rates for OAL, OAM, OAC and OAR were 22%, 25%, 23% and 17%, respectively, all of them mild-moderate. CONCLUSION Antimicrobial susceptibility-guided triple therapies during 10 d for first-line treatment leads to an eradication rate superior to 90% in patients with dual antibiotic H. pylori resistance. PMID:28566898
Tippett, L. O.; Zeleznick, L. D.; Robb, C. A.
A pH indicator and dextrose were incorporated into growth media as a modification of microbial microtiter methods for determining the minimal inhibitory concentration of antimicrobial drugs. This modified method was tested to evaluate the ease of reading end points by changes in the indicator color. Application of the procedure to two media, three indicators, and eight species of bacteria indicated that definitive end points could be reached as a result of indicator color change caused by acid production during bacterial growth. This method is accurate and reproducible. It is a modification which eliminates a need for plating and facilitates the reading of minimal inhibitory concentration end points. PMID:5485717
Libonati, J.P.; Stager, C.E.; Davis, J.R.; Siddiqi, S.H.
Direct-drug-susceptibility tests were performed on clinical specimens positive for acid-fast bacilli by either Ziehl-Neelsen or fluorochrome staining. The results of conventional agar dilution and a modified radiometric (BACTEC) method were compared. A total of 580 smear-positive specimens were tested by the BACTEC method at three separate sites. Three hundred and seventy-seven of these were culture positive for M. tuberculosis, and 343 (91%) yielded acceptable direct-susceptibility-test results. We used the conventional method to determine that 343 of 519 smear-positive specimens were culture positive for M. tuberculosis, and 212 (62%) produced acceptable results within 3 wks. Conventional results were reported in 3-4 wks, while the time required to obtain results with the BACTEC method ranged from 5 to 21 days (average 11.5 days). Results indicate that the radiometric method provides reportable results more frequently with time savings as compared to the conventional method.
This document includes the recommendations from the Spanish antibiogram committee (The MENSURA group, Mesa Española de Normalización de la Sensibilidad y Resistencia a los Antimicrobianos, under the auspices of the Sociedad Española de Quimioterapia and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica) for the selection of antimicrobials for susceptibility testing. Separate tables for each group of organism with proposed susceptibility and resistance breakpoints are updated and comparatively presented with those of other groups, such us NCCLS, CA-SFM and BSAC. The susceptibility breakpoint tends to identify the fully susceptible population, which probably lacks any specific resistance mechanism. The analysis of MIC distributions for different homogeneous populations (same species) is used to define breakpoints for susceptibility. The resistance breakpoint is based on pharmacological and clinical data obtained when the corresponding antibiotic is administered with a conventional schedule. The primary objective of the Spanish MENSURA group is to contribute to the international consensus on the establishment of breakpoints.
Georgi, Enrico; Schacht, Erik; Scholz, Holger C; Splettstoesser, Wolf D
Tularaemia is a widespread zoonosis in Europe caused by Francisella tularensis subsp. holarctica. Because of a lack of standardized CLSI-approved antibiotic susceptibility data from European Francisella strains, the antibiotic susceptibilities of a selection of F. tularensis subsp. holarctica isolates originating from Germany, Austria, France, Spain and other European countries were determined. Rarely isolated species and subspecies of Francisella such as Francisella philomiragia, F. tularensis subsp. novicida and F. tularensis subsp. mediasiatica as well as the type strain of Francisella hispaniensis were included in this study. MIC data were obtained using cation-adjusted Mueller-Hinton broth with a 2% growth supplement. The broth microdilution testing system comprised 14 antibiotics, including gentamicin, streptomycin, ciprofloxacin and tetracycline. All of the 91 strains tested were susceptible to aminoglycosides, quinolones, tetracycline and chloramphenicol. The antimicrobial susceptibility of rare Francisellae was similar to the antibiotic profile of F. tularensis subsp. holarctica strains. For erythromycin, we detected two geographically distinct groups of F. tularensis subsp. holarctica isolates in western Europe. One group was resistant and the other one was susceptible. Both groups overlapped in a small region in Germany. Being performed in accordance with CLSI criteria, this study provides reliable data on antibiotic susceptibility patterns of European Francisella isolates. The standardized methodology of this study can be used for testing of suspicious colonies from clinical specimens for therapeutic guidance. Based on the results, aminoglycosides or quinolones are recommended as first-choice antibiotics for the therapy of F. hispaniensis, F. philomiragia or F. tularensis subsp. novicida infections in immunocompromised patients.
Courcol, R J; Deleersnyder, H; Roussel-Delvallez, M; Martin, G R
An automated microELISA Reader was evaluated for its ability to read and interpret microtitre plates. A total of 309 microtitre plates were investigated by automated and visual methods. There was disagreement between the methods in one hundred and twelve (0.6%) wells. However agreements between the two methods for susceptibility tests and Enterobacteriaceae identification were respectively 98.8% and 89.3%. PMID:6338058
Varela, Norma P; Friendship, Robert; Dewey, Cate; Valdivieso, Alfonso
The primary aim of this study was to evaluate the level of agreement of the E-test for in vitro antimicrobial susceptibility testing of Campylobacter coli using the agar dilution technique, which is the approved method. A convenience sample of 80 Ontario swine farms was chosen for this study; each farm was visited from January to June 2004. A total of 233 isolates of C. coli were tested for susceptibility to 10 antimicrobials by agar dilution and the E-test. Performance of the tests was evaluated using 7 quality control strains: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Campylobacter jejuni ATCC 33560, and Campylobacter coli ATCC 33559 for the E-test and E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and C. jejuni ATCC 33560 for the agar dilution test. Weighted Cohen's kappa and prevalence-adjusted bias-adjusted kappa (PABAK) tests were used for statistical analysis. The E-test and agar dilution test results had a strong agreement when resistance to streptomycin and tetracycline were evaluated (weighted kappa: 0.68 and 0.66, respectively). However, marked disagreement was detected when testing susceptibility to nalidixic acid and ampicillin (0.15 and 0.22, respectively). Almost perfect agreement was detected by PABAK when testing susceptibility to gentamicin (0.99). Agreement was found to be moderate for ciprofloxacin, azithromycin, clindamycin, erythromycin, and chloramphenicol. Although the level of agreement between the E-test and agar dilution depended on the antimicrobial being tested, the E-test always detected a lower proportion of resistant isolates compared to agar dilution.
Varela, Norma P.; Friendship, Robert; Dewey, Cate; Valdivieso, Alfonso
The primary aim of this study was to evaluate the level of agreement of the E-test for in vitro antimicrobial susceptibility testing of Campylobacter coli using the agar dilution technique, which is the approved method. A convenience sample of 80 Ontario swine farms was chosen for this study; each farm was visited from January to June 2004. A total of 233 isolates of C. coli were tested for susceptibility to 10 antimicrobials by agar dilution and the E-test. Performance of the tests was evaluated using 7 quality control strains: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Campylobacter jejuni ATCC 33560, and Campylobacter coli ATCC 33559 for the E-test and E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and C. jejuni ATCC 33560 for the agar dilution test. Weighted Cohen’s kappa and prevalence-adjusted bias-adjusted kappa (PABAK) tests were used for statistical analysis. The E-test and agar dilution test results had a strong agreement when resistance to streptomycin and tetracycline were evaluated (weighted kappa: 0.68 and 0.66, respectively). However, marked disagreement was detected when testing susceptibility to nalidixic acid and ampicillin (0.15 and 0.22, respectively). Almost perfect agreement was detected by PABAK when testing susceptibility to gentamicin (0.99). Agreement was found to be moderate for ciprofloxacin, azithromycin, clindamycin, erythromycin, and chloramphenicol. Although the level of agreement between the E-test and agar dilution depended on the antimicrobial being tested, the E-test always detected a lower proportion of resistant isolates compared to agar dilution. PMID:18505206
Toma, E; Barriault, D
The in vitro activity of fusidic acid was assessed and was compared with those of cloxacillin, cefamandole, vancomycin, teicoplanin, ofloxacin, ciprofloxacin, pefloxacin, and fleroxacin against 500 gram-positive cocci: 151 Staphylococcus aureus, 197 coagulase-negative staphylococci, and 152 Enterococcus faecalis strains. All clinical isolates were concomitantly tested by disk diffusion and agar dilution procedures as outlined by the National Committee for Clinical Laboratory Standards. The results with fusidic acid were further analyzed by regression line and error rate-bounded methods. With control American Type Culture Collection organisms, the values were within the limits of the National Committee for Clinical Laboratory Standards or published limits. The incidence of resistance to fusidic acid was 0.7% for S. aureus, 2.5% for coagulase-negative staphylococci, and 99.3% for E. faecalis. The correlation coefficient between the results of disk diffusion and agar dilution tests with fusidic acid was 0.90. Current interpretive criteria for susceptibility to fusidic acid (i.e., MIC of < 2 micrograms/ml and inhibitory zone of 20 mm) gave 1% false susceptibility (all strains being E. faecalis). This error rate is practically eliminated if a zone diameter of 21 mm is considered the breakpoint for susceptibility.
[Comparative study of the susceptibility to daptomycin and other antimicrobials against Staphylococcus spp. resistant to methicillin and Enterococcus spp. using Wider, E-test, and microdilution methods].
Gómez-Garcés, J L; López-Fabal, F; Burillo, A; Gil, Y
The human and material costs of inappropriate antimicrobial therapy are high. This study was designed to search for a rapid, simple and effective antimicrobial susceptibility test capable of identifying the best treatment strategy against microorganisms causing hospital infections showing resistance or reduced susceptibility to the more traditional antibiotics. The tests compared were the E-test, an automated test (Wider) and broth microdilution ( as the reference test), to determine the susceptibility to vancomycin, teicoplanin, linezolid and daptomycin of clinical isolates of methicillin resistant Staphylococcus aureus (MRSA), methicillin resistant coagulase negative Staphylococcus spp. and Enterococccus spp. The E-test and Wider methods showed good agreement with the reference method indicating their reliability for routine susceptibility testing of staphylococci and enterococci against vancomycin, teicoplanin, linezolid and daptomycin. Notwithstanding, when faced with a serious enterococcal infection, the MIC of daptomycin should be more accurately determined using a reference technique such as broth microdilution.
Ogata, Silvio Kazuo; Gales, Ana Cristina; Kawakami, Elisabete
Antimicrobial susceptibility testing for Helicobacter pylori is increasingly important due to resistance to the most used antimicrobials agents. Only agar dilution method is approved by CLSI, but it is difficult to perform routinely. We evaluated the reliability of E-test and disk diffusion comparing to agar dilution method on Helicobacter pylori antimicrobial susceptibility testing. Susceptibility testing was performed for amoxicillin, clarithromycin, furazolidone, metronidazole and tetracycline using E-test, disk-diffusion and agar dilution method in 77 consecutive Helicobacter pylori strains from dyspeptic children and adolescents. Resistance rates were: amoxicillin - 10.4%, 9% and 68.8%; clarithromycin - 19.5%, 20.8%, 36.3%; metronidazole - 40.2%33.7%, 38.9%, respectively by agar dilution, E-test and disk diffusion method. Furazolidone and tetracycline showed no resistance rates. Metronidazole presented strong correlation to E-test (r = 0.7992, p < 0.0001) and disk diffusion method (r=-0.6962, p < 0.0001). Clarithromycin presented moderate correlation to E-test (r = 0.6369, p < 0.0001) and disk diffusion method (r=-0.5656, p < 0.0001). Amoxicillin presented weak correlation to E-test (r = 0.3565, p = 0.0015) and disk diffusion (r=-0.3565, p = 0.0015). Tetracycline presented weak correlation with E-test (r = 0.2346, p = 0.04) and furazolidone to disk diffusion (r=-0.0288, p = 0.8038). E-test presented better agreement with gold standard. It is an easy and reliable method for Helicobacter pylori susceptibility testing. Disk diffusion method presented high disagreement and high rates of major errors.
Ogata, Silvio Kazuo; Gales, Ana Cristina; Kawakami, Elisabete
Antimicrobial susceptibility testing for Helicobacter pylori is increasingly important due to resistance to the most used antimicrobials agents. Only agar dilution method is approved by CLSI, but it is difficult to perform routinely. We evaluated the reliability of E-test and disk diffusion comparing to agar dilution method on Helicobacter pylori antimicrobial susceptibility testing. Susceptibility testing was performed for amoxicillin, clarithromycin, furazolidone, metronidazole and tetracycline using E-test, disk-diffusion and agar dilution method in 77 consecutive Helicobacter pylori strains from dyspeptic children and adolescents. Resistance rates were: amoxicillin - 10.4%, 9% and 68.8%; clarithromycin - 19.5%, 20.8%, 36.3%; metronidazole - 40.2%33.7%, 38.9%, respectively by agar dilution, E-test and disk diffusion method. Furazolidone and tetracycline showed no resistance rates. Metronidazole presented strong correlation to E-test (r = 0.7992, p < 0.0001) and disk diffusion method (r=-0.6962, p < 0.0001). Clarithromycin presented moderate correlation to E-test (r = 0.6369, p < 0.0001) and disk diffusion method (r=−0.5656, p < 0.0001). Amoxicillin presented weak correlation to E-test (r = 0.3565, p = 0.0015) and disk diffusion (r=−0.3565, p = 0.0015). Tetracycline presented weak correlation with E-test (r = 0.2346, p = 0.04) and furazolidone to disk diffusion (r=−0.0288, p = 0.8038). E-test presented better agreement with gold standard. It is an easy and reliable method for Helicobacter pylori susceptibility testing. Disk diffusion method presented high disagreement and high rates of major errors. PMID:25763052
Rohde, Judith; Kessler, Martina; Baums, Christoph G; Amtsberg, Gunter
In Germany treatment of swine dysentery is hampered by Brachyspira hyodysenteriae strains showing elevated MIC values to the few antibiotics licensed. Therefore, susceptibility testing of clinical isolates is an important service to the swine practitioner. This study compares the established agar dilution procedure for antimicrobial susceptibility testing of this fastidious anaerobe to the broth microdilution test newly developed [Anim. Health Res. 2 (2001) 59; Vet. Microbiol. 84 (2002) 123; J. Clin. Microbiol. 41 (2003) 2596]. A total of 221 isolates were examined twice with either test procedure using tiamulin and valnemulin as antibiotics. Both methods gave reproducible results, and the MIC values for the reference strains B. hyodysenteriae B204 and Staphylococcus aureus ATCC 29213 corresponded to previously published data. However, the results for individual strains differed significantly for both tests (P < 0.001) with MIC values being on average one dilution step lower in the broth dilution method. The 221 strains used for comparing test procedures were isolated between 1989 and 2001. An additional 102 strains isolated in 2002 were tested only with the broth dilution procedure. A significant rise in the average MIC value for both pleuromutilins could be demonstrated when comparing earlier isolates to those from 2000 to 2001 (P < 0.05), while in 2002 the average MIC significantly decreased when compared to the value in 2000 (P < 0.05). However, strains with MIC values for tiamulin as high as 8 microg/ml (broth dilution) could still be isolated.
Singh, Vikram; Kakran, Monika; Ramesh, V
Background A variety of techniques are available for antimicrobial susceptibility testing of Neisseria gonorrhoeae. Objective The aim of this study was to find a cost-effective, reliable and easily applicable microbiological method to detect antimicrobial susceptibilities of N. gonorrhoeae in resource-poor countries. Design Prospective study. Setting Male and female STD clinic of Regional STD Teaching, Training and Research Centre, New Delhi, India. Participants N. gonorrhoeae isolates from all male and female patients presenting with acute gonococcal urethritis and cervical discharge. Material and methods A total of 295 consecutive N. gonorrhoeae isolates during 2005–2010 was used to compare the Clinical and Laboratory Standards Institute (CLSI) and CDS disc diffusion technique with Etest by performing antimicrobial susceptibility testing in parallel for penicillin, tetracycline, ceftriaxone, ciprofloxacin and spectinomycin. WHO reference strains were used as controls. Results CDS disc diffusion zones of inhibition showed that complete percentage agreement for penicillin, ciprofloxacin and tetracycline was high with their analogous Etest minimal inhibitory concentrations in comparison to CLSI disc diffusion technique, that is, 91.5%, 92.9% and 99.3% versus 87.5%, 88.5% and 74.9%, respectively. CDS results had less number of major and minor category discrepancies in comparison to CLSI and CDS method showed excellent correlation coefficient (r=1) with Etest for all five antimicrobial agents tested in comparison to CLSI (r=0.92). It was very poor (r=0.61) by CLSI method for tetracycline. The correlation coefficients between the two methods and the Etest were identical if tetracycline was removed from the CLSI analysis. Conclusions The CDS technique is an attractive alternative for N. gonorrhoeae susceptibility testing and is recommended for monitoring the antimicrobial susceptibility in less developed and resource-poor settings to facilitate enhanced antimicrobial
Singh, Vikram; Bala, Manju; Kakran, Monika; Ramesh, V
A variety of techniques are available for antimicrobial susceptibility testing of Neisseria gonorrhoeae. The aim of this study was to find a cost-effective, reliable and easily applicable microbiological method to detect antimicrobial susceptibilities of N. gonorrhoeae in resource-poor countries. Prospective study. Male and female STD clinic of Regional STD Teaching, Training and Research Centre, New Delhi, India. N. gonorrhoeae isolates from all male and female patients presenting with acute gonococcal urethritis and cervical discharge. A total of 295 consecutive N. gonorrhoeae isolates during 2005-2010 was used to compare the Clinical and Laboratory Standards Institute (CLSI) and CDS disc diffusion technique with Etest by performing antimicrobial susceptibility testing in parallel for penicillin, tetracycline, ceftriaxone, ciprofloxacin and spectinomycin. WHO reference strains were used as controls. CDS disc diffusion zones of inhibition showed that complete percentage agreement for penicillin, ciprofloxacin and tetracycline was high with their analogous Etest minimal inhibitory concentrations in comparison to CLSI disc diffusion technique, that is, 91.5%, 92.9% and 99.3% versus 87.5%, 88.5% and 74.9%, respectively. CDS results had less number of major and minor category discrepancies in comparison to CLSI and CDS method showed excellent correlation coefficient (r=1) with Etest for all five antimicrobial agents tested in comparison to CLSI (r=0.92). It was very poor (r=0.61) by CLSI method for tetracycline. The correlation coefficients between the two methods and the Etest were identical if tetracycline was removed from the CLSI analysis. The CDS technique is an attractive alternative for N. gonorrhoeae susceptibility testing and is recommended for monitoring the antimicrobial susceptibility in less developed and resource-poor settings to facilitate enhanced antimicrobial resistance surveillance when the WHO Gonococcal Antimicrobial Surveillance Programme is
Bobenchik, April M.; Deak, Eszter; Hindler, Janet A.; Charlton, Carmen L.
Vitek 2 (bioMérieux Inc., Durham, NC) is a widely used commercial antimicrobial susceptibility test system. We compared the MIC results obtained using the Vitek 2 AST-GN69 and AST-XN06 cards to those obtained by CLSI broth microdilution (BMD) for 255 isolates of Enterobacteriaceae, including 25 isolates of carbapenem-resistant Enterobacteriaceae. In total, 25 antimicrobial agents were examined. For 10 agents, the MIC data were evaluated using two sets of breakpoints: (i) the Vitek 2 breakpoints, which utilized the 2009 FDA breakpoints at the time of the study and are equivalent to the 2009 CLSI M100-S19 breakpoints, and (ii) the 2014 CLSI M100-S24 breakpoints. There was an overall 98.7% essential agreement (EA). The categorical agreement was 95.5% (CA) using the Vitek 2 breakpoints and 95.7% using the CLSI breakpoints. There was 1 very major error (VME) (0.05%) observed using the Vitek 2 breakpoints (cefazolin) and 8 VMEs (0.5%) using the CLSI breakpoints (2 each for aztreonam, cefepime, and ceftriaxone, and 1 for cefazolin and ceftazidime). Fifteen major errors (MEs) (0.4%) were noted using the Vitek 2 breakpoints and 8 (0.5%) using the CLSI breakpoints. Overall, the Vitek 2 performance was comparable to that of BMD for testing a limited number of Enterobacteriaceae commonly isolated by clinical laboratories. Ongoing studies are warranted to assess performance in isolates with emerging resistance. PMID:25540403
Idelevich, Evgeny A.; Becker, Karsten; Schmitz, Janne; Knaack, Dennis; Peters, Georg; Köck, Robin
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. PMID:27391898
Kirchgässner, C; Schmitt, S; Borgström, A; Wittenbrink, M M
Brachyspira (B.) hyodysenteriae is the causative agent of swine dysentery (SD), a severe mucohaemorrhagic diarrheal disease in pigs worldwide. So far, the antimicrobial susceptibility patterns of B. hyodysenteriae in Switzerland have not been investigated. Therefore, a panel of 30 porcine B. hyodysenteriae isolates were tested against 6 antimicrobial agents by using the VetMIC Brachy panel, a broth microdilution test. Tiamulin and valnemulin showed high antimicrobial activity inhibiting all isolates at low concentrations. The susceptibility testing of doxycycline revealed values from ≤0.25 μg/ ml (47%) to 2 μg/ml (10%). The MIC values of lincomycin ranged between ≤0.5 μg/ml (30%) and 32 μg/ml (43%). For tylosin, 57% of the isolates could not be inhibited at the highest concentration of ≥128 μg/ml. The MIC values for tylvalosin were between ≤0.25 μg/ml (10%) and 8 μg/ml (20%). These findings reveal Switzerland's favourable situation compared to other European countries. Above all, tiamulin and valnemulin are still effective antimicrobial agents and can be further used for the treatment of SD.
Idelevich, Evgeny A.; Schüle, Isabel; Grünastel, Barbara; Wüllenweber, Jörg; Peters, Georg
Briefly incubated agar cultures from positive blood cultures were used for antimicrobial susceptibility testing (AST) by Vitek 2. The cultivation time until inoculation was 3.8 h for Gram-positive cocci and 2.4 h for Gram-negative rods. The error rates were low, providing early and reliable AST without additional time or cost expenditure. PMID:25165084
Idelevich, Evgeny A; Schüle, Isabel; Grünastel, Barbara; Wüllenweber, Jörg; Peters, Georg; Becker, Karsten
Briefly incubated agar cultures from positive blood cultures were used for antimicrobial susceptibility testing (AST) by Vitek 2. The cultivation time until inoculation was 3.8 h for Gram-positive cocci and 2.4 h for Gram-negative rods. The error rates were low, providing early and reliable AST without additional time or cost expenditure.
Valdivieso-García, Alfonso; Imgrund, Ryan; Deckert, Anne; Varughese, Betsy Marie; Harris, Kathleen; Bunimov, Natalie; Reid-Smith, Richard; McEwen, Scott
Although numerous reports have compared the antimicrobial susceptibility of Campylobacter spp., controversy still exists about the use of the E test as an alternative to the agar dilution method suggested by the Clinical and Laboratory Standards Institute. MICs of 8 antimicrobials were determined using the E test and agar dilution methods for 103 Campylobacter jejuni and Campylobacter coli isolates from fresh chicken randomly purchased from stores in 3 southern Ontario counties. Overall, 72.6% of E test MIC values were within 1 log(2) dilution and 95.7% within 2 log(2) dilutions of the corresponding agar dilution MICs. For individual antimicrobials, agreement within 1 log(2) dilution and 2 log(2) dilutions was as follows: ampicillin (n = 103), 90.3% and 98.1%, respectively; chloramphenicol (n = 104), 85.6% and 99%; ciprofloxacin (n = 99), 51.5% and 97.0%; clindamycin (n = 99), 26.3% and 78.8%; erythromycin (n = 99), 52.5% and 96.0%; gentamicin (n = 99), 100% and 100%; nalidixic acid (n = 98), 91.8% and 99.0%; and tetracycline (n = 86), 82.6% and 97.7%. Relative to agar dilution, the E test underestimated the MIC value by a mean of 0.74 (ampicillin), 0.82 (chloramphenicol), 1.44 (ciprofloxacin), 1.94 (clindamycin), 1.40 (erythromycin), 0.21 (gentamicin), 0.94 (nalidixic acid), and 0.20 (tetracycline) log(2) dilutions and by a median of 1 log(2) dilution for all antimicrobials except clindamycin (2), gentamicin (0), and tetracycline (0). Cost analysis, including materials and labor, showed a 39.0% higher cost per analyte for the agar dilution method as compared with the E test. The most relevant advantage of the E test over the agar dilution method is the turnaround time because testing 99 strains by the agar dilution method takes 3.6 times longer compared with the E test using the same number of strains. The E test is an acceptable alternative for antimicrobial susceptibility testing in Campylobacter because it corresponds well with the agar dilution method although
Werckenthin, Christiane; Luhofer, Gabriele; Böttner, Alexander; Gangl, Armin; Goossens, Luc; Hafez, H Mohamed; Hartmann, Katrin; Kaske, Martin; Kehrenberg, Corinna; Kietzmann, Manfred; Klarmann, Dieter; Klein, Günter; Krabisch, Peter; Kühn, Tilman; Richter, Angelika; Schulz, Bianka; Schwarz, Stefan; Sigge, Claudia; Traeder, Wolfgang; Waldmann, Karl-Heinz; Jürgen, Wallmann
The determination of minimum inhibitory concentrations by broth microdilution is recommended as method of choice for susceptibility testing of veterinary bacterial pathogens. Accordingly, broth microdilution is used in veterinary routine diagnostic laboratories at a progressive rate. To reduce the costs of susceptibility testing, it is reasonable to develop widely accepted uniform microtitre plate layouts that are produced in large quantities. Such microtitre plate layouts have already been developed and published for the susceptibility testing of pathogens from food-producing animals. However, a microtitre plate layout, especially designed for the testing of bacteria from dogs and cats, should be available, too. The choice of the antimicrobial agents or combinations of antimicrobial agents to be included in a suitable layout should be based on the following criteria: (1) the approval and availability of an antimicrobial agent or combination of agents, (2) known cross-resistances, and (3) availability of approved clinical breakpoints. The latter point is of particular importance for the choice of the numbers of concentrations per antimicrobial agent tested and the range of test concentrations. Taking into account these aspects, a science-based layout proposal for microtitre plates, which are suitable for routine testing of bacteria from dogs and cats, is presented and discussed.
Bobenchik, April M; Deak, Eszter; Hindler, Janet A; Charlton, Carmen L; Humphries, Romney M
Vitek 2 (bioMérieux Inc., Durham, NC) is a widely used commercial antimicrobial susceptibility test system. We compared the MIC results obtained using the Vitek 2 AST-GN69 and AST-XN06 cards to those obtained by CLSI broth microdilution (BMD) for 255 isolates of Enterobacteriaceae, including 25 isolates of carbapenem-resistant Enterobacteriaceae. In total, 25 antimicrobial agents were examined. For 10 agents, the MIC data were evaluated using two sets of breakpoints: (i) the Vitek 2 breakpoints, which utilized the 2009 FDA breakpoints at the time of the study and are equivalent to the 2009 CLSI M100-S19 breakpoints, and (ii) the 2014 CLSI M100-S24 breakpoints. There was an overall 98.7% essential agreement (EA). The categorical agreement was 95.5% (CA) using the Vitek 2 breakpoints and 95.7% using the CLSI breakpoints. There was 1 very major error (VME) (0.05%) observed using the Vitek 2 breakpoints (cefazolin) and 8 VMEs (0.5%) using the CLSI breakpoints (2 each for aztreonam, cefepime, and ceftriaxone, and 1 for cefazolin and ceftazidime). Fifteen major errors (MEs) (0.4%) were noted using the Vitek 2 breakpoints and 8 (0.5%) using the CLSI breakpoints. Overall, the Vitek 2 performance was comparable to that of BMD for testing a limited number of Enterobacteriaceae commonly isolated by clinical laboratories. Ongoing studies are warranted to assess performance in isolates with emerging resistance. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Okamoto, Kazuaki; Ikeda, Fumiaki; Kanayama, Shoji; Nakajima, Akiko; Matsumoto, Tatsumi; Ishii, Ritsuko; Umehara, Masatoshi; Gotoh, Naomasa; Hayashi, Naoki; Iyoda, Takako; Matsuzaki, Kaoru; Matsumoto, Satoru; Kawashima, Makoto
Benzoyl peroxide (BPO), a therapeutic agent for acne vulgaris, was assessed for in vitro antimicrobial activity against Propionibacterium acnes using a novel broth microdilution testing that improved BPO solubility. We searched for a suitable culture medium to measure the minimum inhibitory concentration (MIC) of BPO against P. acnes and finally found the Gifu anaerobic medium (GAM) broth supplemented with 0.1(v/v)% glycerol and 2(v/v)% Tween 80, in which BPO dissolved up to 1250 μg/mL and P. acnes grew well. The MICs and minimum bactericidal concentrations (MBCs) of BPO against 44 clinical isolates of P. acnes collected from Japanese patients with acne vulgaris were determined by our testing method using the supplemented GAM broth. The MICs of BPO were 128 or 256 μg/mL against all isolates of P. acnes regardless of susceptibility to nadifloxacin or clindamycin. The MBCs of BPO were also 128 or 256 μg/mL against the same isolates. Moreover, BPO at the MIC showed a rapid bactericidal activity against P. acnes ATCC11827 in time-kill assay. In conclusion, we could develop a novel assay for the MIC and MBC determinations of BPO against P. acnes, which is reliable and reproducible as a broth microdilution testing and the present results suggest that BPO has a potent bactericidal activity against P. acnes.
Nyenje, Mirriam Ethel; Tanih, Nicoline Fri; Ndip, Roland Ndip
Agar dilution and broth microdilution are widely recommended quantitative antimicrobial susceptibility test methods, but they are tedious and time consuming to implement as routine tests in many clinical laboratories. Therefore, this study aimed at comparing the broth microdilution and the M.I.C Evaluator method which has been validated for its high accuracy and easy performance for routine diagnostic use. Twenty Enterobacter cloacae strains were isolated following microbiological procedures and confirmation of the isolates used the API 20E test. The strains were evaluated for their susceptibility to seven antimicrobials using the broth microdilution and MIC Evaluator methods. The doubling dilution difference (essential agreement) in the MIC result was derived from: log2 (MIC by BMD) -log2 (MIC by M.I.C Evaluator method). The categorical agreement, interpreted as breakpoints of sensitive and resistance strains was also noted. Categorical agreement between M.I.C Evaluator strip and broth microdilution for amoxicillin, metronidazole and erythromycin was 100%: while categorical agreement for ciprofloxacin was 90%. The essential agreement for erythromycin, ciprofloxacin and tetracycline were 90%, 70% and 15% respectively. Results indicate a high efficiency of the M.I.C Evaluator strip method in determination of minimum inhibitory concentration as compared to broth microdilution method. However, further analysis regarding the suitability of the M.I.C Evaluator for testing Enterobacter cloacae is warranted considering that no consensus guidelines exist for the use of this method with the organism.
McLaughlin, Heather P; Gargis, Amy S; Michel, Pierre; Sue, David; Weigel, Linda M
During high-impact events involving Bacillus anthracis, such as the Amerithrax incident of 2001 or the anthrax outbreaks in Russia and Sweden in 2016, critical decisions to reduce morbidity and mortality include rapid selection and distribution of effective antimicrobial agents for treatment and postexposure prophylaxis. Detection of antimicrobial resistance currently relies on a conventional broth microdilution method that requires a 16- to 20-h incubation time for B. anthracis Advances in high-resolution optical screening offer a new technology to more rapidly evaluate antimicrobial susceptibility and to simultaneously assess the growth characteristics of an isolate. Herein, we describe a new method developed and evaluated as a rapid antimicrobial susceptibility test for B. anthracis This method is based on automated digital time-lapse microscopy to observe the growth and morphological effects of relevant antibiotics with an optical screening instrument, the oCelloScope. B. anthracis strains were monitored over time in the presence or absence of penicillin, ciprofloxacin, or doxycycline. Susceptibility to each antibiotic was determined in ≤4 h, 75 to 80% less than the time required for conventional methods. Time-lapse video imaging compiled from the optical screening images revealed unexpected differences in growth characteristics among strains of B. anthracis, which is considered to be a clonal organism. This technology provides a new approach for rapidly detecting phenotypic antimicrobial resistance and for documenting growth attributes that may be beneficial in the further characterization of individual strains.
Petrovski, K R; Grinberg, A; Williamson, N B; Abdalla, M E; Lopez-Villalobos, N; Parkinson, T J; Tucker, I G; Rapnicki, P
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.
Huys, Geert; D'Haene, Klaas; Cnockaert, Margo; Tosi, Lorenzo; Danielsen, Morten; Flórez, Ana Belén; Mättö, Jaana; Axelsson, Lars; Korhonen, Jenni; Mayrhofer, Sigrid; Egervärn, Maria; Giacomini, Mauro; Vandamme, Peter
In a small-scale harmonization study involving nine laboratories in eight European countries, the intra- and interlaboratory performances of two commercially available systems, i.e., the VetMIC microplate system and Etest, for antimicrobial susceptibility testing of nonenterococcal lactic acid bacteria (NELAB) and bifidobacteria were analyzed. In addition, one laboratory also performed standard broth microdilution as a reference method. MICs of tetracycline, erythromycin, ampicillin, gentamicin, clindamycin, and streptomycin for the type strains of 25 species of NELAB and bifidobacteria and MICs of vancomycin for a selection of relevant taxa were determined. The previously described lactic acid bacterium susceptibility test medium (LSM) and related mixed-medium formulations, all including Iso-Sensitest broth as a basic component, were used as test media. The overall agreement of median MIC ranges ± 1 log2 dilution determined by the VetMIC and Etest methods with the median MICs determined by the reference method was very good for tetracycline, ampicillin, and streptomycin (92.3 to 100%) but low for erythromycin (19.5 to 30.7%) and clindamycin (50.0 to 80.8%). There was a consensus among the participating laboratories that VetMIC was preferred over Etest because of its lower cost, better growth support, and more uniform criteria for MIC end point reading. With the range for acceptable intralaboratory reproducibility being defined as the median MIC ± 1 log2 dilution, VetMIC results (with 69.2% of all data sets in the acceptable range) were shown to display greater reproducibility than Etest results (with 58.8% of all data sets in the acceptable range). Also at the interlaboratory level, the proportion of MIC values obtained with VetMIC that belonged to the complete agreement category (60.0%) was higher than the proportion of such values obtained with Etest (47.0%), which indicates a higher degree of interlaboratory reproducibility for the former method. Apart from
... Testing ; MRSA ; Fungal Tests ; Sputum Culture ; Stool Culture ; Gram Stain ; Body Fluid Analysis ; Pleural Fluid Analysis ; Pericardial ... to Get Tested? As follow up to a positive bacterial or fungal culture ; when you have an ...
Slots, J; Evans, R T; Lobbins, P M; Genco, R J
The agar dilution technique was used for determination of the antibiotic susceptibilities of 57 oral isolates and 2 nonoral isolates of Actinobacillus actinomycetemcomitans. Tetracycline, minocycline, and chloramphenicol inhibited more than 96% of the strains tested at a concentration of less than or equal to 2 micrograms/ml; 89% of the strains were inhibited by 2 micrograms of carbenicillin per ml. The other antimicrobial agents tested were less active. Approximately 10% of the A. actinomycetemcomitans strains were resistant to ampicillin, erythromycin, and penicillin G at concentrations of 32 to 64 micrograms/ml. These data suggest that tetracycline and minocycline may be valuable drugs in the treatment of A. actinomycetemcomitans infections. PMID:6903116
Mittman, Scott A; Huard, Richard C; Della-Latta, Phyllis; Whittier, Susan
The performance of the BD Phoenix Automated Microbiology System (BD Diagnostic Systems) was compared to those of the Vitek 2 (bioMérieux), the MicroScan MICroSTREP plus (Siemens), and Etest (bioMérieux) for antibiotic susceptibility tests (AST) of 311 clinical isolates of Streptococcus pneumoniae. The overall essential agreement (EA) between each test system and the reference microdilution broth reference method for S. pneumoniae AST results was >95%. For Phoenix, the EAs of individual antimicrobial agents ranged from 90.4% (clindamycin) to 100% (vancomycin and gatifloxacin). The categorical agreements (CA) of Phoenix, Vitek 2, MicroScan, and Etest for penicillin were 95.5%, 94.2%, 98.7%, and 97.7%, respectively. The overall CA for Phoenix was 99.3% (1 very major error [VME] and 29 minor errors [mEs]), that for Vitek 2 was 98.8% (7 VMEs and 28 mEs), and those for MicroScan and Etest were 99.5% each (19 and 13 mEs, respectively). The average times to results for Phoenix, Vitek 2, and the manual methods were 12.1 h, 9.8 h, and 24 h, respectively. From these data, the Phoenix AST results demonstrated a high degree of agreement with all systems evaluated, although fewer VMEs were observed with the Phoenix than with the Vitek 2. Overall, both automated systems provided reliable AST results for the S. pneumoniae-antibiotic combinations in half the time required for the manual methods, rendering them more suitable for the demands of expedited reporting in the clinical setting.
Same Day Identification and Full Panel Antimicrobial Susceptibility Testing of Bacteria from Positive Blood Culture Bottles Made Possible by a Combined Lysis-Filtration Method with MALDI-TOF VITEK Mass Spectrometry and the VITEK2 System
Machen, Alexandra; Drake, Tim; Wang, Yun F. (Wayne)
Rapid identification and antimicrobial susceptibility testing of microorganisms causing bloodstream infections or sepsis have the potential to improve patient care. This proof-of-principle study evaluates the Lysis-Filtration Method for identification as well as antimicrobial susceptibility testing of bacteria directly from positive blood culture bottles in a clinical setting. A total of 100 non-duplicated positive blood cultures were tested and 1012 microorganism-antimicrobial combinations were assessed. An aliquot of non-charcoal blood culture broth was incubated with lysis buffer briefly before being filtered and washed. Microorganisms recovered from the filter membrane were first identified by using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight VITEK® Mass Spectrometry (VITEK MS). After quick identification from VITEK MS, filtered microorganisms were inoculated to VITEK®2 system for full panel antimicrobial susceptibility testing analysis. Of 100 bottles tested, the VITEK MS resulted in 94.0% correct organism identification to the species level. Compared to the conventional antimicrobial susceptibility testing methods, direct antimicrobial susceptibility testing from VITEK®2 resulted in 93.5% (946/1012) category agreement of antimicrobials tested, with 3.6% (36/1012) minor error, 1.7% (7/1012) major error, and 1.3% (13/1012) very major error of antimicrobials. The average time to identification and antimicrobial susceptibility testing was 11.4 hours by using the Lysis-Filtration method for both VITEK MS and VITEK®2 compared to 56.3 hours by using conventional methods (p<0.00001). Thus, the same-day results of microorganism identification and antimicrobial susceptibility testing directly from positive blood culture can be achieved and can be used for appropriate antibiotic therapy and antibiotic stewardship. PMID:24551067
Same day identification and full panel antimicrobial susceptibility testing of bacteria from positive blood culture bottles made possible by a combined lysis-filtration method with MALDI-TOF VITEK mass spectrometry and the VITEK2 system.
Machen, Alexandra; Drake, Tim; Wang, Yun F Wayne
Rapid identification and antimicrobial susceptibility testing of microorganisms causing bloodstream infections or sepsis have the potential to improve patient care. This proof-of-principle study evaluates the Lysis-Filtration Method for identification as well as antimicrobial susceptibility testing of bacteria directly from positive blood culture bottles in a clinical setting. A total of 100 non-duplicated positive blood cultures were tested and 1012 microorganism-antimicrobial combinations were assessed. An aliquot of non-charcoal blood culture broth was incubated with lysis buffer briefly before being filtered and washed. Microorganisms recovered from the filter membrane were first identified by using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight VITEK® Mass Spectrometry (VITEK MS). After quick identification from VITEK MS, filtered microorganisms were inoculated to VITEK®2 system for full panel antimicrobial susceptibility testing analysis. Of 100 bottles tested, the VITEK MS resulted in 94.0% correct organism identification to the species level. Compared to the conventional antimicrobial susceptibility testing methods, direct antimicrobial susceptibility testing from VITEK®2 resulted in 93.5% (946/1012) category agreement of antimicrobials tested, with 3.6% (36/1012) minor error, 1.7% (7/1012) major error, and 1.3% (13/1012) very major error of antimicrobials. The average time to identification and antimicrobial susceptibility testing was 11.4 hours by using the Lysis-Filtration method for both VITEK MS and VITEK®2 compared to 56.3 hours by using conventional methods (p<0.00001). Thus, the same-day results of microorganism identification and antimicrobial susceptibility testing directly from positive blood culture can be achieved and can be used for appropriate antibiotic therapy and antibiotic stewardship.
Yeh, Jung-Yong; Lee, Ji-Hye; Yeh, Hye-Ryun; Kim, Aeran; Lee, Ji Youn; Hwang, Jeong-Min; Kang, Bo-Kyu; Kim, Jong-Man; Choi, In-Soo; Lee, Joong-Bok
This study represents the first published data on antimicrobial susceptibility of Asian isolates of Lawsonia intracellularis. We assessed MICs of 16 antimicrobials for two isolates of L. intracellularis recovered from diseased pigs in South Korea, one from a finisher pig with acute proliferative hemorrhagic enteropathy in 2002 and the other from a grower pig with porcine intestinal adenomatosis in 2010. Tylosin and tilmicosin were found to be the most active against L. intracellularis both intracellularly (MICs, 0.25 to 0.5 μg/ml and 0.125 μg/ml, respectively) and extracellularly (MICs, 0.25 to 0.5 μg/ml and 1 μg/ml, respectively). PMID:21690283
Berke, I; Tierno, P M
Antimicrobial susceptibility testing expense may be a significant portion of a clinical microbiology laboratory's budget. This study compares the BIOMIC VIDEO system (Giles Scientific, Inc., New York, N.Y.) with the Vitek system (bioMérieux Vitek, Inc., Hazelwood, Mo.), an established automated method of antimicrobial susceptibility testing with the ability to generate MIC data. The BIOMIC system is relatively inexpensive and automates the reading of the classical disk agar diffusion test to provide both qualitative (susceptibility interpretation) and quantitative (MIC) data. The overall MIC correlation between the two systems for the 2,913 drug-organism combinations tested was 92.6%. The overall agreement for susceptibility interpretation was 97.4%. The BIOMIC system offers a 57.4% savings per test over the Vitek system. The BIOMIC system utilizes an older technology which is more efficient and yet yields results comparable to those of established automated MIC methods. The savings achievable in laboratories and hospitals nationwide may contribute significantly to the containment of national health care expenditures. PMID:8818894
Performance Evaluation of a Newly Developed and Fully Automated Bacteriological Analyzer "RAISUS ANY" for Antimicrobial Susceptibility Testing of Fastidious Bacteria Haemophilus influenzae and Streptococcus pneumoniae.
Ohshima, Toshio; Nomiya, Saori; Yamamoto, Yukari; Miyazawa, Miki; Ohsuga, Jun; Hisada, Akifumi; Iwawaki, Kenji; Asai, Satomi; Miyachi, Hayato
Antimicrobial susceptibility testing for fastidious bacteria, such as Haemophilus influenzae (H. influenzae) and Streptococcus pneumoniae (S. pneumoniae) has been performed manually. We evaluated the performance of a newly developed fully automated system for rapid bacterial identification and antimicrobial susceptibility testing "RAISUS ANY" (Nissui Pharmaceutical Co., Ltd.). We evaluated the performance of "RAISUS ANY" for measurement of minimal inhibitory concentrations (MICs) of H. influenzae and S. pneumoniae, in comparison with the manual method (DP34, Eiken Chem. Co., Ltd.). The repeatability of MICs was studied using the reference strain of these bacteria, obtained from the American Type Culture Collection (ATCC, Manassas, VA, USA). The comparison with the manual method for 35 and 36 clinical strains of H. influenzae and S. pneumonia showed 62.9-100% and 86.1-100% agreement, respectively. Five of 35 H. influenzae strains that showed a trailing effect were stably and accurately measured for MICs without a variation among the examiners. In conclusion, the automated system "RAISUS ANY" provided a reliable MICs data for H. influenzae and S. pneumonia, suggesting its improvement in performance and reliability for routine antimicrobial susceptibility testing in clinical bacteriological laboratories.
Werckenthin, Christiane; Böttner, Alexander; Hafez, H Mohamed; Hartmann, Katrin; Kaske, Martin; Kehrenberg, Corinna; Kietzmann, Manfred; Klarmann, Dieter; Klein, Günter; Krabisch, Peter; Kühn, Tilman; Luhofer, Gabriele; Richter, Angelika; Schulz, Bianka; Schwarz, Stefan; Sigge, Claudia; Traeder, Wolfgang; Waldmann, Karl-Heinz; Wallmann, Jürgen
Phenotypic resistance of veterinary pathogens to more than one antimicrobial agent (multi-resistance) may be caused by intrinsic resistance to the antimicrobial agents, acquired cross-resistance, or acquired co-resistance. Known cross-resistances allow to select so-called "representative substances" which are tested and the results of which can also be regarded as being valid for other members of the same class of antimicrobial agents. In general, a limitation in the number of antimicrobial agents to be tested in routine diagnostics is necessary because of capacity and cost efficiency. This is of particular relevance when the broth microdilution method - recommended as the method of choice - with 96-well microtiter plates is used. The knowledge about the relationship between different resistance phenotypes and the corresponding resistance mechanisms is of major value for both, the laboratory personnel and the veterinary practitioner. This review explains how "representative substances" for the most relevant classes of antimicrobial agents used in veterinary medicine are chosen on the basis of known cross-resistances.
Ghanchi, Najia K; Khan, Erum; Farooqi, Joveria Q; Fasih, Naima; Dojki, Maqboola; Hughes, Molly A
A cross-sectional survey using structured questionnaire was conducted to assess practices of microbiological laboratories working with pathogens. Forty-eight laboratory workers (50%) agreed that laboratory methods to detect antimicrobial resistance are not standardized in Pakistan, and 6% of the laboratory workers were not aware of the standardization of antimicrobial susceptibility testing in Pakistan. Reported rates of awareness regarding the role of waste disposal, disinfection, and handwashing in limiting the spread of antimicrobial resistance were 75%, 42%, and 81%, respectively. Our results provide baseline data for planning programs to train, supervise, and improve the operational quality of microbiological laboratories nationwide to prevent the spread of superbugs. Copyright © 2014 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Mosby, Inc. All rights reserved.
Seyoum, Befikadu; Kefyalew, Hailemariam; Abera, Birhanu; Abdela, Nejash
A cross sectional study was undertaken from November 2016 to March 2017 in and around Asella town, Oromia regional state, southern Ethiopia, to determine the prevalence, associated risk factors and antimicrobial susceptibility of Staphylococcus aureus, in Bovine cross breed mastitis milk. A total of 384 lactating dairy cows were screened for mastitis based on clinical examinations and California mastitis test (CMT). Out of 230 lactating crossbred cows with either clinical or subclinical mastitis examined for the involvement of Staphylococcus aureus. Staphylococcus aureus was isolated at a rate of 47.2% (N=92) and 42.9% (N=15) of the sub- clinical and clinical cases, respectively. The overall prevalence of Staphylococcus aureus scored in this study was 46.5% (N=107). Descriptive statistics and chi-square were used in order to assess the magnitude of the difference of comparable variables, as a result, among risk factors considered, Age, parity, and lactation stage were found significantly associated with the occurrence of S. aureus in mastitis milk (p<0.05). The current study revealed that S. aureus has 0% susceptibility to penicillinG, followed by tetracycline (14.2%). However, these randomly selected isolates were found to be totally (100%) susceptible to the Kanamycin. The possible justification for, low antimicrobial susceptibility to these commonly used antimicrobials might be repeated and uncontrolled use of these drugs without veterinarian's prescription. Proper provention and regular antimicrobial sensitivity testing helps to select effective antibiotics and ultimately reduce the development of resistance towards commonly used antibiotics. To conclude, the study was able to show that, mastitis caused by S. aureus is one of the major problems of dairy cows in milk production and imposing public health hazard in study area. Hence, every possible control and prevention strategies should be implemented. Copyright © 2017 Elsevier B.V. All rights reserved.
Guardabassi, Luca; Hedberg, Sandra; Jessen, Lisbeth Rem; Damborg, Peter
Urinary tract infection (UTI) is a common reason for antimicrobial prescription in dogs and cats. The objective of this study was to optimize and evaluate a culture-based point-of-care test for detection, identification and antimicrobial susceptibility testing of bacterial uro-pathogens in veterinary practice. Seventy-two urine samples from dogs and cats with suspected UTI presenting to seven veterinary facilities were used by clinical staff and an investigator to estimate sensitivity and specificity of Flexicult Vet A compared to laboratory reference standards for culture and susceptibility testing. Subsequently, the test was modified by inclusion of an oxacillin-containing compartment for detection of methicillin-resistant staphylococci. The performance of the modified product (Flexicult Vet B) for susceptibility testing was evaluated in vitro using a collection of 110 clinical isolates. Bacteriuria was reported by the laboratory in 25 (35 %) samples from the field study. The sensitivity and specificity of Flexicult Vet A for detection of bacteriuria were 83 and 100 %, respectively. Bacterial species were correctly identified in 53 and 100 % of the positive samples by clinical staff and the investigator, respectively. The susceptibility results were interpreted correctly by clinical staff for 70 % of the 94 drug-strain combinations. Higher percentages of correct interpretation were observed when the results were interpreted by the investigator in both the field (76 %) and the in vitro study (94 %). The most frequent errors were false resistance to β-lactams (ampicillin, amoxicillin-clavulanate and cephalotin) in Escherichia coli for Flexicult Vet A, and false amoxicillin-clavulanate resistance in E. coli and false ampicillin susceptibility in Staphylococcus pseudintermedius for Flexicult Vet B. The latter error can be prevented by categorizing staphylococcal strains growing in the oxacillin compartment as resistant to all β-lactams. Despite the
Comparison of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Etest Methods with the CLSI Broth Microdilution Method for Echinocandin Susceptibility Testing of Candida Species▿
Pfaller, M. A.; Castanheira, M.; Diekema, D. J.; Messer, S. A.; Moet, G. J.; Jones, R. N.
The antifungal broth microdilution (BMD) method of the European Committee on Antibiotic Susceptibility Testing (EUCAST) and the Etest agar diffusion method were compared with the Clinical and Laboratory Standards Institute (CLSI) BMD method M27-A3 for anidulafungin, caspofungin, and micafungin susceptibility testing of 133 clinical isolates of Candida species. The isolates were characterized for the presence or absence of fks1 and/or fks2 gene mutations and included 34 isolates of C. glabrata (4 mutant strains), 32 of C. albicans (1 mutant strain), 25 of C. parapsilosis, 19 of C. guilliermondii, 12 of C. tropicalis (2 mutant strains), and 11 of C. krusei. Excellent essential agreement (EA; within 2 dilutions) between the CLSI and EUCAST and CLSI and Etest MIC results was observed. The overall EA between the EUCAST and CLSI results ranged from 89.5% (caspofungin) to 99.2% (micafungin), whereas the EA between the Etest and CLSI results ranged from 90.2% (caspofungin) to 93.2% (anidulafungin). The categorical agreement (CA) between methods for each antifungal agent was assessed using previously determined epidemiological cutoff values (ECVs). Excellent CA (>90%) was observed for all comparisons between the EUCAST and CLSI results with the exceptions of C. glabrata and caspofungin (85.3%) and C. krusei and caspofungin (54.5%). The CA between the Etest and CLSI results was also excellent for all comparisons, with the exception of C. krusei and caspofungin (81.8%). All three methods were able to differentiate wild-type (WT) strains from those with fks mutations. With anidulafungin as the test reagent, the CLSI method identified 5 of 7 mutant strains, whereas the EUCAST method and the Etest identified 6 of 7 mutant strains. With either caspofungin or micafungin as the test reagent, the CLSI method identified all 7 mutant strains and the EUCAST method identified 6 of 7 mutant strains. The Etest identified all 7 mutant strains using caspofungin as the reagent. All three
Comparison of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Etest methods with the CLSI broth microdilution method for echinocandin susceptibility testing of Candida species.
Pfaller, M A; Castanheira, M; Diekema, D J; Messer, S A; Moet, G J; Jones, R N
The antifungal broth microdilution (BMD) method of the European Committee on Antibiotic Susceptibility Testing (EUCAST) and the Etest agar diffusion method were compared with the Clinical and Laboratory Standards Institute (CLSI) BMD method M27-A3 for anidulafungin, caspofungin, and micafungin susceptibility testing of 133 clinical isolates of Candida species. The isolates were characterized for the presence or absence of fks1 and/or fks2 gene mutations and included 34 isolates of C. glabrata (4 mutant strains), 32 of C. albicans (1 mutant strain), 25 of C. parapsilosis, 19 of C. guilliermondii, 12 of C. tropicalis (2 mutant strains), and 11 of C. krusei. Excellent essential agreement (EA; within 2 dilutions) between the CLSI and EUCAST and CLSI and Etest MIC results was observed. The overall EA between the EUCAST and CLSI results ranged from 89.5% (caspofungin) to 99.2% (micafungin), whereas the EA between the Etest and CLSI results ranged from 90.2% (caspofungin) to 93.2% (anidulafungin). The categorical agreement (CA) between methods for each antifungal agent was assessed using previously determined epidemiological cutoff values (ECVs). Excellent CA (>90%) was observed for all comparisons between the EUCAST and CLSI results with the exceptions of C. glabrata and caspofungin (85.3%) and C. krusei and caspofungin (54.5%). The CA between the Etest and CLSI results was also excellent for all comparisons, with the exception of C. krusei and caspofungin (81.8%). All three methods were able to differentiate wild-type (WT) strains from those with fks mutations. With anidulafungin as the test reagent, the CLSI method identified 5 of 7 mutant strains, whereas the EUCAST method and the Etest identified 6 of 7 mutant strains. With either caspofungin or micafungin as the test reagent, the CLSI method identified all 7 mutant strains and the EUCAST method identified 6 of 7 mutant strains. The Etest identified all 7 mutant strains using caspofungin as the reagent. All three
Verroken, Alexia; Defourny, Lydwine; le Polain de Waroux, Olivier; Belkhir, Leïla; Laterre, Pierre-François; Delmée, Michel; Glupczynski, Youri
Shortening the turn-around time (TAT) of positive blood culture (BC) identification (ID) and susceptibility results is essential to optimize antimicrobial treatment in patients with sepsis. We aimed to evaluate the impact on antimicrobial prescription of a modified workflow of positive BCs providing ID and partial susceptibility results for Enterobacteriaceae (EB), Pseudomonas aeruginosa and Staphylococcus aureus on the day of BC positivity detection. This study was divided into a pre-intervention period (P0) with a standard BC workflow followed by 2 intervention periods (P1, P2) with an identical modified workflow. ID was performed with MALDI-TOF MS from blood, on early or on overnight subcultures. According to ID results, rapid phenotypic assays were realized to detect third generation cephalosporin resistant EB/P. aeruginosa or methicillin resistant S. aureus. Results were transmitted to the antimicrobial stewardship team for patient’s treatment revision. Times to ID, to susceptibility results and to optimal antimicrobial treatment (OAT) were compared across the three study periods. Overall, 134, 112 and 154 positive BC episodes in P0, P1 and P2 respectively were included in the analysis. Mean time to ID (28.3 hours in P0) was reduced by 65.3% in P1 (10.2 hours) and 61.8% in P2 (10.8 hours). Mean time to complete susceptibility results was reduced by 27.5% in P1 and 27% in P2, with results obtained after 32.4 and 32.6 hours compared to 44.7 hours in P0. Rapid tests allowed partial susceptibility results to be obtained after a mean time of 11.8 hours in P1 and 11.7 hours in P2. Mean time to OAT was decreased to 21.6 hours in P1 and to 17.9 hours in P2 compared to 36.1 hours in P0. Reducing TAT of positive BC with MALDI-TOF MS ID and rapid susceptibility testing accelerated prescription of targeted antimicrobial treatment thereby potentially improving the patients’ clinical outcome. PMID:27228001
Verroken, Alexia; Defourny, Lydwine; le Polain de Waroux, Olivier; Belkhir, Leïla; Laterre, Pierre-François; Delmée, Michel; Glupczynski, Youri
Shortening the turn-around time (TAT) of positive blood culture (BC) identification (ID) and susceptibility results is essential to optimize antimicrobial treatment in patients with sepsis. We aimed to evaluate the impact on antimicrobial prescription of a modified workflow of positive BCs providing ID and partial susceptibility results for Enterobacteriaceae (EB), Pseudomonas aeruginosa and Staphylococcus aureus on the day of BC positivity detection. This study was divided into a pre-intervention period (P0) with a standard BC workflow followed by 2 intervention periods (P1, P2) with an identical modified workflow. ID was performed with MALDI-TOF MS from blood, on early or on overnight subcultures. According to ID results, rapid phenotypic assays were realized to detect third generation cephalosporin resistant EB/P. aeruginosa or methicillin resistant S. aureus. Results were transmitted to the antimicrobial stewardship team for patient's treatment revision. Times to ID, to susceptibility results and to optimal antimicrobial treatment (OAT) were compared across the three study periods. Overall, 134, 112 and 154 positive BC episodes in P0, P1 and P2 respectively were included in the analysis. Mean time to ID (28.3 hours in P0) was reduced by 65.3% in P1 (10.2 hours) and 61.8% in P2 (10.8 hours). Mean time to complete susceptibility results was reduced by 27.5% in P1 and 27% in P2, with results obtained after 32.4 and 32.6 hours compared to 44.7 hours in P0. Rapid tests allowed partial susceptibility results to be obtained after a mean time of 11.8 hours in P1 and 11.7 hours in P2. Mean time to OAT was decreased to 21.6 hours in P1 and to 17.9 hours in P2 compared to 36.1 hours in P0. Reducing TAT of positive BC with MALDI-TOF MS ID and rapid susceptibility testing accelerated prescription of targeted antimicrobial treatment thereby potentially improving the patients' clinical outcome.
Yamada, Hiroyuki; Koike, Naohito; Ehara, Tomoko; Matsumoto, Tetsuya
Pseudomonas aeruginosa is a Gram-negative bacterium that causes various opportunistic infections. Chronic and intractable infections with P. aeruginosa are closely related to the high levels of resistance displayed by this organism to antimicrobial agents and its ability to form biofilms. Although the standard method for examining antimicrobial resistance involves susceptibility testing using Mueller-Hinton agar or broth, this method does not take into account the influence of biofilm formation on antimicrobial susceptibility. Poloxamer 407 is a hydrophilic, nonionic surfactant of the more general class of copolymers that can be used to culture bacteria with similar properties as cells in a biofilm environment. Therefore, the aim of this study was to compare the antimicrobial susceptibility of bacteria cultured in Poloxamer 407 gel to those grown on Mueller-Hinton agar using the Kirby-Bauer disk diffusion method with 24 strains of P. aeruginosa. Antimicrobial sensibility differed between the two mediums, with >60% of the strains displaying increased resistance to β-lactams when cultured on Poloxamer 407 gel. In addition, scanning electron microscopy revealed that typical biofilm formation and extracellular polymeric substance production was only observed with bacteria grown on Poloxamer 407 gel. Therefore, antimicrobial susceptibility test using Poloxamer 407 gel may provide more accurate information and allow the selection of suitable antimicrobial agents for treating patients infected with biofilm-forming pathogens.
Sedighi, Iraj; Solgi, Abbas; Amanati, Ali; Alikhani, Mohammad Yousef
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.
Campana, Eloiza H; Carvalhaes, Cecilia G; Nonato, Bruna; Machado, Antonia M de O; Gales, Ana C
The main objective of this study was to comparatively evaluate the performance of M.I.C.E. and Etest methodologies to that of agar dilution for determining the antimicrobial susceptibility profile of oxacillin-resistant Staphylococcus spp. A total of 100 oxacillin-resistant Staphylococcus spp. isolates were collected from hospitalized patients at a teaching hospital. Antimicrobial susceptibility testing for vancomycin, teicoplanin and linezolid was performed using the reference CLSI agar dilution method (2009), Etest and M.I.C.E. methodologies. The MIC values were interpreted according to CLSI susceptibility breakpoints and compared by regression analysis. In general, the essential agreement (±1-log2) between M.I.C.E. and CLSI agar dilution was 93.0%, 84.0% and 77.0% for linezolid, teicoplanin and vancomycin, respectively. Essential agreement rates between M.I.C.E. and Etest were excellent (>90.0%) for all antibiotics tested. Both strips (M.I.C.E. and Etest) yielded two very major errors for linezolid. Unacceptable minor rates were observed for teicoplanin against CoNS and for vancomycin against S. aureus. According to our results, linezolid and teicoplanin MICs against all staphylococci and S. aureus, respectively, were more accurately predicted by M.I.C.E. strips. However, the Etest showed better performance than M.I.C.E. for predicting vancomycin MICs against all staphylococci. Thus, microbiologists must be aware of the different performance of commercially available gradient strips against staphylococci.
Golus, J; Sawicki, R; Widelski, J; Ginalska, G
To develop a new agar microdilution technique suitable for the assessment of the antimicrobial activity of natural plant products such as essential oils or plant extracts as well as to evaluate the antimicrobial effect of several essential oils and plant extracts. The proposed agar microdilution method was evolved on the basis of the CLSI agar dilution method, approved for conventional antimicrobials. However, this new method combines convenience and time/cost effectiveness typical for microtitre methods with the advantages of the agar dilution of hydrophobic or coloured substances. Different concentrations of the tested agents were added to Eppendorf tubes with molten Mueller-Hinton agar, vortexed and dispensed into the 96-well microplate in a small volume of 100 μl per well which allows for rapid, easy and economical preparation of samples as well as providing a uniform and stable dispersion without separation of the oil-water phases which occurs in methods with liquid medium. Next, the agar microdilution plates were inoculated with four reference bacterial strains. The results of our study demonstrated that the minimal inhibitory concentrations (MICs) were successfully determined using the agar microdilution method even with hydrophobic essential oils or strongly coloured plant extracts. The new agar microdilution method avoids the problems associated with testing of water insoluble, oily or strongly coloured plant natural products. Moreover, it enables the reliable, cheap and easy MIC determination of such agents. In the era of increasing antibiotic resistance high hopes are associated with new drugs of plant origin. However, the lack of standardized and reliable testing methods for assessing antibacterial activity of plant natural products causes impediment to research into this area. This study demonstrated that the agar microdilution method can be used successfully for testing oily and coloured substances. © 2016 The Society for Applied Microbiology.
Zmudzki, J; Szczotka, A; Nowak, A; Strzelecka, H; Grzesiak, A; Pejsak, Z
Swine dysentery (SD) is a common disease among pigs worldwide, which contributes to major production losses. Antimicrobial susceptibility testing of B. hyodysenteriae, the etiological agent of SD, is mainly performed by the agar dilution method. This method has certain limitations due to difficulties in interpretation of results. The aim of this study was the analysis of antimicrobial susceptibility of Brachyspira hyodysenteriae (B. hyodysenteriae) Polish field isolates by broth microdilution procedure. The study was performed on 21 isolates of B. hyodysenteriae, collected between January 2006 to December 2010 from cases of swine dysentery. VetMIC Brachyspira panels with antimicrobial agents (tiamulin, valnemulin, doxycycline, lincomycin, tylosin and ampicillin) were used for susceptibility testing of B. hyodysenteriae. The minimal inhibitory concentration (MIC) was determined by the broth dilution procedure. The lowest antimicrobial activity was demonstrated for tylosin and lincomycin, with inhibition of bacterial growth using concentrations > 128 microg/ml and 32 microg/ml, respectively. In the case of doxycycline, the MIC values were < or = 2.0 microg/ml. No decreased susceptibility to tiamulin was found among the Polish isolates and MIC values for this antibiotic did not exceed 1.0 microg/ml. The results of the present study confirmed that Polish B. hyodysenteriae isolates were susceptible to the main antibiotics (tiamulin and valnemulin) used in treatment of swine dysentery. Further studies are necessary to evaluate a possible slow decrease in susceptibility to tiamulin and valnemulin of B. hyodysenteriae strains in Poland.
Pre-clinical development of antifungal susceptibility test methods for the testing of the novel antifungal agent E1210 versus Candida: comparison of CLSI and European Committee on Antimicrobial Susceptibility Testing methods.
Pfaller, Michael A; Watanabe, Naoaki; Castanheira, Mariana; Messer, Shawn A; Jones, Ronald N
To compare European Committee on Antimicrobial Susceptibility Testing (EUCAST) and CLSI broth microdilution (BMD) methods for testing the novel antifungal E1210 against a recent collection of 102 clinical isolates of Candida spp. Candida isolates (102) were tested by CLSI and EUCAST methods; 21 Candida albicans, 20 Candida glabrata, 25 Candida parapsilosis, 24 Candida tropicalis and 12 Candida krusei, including echinocandin- and azole-resistant isolates. CLSI and EUCAST MIC endpoints of 50% and 100% inhibition were determined using visual reading at 24 and 48 h of incubation and spectrophotometric reading at 24 h of incubation, respectively. E1210 CLSI MIC results ranged from ≤0.008 to only 1 mg/L (excluding C. krusei) depending on species, duration of incubation and endpoint criteria (EC). E1210 was not active against C. krusei (MIC(50) >16 mg/L). Overall essential agreement (EA; ±2 doubling dilutions) between the 24 and 48 h CLSI readings was 100% and 97.6% using the 50% and 100% inhibition EC, respectively. Slightly more trailing growth at 48 h was observed with the 100% inhibition EC. Comparison of the 50% and 100% endpoints at 24 h of incubation showed an overall EA of 100%. Comparison of CLSI and EUCAST read at 24 h of incubation and either 50% or 100% inhibition revealed an EA of 97.8% using the 50% inhibition EC and 88.9% using the 100% inhibition EC. E1210 was found to have potent in vitro activity against Candida spp. when tested by both CLSI and EUCAST BMD methods, with the highest overall EA (97.8%) obtained when E1210 MIC results were read after 24 h of incubation using a partial inhibition EC.
de MELO, Simone Cristina Castanho Sabaini; SANTOS, Nathally Claudiane de Souza; de OLIVEIRA, Marcia; SCODRO, Regiane Bertin de Lima; CARDOSO, Rosilene Fressatti; PÁDUA, Rúbia Andreia Falleiros; SILVA, Flavia Teixeira Ribeiro; COSTA, Aline Balandis; CARVALHO, Maria Dalva de Barros; PELLOSO, Sandra Marisa
SUMMARY Introduction: Group B streptococcus (GBS) or Streptococcus agalactiae can colonize the gastrointestinal and genitourinary tracts and has been considered one of the most important risk factors for the development of neonatal disease. The present study evaluated the antimicrobial susceptibility of GBS isolates from pregnant women who were attended at a public health service in Northern Paraná, Brazil. Methods: A descriptive analytical cross-sectional study was performed with 544 pregnant women, at ≥ 35 weeks of gestation. One hundred and thirty-six GBS isolates from pregnant women were tested for antimicrobial susceptibility. Results: All of the GBS isolates showed susceptibility to the drug that is most frequently used for intrapartum prophylaxis: penicillin. Resistance to clindamycin and erythromycin was detected, thus decreasing the options of prophylaxis in women who are allergic to penicillin. Conclusions: Additional studies should be conducted to increase the knowledge of GBS sensitivity profile to antimicrobials in other health centers. PMID:27828624
[First Argentine consensus guidelines for in vitro antimicrobial susceptibility testing of clinically relevant anaerobic bacteria in humans/ Anaerobic Subcommittee of the Asociación Argentina de Microbiología].
Legaria, María C; Bianchini, Hebe M; Castello, Liliana; Carloni, Graciela; Di Martino, Ana; Fernández Canigia, Liliana; Litterio, Mirta; Rollet, Raquel; Rossetti, Adelaida; Predari, Silvia C
Through time, anaerobic bacteria have shown good susceptibility to clinically useful antianaerobic agents. Nevertheless, the antimicrobial resistance profile of most of the anaerobic species related to severe infections in humans has been modified in the last years and different kinds of resistance to the most active agents have emerged, making their effectiveness less predictable. With the aim of finding an answer and for the purpose of facilitating the detection of anaerobic antimicrobial resistance, the Anaerobic Subcommittee of the Asociación Argentina de Microbiología developed the First Argentine consensus guidelines for in vitro antimicrobial susceptibility testing of clinically relevant anaerobic bacteria in humans. This document resulted from the compatibilization of the Clinical and Laboratory Standards Institute recommendations, the international literature and the work and experience of the Subcommittee. The Consensus document provides a brief taxonomy review, and exposes why and when anaerobic antimicrobial susceptibility tests should be conducted, and which antimicrobial agents can be used according to the species involved. The recommendations on how to perform, read and interpret in vitro anaerobic antimicrobial susceptibility tests with each method are exposed. Finally, the antibiotic susceptibility profile, the classification of antibiotics according to their in vitro activities, the natural and acquired mechanisms of resistance, the emerging resistance and the regional antibiotic resistance profile of clinically relevant anaerobic species are shown.
Antibiotic susceptibility of Stenotrophomonas (Xanthomonas) maltophilia: comparative (NCCLS criteria) evaluation of antimicrobial drugs with the agar dilution and the agar disk diffusion (Bauer-Kirby) tests.
Traub, W H; Leonhard, B; Bauer, D
Ninety-six clinical isolates of Stenotrophomonas maltophilia were examined with the agar dilution method for susceptibility to 19 antimicrobial drugs. Doxycycline, cotrimoxazole, timentin, ofloxacin, fosfomycin, and piperacillin + tazobactam, in that order, inhibited the majority of strains. All isolates were resistant to nitrofurantoin. Concurrent disk susceptibility (Bauer-Kirby method) testing, using currently valid NCCLS interpretative criteria for Pseudomonas aeruginosa, uncovered a significant incidence of very major (category I), major (category II), and minor (categories III and IV) discrepancies for aminoglycosides, cephalosporins, chloramphenicol, and piperacillin + tazobactam and ticarcillin + clavulanic acid. Therefore, new interpretative criteria indicative of intermediate (I) susceptibility of S. maltophilia to these various antibiotics were proposed. In addition, new intermediate susceptibility criteria were proposed for the two beta-lactam-beta-lactamase inhibitor combinations. It was recommended to exclude ciprofloxacin from test batteries against this microorganism due to the wide scatter of minimal inhibitory concentration values and diameters of inhibition zones; the same was true for polymyxin B. It is hoped that the proposed modified, species-specific criteria will improve the clinical utility of laboratory-generated disk antibiograms with respect to the inherently multiple antibiotic-resistant, opportunistic pathogen S. maltophilia.
Hammer, Timo R; Mucha, Helmut; Hoefer, Dirk
Dermatophytoses are a widespread problem worldwide. Textiles in contact with infected skin can serve as a carrier for fungus propagation. Hitherto, it is unknown, whether antifungal textiles could contribute in controlling dermatophytes e.g. by disrupting the chain of infection. Testing of antimicrobial fabrics for their antifungal activities therefore is a fundamental prerequisite to assess the putative clinical relevance of textiles for dermatophyte prevention. Fabrics finished with either didecyldimethylammonium chloride (DDAC), poly-hexamethylenbiguanide, copper and two silver chloride concentrations were tested for their antifungal activity against Trichophyton rubrum, Trichophyton mentagrophytes and Candida albicans. To prove dermatophyte susceptibility towards the textiles, swatches were subjected to DIN EN 14199 (Trichophyton sp.) or DIN EN ISO 20743 (C. albicans) respectively. In addition, samples were embedded, and semi-thin sections were analysed microscopically. While all samples showed a clear inhibition of C. albicans, activity against Trichophyton sp. varied significantly: For example, DDAC completely inhibited T. rubrum growth, whereas T. mentagrophytes growth remained unaffected even in direct contact to the fibres. The results favour to add T. mentagrophytes as a test organism in textile dermatophyte efficacy tests. Microscopic analysis of swatches allowed detailed evaluation of additional parameters like mycelium thickness, density and hyphae penetration depth into the fabric.
Byrne, S K; Crawford, C E; Geddes, G L; Black, W A
After preliminary in vitro screening of 10 antimicrobial agents against Mycobacterium tuberculosis, the MICs of the 6 most promising agents against 27 clinical isolates were determined by agar dilution. The two quinolone compounds tested (difloxacin and A-56620) were the most active, each inhibiting 50% of the strains at concentrations of 4 micrograms/ml. M. tuberculosis strains previously shown to be resistant to isoniazid, streptomycin, rifampin, or ethambutol were as susceptible to these quinolone compounds as susceptible strains. PMID:3143305
Hammerberg, S.; Sorger, S.; Marks, M. I.
Agar dilution antimicrobial susceptibility tests were carried out against recent clinical isolates of Yersinia enterocolitica biotype 4, serotype O:3. Aminoglycosides and co-trimoxazole were the most active drugs. All isolates were resistant to ampicillin, carbenicillin, cloxacillin, and erythromycin. PMID:856005
Wong, J D; Barash, J R; Sandfort, R F; Janda, J M
Ninety-two strains of Yersinia pestis recovered over a 21-year period were evaluated for susceptibility to traditional and newer antimicrobial agents. In vitro resistance was noted only against rifampin and imipenem (approximately 20% of strains). The most active compounds (MIC at which 90% of the isolates tested are inhibited) against Y. pestis were cefixime, ceftriaxone, trimethoprim-sulfamethoxazole, and trovafloxacin.
Tikofsky, Linda L; Barlow, John W; Santisteban, Carlos; Schukken, Ynte H
Selective pressure from antimicrobial use, mutations, or acquisition of foreign resistance determinants mediate antimicrobial resistance. If antimicrobial use is the major selective pressure encouraging the development of resistance, then reduced use should result in decreased resistance. We compared antimicrobial susceptibility patterns of Staphylococcus aureus isolates obtained from milk samples from 22 organic (nonantibiotic using) dairy herds to isolates from 16 conventional dairy herds. Susceptibility testing was performed by disk diffusion, and zone diameters were recorded in millimeters for 144 isolates from organic farms and 117 isolates from conventional farms and were also classified as susceptible or not-susceptible (intermediate and resistant categories combined). Strength of association between high or low use and proportion susceptible was evaluated by Chi-square analysis and differences in mean zone diameter for isolates from organic farms versus isolates from conventional farms were compared by analysis of variance. Analysis was done for each antimicrobial and deemed significant at p < or = 0.05. Differences in antimicrobial susceptibility were observed between S. aureus isolates from organic and conventional herds for seven of the nine antibiotics studied. Herds that were certified organic had S. aureus isolates that were more susceptible to antimicrobials. Overall, S. aureus isolates from both organic and conventional herds showed good susceptibility to most commonly used bovine mastitis antimicrobials; however, isolates from organic herds were significantly more susceptible. Longitudinal studies of herds undergoing the transition to organic farming would help elucidate the dynamics of antimicrobial resistance and the potential return of antimicrobial susceptibility.
Koru, Ozgur; Ozyurt, Mustafa
A total of 60 anaerobic strains were isolated from 322 clinical specimens. These isolates were tested for susceptibility to seven antibiotics (penicillin G, amoxicillin/clavulanic acid, cefoxitin, imipenem, chloramphenicol, metronidazole, clindamycin) by using ATB-ANA and Epsilometer test (E-test) strips and the results were compared with the gold standard agar dilution method. Imipenem was found as the most effective agent in vitro among the agents tested (100%). Susceptibility to penicillin G, amoxicillin/clavulanic acid, cefoxitin, chloramphenicol, metronidazole and clindamycin are 36.7%, 83.3%, 88.3%, 96.6%, 85% and 90%, respectively. E-test has showed a good correlation (r=0.62, p=0.001) statistically with the results of agar dilution (total agreement for all antibiotics changing between 90.01% and 98.45%) and a moderate correlation (r=0.45, p=0.048) with the results of ATB-ANA method (total agreement for all antibiotics changing between 75.46% and 98.76%). However, the routine use of agar dilution procedure is concluded to be cumbersome, whereas E-test method offers a reliable alternative.
The Quality Assurance Program (QAP) of the Deutsches Krebsforschungszentrum (DKFZ) was a proficiency testing system developed to service the laboratory animal discipline. The QAP comprised the distribution of bacterial strains from various species of animals for identification to species level and antibiotic susceptibility testing (AST). Identification capabilities were below acceptable standards. This study evaluated AST results using the DKFZ compilations of test results for all bacterial strains showing the number of participants reporting the strain as resistant (R), sensitive (S) or intermediate susceptible (I) to each antibiotic substance used. Due to lack of information about methods used, it was assumed that what the majority of the participants reported (R or S) was the correct test result and that an opposite result was a major error (ME). MEs occurred in 1375 of 14,258 (9.7%) of test results and ME% ranged from 0% to 23.2% per bacterial group-agent group combination. Considerable variation in MEs was found within groups of bacteria and within groups of agents. In addition to poor performance in proper species classification, the quality of AST in laboratory animal diagnostic laboratories seems far below standards considered acceptable in human diagnostic microbiology.
Kohlmann, Rebekka; Gatermann, Sören G
Many clinical microbiology laboratories report on cumulative antimicrobial susceptibility testing (cAST) data on a regular basis. Criteria for generation of cAST reports, however, are often obscure and inconsistent. Whereas the CLSI has published a guideline for analysis and presentation of cAST data, national guidelines directed at clinical microbiology laboratories are not available in Europe. Thus, we sought to describe the influence of different parameters in the process of cAST data analysis in the setting of a German routine clinical microbiology laboratory during 2 consecutive years. We developed various program scripts to assess the consequences ensuing from different algorithms for calculation of cumulative antibiograms from the data collected in our clinical microbiology laboratory in 2013 and 2014. One of the most pronounced effects was caused by exclusion of screening cultures for multi-drug resistant organisms which decreased the MRSA rate in some cases to one third. Dependent on the handling of duplicate isolates, i.e. isolates of the same species recovered from successive cultures on the same patient during the time period analyzed, we recorded differences in resistance rates of up to 5 percentage points for S. aureus, E. coli and K. pneumoniae and up to 10 percentage points for P. aeruginosa. Stratification by site of care and specimen type, testing of antimicrobials selectively on resistant isolates, change of interpretation rules and analysis at genus level instead of species level resulted in further changes of calculated antimicrobial resistance rates. The choice of parameters for cAST data analysis may have a substantial influence on calculated antimicrobial resistance rates. Consequently, comparability of cAST reports from different clinical microbiology laboratories may be limited. We suggest that laboratories communicate the strategy used for cAST data analysis as long as national guidelines for standardized cAST data analysis and reporting
Kohlmann, Rebekka; Gatermann, Sören G.
Introduction Many clinical microbiology laboratories report on cumulative antimicrobial susceptibility testing (cAST) data on a regular basis. Criteria for generation of cAST reports, however, are often obscure and inconsistent. Whereas the CLSI has published a guideline for analysis and presentation of cAST data, national guidelines directed at clinical microbiology laboratories are not available in Europe. Thus, we sought to describe the influence of different parameters in the process of cAST data analysis in the setting of a German routine clinical microbiology laboratory during 2 consecutive years. Material and Methods We developed various program scripts to assess the consequences ensuing from different algorithms for calculation of cumulative antibiograms from the data collected in our clinical microbiology laboratory in 2013 and 2014. Results One of the most pronounced effects was caused by exclusion of screening cultures for multi-drug resistant organisms which decreased the MRSA rate in some cases to one third. Dependent on the handling of duplicate isolates, i.e. isolates of the same species recovered from successive cultures on the same patient during the time period analyzed, we recorded differences in resistance rates of up to 5 percentage points for S. aureus, E. coli and K. pneumoniae and up to 10 percentage points for P. aeruginosa. Stratification by site of care and specimen type, testing of antimicrobials selectively on resistant isolates, change of interpretation rules and analysis at genus level instead of species level resulted in further changes of calculated antimicrobial resistance rates. Conclusion The choice of parameters for cAST data analysis may have a substantial influence on calculated antimicrobial resistance rates. Consequently, comparability of cAST reports from different clinical microbiology laboratories may be limited. We suggest that laboratories communicate the strategy used for cAST data analysis as long as national
Cao, Xiaoli; Cavaco, Lina M.; Lv, Yuan; Li, Yun; Zheng, Bo; Wang, Pengyuan; Hasman, Henrik; Liu, Yucun; Aarestrup, Frank M.
A total of 222 urinary Escherichia coli isolates from 20 tertiary hospitals in 15 different provinces and 4 municipalities in mainland China were characterized by antimicrobial susceptibility, phylogrouping, and the presence of plasmid-mediated quinolone resistance genes. A subset of 138 suspected extended-spectrum cephalosporinase (ESC) producers were examined for genes encoding cephalosporin resistance. Forty-three isolates harboring blaCTX-M-14 or blaCTX-M-15 were analyzed by pulsed-field gel electrophoresis (PFGE), and plasmids containing these genes were typed using PCR-based replicon typing (PBRT). Thirteen phylogroup B2 blaCTX-M-14- and blaCTX-M-15-positive isolates were analyzed by multilocus sequence typing (MLST). A frequent occurrence of resistance (>46%) was observed toward cephalosporins, gentamicin, and fluoroquinolones. Among the 222 isolates, 4 qnrS1, 4 qepA, and 16 aac(6′)-Ib-cr genes were confirmed. Four major phylogroups (A, B1, B2, and D) and nontypeable isolates (NTs) were found among the isolates, with phylogroup D (54%) being the most common phylogroup. A total of 110 (80%) of the 138 screened isolates harbored blaCTX-M genes, with blaCTX-M-14 (71%) and blaCTX-M-15 (24%) being the most prevalent of these genes. Nine of the 13 CTX-M-15- or CTX-M-14-containing B2 isolates belonged to ST131. PFGE typing showed a high level of diversity, and plasmid analysis indicated a very large pool of different resistance plasmids mediating the spread of blaCTX-M genes in mainland China. An equally very high frequency of resistance and equally high levels of diversity in phylogroups, PFGE types, and plasmids were observed among community- and hospital-acquired E. coli isolates, indicating the presence of a large reservoir in the community and a long-term spread of cephalosporin resistance in China. PMID:21525216
Comparison of Clinical Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing guidelines for the interpretation of antibiotic susceptibility at a University teaching hospital in Nairobi, Kenya: a cross-sectional study.
Kassim, Ali; Omuse, Geoffrey; Premji, Zul; Revathi, Gunturu
The Clinical Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines are the most popular breakpoint guidelines used in antimicrobial susceptibility testing worldwide. The EUCAST guidelines are freely available to users while CLSI is available for non-members as a package of three documents for US $500 annually. This is prohibitive for clinical microbiology laboratories in resource poor settings. We set out to compare antibiotic susceptibility determined by the two guidelines to determine whether adoption of EUCAST guidelines would significantly affect our susceptibility patterns. We reviewed minimum inhibitory concentrations (MIC) of various antibiotics routinely reported for Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) isolates from an automated microbiology identification system (VITEK-2) at the Aga Khan University Hospital Nairobi's Pathology department. These MICs were then analyzed using both CLSI 2015 and EUCAST 2015 guidelines and classified as resistant, intermediate or susceptible. We compared the susceptibility and agreement between the CLSI and EUCAST categorizations. Susceptibility data from a total of 5165 E. coli, 1103 S. aureus and 532 P. aeruginosa isolates were included. The concordance rates of the two guidelines for E. coli, S. aureus and P. aeruginosa ranged from 78.2 to 100 %, 94.6 to 100 % and 89.1 to 95.5 % respectively. The kappa statistics for E. coli MICs revealed perfect agreement between CLSI and EUCAST for cefotaxime, ceftriaxone and trimethoprim-sulfamethoxazole, almost perfect agreement for ampicillin, ciprofloxacin, cefuroxime, gentamicin and ceftazidime, substantial agreement for meropenem, moderate agreement for cefepime and amoxicillin-clavulanate, fair agreement for nitrofurantoin and poor agreement for amikacin. For S. aureus the kappa statistics revealed perfect agreement for penicillin
Ray, K A; Warnick, L D; Mitchell, R M; Kaneene, J B; Ruegg, P L; Wells, S J; Fossler, C P; Halbert, L W; May, K
The objective of this study was to compare antimicrobial susceptibility of Salmonella isolated from conventional and organic dairy farms in the Midwest and Northeast United States. Environmental and fecal samples were collected from organic (n = 26) and conventional (n = 69) farms in Michigan, Minnesota, New York, and Wisconsin every 2 mo from August 2000 to October 2001. Salmonella isolates (n = 1,243) were tested using a broth microdilution method for susceptibility to amoxicillin-clavulanic acid, ampicillin, ceftiofur, ceftriaxone, cephalothin, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, nalidixic acid, streptomycin, sulfamethoxazole, tetracycline, and trimethoprim-sulfamethoxazole. Herd-level logistic regression and logistic proportional hazards multivariable models were used to examine the association between farm management type and susceptibility to antimicrobial agents. For most antimicrobial agents tested, susceptibility of Salmonella isolates was similar on organic and conventional herds when controlling for herd size and state. Conventional farms were more likely to have at least one Salmonella isolate resistant to streptomycin using logistic regression (odds ratio = 7.5; 95% confidence interval = 1.7-5.4). Conventional farms were more likely to have Salmonella isolates with greater resistance to streptomycin (odds ratio = 5.4; 95% confidence interval = 1.5-19.0) and sulfamethoxazole (odds ratio = 4.2; 95% confidence interval = 1.2-14.1) using logistic proportional hazards models. Although not statistically significant, conventional farms tended to be more likely to have at least one Salmonella isolate resistant to 5 or more antimicrobial agents when compared with organic farms.
Cosme, A; Montes, M; Martos, M; Gil, I; Mendarte, U; Salicio, Y; Piñeiro, L; Recasens, M T; Ibarra, B; Sarasqueta, C; Bujanda, L
The rate of eradication of Helicobacter pylori with standard triple therapy using omeprazole, amoxicillin and clarithromycin (OAC) is unacceptable in populations with high rates of clarithromycin resistance (15-20%). The aim of this study was to compare the efficacy of 10-day OAC therapy as the first-line treatment in patients diagnosed by culture with antimicrobial susceptibility or diagnosed by a (13) C-labelled urea breath test (UBT) without antimicrobial susceptibility in an area where the clarithromycin resistance rate was 15-20%. This was a retrospective cohort study of 266 patients, recruited consecutively throughout 2008. A total of 247 H. pylori-infected patients received antibiotic therapy (221 received the 10-day OAC therapy and 26 received other regimens) of which 134 patients were diagnosed by culture of gastric samples followed by antimicrobial susceptibility testing and 113 were diagnosed by UBT. In all patients, the eradication of H. pylori was checked by UBT. The cost of eradication by 10-day OAC treatment was assessed in each patient. The success rate of 10-day OAC therapy in patients diagnosed by culture and by UBT was 88% (103/117) and 49% (51/104), respectively (p <0.0005). The treatment was also more cost-effective in the former of these two groups (€571 versus €666). To perform culture and antimicrobial susceptibility of the H. pylori isolates was a more successful and cost effective strategy than empirical 10-day OAC treatment in populations with high rates of resistance to clarithromycin.
Jones, Ronald N; Glick, Teri; Sader, Helio S; Flamm, Robert K; Ross, James E; Rhomberg, Paul R; Edson, Daniel C
External laboratory proficiency programs are an important requirement for test quality assurance (EQA) and compliance to regulatory guidelines (Clinical Laboratory Improvement Amendments and inspections). The American Proficiency Institute (API) regularly distributes EQA sample challenges (test events) including an Educational Sample (ES) for antimicrobial susceptibility testing. Beginning in 2007, API has sent 3 ES samples annually, each a well-characterized (molecular/phenotypic methods) strain having an interesting/emerging mechanism of resistance. Hundreds of USA laboratories, usually serving small- to medium-size hospitals and clinics, participate in the API ungraded ES test event. Analysis of responses is made and reported electronically as ES critiques addressing contemporary susceptibility testing issues that affect patient therapy. Seven Gram-positive (+) and 8 Gram-negative (-) ES strains were tested over the 5 years (2007-2011) with organism identification (graded) accuracy of 95.3% (range, 91.0-99.2%) for Gram (-) and 97.0% (range, 94.2-100.0%) for Gram (+) challenges. Susceptibility testing categorical accuracy was generally greatest for the disk diffusion test (91.0/97.0%) compared to the MIC methods (commercial automated or manual) combined (89.9/96.1%, for Gram [-]/Gram [+], respectively). The most worrisome observations of these ES samples were as follows: 1) poor recognition of ESBL- and serine carbapenemase-producing strains (various types including Klebsiella pneumoniae carbapanemase) due to delayed application of Clinical and Laboratory Standards Institute [CLSI] guidelines; 2) overcalling of ESBL in organisms having wild-type non-ESBL enzymes (OXA series; OXA, 1/30) due to commercial system or participant interpretive error; and 3) occasional drug-bug discords noted in nonfermentative Gram (-) bacilli. In conclusion, the API ES series of ungraded susceptibility testing challenges (accuracy was >90%) has been well received by subscribers and
Pailhoriès, Hélène; Lemarié, Carole; Kouatchet, Achille; Lasocki, Sigismond; Sargentini, Cyril; Kempf, Marie; Coron, Noémie; Mahaza, Chetaou; Joly-Guillou, Marie-laure; Eveillard, Matthieu
We previously demonstrated the positive impact of performing bacterial identification and antimicrobial susceptibility testing (AST) after day hours (night service [NS]) for certain clinical samples on the treatment of infected patients. Our objective was to evaluate the impact of including positive bronchoalveolar lavage (BAL) cultures in our NS. Two major positive consequences were recorded: initiation of earlier appropriate treatment and earlier change to a reduced-spectrum but still effective regimen. Reductions in delay were defined as the differences between the hours actually spent and hours estimated as though laboratory tests had been performed in the absence of NS. Fifty BALs were included. The NS led to the implementation of earlier appropriate therapy in 10 cases (20%), to earlier de-escalation in 15 cases (30%), and to earlier appropriate therapy and de-escalation in 4 cases (8%). In conclusion, performing bacterial identification and AST for positive BAL after laboratory opening hours could be relevant.
Eveillard, M; Lemarié, C; Cottin, J; Hitoto, H; Mahaza, C; Kempf, M; Joly-Guillou, M-L
The impact of inoculating agar media with positive blood cultures and of performing bacterial identification and antimicrobial susceptibility testing (AST) for positive urine cultures, blood cultures and certain fluid cultures after day hours (night service (NS)) was evaluated in a clinical microbiology laboratory. The impact of the NS was assessed in terms of decreases in the delays from the time of sampling to the time at which results became available and of the consequences for patient management and antimicrobial treatment. Two major benefits were obtained: initiation of earlier appropriate treatment, and change to a reduced-spectrum but still efficient regimen. The hours of laboratory testing and the availability and transmission of results to the clinical staff were recorded. Concurrently, these hours were estimated as though laboratory tests had been performed in the absence of NS. Reductions in delay were defined as the differences between the hours actually spent and the estimated hours. Economic concerns were also considered. Overall, 430 samples for which an identification and/or AST were performed during the NS were included in the study. The NS led to the implementation of earlier appropriate therapy in 97 cases (22.6%), and to the change to reduced-spectrum but still efficient regimens in 23 additional cases (5.3%). In conclusion, there appeared to be benefits from a system providing bacterial identification and AST overnight, but a study of the cost-effectiveness of the NS would be useful to back up this observation.
Filioussis, George; Petridou, Evanthia; Giadinis, Nektarios D; Kritas, Spyridon K
The minimum inhibitory concentrations (MICs) of enrofloxacin, ciprofloxacin, spectinomycin, tetracycline, spiramycin and erythromycin against 30 caprine Greek isolates of Mycoplasma agalactiae were determined using E test methodology. The E test strips were placed on Eaton's agar medium without antimicrobials and phenol red. MICs were then read by determining where the growth inhibition zone intersected with the MIC scale on the strip. An MIC value of 8 µg/mL was considered as a guide to mycoplasma resistance. All isolates were sensitive to fluoroquinolones (MIC50, 0.19 g/mL; MIC90, 0.38 µg/mL; highest MIC, 0.5 µg/mL), spectinomycin (MIC50, 0.5 µg/mL; MIC90, 1 µg/mL; highest MIC, 1 µg/mL), and spiramycin (MIC50, 1 µg/mL; MIC90, 1.5 µg/mL; highest MIC, 2 µg/mL). Two strains exhibited resistance to tetracycline (MIC 32 µg/mL) but these were not found to carry any of the tet(M), tet(O), and tet(S) resistance genes. Finally all isolates expressed resistance to erythromycin (MIC50, 128 µg/mL; MIC90, >256 µg/mL). Copyright © 2014 Elsevier Ltd. All rights reserved.
Comparison of the Broth Microdilution (BMD) Method of the European Committee on Antimicrobial Susceptibility Testing with the 24-Hour CLSI BMD Method for Testing Susceptibility of Candida Species to Fluconazole, Posaconazole, and Voriconazole by Use of Epidemiological Cutoff Values▿
Pfaller, M. A.; Espinel-Ingroff, A.; Boyken, L.; Hollis, R. J.; Kroeger, J.; Messer, S. A.; Tendolkar, S.; Diekema, D. J.
The antifungal broth microdilution (BMD) method of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) was compared with CLSI BMD method M27-A3 for fluconazole, posaconazole, and voriconazole susceptibility testing of 1,056 isolates of Candida. The isolates were obtained in 2009 from more than 60 centers worldwide and included 560 isolates of C. albicans, 175 of C. glabrata, 162 of C. parapsilosis, 124 of C. tropicalis, and 35 of C. krusei. The overall essential agreement (EA) between EUCAST and CLSI results ranged from 96.9% (voriconazole) to 98.6% (fluconazole). The categorical agreement (CA) between methods and species of Candida was assessed using previously determined epidemiological cutoff values (ECVs). The ECVs (expressed as μg/ml) for fluconazole, posaconazole, and voriconazole, respectively, were as follows: 0.12, 0.06, and 0.03 for C. albicans; 32, 2, and 0.5 for C. glabrata; 2, 0.25, and 0.12 for C. parapsilosis; 2, 0.12, and 0.06 for C. tropicalis; 64, 0.5, and 0.5 for C. krusei. Excellent CA was observed for all comparisons between the EUCAST and CLSI results for fluconazole, posaconazole, and voriconazole, respectively, for each species: 98.9%, 93.6%, and 98.6% for C. albicans; 96.0%, 98.9%, and 93.7% for C. glabrata; 90.8%, 98.1%, and 98.1% for C. parapsilosis; 99.2%, 99.2%, and 96.8% for C. tropicalis; 97.1%, 97.1%, and 97.1% for C. krusei. We demonstrate high levels of EA and CA between the CLSI and EUCAST BMD methods for testing of triazoles against Candida when the MICs were determined after 24 h and ECVs were used to differentiate wild-type (WT) from non-WT strains. These results provide additional data in favor of the harmonization of these two methods. PMID:21227994
Comparison of the broth microdilution (BMD) method of the European Committee on Antimicrobial Susceptibility Testing with the 24-hour CLSI BMD method for testing susceptibility of Candida species to fluconazole, posaconazole, and voriconazole by use of epidemiological cutoff values.
Pfaller, M A; Espinel-Ingroff, A; Boyken, L; Hollis, R J; Kroeger, J; Messer, S A; Tendolkar, S; Diekema, D J
The antifungal broth microdilution (BMD) method of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) was compared with CLSI BMD method M27-A3 for fluconazole, posaconazole, and voriconazole susceptibility testing of 1,056 isolates of Candida. The isolates were obtained in 2009 from more than 60 centers worldwide and included 560 isolates of C. albicans, 175 of C. glabrata, 162 of C. parapsilosis, 124 of C. tropicalis, and 35 of C. krusei. The overall essential agreement (EA) between EUCAST and CLSI results ranged from 96.9% (voriconazole) to 98.6% (fluconazole). The categorical agreement (CA) between methods and species of Candida was assessed using previously determined epidemiological cutoff values (ECVs). The ECVs (expressed as μg/ml) for fluconazole, posaconazole, and voriconazole, respectively, were as follows: 0.12, 0.06, and 0.03 for C. albicans; 32, 2, and 0.5 for C. glabrata; 2, 0.25, and 0.12 for C. parapsilosis; 2, 0.12, and 0.06 for C. tropicalis; 64, 0.5, and 0.5 for C. krusei. Excellent CA was observed for all comparisons between the EUCAST and CLSI results for fluconazole, posaconazole, and voriconazole, respectively, for each species: 98.9%, 93.6%, and 98.6% for C. albicans; 96.0%, 98.9%, and 93.7% for C. glabrata; 90.8%, 98.1%, and 98.1% for C. parapsilosis; 99.2%, 99.2%, and 96.8% for C. tropicalis; 97.1%, 97.1%, and 97.1% for C. krusei. We demonstrate high levels of EA and CA between the CLSI and EUCAST BMD methods for testing of triazoles against Candida when the MICs were determined after 24 h and ECVs were used to differentiate wild-type (WT) from non-WT strains. These results provide additional data in favor of the harmonization of these two methods.
Romeu Alvarez, Beatriz; Salazar Jiménez, Paloma; Lugo Moya, Daysi; Rojas Hernández, Nidia M; Eslava Campos, Carlos A
Antimicrobial resistance is one of the biggest problems facing global public health. The emergence of resistant clinical and environmental strains worsens the situation. Among the microorganisms with antimicrobial resistance, Escherichia coil species stands out due to its dual role as fecal contamination indicator and pathogen. To isolate and identify Escherichia coil isolates from water samples from polluted rivers located in La Habana, and to determine their antimicrobial in vitro susceptibility. One hundred thirteen isolates of coliform bacteria isolated from 10 sampling stations in the capital's urban areas near Almendares, Quibú and Luyanó rivers were studied in the period of February 2008 to June 2010. The identification of isolates, the determination of antimicrobial susceptibility and the search for extended-spectrum beta-lactamase were all performed using VITEK automated method. One hundred thirteen environmental strains of Escherichia coli were identified. It showed that 23% of the isolates were resistant to at least one of the tested antimicrobials. The highest percentages of resistance were observed to ampicilline, sulfamethoxazole-trimethoprim and ciprofloxacin. The presence of E. coil isolates with multiple antimicrobial resistances in these rivers clearly indicates the biological risk involving the use of their waters.
Pol, M; Ruegg, P L
The objective of this study was to analyze relationships between usage of antimicrobial drugs on dairy farms and results of antimicrobial susceptibility testing of mastitis pathogens. Exposure to selected antimicrobial drugs (n = 10) was standardized by calculation of the number of defined daily doses used per cow. Farms (n = 40) were categorized based on amount of antimicrobial exposure: organic (no usage); conventional-low usage (conventional farms not using or using less than or equal to the first quartile of use of each compound); and conventional-high usage (conventional farms using more than the first quartile of a particular compound). The minimum inhibitory concentration (MIC) of selected antimicrobial drugs was determined using a commercial microbroth dilution system for isolates of Staphylococcus aureus (n = 137), coagulase-negative staphylococci (CNS, n = 294), and Streptococcus spp. (n = 95) obtained from subclinical mastitis infections. Most isolates were inhibited at the lowest dilution tested of most antimicrobial drugs. Survival curves for Staph. aureus and CNS demonstrated heterogeneity in MIC based on the amount of exposure to penicillin and pirlimycin. For CNS, farm type was associated with the MIC of ampicillin and tetracycline. For Streptococcus spp., farm type was associated with MIC of pirlimycin and tetracycline. For all mastitis pathogens studied, the MIC of pirlimycin increased with increasing exposure to defined daily doses of pirlimycin. The level of exposure to most other antimicrobial drugs was not associated with MIC of mastitis pathogens. A dose-response effect between antimicrobial exposure and susceptibility was observed for some pathogen-antimicrobial combinations, but exposure to other antimicrobial drugs commonly used for prevention and treatment of mastitis was not associated with resistance.
Tchesnokova, Veronika; Avagyan, Hovhannes; Billig, Mariya; Chattopadhyay, Sujay; Aprikian, Pavel; Chan, Diana; Pseunova, Julietta; Rechkina, Elena; Riddell, Kim; Scholes, Delia; Fang, Ferric C.; Johnson, James R.; Sokurenko, Evgeni V.
Background. Escherichia coli is a highly clonal pathogen. Extraintestinal isolates belong to a limited number of genetically related groups, which often exhibit characteristic antimicrobial resistance profiles. Methods. We developed a rapid clonotyping method for extraintestinal E coli based on detection of the presence or absence of 7 single nucleotide polymorphisms (SNPs) within 2 genes (fumC and fimH). A reference set of 2559 E coli isolates, primarily of urinary origin, was used to predict the resolving power of the 7-SNP-based typing method, and 582 representative strains from this set were used to evaluate test robustness. Results. Fifty-four unique SNP combinations (“septatypes”) were identified in the reference strains. These septatypes yielded a clonal group resolution power on par with that of traditional multilocus sequence typing. In 72% of isolates, septatype identity predicted sequence type identity with at least 90% (mean, 97%) accuracy. Most septatypes exhibited highly distinctive antimicrobial susceptibility profiles. The 7-SNP-based test could be performed with high specificity and sensitivity using single or multiplex conventional polymerase chain reaction (PCR) and quantitative PCR. In the latter format, E coli presence and septatype identity were determined directly in urine specimens within 45 minutes with bacterial loads as low as 102 colony-forming units/mL and, at clinically significant bacterial loads, with 100% sensitivity and specificity. Conclusions. 7-SNP-based typing of E coli can be used for both epidemiological studies and clinical diagnostics, which could greatly improve the empirical selection of antimicrobial therapy. PMID:26925427
Antimicrobial susceptibility of gram-negative and gram-positive bacteria collected from countries in Eastern Europe: results from the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) 2004-2010.
Balode, Arta; Punda-Polić, Volga; Dowzicky, Michael J
The Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) commenced in 2004 to longitudinally monitor global changes in bacterial susceptibility to a suite of antimicrobial agents. The current study examined the activity of tigecycline and comparators against isolates collected across Eastern Europe between 2004 and 2010. Minimum inhibitory concentrations were determined using Clinical and Laboratory Standards Institute (CLSI) broth microdilution methodologies. Antimicrobial susceptibility was determined using CLSI interpretive criteria, and tigecycline susceptibility was established using European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints. This study included 10 295 Gram-negative and 4611 Gram-positive isolates from 42 centres. Extended-spectrum β-lactamases (ESBLs) were reported among 15.3% of Escherichia coli and 39.3% of Klebsiella pneumoniae isolates; the highest rates were observed in Turkey (30.9%) and Bulgaria (53.8%), respectively. Imipenem-non-susceptible K. pneumoniae were identified only in Turkey. ESBL-positive E. coli were highly susceptible to imipenem (95.1%), meropenem (98.0%) and tigecycline (98.5%). Most antimicrobials showed poor activity against Acinetobacter baumannii and Pseudomonas aeruginosa. Vancomycin resistance was noted among 0.9% of Enterococcus faecalis and 11.7% of Enterococcus faecium isolates. High rates of susceptibility were reported for linezolid (99.7%) and tigecycline (100%) against E. faecium. One-quarter of Staphylococcus aureus isolates were meticillin-resistant S. aureus (MRSA), with the highest rate in Romania (51.5%); all MRSA were susceptible to linezolid, tigecycline and vancomycin. Antimicrobial resistance is high in much of Eastern Europe, with considerable variation seen among countries. Tigecycline and the carbapenems retain excellent activity against many pathogens from Eastern Europe; linezolid and vancomycin are active against most Gram-positive pathogens.
Rex, J H; Pfaller, M A; Rinaldi, M G; Polak, A; Galgiani, J N
Unlike antibacterial susceptibility testing, reliable antifungal susceptibility testing is still largely in its infancy. Many methods have been described, but they produce widely discrepant results unless such factors as pH, inoculum size, medium formulation, incubation time, and incubation temperature are carefully controlled. Even when laboratories agree upon a common method, interlaboratory agreement may be poor. As a result of numerous collaborative projects carried out both independently and under the aegis of the Subcommittee on Antifungal Susceptibility Testing of the National Committee for Clinical Laboratory Standards, the effects of varying these factors have been extensively studied and a standard method which minimizes interlaboratory variability during the testing of Candida spp. and Cryptococcus neoformans has been proposed. This review summarizes this work, reviews the strengths and weaknesses of the proposed susceptibility testing standard, and identifies directions for future work. PMID:8269392
Rex, J H; Pfaller, M A; Rinaldi, M G; Polak, A; Galgiani, J N
Unlike antibacterial susceptibility testing, reliable antifungal susceptibility testing is still largely in its infancy. Many methods have been described, but they produce widely discrepant results unless such factors as pH, inoculum size, medium formulation, incubation time, and incubation temperature are carefully controlled. Even when laboratories agree upon a common method, interlaboratory agreement may be poor. As a result of numerous collaborative projects carried out both independently and under the aegis of the Subcommittee on Antifungal Susceptibility Testing of the National Committee for Clinical Laboratory Standards, the effects of varying these factors have been extensively studied and a standard method which minimizes interlaboratory variability during the testing of Candida spp. and Cryptococcus neoformans has been proposed. This review summarizes this work, reviews the strengths and weaknesses of the proposed susceptibility testing standard, and identifies directions for future work.
Sellyei, Boglárka; Varga, Zsuzsanna; Szentesi-Samu, Katalin; Kaszanyitzky, Eva; Magyar, Tibor
Pasteurella multocida causes infectious diseases in a wide range of animal species. Antimicrobial therapy is still an effective tool for treatment. Generally, P. multocida isolates are susceptible to most of the widely used commercial antimicrobial agents but their excessive and unjustified use accelerates the emergence of resistant strains. We defined the antimicrobial sensitivity pattern of 56 P. multocida strains isolated from poultry (20) and swine [16 P. multocida toxin (PMT) positive and 20 PMT negative] to 16 widely applied antibiotics (apramycin, cefquinome, chloramphenicol, colistin, doxycycline, enrofloxacin, erythromycin, florfenicol, flumequine, neomycin, oxolinic acid, penicillin, trimethoprim potentiated sulphamethoxazole, sulphonamide compounds, tetracycline, tulathromycin) by the disk diffusion method. The majority of the strains was susceptible to most of the antimicrobial agents tested. However, the resistance to sulphonamides, tetracyclines, first-generation quinolones and aminoglycosides was remarkable, and thus the use of these compounds for the treatment of infection caused by P. multocida is not recommended. On the other hand, the antimicrobial activity of the classical penicillin, the newer macrolide (tulathromycin), the third-generation fluoroquinolone (enrofloxacin) and the fourth-generation cephalosporin (cefquinome) proved to be satisfactory against this bacterium.
Due to the great variability in antimicrobial resistance patterns, local reports of cumulative antimicrobial susceptibility data are necessary in every health center. The purpose is to guide clinical decisions and the early detection of patterns that allow preventive measures to avoid dissemination of resistant strains. The main objective of this guide is to provide recommendations for the analysis of antimicrobial susceptibility data and elaboration of a local report. Recommendations provided in this guide are based on the Clinical and Laboratory Standards Institute (CLSI) document "Analysis and Presentation of Cumulative Antimicrobial Susceptibility Test Data" (3). Key aspects related to information gathering and data processing, analysis and presentation are described.
Antimicrobial susceptibility testing of aquatic bacteria: quality control disk diffusion ranges for Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658 at 22 and 28 degrees C.
Miller, R A; Walker, R D; Baya, A; Clemens, K; Coles, M; Hawke, J P; Henricson, B E; Hsu, H M; Mathers, J J; Oaks, J L; Papapetropoulou, M; Reimschuessel, R
Quality control (QC) ranges for disk diffusion susceptibility testing of aquatic bacterial isolates were proposed as a result of a multilaboratory study conducted according to procedures established by the National Committee for Clinical Laboratory Standards (NCCLS). Ranges were proposed for Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658 at 22 and 28 degrees C for nine different antimicrobial agents (ampicillin, enrofloxacin, erythromycin, florfenicol, gentamicin, oxolinic acid, oxytetracycline, ormetoprim-sulfadimethoxine, and trimethoprim-sulfamethoxazole). All tests were conducted on standard Mueller-Hinton agar. With >/=95% of all data points fitting within the proposed QC ranges, the results from this study comply with NCCLS guidelines and have been accepted by the NCCLS Subcommittee for Veterinary Antimicrobial Susceptibility Testing. These QC guidelines will permit greater accuracy in interpreting results and, for the first time, the ability to reliably compare susceptibility test data between aquatic animal disease diagnostic laboratories.
Miller, R. A.; Walker, R. D.; Baya, A.; Clemens, K.; Coles, M.; Hawke, J. P.; Henricson, B. E.; Hsu, H. M.; Mathers, J. J.; Oaks, J. L.; Papapetropoulou, M.; Reimschuessel, R.
Quality control (QC) ranges for disk diffusion susceptibility testing of aquatic bacterial isolates were proposed as a result of a multilaboratory study conducted according to procedures established by the National Committee for Clinical Laboratory Standards (NCCLS). Ranges were proposed for Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658 at 22 and 28°C for nine different antimicrobial agents (ampicillin, enrofloxacin, erythromycin, florfenicol, gentamicin, oxolinic acid, oxytetracycline, ormetoprim-sulfadimethoxine, and trimethoprim-sulfamethoxazole). All tests were conducted on standard Mueller-Hinton agar. With ≥95% of all data points fitting within the proposed QC ranges, the results from this study comply with NCCLS guidelines and have been accepted by the NCCLS Subcommittee for Veterinary Antimicrobial Susceptibility Testing. These QC guidelines will permit greater accuracy in interpreting results and, for the first time, the ability to reliably compare susceptibility test data between aquatic animal disease diagnostic laboratories. PMID:12958263
Two-Center Collaborative Evaluation of the Performance of the BD Phoenix Automated Microbiology System for Identification and Antimicrobial Susceptibility Testing of Enterococcus spp. and Staphylococcus spp.
Fahr, Anne-Marie; Eigner, Ulrich; Armbrust, Martina; Caganic, Alexandra; Dettori, Giuseppe; Chezzi, Carlo; Bertoncini, Luca; Benecchi, Magda; Menozzi, Maria Grazia
The performance of the BD Phoenix Automated Microbiology System (BD Diagnostic Systems, Sparks, Md.) was assessed for identification (ID) and antimicrobial susceptibility testing (AST) for the majority of clinically encountered bacterial isolates in a European collaborative two-center trial. A total of 469 bacterial isolates of the genera Staphylococcus (275 isolates), Enterococcus (179 isolates), and Streptococcus (15 isolates, for ID only) were investigated; of these, 367 were single patient isolates, and 102 were challenge strains tested at one center. Sixty-four antimicrobial drugs were tested, including the following drug classes: aminoglycosides, beta-lactam antibiotics, beta-lactam-beta-lactamase inhibitors, carbapenems, cephems, folate antagonists, quinolones, glycopeptides, macrolides-lincosamides-streptogramin B (MLS), and others. Phoenix ID results were compared to those of the laboratories' routine ID systems (API 32 Staph, API 32 Strep, and VITEK 2 [bioMérieux, Marcy l'Etoile, France]); Phoenix AST results were compared to those of frozen standard broth microdilution (SBM) panels according to NCCLS guidelines (NCCLS document M 100-S 9, approved standard M 7-A 4). Discrepant results were repeated in duplicate. Concordant IDs of 97.1, 98.9, and 100% were observed for staphylococci, enterococci, and streptococci, respectively. For AST results the overall essential agreement was 93.3%; the category agreement was 97.3%; and the very major error rate, major error rate, and minor error rate were 1.2, 1.9, and 1.3%, respectively. In conclusion, the Phoenix ID results showed high agreement with results of the systems to which they were being compared; the AST performance was highly equivalent to that of the SBM reference method. PMID:12624042
Amachawadi, Raghavendra G.; Renter, David G.; Volkova, Victoriya V.
Antimicrobial treatments result in the host’s enteric bacteria being exposed to the antimicrobials. Pharmacodynamic models can describe how this exposure affects the enteric bacteria and their antimicrobial resistance. The models utilize measurements of bacterial antimicrobial susceptibility traditionally obtained in vitro in aerobic conditions. However, in vivo enteric bacteria are exposed to antimicrobials in anaerobic conditions of the lower intestine. Some of enteric bacteria of food animals are potential foodborne pathogens, e.g., Gram-negative bacilli Escherichia coli and Salmonella enterica. These are facultative anaerobes; their physiology and growth rates change in anaerobic conditions. We hypothesized that their antimicrobial susceptibility also changes, and evaluated differences in the susceptibility in aerobic vs. anaerobic conditions of generic E. coli and Salmonella enterica of diverse serovars isolated from cattle feces. Susceptibility of an isolate was evaluated as its minimum inhibitory concentration (MIC) measured by E-Test® following 24 hours of adaptation to the conditions on Mueller-Hinton agar, and on a more complex tryptic soy agar with 5% sheep blood (BAP) media. We considered all major antimicrobial drug classes used in the U.S. to treat cattle: β-lactams (specifically, ampicillin and ceftriaxone E-Test®), aminoglycosides (gentamicin and kanamycin), fluoroquinolones (enrofloxacin), classical macrolides (erythromycin), azalides (azithromycin), sulfanomides (sulfamethoxazole/trimethoprim), and tetracyclines (tetracycline). Statistical analyses were conducted for the isolates (n≥30) interpreted as susceptible to the antimicrobials based on the clinical breakpoint interpretation for human infection. Bacterial susceptibility to every antimicrobial tested was statistically significantly different in anaerobic vs. aerobic conditions on both media, except for no difference in susceptibility to ceftriaxone on BAP agar. A satellite experiment
Rüegsegger, F; Ruf, J; Tschuor, A; Sigrist, Y; Rosskopf, M; Hässig, M
This study evaluates the antimicrobial resistance of pathogens cultured from 3'954 quarter milk samples from dairy cows in Switzerland. A total of 1'228 Streptococcus (Strep.) uberis, 1'107 Staphylococcus (Staph.) spp. other than Staph. aureus, 598 coliform, 490 Staph. aureus, 270 Enterococcus spp. and 213 Strep. dysgalactiae isolates were tested for susceptibility to 9 antimicrobial drugs using agar diffusion. Streptococcus uberis, Strep. dysgalactiae and Staph. aureus had the highest antimicrobial sensitivities to amoxicillin clavulanic acid (99.6 %, 100 % and 98.8 %, respectively). Of all isolated pathogens, only 2.6 % were resistant to amoxicillin clavulanic acid and 8.0 % to cefoperazone. The overall resistance level to gentamicin was 45.5 %, to penicillin 39.2 %, and to ampicillin 26.7 %. The highest resistance levels occurred with polymyxin (86.0 %), oxacillin (64.7 %) and lincomycin (53.7 %). Our results showed that at least one resistance exists to one antimicrobial agent examined in this study. Ideally the selection of the antibacterial drug for the treatment of intramammary infection should be based on antibiotic susceptibility testing.
Marschal, Matthias; Bachmaier, Johanna; Autenrieth, Ingo; Oberhettinger, Philipp; Willmann, Matthias; Peter, Silke
Bloodstream infections (BSI) are an important cause of morbidity and mortality. Increasing rates of antimicrobial-resistant pathogens limit treatment options, prompting an empirical use of broad-range antibiotics. Fast and reliable diagnostic tools are needed to provide adequate therapy in a timely manner and to enable a de-escalation of treatment. The Accelerate Pheno system (Accelerate Diagnostics, USA) is a fully automated test system that performs both identification and antimicrobial susceptibility testing (AST) directly from positive blood cultures within approximately 7 h. In total, 115 episodes of BSI with Gram-negative bacteria were included in our study and compared to conventional culture-based methods. The Accelerate Pheno system correctly identified 88.7% (102 of 115) of all BSI episodes and 97.1% (102 of 105) of isolates that are covered by the system's identification panel. The Accelerate Pheno system generated an AST result for 91.3% (95 of 104) samples in which the Accelerate Pheno system identified a Gram-negative pathogen. The overall category agreement between the Accelerate Pheno system and culture-based AST was 96.4%, the rates for minor discrepancies 1.4%, major discrepancies 2.3%, and very major discrepancies 1.0%. Of note, ceftriaxone, piperacillin-tazobactam, and carbapenem resistance was correctly detected in blood culture specimens with extended-spectrum beta-lactamase-producing Escherichia coli (n = 7) and multidrug-resistant Pseudomonas aeruginosa (n = 3) strains. The utilization of the Accelerate Pheno system reduced the time to result for identification by 27.49 h (P < 0.0001) and for AST by 40.39 h (P < 0.0001) compared to culture-based methods in our laboratory setting. In conclusion, the Accelerate Pheno system provided fast, reliable results while significantly improving turnaround time in blood culture diagnostics of Gram-negative BSI. Copyright © 2017 American Society for Microbiology.
Goldspink, Lauren K; Mollinger, Joanne L; Barnes, Tamsin S; Groves, Mitchell; Mahony, Timothy J; Gibson, Justine S
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.
Comparison of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and CLSI screening parameters for the detection of extended-spectrum β-lactamase production in clinical Enterobacteriaceae isolates.
Polsfuss, Silke; Bloemberg, Guido V; Giger, Jacqueline; Meyer, Vera; Hombach, Michael
To compare the performance of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and CLSI breakpoints following their revision in 2010, for the detection of extended-spectrum β-lactamase (ESBL) production in Enterobacteriaceae. 236 well-characterized clinical isolates (including 118 ESBL producers) were investigated by antibiotic disc testing with cefpodoxime, ceftriaxone, cefepime, cefotaxime EUCAST (5 μg/disc), ceftazidime EUCAST (10 μg/disc), cefotaxime CLSI (30 μg/disc) and ceftazidime CLSI (30 μg/disc) with the Kirby-Bauer method. Additionally, synergy phenomena were recorded between amoxicillin/clavulanic acid discs (20/10 μg/disc) and cefepime (30 μg/disc), EUCAST cefotaxime (5 μg/disc), EUCAST ceftazidime (10 μg/disc), CLSI cefotaxime (30 μg/disc) and CLSI ceftazidime [30 μg/disc; disc approximation method (DAM)]. Overall sensitivity of the cefotaxime EUCAST non-susceptible breakpoint equalled sensitivity of the cefotaxime CLSI ESBL screening breakpoint (99.2%). With the ceftazidime EUCAST non-susceptible breakpoint, 27/118 ESBL-producing isolates were not detected, whereas the ceftazidime CLSI ESBL screening breakpoint missed 41/118 ESBL-producing isolates. For cefpodoxime the resistant EUCAST breakpoint showed higher sensitivity for ESBL detection compared with the CLSI ESBL screening breakpoint/disc content (100% versus 98.3%, respectively). Sensitivities of ceftazidime and cefotaxime DAM with CLSI or EUCAST disc contents were comparable (sensitivities ranging from 84.7% to 89.8%). DAM with cefepime displayed the highest overall sensitivity (96.6%). In AmpC-producing isolates, synergy of amoxicillin/clavulanic acid with cefepime showed sensitivity and specificity for ESBL detection of 100% and 97.4%, respectively. EUCAST non-susceptible breakpoints for ceftazidime and cefpodoxime detect more ESBL-producing Enterobacteriaceae isolates compared with corresponding CLSI ESBL screening breakpoints. Implementation of the cefepime
Båverud, V; Gunnarsson, A; Karlsson, M; Franklin, A
The antimicrobial susceptibility of 50 Clostridium difficile isolates, 36 of them from horse feces and 14 from environmental sites, was determined by broth microdilution. The antimicrobial agents tested were avilamycin, cephalothin, chloramphenicol, clindamycin, erythromycin, gentamicin, neomycin, oxacillin, oxytetracycline, penicillin, spiramycin, streptomycin, trimethoprim/sulfamethoxazole, vancomycin, and virginiamycin. All isolates were susceptible to vancomycin (MIC =1 microg/ml). The MICs of erythromycin, oxytetracycline, spiramycin, and virginiamycin showed a bimodal distribution. Compared with the majority of isolates, the MICs of erythromycin (MIC > 16 microg/ml), oxytetracycline (MIC >/=32 microg/ml), spiramycin (MIC > 16 microg/ml), and virginiamycin (MIC 8-16 microg/ml) were higher for 18 isolates. Those were mainly isolated from horses at animal hospitals and further from environmental sites at a stud farm. In contrast, all isolates, except one, from healthy foals had low MICs of erythromycin, spiramycin, virginiamycin, and oxytetracycline. The isolates from soil in public parks had also low MICs of these antimicrobial agents. Broth microdilution appeared both reliable and reproducible for susceptibility testing of C. difficile. The method was also readily performed and the MIC endpoints were easily read.
Antos-Bielska, Małgorzata; Lau-Dworak, Magdalena; Olszewska-Sosińska, Olga; Zielnik-Jurkiewicz, Beata; Trafny, Elżbieta A
Eleven out of 40 children with adenoiditis were colonized with multiple genotypes of Haemophilus influenzae. Heterogeneous antibiotic susceptibility to ampicillin and cotrimoxazole was observed in 6 children. A multiple-colony methodology may potentially help to find the resistant strains of H. influenzae in patients who do not respond to the antibiotic treatment.
Di Bonaventura, Giovanni; Ricci, Evandro; Della Loggia, Nicoletta; Catamo, Giovanni; Piccolomini, Raffaele
The E test was evaluated in comparison with reference agar methods (National Committee for Clinical Laboratory Standards) for the susceptibility testing of 248 Pseudomonas aeruginosa isolates from bladder-catheterized patients against nine antibiotics. The E-test MICs correlated well with those determined by the agar dilution and disk diffusion reference methods (88 and 92.5% within 1 log2 dilution step, respectively), confirming that the E test is a reliable method for the determination of MICs of antibiotics for catheterization-associated P. aeruginosa isolates. PMID:9508323
Halford, Colin; Gonzalez, Rodrigo; Campuzano, Susana; Hu, Bo; Babbitt, Jane T; Liu, Jun; Wang, Joseph; Churchill, Bernard M; Haake, David A
Precursor rRNA (pre-rRNA) is an intermediate stage in the formation of mature rRNA and is a useful marker for cellular metabolism and growth rate. We developed an electrochemical sensor assay for Escherichia coli pre-rRNA involving hybridization of capture and detector probes with tail sections that are spliced away during rRNA maturation. A ternary self-assembled monolayer (SAM) prepared on gold electrode surfaces by coassembly of thiolated capture probes with hexanedithiol and posttreatment with 6-mercapto-1-hexanol minimized the background signal and maximized the signal-to-noise ratio. Inclusion of internal calibration controls allowed accurate estimation of the pre-rRNA copy number per cell. As expected, the ratio of pre-rRNA to mature rRNA was low during stationary phase and high during log phase. Pre-rRNA levels were highly dynamic, ranging from 2 copies per cell during stationary phase to ~1,200 copies per cell within 60 min of inoculation into fresh growth medium. Specificity of the assay for pre-rRNA was validated using rifampin and chloramphenicol, which are known inhibitors of pre-rRNA synthesis and processing, respectively. The DNA gyrase inhibitor, ciprofloxacin, was found to act similarly to rifampin; a decline in pre-rRNA was detectable within 15 min in ciprofloxacin-susceptible bacteria. Assays for pre-rRNA provide insight into cellular metabolism and are promising predictors of antibiotic susceptibility.
Halford, Colin; Gonzalez, Rodrigo; Campuzano, Susana; Hu, Bo; Babbitt, Jane T.; Liu, Jun; Wang, Joseph; Churchill, Bernard M.
Precursor rRNA (pre-rRNA) is an intermediate stage in the formation of mature rRNA and is a useful marker for cellular metabolism and growth rate. We developed an electrochemical sensor assay for Escherichia coli pre-rRNA involving hybridization of capture and detector probes with tail sections that are spliced away during rRNA maturation. A ternary self-assembled monolayer (SAM) prepared on gold electrode surfaces by coassembly of thiolated capture probes with hexanedithiol and posttreatment with 6-mercapto-1-hexanol minimized the background signal and maximized the signal-to-noise ratio. Inclusion of internal calibration controls allowed accurate estimation of the pre-rRNA copy number per cell. As expected, the ratio of pre-rRNA to mature rRNA was low during stationary phase and high during log phase. Pre-rRNA levels were highly dynamic, ranging from 2 copies per cell during stationary phase to ∼1,200 copies per cell within 60 min of inoculation into fresh growth medium. Specificity of the assay for pre-rRNA was validated using rifampin and chloramphenicol, which are known inhibitors of pre-rRNA synthesis and processing, respectively. The DNA gyrase inhibitor, ciprofloxacin, was found to act similarly to rifampin; a decline in pre-rRNA was detectable within 15 min in ciprofloxacin-susceptible bacteria. Assays for pre-rRNA provide insight into cellular metabolism and are promising predictors of antibiotic susceptibility. PMID:23229486
Lilenbaum, W; Veras, M; Blum, E; Souza, G N
Samples were obtained from 65 unmedicated adult dogs, processed for isolation of Staphylococcus species and tested for susceptibility to penicillin G, gentamicin, oxacillin, tetracycline, trimethoprim-sulphamethoxazole, streptomycin, ampicillin and rifampin. Forty-four isolates were obtained, which represents 67.7% of samples. Coagulase-negative species were most commonly found, and the most frequently isolated staphylococcus species were Staph. epidermidis and Staph. aureus. Other species, such as Staph. simulans, Staph. haemolyticus, Staph. saprophyticus and Staph. intermedius were also isolated. Resistance to antibiotics was frequently observed, with 90.9% of the isolates showing resistance to at least one drug. The most active antimicrobial agents against staphylococci isolated from otitis externa of dogs were rifampin and oxacillin. Multidrug resistance was a common finding, and one strain of Staph. haemolyticus species, was resistant to all tested antimicrobial agents. Resistance to three or more different drugs was a common finding, observed in 16 strains (36.4%) of both coagulase-positive and coagulase-negative staphylococci. This study highlights the emergence of cases of otitis externa determined by coagulase-negative staphylococcus strains and once more emphasizes the need for bacterial culture with species identification and susceptibility testing of swab specimens from the ear canal in order to choose appropriate antimicrobial agents.
Kelman, Alina; Soong, Yee-Ann; Dupuy, Nicole; Shafer, Daniel; Richbourg, William; Johnson, Kourtney; Brown, Twain; Kestler, Edward; Li, Yi; Zheng, Jie; McDermott, Patrick; Meng, Jianghong
The aim of this study was to characterize antimicrobial resistance in Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), recovered from raw retail meat products purchased in the Washington, D.C., area. From March to August 2008, 694 samples of ground beef (n = 198), ground pork (n = 300), and ground turkey (n = 196) were collected by random sampling from stores of three grocery chains. In total, 200 S. aureus isolates (29%) were recovered by direct plating. When tested for susceptibility to 22 antimicrobials, 69% of the S. aureus isolates were resistant to tetracycline, 26% to penicillin, 17% to ampicillin, 13% to methicillin, 8% to erythromycin, 4.5% to clindamycin, 1.5% to gentamicin, and 0.5% to chloramphenicol, oxacillin, cefoxitin, or quinupristin-dalfopristin. However, 27% of the isolates were susceptible to all tested antimicrobials. More turkey and pork isolates were resistant to ampicillin, penicillin, and tetracycline than were beef isolates (P < 0.05). Additionally, 17% of the turkey and 17% of the pork isolates were resistant to methicillin (MIC ≥ 16 μg/ml), whereas no beef isolates were resistant to the antimicrobial agent. A single MRSA (methicillin MIC > 32 μg/ml) isolate containing the mecA gene with additional resistance to erythromycin, clindamycin, oxacillin plus 2% NaCl, cefoxitin, ampicillin, penicillin, quinupristin-dalfopristin, tetracycline, and gentamicin was recovered from one pork sample. The presence of antimicrobial-resistant S. aureus, coupled with the relative lack of such studies in the United States, suggests that further investigations on MRSA in the food supply are needed despite the low rate of MRSA found in this particular study.
Lob, Sibylle H; Hoban, Daryl J; Sahm, Daniel F; Badal, Robert E
Acinetobacter baumannii, although representing a small percentage of Gram-negative bacilli isolates in intra-abdominal infections (IAIs) and urinary tract infections (UTIs), is frequently multidrug-resistant (MDR) and can pose difficult therapeutic challenges. From 2011 to 2014, 2337 A. baumannii were collected from IAIs and UTIs at 453 hospital sites in 48 countries as part of the SMART ongoing surveillance initiative. Current susceptibility and multidrug resistance, defined as resistance to at least three of the tested drug classes, were determined in a subset of 1011 isolates from 2013 to 2014. A. baumannii comprised 0.7-4.6% of all aerobic and facultative Gram-negative bacilli isolated in six global regions. MDR rates were lowest in North America (47%) and highest in Europe and the Middle East (>93%), with higher rates in ICUs than in non-ICU wards in almost all regions. Antimicrobial susceptibility profiles varied by region but resistance was high everywhere, with no drug inhibiting >70% of A. baumannii isolates in any region. Susceptibility to imipenem was highest in North America (64%) and lowest in Europe and the Middle East (≤11%). Amikacin overall was the most active of the studied agents, including against MDR isolates (of which 11-38% were susceptible). Trend analysis of only those countries that contributed isolates in each study year (2011-2014) demonstrated an increasing trend in MDR rates in the Middle East as well as decreasing susceptibility to several single antimicrobial agents in Africa, Europe and the Middle East. These patterns and trends can help direct antimicrobial therapy and infection control efforts.
Menozzi, Maria Grazia; Eigner, Ulrich; Covan, Silvia; Rossi, Sabina; Somenzi, Pietro; Dettori, Giuseppe; Chezzi, Carlo; Fahr, Anne-Marie
The performance of the BD Phoenix Automated Microbiology System (BD Diagnostic Systems, Sparks, MD) was assessed for identification (ID) and antimicrobial susceptibility testing (AST) of the majority of clinically encountered bacterial isolates in a European collaborative two-center trial. A total of 494 bacterial isolates including various species of the Enterobacteriaceae and 110 nonfermentative gram-negative bacteria were investigated: of these, 385 were single patient isolates, and 109 were challenge strains tested at one center. The performance of the Phoenix extended-spectrum beta-lactamase (ESBL) test was also evaluated for 203 strains of Escherichia coli, Klebsiella pneumoniae, and Klebsiella oxytoca included in the study. Forty-two antimicrobial drugs were tested, including members of the following drug classes: aminoglycosides, beta-lactam antibiotics, beta-lactam/beta-lactamase inhibitors, carbapenems, cephems, monobactams, folate antagonists, quinolones, and others. Phoenix system ID results were compared to those of the laboratories' routine ID systems (API 20E and API CHE, ATB ID32E, ID32GN, and VITEK 2 [bioMérieux, Marcy l'Etoile, France]); Phoenix AST results were compared to those of frozen standard broth microdilution (SBM) panels according to NCCLS (now CLSI) guidelines (NCCLS document M100-S9, approved standard M7-A4). Discrepant results were repeated in duplicate. Concordant IDs of 98.4 and 99.1% were observed for the Enterobacteriaceae and the nonfermentative group, respectively. For AST results, the overall essential agreement was 94.2%; the category agreement was 97.3%; and the very major error rate, major error rate, and minor error rate were 1.6, 0.6, and 1.9%, respectively. In terms of ESBL detection, Phoenix results were 98.5% concordant with those of the reference system, with 98.0% sensitivity and 98.7% specificity. In conclusion, the Phoenix ID results showed high agreement with results of the systems to which they were being
Menozzi, Maria Grazia; Eigner, Ulrich; Covan, Silvia; Rossi, Sabina; Somenzi, Pietro; Dettori, Giuseppe; Chezzi, Carlo; Fahr, Anne-Marie
The performance of the BD Phoenix Automated Microbiology System (BD Diagnostic Systems, Sparks, MD) was assessed for identification (ID) and antimicrobial susceptibility testing (AST) of the majority of clinically encountered bacterial isolates in a European collaborative two-center trial. A total of 494 bacterial isolates including various species of the Enterobacteriaceae and 110 nonfermentative gram-negative bacteria were investigated: of these, 385 were single patient isolates, and 109 were challenge strains tested at one center. The performance of the Phoenix extended-spectrum β-lactamase (ESBL) test was also evaluated for 203 strains of Escherichia coli, Klebsiella pneumoniae, and Klebsiella oxytoca included in the study. Forty-two antimicrobial drugs were tested, including members of the following drug classes: aminoglycosides, β-lactam antibiotics, β-lactam/β-lactamase inhibitors, carbapenems, cephems, monobactams, folate antagonists, quinolones, and others. Phoenix system ID results were compared to those of the laboratories' routine ID systems (API 20E and API CHE, ATB ID32E, ID32GN, and VITEK 2 [bioMérieux, Marcy l'Etoile, France]); Phoenix AST results were compared to those of frozen standard broth microdilution (SBM) panels according to NCCLS (now CLSI) guidelines (NCCLS document M100-S9, approved standard M7-A4). Discrepant results were repeated in duplicate. Concordant IDs of 98.4 and 99.1% were observed for the Enterobacteriaceae and the nonfermentative group, respectively. For AST results, the overall essential agreement was 94.2%; the category agreement was 97.3%; and the very major error rate, major error rate, and minor error rate were 1.6, 0.6, and 1.9%, respectively. In terms of ESBL detection, Phoenix results were 98.5% concordant with those of the reference system, with 98.0% sensitivity and 98.7% specificity. In conclusion, the Phoenix ID results showed high agreement with results of the systems to which they were being compared: the
A multi-laboratory broth microdilution method trial was performed to standardize the specialized test conditions required for fish pathogens Flavobacterium columnare and F. pyschrophilum. Nine laboratories tested the quality control (QC) strains Escherichia coli ATCC 25922 and Aeromonas salmonicid...
Baron, Sandrine; Lesne, Jean; Jouy, Eric; Larvor, Emeline; Kempf, Isabelle; Boncy, Jacques; Rebaudet, Stanilas; Piarroux, Renaud
We investigated the antimicrobial susceptibility of 50 environmental isolates of Vibrio cholerae non-O1/non-O139 collected in surface waters in Haiti in July 2012, during an active cholera outbreak. A panel of 16 antibiotics was tested on the isolates using the disk diffusion method and PCR detection of seven resistance-associated genes (strA/B, sul1/2, ermA/B, and mefA). All isolates were susceptible to amoxicillin-clavulanic acid, cefotaxime, imipenem, ciprofloxacin, norfloxacin, amikacin, and gentamicin. Nearly a quarter (22.0%) of the isolates were susceptible to all 16 antimicrobials tested and only 8.0% of the isolates (n = 4) were multidrug-resistant. The highest proportions of resistant isolates were observed for sulfonamide (70.0%), amoxicillin (12.0%), and trimethoprim-sulfamethoxazole (10.0%). One strain was resistant to erythromycin and one to doxycycline, two antibiotics used to treat cholera in Haiti. Among the 50 isolates, 78% possessed at least two resistance-associated genes, and the genes sul1, ermA, and strB were detected in all four multidrug-resistant isolates. Our results clearly indicate that the autochthonous population of V. cholerae non-O1/non-O139 found in surface waters in Haiti shows antimicrobial patterns different from that of the outbreak strain. The presence in the Haitian aquatic environment of V. cholerae non-O1/non-O139 with reduced susceptibility or resistance to antibiotics used in human medicine may constitute a mild public health threat.
Baron, Sandrine; Lesne, Jean; Jouy, Eric; Larvor, Emeline; Kempf, Isabelle; Boncy, Jacques; Rebaudet, Stanilas; Piarroux, Renaud
We investigated the antimicrobial susceptibility of 50 environmental isolates of Vibrio cholerae non-O1/non-O139 collected in surface waters in Haiti in July 2012, during an active cholera outbreak. A panel of 16 antibiotics was tested on the isolates using the disk diffusion method and PCR detection of seven resistance-associated genes (strA/B, sul1/2, ermA/B, and mefA). All isolates were susceptible to amoxicillin-clavulanic acid, cefotaxime, imipenem, ciprofloxacin, norfloxacin, amikacin, and gentamicin. Nearly a quarter (22.0%) of the isolates were susceptible to all 16 antimicrobials tested and only 8.0% of the isolates (n = 4) were multidrug-resistant. The highest proportions of resistant isolates were observed for sulfonamide (70.0%), amoxicillin (12.0%), and trimethoprim-sulfamethoxazole (10.0%). One strain was resistant to erythromycin and one to doxycycline, two antibiotics used to treat cholera in Haiti. Among the 50 isolates, 78% possessed at least two resistance-associated genes, and the genes sul1, ermA, and strB were detected in all four multidrug-resistant isolates. Our results clearly indicate that the autochthonous population of V. cholerae non-O1/non-O139 found in surface waters in Haiti shows antimicrobial patterns different from that of the outbreak strain. The presence in the Haitian aquatic environment of V. cholerae non-O1/non-O139 with reduced susceptibility or resistance to antibiotics used in human medicine may constitute a mild public health threat. PMID:27818656
Chen, Derrick; Cunningham, Scott A; Cole, Nicolynn C; Kohner, Peggy C; Mandrekar, Jayawant N; Patel, Robin
Failure to eradicate Helicobacter pylori infection is often a result of antimicrobial resistance, which for clarithromycin is typically mediated by specific point mutations in the 23S rRNA gene. The purpose of this study was to define current patterns of antimicrobial susceptibility in H. pylori isolates derived primarily from the United States and to survey them for the presence of point mutations in the 23S rRNA gene and assess the ability of these mutations to predict phenotypic clarithromycin susceptibility. Antimicrobial susceptibility testing was performed using agar dilution on 413 H. pylori isolates submitted to Mayo Medical Laboratories for susceptibility testing. For a subset of these isolates, a 150-bp segment of the 23S rRNA gene was sequenced. A total of 1,970 MICs were reported over the 4-year study period. The rate of clarithromycin resistance was high (70.4%), and elevated MICs were frequently observed for metronidazole (82.4% of isolates had an MIC of >8 μg/ml) and ciprofloxacin (53.5% of isolates had an MIC of >1 μg/ml). A total of 111 archived H. pylori isolates underwent 23S rRNA gene sequencing; we found 95% concordance between genotypes and phenotypes (P = 0.9802). Resistance to clarithromycin was most commonly due to an A2143G mutation (82%), followed by A2142G (14%) and A2142C (4%) mutations. Clinical H. pylori isolates derived primarily from the United States demonstrated a high rate of clarithromycin resistance and elevated metronidazole and ciprofloxacin MICs. The relative distribution of point mutations at positions 2143 and 2142 in the 23S rRNA gene in clarithromycin-resistant H. pylori was similar to that reported from other parts of the world; these mutations predict phenotypic resistance to clarithromycin.
Pereyra, Laura Del V; Gorordo Ipiña, Rosa C; Berruezo, Fabiana A; Amieva, Cristian A; García, Maria E; Bottiglieri, Marina T
Antimicrobial susceptibility was evaluated by two diffusion methods: E-test strips to determine minimum inhibitory concentration (MIC) and disk diffusion for amoxicillin, clarithromycin, metronidazole and ciprofloxacin in 30 Helicobacter pylori strains isolated from gastric biopsies. No strains were resistant to amoxicillin, 17% (5/30) were resistant to clarithromycin, 20% (6/30) ciprofloxacin by both methods, and 37% (11/30) to metronidazole by the E-test. Although the number of strains studied was reduced, there was a single mismatch in interpreting susceptibility when both methods were compared; the same mismatch was observed for metronidazole, being categorized as sensitive by the E-test and as intermediate by disk diffusion. No association between the histological type of lesion and the resistance pattern found could be determined. Copyright © 2017 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.
Background The Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) was designed to monitor in vitro antimicrobial susceptibility to tigecycline and comparator agents. We present susceptibility data on Gram-negative organisms collected between 2005 and 2011 from nine United States census regions. Methods T.E.S.T. was conducted using standardized CLSI methodologies or FDA-approved breakpoints. Results Tigecycline was highly active (MIC90 ≤ 2 mg/L) against Enterobacteriaceae irrespective of species or region of collection (N = 25011). The isolates were also highly susceptible to the carbapenems when all regional data are combined, except for ESBL-producing Klebsiella pneumoniae (MIC90 16 mg/L) and Acinetobacter baumannii (MIC90 ≥ 32 mg/L). In addition, 883 (30%) of 2900 A. baumannii isolates were classified as multidrug-resistant (MDR): these MDR organisms were most susceptible to tigecycline (MIC90 2 mg/L) and minocycline (MIC90 8 mg/L) when all regional data are considered together. Susceptibility patterns also varied widely among the regions Conclusions The findings highlight the importance of monitoring antimicrobial susceptibility patterns and implementing effective methods to curb increased resistance and also confirm that additional studies to determine the efficacy of tigecycline in vivo, especially for treating infections with MDR organisms, are warranted. PMID:24006892
Zamankhan Malayeri, Hamed; Jamshidi, Shahram; Zahraei Salehi, Taghi
Bacterial agents are considered important pathogens causing external otitis in dogs. It is essential to carry out bacterial culture and antimicrobial susceptibility test in the case of otitis externa, particularly for chronic or recurring cases. Sterile swab samples were obtained from terminal part of vertical ear canals of 74 dogs with otitis externa for cytology, bacterial culture and antimicrobial susceptibility test. Cytologic smears were stained using Gram and Giemsa staining methods. Aerobic bacterial culture performed on blood agar and MacConkey agar. Among total number of 92 isolated bacteria, 68 were Staphylococcus intermedius. Other isolated bacteria included: Pseudomonas aeruginosa, Proteus mirabilis, Escherichia coli, Pasteurella canis, and six other species of coagulase-negative Staphylococcus. Antimicrobial susceptibility test were performed for all isolated bacteria using 14 antibiotics. Based on the results of this study, all isolated Staphylococcus spp. were sensitive to amikacin, enrofloxacin, and rifampin, and had low resistance to gentamicin, cephalothin and ceftriaxone. More than half of gram-positive isolates were resistant to penicillin and ampicillin. Generally, all isolated gram-negative bacteria, were sensitive to amikacin and enrofloxacin, and had low resistance to ceftriaxone and gentamicin. They were highly resistant to penicillin, eythromycin, and cephalothin. Regarding the results of this study, in cases of uncomplicated otitis externa, it is possible to select antimicrobial drugs merely based on cytology, but it is recommended to perform bacterial culture and antimicrobial susceptibility test. However, in complicated or refractory cases, antimicrobials should be selected based on bacterial culture and antimicrobial susceptibility test.
[Proposals of the working group "Antibiotic resistance" for the configuration of microtitre plates to be used in routine antimicrobial susceptibility testing of bacterial pathogens from infections of large food-producing animals and mastitis cases].
Luhofer, Gabriele; Böttner, Alexander; Hafez, H Mohamed; Kaske, Martin; Kehrenberg, Corinna; Kietzmann, Manfred; Klarmann, Dieter; Klein, Günter; Krabisch, Peter; Kühn, Tilman; Richter, Angelika; Sigge, Claudia; Traeder, Wolfgang; Waldmann, Karl-Heinz; Wallmann, Jürgen; Werckenthin, Christiane; Schwarz, Stefan
Two layouts for microtitre plates, which should serve for in-vitro susceptibility testing in routine diagnostics, have been set up by the working group "Antibiotic resistance" of the German Society for Veterinary Medicine. One of these layouts was designed for the testing of bacteria from cases of mastitis and the other for bacteria from infections in large food-producing animals. The choice of the antimicrobial agents and their concentrations to be included in these layouts were based on (1) the bacteria frequently associated with the respective diseases/animals, (2) the antimicrobial agents licensed for therapeutic use in these diseases/animals, (3) the currently available breakpoints, and (4) cross-resistances between the antimicrobial agerts so far known to occur in the respective bacteria.
Mittman, Scott A.; Huard, Richard C.; Della-Latta, Phyllis; Whittier, Susan
The performance of the BD Phoenix Automated Microbiology System (BD Diagnostic Systems) was compared to those of the Vitek 2 (bioMérieux), the MicroScan MICroSTREP plus (Siemens), and Etest (bioMérieux) for antibiotic susceptibility tests (AST) of 311 clinical isolates of Streptococcus pneumoniae. The overall essential agreement (EA) between each test system and the reference microdilution broth reference method for S. pneumoniae AST results was >95%. For Phoenix, the EAs of individual antimicrobial agents ranged from 90.4% (clindamycin) to 100% (vancomycin and gatifloxacin). The categorical agreements (CA) of Phoenix, Vitek 2, MicroScan, and Etest for penicillin were 95.5%, 94.2%, 98.7%, and 97.7%, respectively. The overall CA for Phoenix was 99.3% (1 very major error [VME] and 29 minor errors [mEs]), that for Vitek 2 was 98.8% (7 VMEs and 28 mEs), and those for MicroScan and Etest were 99.5% each (19 and 13 mEs, respectively). The average times to results for Phoenix, Vitek 2, and the manual methods were 12.1 h, 9.8 h, and 24 h, respectively. From these data, the Phoenix AST results demonstrated a high degree of agreement with all systems evaluated, although fewer VMEs were observed with the Phoenix than with the Vitek 2. Overall, both automated systems provided reliable AST results for the S. pneumoniae-antibiotic combinations in half the time required for the manual methods, rendering them more suitable for the demands of expedited reporting in the clinical setting. PMID:19741088
Gilbride, K A; Rosendal, S
Fifty-one strains of Haemophilus pleuropneumoniae were tested for susceptibility to 27 antimicrobial agents using agar disc diffusion, broth-tube dilution and microdilution methods. There was generally good agreement between the interpretation of the disc diffusion inhibition zones and the actual minimal inhibitory concentrations obtained with the dilution methods. The agreement between the results obtained with the broth-tube dilution method and the microdilution method was very good. Three strains were resistant to penicillin, ampicillin, carbenicillin, methicillin and tetracycline. One of those was also resistant to chloramphenicol. Forty strains were resistant to streptomycin, 23 strains were resistant to novobiocin and seven were resistant to triple sulfa. It is thus necessary to consider resistance development against antimicrobial agents chosen for the treatment of pleuro-pneumonia in pigs caused by Haemophilus pleuropneumoniae. PMID:6713256
Narita, Masato; Shibahara, Takahiko; Takano, Nobuo; Fujii, Rie; Okuda, Katsuji; Ishihara, Kazuyuki
Periapical periodontitis usually results from microbial infection, with these microorganisms occasionally migrating to the root canal, which can lead to further, potentially life-threatening, complications. Here, the susceptibility of 27 bacterial strains to various antimicrobial agents was evaluated. These strains comprised 13 species; 16 of the strains were clinical isolates from periapical lesions. Each strain was inoculated onto blood agar plates containing one of the antimicrobial agents. The plates were incubated anaerobically at 37°C for 96 hr and the minimal inhibitory concentrations (MICs) determined. Ten strains required an MIC of 32 μg/ml or greater for amoxicillin, 6 for cefmetazole, and 5 for cefcapene among β-lactam antibiotics; 8 strains required an MIC of 32 μg/ml or greater for clindamycin, 4 for azithromycin, and 11 for clarithromycin among macrolide antibiotics; 3 strains required an MIC of 32 μg/ml or greater for ciprofloxacin and 2 for ofloxacin among fluoroquinolones. The effect of cefcapene on 5 strains was evaluated after biofilm formation to investigate the relationship between biofilm formation and susceptibility. All strains showed a decrease in susceptibility after biofilm formation. The results revealed that several antimicrobial agents commonly used in a clinical setting, including amoxicillin, cefmetazole, and clindamycin, are potentially effective in the treatment of orofacial odontogenic infections. The development of resistant strains, however, means that this can no longer be guaranteed. In addition, azithromycin, ciprofloxacin, and ofloxacin were more effective than the 3 β-lactam antibiotics tested. These results suggest that sensitivity testing is needed if odontogenic infections are to be treated safely and effectively.
Hindler, Janet A.
Aerococcus urinae may cause urinary tract infections, bacteremia, and endocarditis. No standardized susceptibility test methods or interpretive criteria have been proposed for this organism. This study reports the MIC results for 128 A. urinae isolates tested by broth microdilution. The isolates had low MICs to amoxicillin, cefotaxime, ceftriaxone, doxycycline, linezolid, meropenem, penicillin, rifampin, tetracycline, trimethoprim-sulfamethoxazole, and vancomycin. However, 55% of the isolates had MICs to clindamycin of >0.25 μg/ml, 44% had MICs to erythromycin of >0.25 μg/ml, and 16% had MICs to levofloxacin of >2 μg/ml. PMID:24671781
Humphries, Romney M; Hindler, Janet A
Aerococcus urinae may cause urinary tract infections, bacteremia, and endocarditis. No standardized susceptibility test methods or interpretive criteria have been proposed for this organism. This study reports the MIC results for 128 A. urinae isolates tested by broth microdilution. The isolates had low MICs to amoxicillin, cefotaxime, ceftriaxone, doxycycline, linezolid, meropenem, penicillin, rifampin, tetracycline, trimethoprim-sulfamethoxazole, and vancomycin. However, 55% of the isolates had MICs to clindamycin of >0.25 μg/ml, 44% had MICs to erythromycin of >0.25 μg/ml, and 16% had MICs to levofloxacin of >2 μg/ml.
Igari, J; Hayashi, Y; Shitara, S; Shitara, M; Yoshimoto, K; Ohmizu, Y; Umetsu, M; Sasaki, J; Kawana, R; Yoshida, T
We discussed the antimicrobial susceptibilities of Proteeae isolated in Japan, 1989. Eight hundred six clinical isolates were collected from 47 hospitals. These were comprised of 431 strains of Proteus mirabilis, 155 Proteus vulgaris, 154 Morganella morganii, 44 Providencia rettgeri and 22 Providencia stuartii. Antibiotics tested in this study were 2 penicillins, 5 cephems, 1 carbapenem and 2 aminoglycosides. The MIC's were determined using the standard method of the Japan Society of Chemotherapy. Susceptibilities of the above strains to these antibiotics are described below; 1. Latamoxef, ceftizoxime and imipenem had excellent activities with no evident differences among the species of Proteeae. 2. Ampicillin and cefazolin were less active against Indol-positive Proteeae. 3. Piperacillin and cefmetazole were also strongly active drugs against P. mirabilis, P. vulgaris and P. stuartii, and cefotiam against P. mirabilis and P. stuartii. 4. Gentamicin and netilmicin showed excellent activities against M. morganii.
Andrés, María T.; Chung, Whasun O.; Roberts, Marilyn C.; Fierro, José F.
The susceptibilities of 143 Porphyromonas gingivalis, Prevotella intermedia, and Prevotella nigrescens isolates to 18 antimicrobial agents were tested. All P. gingivalis isolates were susceptible. In contrast, some Prevotella spp. (17%) were resistant to β-lactams, erythromycin, clindamycin, or tetracycline and carried resistance genes, ermF or tetQ, or β-lactamases. PMID:9797247
de la Fuente, A J Martín; Tucker, A W; Navas, J; Blanco, M; Morris, S J; Gutiérrez-Martín, C B
A total of 30 British and 30 Spanish Haemophilus parasuis isolates were tested for their susceptibility to 19 of the antimicrobials currently used in swine practice with a broth microdilution method in order to know the emergence of resistance against these compounds in this porcine pathogen. All the British isolates were susceptible to penicillin, ceftiofur, erythromycin, tilmicosin, enrofloxacin, and florfenicol, and most of them were susceptible to the remaining antimicrobials (the highest resistance rate found was of 20% to neomycin). In contrast, all the Spanish isolates were susceptible exclusively to florfenicol, and high proportions of resistance were encountered for penicillin, ampicillin, oxytetracycline, erythromycin, tilmicosin, tiamulin and trimethoprim+sulphamethoxazole; in addition, a bimodal or multimodal distribution, or tailing of Spanish isolates over the MIC range was observed for clindamycin, sulphonamides and tylosine tartrate, suggesting the development of acquired resistance. In addition, several multiresistance patterns were found among the Spanish isolates, 23.3% of them being resistant to at least eight antimicrobials, the same rate as that encountered for those being susceptible to all antimicrobials tested. This study showed that in general British H. parasuis isolates are susceptible to antimicrobial agents routinely used for treatment of porcine respiratory diseases; however, the Spanish isolates need a more continuous surveillance of their susceptibility patterns.
Horn, Nicole Nari; Kresken, Michael; Körber-Irrgang, Barbara; Göttig, Stephan; Wichelhaus, Cornelia; Wichelhaus, Thomas A
Antimicrobial drug resistance in Neisseria gonorrhoeae has become an increasing public health problem. Hence, surveillance of resistance development is of crucial importance to implement adequate treatment guidelines. Data on the spread of antibiotic resistance among gonococcal isolates in Germany, however, is scarce. In a resistance surveillance study conducted by the Paul Ehrlich Society for Chemotherapy between October 2010 and December 2011, 23 laboratories all over Germany were requested to send N. gonorrhoeae isolates to the study laboratory in Frankfurt am Main. Species verification was performed biochemically using ApiNH and with Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS). Antimicrobial susceptibility testing was performed using the Etest method. For molecular epidemiological analysis, N. gonorrhoeae strains were genotyped by means of N. gonorrhoeae multi-antigen sequence typing. A total of 213 consecutive gonococcal isolates were analyzed in this nationwide study. Applying EUCAST breakpoints, high resistance rates were found for ciprofloxacin (74%) and tetracycline (41%). Penicillin non-susceptibility was detected in 80% of isolates. The rate of azithromycin resistance was 6%, while all strains were susceptible to spectinomycin, cefixime, and ceftriaxone. Molecular typing of gonococcal isolates revealed a great heterogeneity of 99 different sequence types (ST), but ST1407 predominated (n=39). This is the first comprehensive German multi-centre surveillance study on antibiotic susceptibility and molecular epidemiology of N. gonorrhoeae with implications for antibiotic choice for treatment of gonorrhoea. The World Health Organization supports the concept that an efficacious treatment of gonorrhoea results in at least 95% of infections being cured. Accordingly, as spectinomycin is not available on the German market, only the third generation cephalosporins cefixime and ceftriaxone are regarded as valuable drugs
Rowland, M D; Del Bene, V E; Lewis, J W
Fifteen clinical isolates of Fusobacterium species were studied to determine their quality of growth on five agar media, their susceptibility to penicillin, cephalothin, cefoxitin, and cefotaxime, the inoculum effect, and the presence of L forms and beta-lactamase. Wilkins-Chalgren agar supported confluent growth best, but Fusobacterium nucleatum exhibited poor growth on all agar media. Most isolates exhibited poor reproducibility of MIC results with repeated agar dilution testing. However, most isolates were susceptible to all antibiotics at the breakpoint concentrations. No inoculum effect was observed, but preparation of an inoculum at a 0.5 McFarland nephelometric standard produced a lower than expected number of CFU (10(6) CFU) in some isolates. L forms were frequently seen. No beta-lactamase was found. The variability in MICs seen with beta-lactam antibiotics was not found when clindamycin was tested. MIC studies with Fusobacterium spp. may be complicated by poor growth on agar media, poor reproducibility, and small inoculum size. PMID:3494743
[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].
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
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.
Han, D U; Choi, C; Ham, H J; Jung, J H; Cho, W S; Kim, J; Higgins, R; Chae, C
This study was undertaken to determine the prevalence, capsular serotype, and antimicrobial susceptibility of Streptococcus suis isolated from slaughter pigs. Capsular serotype and antimicrobial susceptibility were determined by coagglutination test and agar dilution minimum inhibitory concentration, respectively. Streptococcus suis was isolated from 55 of the 406 palatine tonsillar samples tested (13.8%) and 14 of the 29 sampled herds (48.3%). Of the 55 isolates recovered from slaughter pigs, 26 (47.3%) were untypeable. Of the remaining 29 isolates, capsular serotypes 9 (9 isolates) and 16 (4 isolates) were the most common, followed by capsular serotypes 4 (3 isolates) and 7 (3 isolates). Every capsulated isolate was typeable and no palatine tonsillar sample yielded more than one serotype. Most of isolates were susceptible to low concentrations (MIC90) of amoxicillin (2 microg/mL), ceftiofur (1 microg/mL), and penicillin (1 microg/mL). No correlation was found between antimicrobial susceptibility and capsular serotype. PMID:11480519
Aguila, Adalberto; Bernedo, Robert; Llop, Alina; Ramírez, Margarita; Bravo, Laura; Fernández, Anabel; Ledo, Yudith
Forty strains of Escherichia coli isolated from children under 5 years of age with acute diarreas, coming from different provinces of the country , were analyzed. Four important phenotypical determinants were tested: sorbosa, sorbitol, enterohemolysin and 0157:H7 serology, in order to select those strains from enterohemorrhagic or Shiga toxin-producing category. Likewise, they were characterized by biotyping and antimicrobial susceptibility methods. The use of phenotypical tests showed six strains with presumptive characteristics, four of which were most likely to be Shiga toxin-producing strains. In antimicrobial susceptibility test, the strains showed high resistance mainly to ampicillin and trimethrophin-sulfamethoxasole. Another interesting finding were intermediate resistance and susceptibility values to augmentin, aztreonan and ceftriaxone. There were 12 antimicrobial resistance patterns of which 10 were multi-resistant.
Dai, Jing; Hamon, Morgan; Jambovane, Sachin
The recent emergence of antimicrobial resistance has become a major concern for worldwide policy makers as very few new antibiotics have been developed in the last twenty-five years. To prevent the death of millions of people worldwide, there is an urgent need for a cheap, fast and accurate set of tools and techniques that can help to discover and develop new antimicrobial drugs. In the past decade, microfluidic platforms have emerged as potential systems for conducting pharmacological studies. Recent studies have demonstrated that microfluidic platforms can perform rapid antibiotic susceptibility tests to evaluate antimicrobial drugs’ efficacy. In addition, the development of cell-on-a-chip and organ-on-a-chip platforms have enabled the early drug testing, providing more accurate insights into conventional cell cultures on the drug pharmacokinetics and toxicity, at the early and cheaper stage of drug development, i.e., prior to animal and human testing. In this review, we focus on the recent developments of microfluidic platforms for rapid antibiotics susceptibility testing, investigating bacterial persistence and non-growing but metabolically active (NGMA) bacteria, evaluating antibiotic effectiveness on biofilms and combinatorial effect of antibiotics, as well as microfluidic platforms that can be used for in vitro antibiotic toxicity testing. PMID:28952587
Fenticonazole activity measured by the methods of the European Committee on Antimicrobial Susceptibility Testing and CLSI against 260 Candida vulvovaginitis isolates from two European regions and annotations on the prevalent genotypes.
Antonopoulou, Stavroula; Aoun, Michel; Alexopoulos, Evangelos C; Baka, Stavroula; Logothetis, Emanuel; Kalambokas, Theodoros; Zannos, Andreas; Papadias, Konstantine; Grigoriou, Odysseas; Kouskouni, Evangelia; Velegraki, Aristea
The activity of fenticonazole was studied against 260 West and Southeast European vulvovaginal candidiasis isolates, and low MICs were displayed. Fenticonazole was assessed by European Committee on Antimicrobial Susceptibility Testing and CLSI microdilution methods for the first time, and the results showed excellent agreement (97%) and significant interclass correlation coefficient (P < 0.0001). Also, the levels of agreement for the results for itraconazole, fluconazole, and ketoconazole were 84%, 90%, and 98% (P < 0.0001), respectively. Multilocus typing by PCR fingerprinting and subsequent cluster analysis delineated geographically associated alignments for Candida albicans and fluconazole resistance-related clusters for Candida glabrata.
Fenticonazole Activity Measured by the Methods of the European Committee on Antimicrobial Susceptibility Testing and CLSI against 260 Candida Vulvovaginitis Isolates from Two European Regions and Annotations on the Prevalent Genotypes▿
Antonopoulou, Stavroula; Aoun, Michel; Alexopoulos, Evangelos C.; Baka, Stavroula; Logothetis, Emanuel; Kalambokas, Theodoros; Zannos, Andreas; Papadias, Konstantine; Grigoriou, Odysseas; Kouskouni, Evangelia; Velegraki, Aristea
The activity of fenticonazole was studied against 260 West and Southeast European vulvovaginal candidiasis isolates, and low MICs were displayed. Fenticonazole was assessed by European Committee on Antimicrobial Susceptibility Testing and CLSI microdilution methods for the first time, and the results showed excellent agreement (97%) and significant interclass correlation coefficient (P < 0.0001). Also, the levels of agreement for the results for itraconazole, fluconazole, and ketoconazole were 84%, 90%, and 98% (P < 0.0001), respectively. Multilocus typing by PCR fingerprinting and subsequent cluster analysis delineated geographically associated alignments for Candida albicans and fluconazole resistance-related clusters for Candida glabrata. PMID:19223627
García, Patricia C; Valenzuela, Natalia S; Rodríguez, M Victoria L; León, Eugenia C; Fernández, Heríberto J
Campylobacter jejuni is a common agent of enterocolitis in humans. Campylobacteriosis has been recognized as a zoonotic disease whose reservoir is the intestinal flora of poultry. The reposition of fluid and electrolytes is the recommended treatment, and antimicrobials are required only in severe and/or in prolonged disease. Given the emergence of resistance to drugs commonly used in the treatment of acute diarrhea, we studied the antimicrobial susceptibility of 73 strains of Campylobacter jejuni isolated from stool culture. The antimicrobials tested were: erythromycin, azithromycin, ampicillin and ciprofloxacin. Of the 73 strains tested by E-test, 32.4% were resistant to ciprofloxacin and 6.4% were resistant to ampicillin. Resistance to erythromycin and azithromycin was not detected. The surveillance of antimicrobial resistance of Campylobacter jejuni is important in the evaluation of empirically used antimicrobials in the treatment of bacterial enterocolitis.
Sekhar, Sm; Vyas, N; Unnikrishnan, Mk; Rodrigues, Gs; Mukhopadhyay, C
Diabetic foot infections (DFIs) are major public health problems and knowledge of microbes that cause infections are helpful to determine proper antibiotic therapy. The aim was to investigate the antimicrobial susceptibility pattern of microbes in DFIs. A cross-sectional study was conducted for a period of 6 months at the Department of General Surgery, KMC hospital, Manipal University, Manipal, India. During this period, 108 patients having DFIs admitted in the general surgery wards were tracked from the hospital data management system. These patients' pus samples were examined as Gram-stained smear and cultured aerobically on blood agar and MacConkey agar plates. Antimicrobial susceptibility test was performed by disc diffusion techniques according to Clinical and Laboratory Standards Institute guidelines. Of the 108 specimens of the diabetic foot lesions, culture showed polymicrobial growth in 44.4% (48/108). Prevalence of Gram-negative organisms (56%, 84/150) was found to be more than Gram-positive organisms (44%, 66/150). However, Staphylococcus aureus was the most frequent pathogen (28%, 42/150). All Gram-positive aerobes were sensitive to doxycycline. All Gram-negative isolates, including extended spectrum beta lactamase producing strains of Proteus mirabilis and Klebsiella oxytoca except Acinetobacter were highly sensitive to amikacin, cefoperazone/sulbactam, and meropenem. Acinetobacter was completely resistant to all the common antibiotics tested. Prevalence showed Gram-negative bacteria was slightly more than Gram-positive bacteria in diabetic foot ulcers. This study recommends doxycycline should be empirical treatment of choice for Gram-positive isolates and amikacin, cefoperazone/sulbactam, and meropenem should be considered for most of the Gram-negatives aerobes.
Jones, R N; Barry, A L; Fuchs, P C; Thornsberry, C
The 15-micrograms erythromycin disk was twice evaluated for interpretive accuracy against 417 and then 266 strains of gram-positive cocci, Neisseria meningitidis, and Haemophilus influenzae by using the criteria suggested by the National Committee for Clinical Laboratory Standards. These studies suggest a revision of streptococcal and Staphylococcus sp. interpretive guidelines to criteria (greater than or equal to 23 mm = susceptible, less than or equal to 13 mm = resistant) that are more compatible with in vivo erythromycin concentrations. It is also recommended that zone diameters be modified for H. influenzae (greater than or equal to 23 mm = susceptible, less than 22 mm = resistant) and that meningococci not be tested. A wide moderately susceptible category (1.0 to 4.0 micrograms/ml) would primarily include enterococcus strains and those organisms that would then respond only to parenteral administration of erythromycin. Roxithromycin (RU 965 or RU 28965), a new oxime ether erythromycin derivative, was also evaluated by investigator-prepared 15-micrograms disks and later with 30- and 60-micrograms commercial disks. Although roxithromycin was comparable to erythromycin in activity and regression line statistics, changes in the susceptible disk criteria were necessary because of superior roxithromycin serum concentrations and a longer serum half-life. Preliminary susceptible breakpoint criteria were greater than 21 mm = susceptible, 10 to 20 mm = indeterminate, and less than or equal to 9 mm = resistant. By using the recommended interpretive criteria for both macrolides, less than 98% absolute agreement was obtained, therefore suggesting the application of a spectrum class concept. PMID:3091634
Wolfensberger, Aline; Kuster, Stefan P.; Böttger, Erik C.
Multidrug resistance (MDR) rates of Gram-negative rods were analyzed comparing CLSI 2009 and EUCAST 2011 antibiotic susceptibility testing guidelines. After EUCAST 2011 was applied, the MDR rates increased for Klebsiella pneumoniae (2.2%), Enterobacter cloacae (1.1%), Pseudomonas aeruginosa (0.7%), and Escherichia coli (0.4%). A total of 24% of Enterobacteriaceae MDR isolates and 12% of P. aeruginosa MDR isolates were categorized as MDR due to breakpoint changes. PMID:23596246
Hombach, Michael; Wolfensberger, Aline; Kuster, Stefan P; Böttger, Erik C
Multidrug resistance (MDR) rates of Gram-negative rods were analyzed comparing CLSI 2009 and EUCAST 2011 antibiotic susceptibility testing guidelines. After EUCAST 2011 was applied, the MDR rates increased for Klebsiella pneumoniae (2.2%), Enterobacter cloacae (1.1%), Pseudomonas aeruginosa (0.7%), and Escherichia coli (0.4%). A total of 24% of Enterobacteriaceae MDR isolates and 12% of P. aeruginosa MDR isolates were categorized as MDR due to breakpoint changes.
Penna, B.; Varges, R.; Martins, G.M.; Martins, R.R.; Lilenbaum, W.
The study aimed to determine the etiology and antimicrobial resistance of staphylococci isolated from canine pyoderma. Samples were obtained from dogs with pyoderma and isolates were identified by biochemical reactions and tested for susceptibility to 15 antimicrobials. Thirty nine staphylococci isolates were obtained, and S. pseudintermedius was the most frequent (47.4%). All isolates showed resistance to at least one drug and 77.1% were multiresistant. The most effective drug was oxacillin. The study reports the alarming antimicrobial resistance of Staphylococcus isolated from canine pyoderma samples. PMID:24031392
Introduction: Campylobacter spp. are recognized as important agents of human foodborne gastroenteritis. To monitor trends in food safety and public health, antimicrobial susceptibility testing of Campylobacter derived from poultry products and infected patients has become common practice in both r...
Brownstein, Deborah; Miller, Melissa A; Oates, Stori C; Byrne, Barbara A; Jang, Spencer; Murray, Michael J; Gill, Verena A; Jessup, David A
Bacterial infections are an important cause of sea otter (Enhydra lutris) mortality, and some of these infections may originate from terrestrial and anthropogenic sources. Antimicrobials are an important therapeutic tool for management of bacterial infections in stranded sea otters and for prevention of infection following invasive procedures in free-ranging otters. In this study, susceptibility to commonly used antimicrobials was determined for 126 isolates of 15 bacterial species or groups from necropsied, live-stranded injured or sick, and apparently healthy wild sea otters examined between 1998 and 2005. These isolates included both gram-positive and gram-negative strains of primary pathogens, opportunistic pathogens, and environmental flora, including bacterial species with proven zoonotic potential. Minimal evidence of antimicrobial resistance and no strains with unusual or clinically significant multiple-drug resistance patterns were identified. Collectively, these findings will help optimize selection of appropriate antimicrobials for treatment of bacterial diseases in sea otters and other marine species.
Yeh, Jih-Ching; Lo, Dan-Yuan; Chang, Shao-Kuang; Chou, Chi-Chung; Kuo, Hung-Chih
Pasteurella multocida (PM) can cause progressive atrophic rhinitis and suppurative bronchopneumonia in pigs. The present study performed antimicrobial susceptibility testing and serotype and genotype identification on the 62 PM strains isolated from the lungs of diseased pigs with respiratory symptoms. Antimicrobial susceptibility testing examined 13 antimicrobial agents (amoxicillin, cefazolin, doxycycline, flumequine, enrofloxacin, florfenicol, kanamycin, lincomycin, Linco-Spectin (lincomycin and spectinomycin), erythromycin, tylosin, tilmicosin and tiamulin). Antimicrobial resistance ratios were over 40% in all of the antimicrobial agents except for cefazolin. The highest levels of resistance (100%) were found for kanamycin, erythromycin and tylosin. The majority of isolated strains was serotype D:L6 (n=35) followed by A:L3 (n=17). Comparison of the antimicrobial resistance levels between the two serotypes showed that the antimicrobial resistance rates were higher in D:L6 than in A:L3 for all the tested antimicrobials except for tylosin and tilmicosin. For PM with erm(B), erm(T) or erm(42), the results showed no significant difference compared with non-resistance gene strains in phenotype. Pulsed-field gel electrophoresis genotyping using ApaI restriction digestion of the genomic DNA demonstrated that there were 17 distinct clusters with a similarity of 85% or more, and the genotyping result was similar to that of serotyping. The results of the present study demonstrated that the PM isolated from diseased pigs in Taiwan was resistant to multiple antimicrobials, and the distribution of antimicrobial resistance was associated with pulsotype and serotype. © British Veterinary Association (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.
Di Luca, Mariagrazia; Navari, Elena; Esin, Semih; Menichini, Melissa; Barnini, Simona; Trampuz, Andrej; Casani, Augusto; Batoni, Giovanna
Chronic rhinosinusitis (CRS) is the most common illness among chronic disorders that remains poorly understood from a pathogenic standpoint and has a significant impact on patient quality of life, as well as healthcare costs. Despite being widespread, little is known about the etiology of the CRS. Recent evidence, showing the presence of biofilms within the paranasal sinuses, suggests a role for biofilm in the pathogenesis. To elucidate the role of biofilm in the pathogenesis of CRS, we assessed the presence of biofilm at the infection site and the ability of the aerobic flora isolated from CRS patients to form biofilm in vitro. For selected bacterial strains the susceptibility profiles to antibiotics in biofilm condition was also evaluated.Staphylococci represented the majority of the isolates obtained from the infection site, with S. epidermidis being the most frequently isolated species. Other isolates were represented by Enterobacteriaceae or by species present in the oral flora. Confocal laser scanning microscopy (CLSM) of the mucosal biopsies taken from patients with CRS revealed the presence of biofilm in the majority of the samples. Strains isolated from the specific infection site of the CRS patients were able to form biofilm in vitro at moderate or high levels, when tested in optimized conditions. No biofilm was observed by CLSM in the biopsies from control patients, although the same biopsies were positive for staphylococci in microbiological culture analysis. Drug-susceptibility tests demonstrated that the susceptibility profile of planktonic bacteria differs from that of sessile bacteria in biofilms.
Saad, Uzma; Anwar, Sana; Kahara, Usman Zafar; Siddiqui, Maham; Hina, Hina
Intra-abdominal infections are associated with significant morbidity and mortality. The most frequent pathogens involved are the gastrointestinal flora which can cause poly-microbial infections. Microbiological diagnosis is required to determine the aetiology and antimicrobial susceptibility of the organisms involved. Prompt initiation of antimicrobials is essential for improving patient's outcome. Knowledge of local trends of antimicrobial resistance in nosocomial isolates is essential for empiric therapy. A total of 190 clinical isolates collected from intra-abdominal infections during July 2013 to July 2014 were included in the study. Organism identification and Antimicrobial sensitivity testing using standard biochemical tests and CLSI recommended criteria was carried out. Of the total 190 isolates from abdominal infection sources 52% were from fluid sources (peritoneal & ascitic fluid), 41% were from gall bladder and 6.5% were from other abdominal sources. E. coli (46.8%) was the most frequently isolated gram negative and Enterococcus (13.1%) was the most frequently isolated gram positive organism. Carbapenem (imipenem) was the most active agent against enterobacteraceae exhibiting, 94.4% and 91.3% sensitivity against E. coli and Klebsiella respectively. While vancomycin was the most active agent against gram positive organisms. Eighty-four percent of the Enterococci isolated were sensitive to vancomycin. Most isolates exhibited resistance to one or more antibiotics. Continuous evolution of antimicrobial resistance patterns in bacteria necessitates updating of local data on antimicrobial susceptibility profiles to ensure the safety and efficacy of pathogen specific antimicrobial therapies.
López-Hernández, S; Alarcón, T; López-Brea, M
Acinetobacter baumannii is a microorganism frequently implicated in colonization and infection in hospitalized patients. An increase of resistance has been observed in recent years making these infections difficult to treat. The in vitro activity of 24 antibiotics, 15 betalactam agents and nine nonbetalactams, was studied in 156 A. baumannii clinical isolates. The strains were collected from different clinical samples obtained from inpatients (92%) and 8% were from outpatients. Evolution of susceptibility from January 1995 to December 1997 was studied. MIC of the following antibiotics was determined by the agar dilution method: ampicillin, ticarcillin, piperacillin, ampicillin-sulbactam, amoxicillin- clavulanic acid, ticarcillin-clavulanic acid, piperacillin-tazobactam, cefotaxime, ceftazidime, cefepime, imipenem, meropenem, clavulanic acid, sulbactam, tazobactam, amikacin, gentamicin, tobramycin, ofloxacin, doxycycline, fosfomycin, rifampin, azithromycin and colistin. Low antimicrobial susceptibility was observed in most A. baumannii strains. Colistin, imipenem, meropenem and ampicillin-sulbactam showed the greatest susceptibility (100, 88.4, 88.4 and 84.6%, respectively). A. baumannii strains from inpatients showed a lower antimicrobial susceptibility than strains from outpatients, who showed a high percentage of susceptibility to most antibiotics. Rifampin and azithromycin showed certain in vitro activity against the most susceptible A. baumannii strains. A progressive decrease in susceptibility to most antibiotics was observed during the period studied. Carbapenem-resistant A. baumannii emerged in 1996 and increased in 1997.
Llanes Caballero, R; Acosta Giraldo, J C; Sosa Puente, J; Guzmán Hernández, D; Gutiérrez González, O; Llop Hernández, A
The Gonoccocus Laboratory of "Pedro Kourí" Tropical Medicine Institute carried out a study of in vitro susceptibility of Neisseria gonorrhoeae to penicillin, tetracycline, cefuroxime ceftriaxone, cefotaxine and ciprofoxacin by means of a disk diffusion method with the culture medium agar base GC plus supplement. In the first phase, the method was standardized and the reference N. gonorrhoeae ATCC 49226 strain was used whereas in the second phase, 50 gonococcal strains isolated in 8 provinces during 1995 and 1996 were examined. The results of such standardization confirmed that the antimicrobial susceptibility values were within the allowable limits. 52 and 34% of strains were resistant to penicillin and tetracycline respectively and all of them showed susceptibility to the rest of evaluated antimicrobial drugs. We recommend the use of the disk diffusion method for surveillance of gonococci resistance to these drugs in our country.
Lee, Young-ju; Kim, Ki-seuk; Kwon, Yong-kuk; Tak, Ryun-bin
Fowl typhoid (FT) reported since 1992 in Korea is a septicemic disease of domestic birds caused by Salmonella gallinarum (S. gallinarum). The purpose of this study was to investigate the biochemical characteristics and antimicrobials susceptibility of field isolates of S. gallinarum isolated by year in Korea. A total of 258 isolates of S. gallinarum from 1995 to 2001 showed the same pattern in the majority of biochemical test such as IMViC (indole, methyl red, Voges-Proskauer and citrate utilization), carbohydrate fermentation and amino acid decarboxylation, and these results were almost in accordance with the traditional biochemical characteristics of S. gallinarum strain. When the antimicrobial susceptibility test against 258 isolates of S. gallinarum was performed by the disk diffusion method using 12 antimicrobial agents, all isolates from 1995 appeared to be susceptible to all of the antimicrobial agents tested except for tetracycline and oxytetracycline, whereas the vast majority of isolates from 2001 showed the reduced susceptibility to ampicillin (13.0%), gentamicin (43.4%), kanamycin (69.6%), enrofloxacin (6.5%), ciprofloxacin (10.9%), norfloxacin (52.5%) and ofloxacin (82. 6%). The prevalence of the prevalence of completely resistant isolates resistant isolates to one or more drugs rapidly increased from 0% in 1995 to 93.5% in 2001. The minimal concentrations range of the majority of antimicrobial agents to inhibit 50% (MIC50s) against S. gallinarum isolates increased from 0.06 approximately 8 microg/ml in 1997 to 2 approximately 256 microg/ml in 2001. Especially, MIC50s for gentamicin and fluoroquinolones of isolates from 2001 increased over 10-fold than those of isolates from 1997. Therefore, our results indicate that sorbitol fermentation and arginine decarboxylation showed the diversity by isolates and the vast majority of isolates from 2001 showed the reduced susceptibility to antimicrobials tested.
Geornaras, Ifigenia; Hastings, John W.; von Holy, Alexander
Plasmid profiling and amplified fragment length polymorphism (AFLP) analysis were used to genotype 50 Escherichia coli strains from poultry carcasses. Thirty different plasmid profiles were evident, and clustering of the AFLP data showed that they were a distinctly heterogeneous group of strains. Susceptibility testing against five antimicrobial agents used in the South African poultry industry showed all strains to be susceptible to danofloxacin and colistin, while the majority (96%) were resistant to two tetracyclines. PMID:11282652
Comparability of antimicrobial susceptibility test results from 22 European countries and Israel: an external quality assurance exercise of the European Antimicrobial Resistance Surveillance System (EARSS) in collaboration with the United Kingdom National External Quality Assurance Scheme (UK NEQAS).
Bronzwaer, S; Buchholz, U; Courvalin, P; Snell, J; Cornaglia, G; de Neeling, A; Aubry-Damon, H; Degener, J
The goal of this exercise was to organize external quality assurance (QA) of antibiotic susceptibility testing for laboratories participating in EARSS and to assess the comparability of susceptibility test results across countries, and guidelines. In September 2000, UK NEQAS distributed a set of three Streptococcus pneumoniae strains, two Staphylococcus aureus strains and one Streptococcus haemolyticus strain. Laboratories reported the guideline followed, the interpretation of the susceptibility test result and the MIC, if tested. In this study we considered results 'concordant' if the reported interpretation of the participating laboratory agreed with the designated interpretation of reference laboratories. Overall, 433 (92%) of 471 laboratories from 23 countries reported back. Of the 8685 tests that were assessed, 8322 (96%) were interpreted correctly by the participants. Concordance for detection of penicillin non-susceptibility in the three S. pneumoniae strains was 96%, 90% and 87%, respectively. Laboratories performed extremely well in detecting oxacillin resistance in the homogeneously methicillin-resistant S. aureus (MRSA) strain, but the concordance rate dropped from 100% to 77% in the heterogeneously resistant MRSA strain. Concordance for detection of teicoplanin resistance in the S. haemolyticus strain was 82%. We stratified concordance rates first for country and then for guideline used, but observed only minor differences among countries and guidelines. Quantitative methods yielding an MIC were more concordant than non-MIC methods for penicillin resistance in the S. pneumoniae strains (94% versus 79%). The NCCLS guideline was the most frequently followed, by 61% of laboratories from 19 countries. This exercise shows that, overall, countries participating in EARSS are capable of delivering susceptibility data of good quality. The comparability of susceptibility data for penicillin resistance in S. pneumoniae and for homogeneous methicillin resistance in
Cantón, Rafael; Alós, Juan Ignacio; Baquero, Fernando; Calvo, Jorge; Campos, José; Castillo, Javier; Cercenado, Emilia; Domínguez, M Angeles; Liñares, Josefina; López-Cerezo, Lorena; Marco, Francesc; Mirelis, Beatriz; Morosini, María-Isabel; Navarro, Ferran; Oliver, Antonio; Pérez-Trallero, Emilio; Torres, Carmen; Martínez-Martínez, Luis
The number of clinical microbiology laboratories that have incorporated automatic susceptibility testing devices has increased in recent years. The majority of these systems determine MIC values using microdilution panels or specific cards, with grouping into clinical categories (susceptible, intermediate or resistant) and incorporate expert systems to infer resistance mechanisms. This document presents the recommendations of a group of experts designated by Grupo de Estudio de los Mecanismos de Acción y Resistencia a los Antimicrobianos (GEMARA, Study group on mechanisms of action and resistance to antimicrobial agents) and Mesa Española de Normalización de la Sensibilidad y Resistencia a los Antimicrobianos (MENSURA, Spanish Group for Normalizing Antimicrobial Susceptibility and Antimicrobial Resistance), with the aim of including antimicrobial agents and selecting concentrations for the susceptibility testing panels of automatic systems. The following have been defined: various antimicrobial categories (A: must be included in the study panel; B: inclusion is recommended; and C: inclusion is secondary, but may facilitate interpretative reading of the antibiogram) and groups (0: not used in therapeutics but may facilitate the detection of resistance mechanisms; 1: must be studied and always reported; 2: must be studied and selectively reported; 3: must be studied and reported at a second level; and 4: should be studied in urinary tract pathogens isolated in urine and other specimens). Recommended antimicrobial concentrations are adapted from the breakpoints established by EUCAST, CLSI and MENSURA. This approach will lead to more accurate susceptibility testing results with better detection of resistance mechanisms, and allowing to reach the clinical goal of the antibiogram.
Soriano, V E; Vera, N A; Salado, C R; Fernández, R P; Blackall, P J
As part of the basic characterization of Ornithobacterium rhinotracheale, the minimal inhibitory concentrations of 10 antimicrobial drugs were determined for reference strains and Mexican isolates by a broth microdilution method. For optimal growth of the organisms, a supplemented brain-heart infusion broth was used. The susceptibility of O. rhinotracheale to amoxicillin, enrofloxacin, and oxytetracycline was variable. However, consistent higher minimal inhibitory concentrations values were obtained for gentamicin, fosfomycin, trimethoprim, sulfamethazine, sulfamerazine, sulfaquinoxaline, and sulfachloropyridazine. Obtained results among Mexican isolates indicate a marked antimicrobial drug resistance trend.
Blunt, Catherine A; van Vuuren, Moritz; Picard, Jacqueline
Successful treatment of canine pyoderma has become compromised owing to the development of antimicrobial resistance with accompanying recurrence of infection. Canine skin samples submitted to a veterinary diagnostic laboratory for microbiological culture and sensitivity between January 2007 and June 2010, from which Staphylococcus intermedius was isolated, were selected for this investigation. Antimicrobial resistance of S. intermedius was most prevalent with reference to ampicillin followed by resistance to tetracycline and then potentiated sulphonamides. In general, antimicrobial resistance was low and very few methicillin-resistant isolates were detected. Temporal trends were not noted, except for ampicillin, with isolates becoming more susceptible, and potentiated sulphonamides (co-trimoxazole), with isolates becoming more resistant. In general, both the Kirby-Bauer disc diffusion and broth dilution minimum inhibitory concentration tests yielded similar results for the antimicrobial agents tested. The main difference was evident in the over-estimation of resistance by the Kirby-Bauer test for ampicillin, co-trimoxazole, penicillin and doxycycline. Knowledge of trends in bacterial resistance is important for veterinarians when presented with canine pyoderma. Analysis of antimicrobial susceptibility profiles of S. intermedius isolated from canine pyodermas will guide veterinarians' use of the most appropriate agent and encourage prudent use of antimicrobials in companion animals.
Santos, J I; De la Maza, L; Tanaka, J
We conducted an in vitro susceptibility study of bacterial pathogens to various antimicrobials. Strains of Shigella, Salmonella, Escherichia coli, and Klebsiella pneumoniae collected in the 1960s, 1970s, and 1980s at the Hospital Infantil de Mexico Federico Gomez were tested against ampicillin, chloramphenicol, tetracycline, trimethoprim-sulfamethoxazole, amikacin, gentamicin, and furazolidone. Over the 3-decade period, the resistance of enteropathogens to furazolidone showed the least overall increase. Klebsiella susceptibility to the aminoglycosides decreased during the same period. Worldwide reports of enteropathogenic resistance to antimicrobials are also reviewed. In comparing the results of these worldwide studies with our own, we conclude that there is a need for periodic surveillance and testing of bacterial resistance to antimicrobials.
von Altrock, Alexandra; Hamedy, Ahmad; Merle, Roswitha; Waldmann, Karl-Heinz
The objective of the study was to determine the prevalence of Campylobacter spp. on surfaces of slaughtered pig livers. Multilocus sequence typing (MLST) was performed to determine the sequence types (STs) of selected Campylobacter coli isolates. Additionally, C. coli and Campylobacter jejuni isolates were tested for antimicrobial susceptibility by the broth dilution method. The minimal inhibitory concentrations were determined for erythromycin, gentamicin, ampicillin, ampicillin/sulbactam, nalidixic acid, ciprofloxacin, tetracycline and trimethoprim/sulphamethoxazole. Samples were taken during the slaughtering process in a slaughterhouse in Lower Saxony, Germany. Altogether, 10% of 1500 surfaces of pig livers from 50 fattening herds was found to be Campylobacter positive, with C. coli as the predominant species (76%) followed by C. jejuni (21%). Resistance to erythromycin and tetracycline was higher in C. jejuni compared to C. coli, whereas C. coli were more resistant to quinolone compared to C. jejuni. Fluoroquinolone resistance is usually associated with cross-resistance to quinolone, but in the presented investigation C. coli as well as C. jejuni showed a higher resistance to ciprofloxacin (28.6% and 20.0%, respectively) than to nalidixic acid (9.5% and 0%, respectively). A high genetic diversity of the C. coli isolates was demonstrated by MLST. Differences in STs and antimicrobial resistance pattern indicate that the Campylobacter strains originated from the pig itself and not from the slaughterhouse. A comparison of the STs with those reported in the C. jejuni/coli PubMLST database showed an overlap of porcine and human isolates, indicating that C. coli isolates from pigs should be considered as potential sources of human infection.
Lee, Yangsoon; Park, Yeon-Joon; Kim, Mi-Na; Uh, Young; Kim, Myung Sook
Background Periodic monitoring of regional or institutional resistance trends of clinically important anaerobic bacteria is recommended, because the resistance of anaerobic pathogens to antimicrobial drugs and inappropriate therapy are associated with poor clinical outcomes. There has been no multicenter study of clinical anaerobic isolates in Korea. We aimed to determine the antimicrobial resistance patterns of clinically important anaerobes at multiple centers in Korea. Methods A total of 268 non-duplicated clinical isolates of anaerobic bacteria were collected from four large medical centers in Korea in 2012. Antimicrobial susceptibility was tested by the agar dilution method according to the CLSI guidelines. The following antimicrobials were tested: piperacillin, piperacillin-tazobactam, cefoxitin, cefotetan, imipenem, meropenem, clindamycin, moxifloxacin, chloramphenicol, metronidazole, and tigecycline. Results Organisms of the Bacteroides fragilis group were highly susceptible to piperacillin-tazobactam, imipenem, and meropenem, as their resistance rates to these three antimicrobials were lower than 6%. For B. fragilis group isolates and anaerobic gram-positive cocci, the resistance rates to moxifloxacin were 12-25% and 11-13%, respectively. Among B. fragilis group organisms, the resistance rates to tigecycline were 16-17%. Two isolates of Finegoldia magna were non-susceptible to chloramphenicol (minimum inhibitory concentrations of 16-32 mg/L). Resistance patterns were different among the different hospitals. Conclusions Piperacillin-tazobactam, cefoxitin, and carbapemems are highly active β-lactam agents against most of the anaerobes. The resistance rates to moxifloxacin and tigecycline are slightly higher than those in the previous study. PMID:26206683
Pringle, Märit; Landén, Annica; Unnerstad, Helle Ericsson; Molander, Benedicta; Bengtsson, Björn
The anaerobic spirochetes Brachyspira hyodysenteriae and Brachyspira pilosicoli cause diarrheal diseases in pigs. Their fastidious nature has hampered standardization of methods for antimicrobial susceptibility testing. For monitoring of antimicrobial susceptibility wild type cutoff values are needed to define where the wild type distribution of MICs ends and no approved cutoffs are available for Brachyspira spp. In this study antimicrobial susceptibility data for both species (in total 906 isolates) were compiled and analyzed and wild type cut off values for B. hyodysenteriae proposed. The MICs of tiamulin, valnemulin, tylosin, tylvalosin, doxycycline and lincomycin were determined by broth dilution in brain heart infusion broth supplemented with 10% fetal calf serum. The compiled MICs from the broth dilution tests of the B. hyodysenteriae type strain, B78T (ATCC® 27164T), showed that the method yields reproducible results. In an international perspective the frequencies of isolates with decreased antimicrobial susceptibility were low among both B. hyodysenteriae and B. pilosicoli. However, in B. pilosicoli a constant level of 10-15% isolates with tiamulin MICs >4 μg/ml was detected between 2002 and 2010 and in B. hyodysenteriae a gradual increase in tiamulin MICs was seen between 1990 and 2003 although this increase has ceased during the last years. The wild type cutoff values proposed for B. hyodysenteriae are: tiamulin >0.25 μg/ml, valnemulin >0.125 μg/ml, tylosin >16 μg/ml, tylvalosin >1 μg/ml, lincomycin >1 μg/ml and doxycycline >0.5 μg/ml. The broth dilution method used in this study has over the years generated tightly grouped MIC populations for the field isolates and reproducible results for the control strain B78T and is therefore a suitable antimicrobial susceptibility test method for monitoring of Brachyspira spp. Here we propose wild type cutoff values for six antimicrobial agents for B. hyodysenteriae tested by broth dilution based on MIC
Background The anaerobic spirochetes Brachyspira hyodysenteriae and Brachyspira pilosicoli cause diarrheal diseases in pigs. Their fastidious nature has hampered standardization of methods for antimicrobial susceptibility testing. For monitoring of antimicrobial susceptibility wild type cutoff values are needed to define where the wild type distribution of MICs ends and no approved cutoffs are available for Brachyspira spp. In this study antimicrobial susceptibility data for both species (in total 906 isolates) were compiled and analyzed and wild type cut off values for B. hyodysenteriae proposed. Methods The MICs of tiamulin, valnemulin, tylosin, tylvalosin, doxycycline and lincomycin were determined by broth dilution in brain heart infusion broth supplemented with 10% fetal calf serum. Results The compiled MICs from the broth dilution tests of the B. hyodysenteriae type strain, B78T (ATCC® 27164T), showed that the method yields reproducible results. In an international perspective the frequencies of isolates with decreased antimicrobial susceptibility were low among both B. hyodysenteriae and B. pilosicoli. However, in B. pilosicoli a constant level of 10-15% isolates with tiamulin MICs >4 μg/ml was detected between 2002 and 2010 and in B. hyodysenteriae a gradual increase in tiamulin MICs was seen between 1990 and 2003 although this increase has ceased during the last years. The wild type cutoff values proposed for B. hyodysenteriae are: tiamulin >0.25 μg/ml, valnemulin >0.125 μg/ml, tylosin >16 μg/ml, tylvalosin >1 μg/ml, lincomycin >1 μg/ml and doxycycline >0.5 μg/ml. Conclusions The broth dilution method used in this study has over the years generated tightly grouped MIC populations for the field isolates and reproducible results for the control strain B78T and is therefore a suitable antimicrobial susceptibility test method for monitoring of Brachyspira spp. Here we propose wild type cutoff values for six antimicrobial agents for B. hyodysenteriae
Cameron, Marguerite; Saab, Matthew; Heider, Luke; McClure, J Trenton; Rodriguez-Lecompte, Juan Carlos; Sanchez, Javier
Determination of antimicrobial susceptibility of bovine mastitis pathogens is important for guiding antimicrobial treatment decisions and for the detection of emerging resistance. Environmental streptococci are ubiquitous in the farm environment and are a frequent cause of mastitis in dairy cows. The aim of the study was to determine patterns of antimicrobial susceptibility among species of environmental streptococci isolated from dairy cows in the Maritime Provinces of Canada. The collection consisted of 192 isolates identified in milk samples collected from 177 cows originating from 18 dairy herds. Results were aggregated into: (1) Streptococcus uberis (n = 70), (2) Streptococcus dysgalactiae (n = 28), (3) other Streptococci spp. (n = 35), (4), Lactococcus spp. (n = 32), and (5) Enterococcus spp. (n = 27). Minimum inhibitory concentrations (MICs) were determined using the Sensititre microdilution system and mastitis plate format. Multilevel logistic regression models were used to analyze the data, with antimicrobial susceptibility as the outcome. The proportion of susceptible S. uberis ranged from 23% (for penicillin) to 99% (for penicillin/novobiocin), with a median of 82%. All S. dysgalactiae were susceptible to all antimicrobials except for penicillin (93% susceptible) and tetracycline (18% susceptible). The range of susceptibility for other Streptococcus spp. was 43% (for tetracycline) to 100%, with a median percent susceptibility of 92%. Lactococcus spp. isolates displayed percent susceptibilities ranging from 0% (for penicillin) to 97% (for erythromycin), median 75%. For the antimicrobials tested, the minimum inhibitory concentrations were higher for Enterococcus spp. than for the other species. According to the multilevel models, there was a significant interaction between antimicrobial and bacterial species, indicating that susceptibility against a particular antimicrobial varied among the species of environmental streptococci and vice
Gharaibeh, Saad; Al-Rashdan, Mohammad
This study compares the antimicrobial susceptibility over time between two groups of Mycoplasma gallisepticum (MG) isolates from the same geographical area. Minimum inhibitory concentration of 13 antimicrobials was determined against two groups of MG isolates from chickens. Group 1 strains (n=22) were isolated in 2004-2005 while group 2 strains (n=7) were isolated in 2007-2008. Minimum inhibitory concentration 50 for group 1 versus group 2 was 4/4, 0.5/0.5, ≤ 0.031/≥ 64, ≤ 0.031/2, ≤ 0.031/0.125, 1/0.5, 1/1, ≤ 0.031/≤ 0.031, ≤ 0.031/2, ≤ 0.031/2, 1/4, ≤ 0.031/0.062, and 0.062/2 μg/ml against gentamicin, spectinomycin, erythromycin, tilmicosin, tylosin, florfenicol, thiamphenicol, tiamulin, ciprofloxacin, enrofloxacin, chlortetracycline, doxycycline, and oxytetracycline, respectively. There was a statistically significant increase in resistance of group 2 to erythromycin, tilmicosin, tylosin, ciprofloxacin, enrofloxacin, chlortetracycline, doxycycline, and oxytetracycline. This dramatic increase in resistance against 8 antimicrobials belonging to three different families of antimicrobials in a relatively short period of time appears to be rare and of concern. The cause of this increased resistance observed in group 2 of MG isolates was not determined and should be further investigated. Monitoring of MG field strain susceptibility is highly recommended to implement successful treatment and prophylaxis programs in endemic areas. Copyright © 2011 Elsevier B.V. All rights reserved.
email@example.com Received 14 April 2003 Accepted 24 August 2003 Susceptibility of oral bacteria to an antimicrobial decapeptide S. P. Concannon,1† T...resident saliva bacteria collected from human subjects. Cytotoxic activity of KSL against mammalian cells and the structural features of this...decapeptide were also investigated, the latter by using two-dimensional NMR in aqueous and DMSO solutions. MICs of KSL for the majority of oral bacteria
von Eiff, C; Herrmann, M; Peters, G
The in vitro susceptibilities of 63 isolates of Stomatococcus mucilaginosus and of 188 isolates of Micrococcus spp. to 18 antimicrobial agents were determined by the agar dilution method. Many beta-lactams, imipenem, rifampin, and the glycopeptides were shown to be active in vitro against Stomatococcus and Micrococcus isolates, whereas the activities of antibiotics such as some aminoglycosides, erythromycin, and fosfomycin against an important number of these microorganisms are limited. PMID:7695321
ter Laak, E A; Noordergraaf, J H; Verschure, M H
The purpose of this study was to determine the susceptibility of various strains of Mycoplasma bovis, Mycoplasma dispar, and Ureaplasma diversum, which are prevalent causes of pneumonia in calves, to 16 antimicrobial agents in vitro. The MICs of the antimicrobial agents were determined by a serial broth dilution method for 16 field strains and the type strain of M. bovis, for 19 field strains and the type strain of M. dispar, and for 17 field strains of U. diversum. Final MICs for M. bovis and M. dispar were read after 7 days and final MICs for U. diversum after 1 to 2 days. All strains tested were susceptible to tylosin, kitasamycin, and tiamulin but were resistant to nifuroquine and streptomycin. Most strains of U. diversum were intermediately susceptible to oxytetracycline but fully susceptible to chlortetracycline; most strains of M. bovis and M. dispar, however, were resistant to both agents. Strains of M. dispar and U. diversum were susceptible to doxycycline and minocycline, but strains of M. bovis were only intermediately susceptible. Susceptibility or resistance to chloramphenicol, spiramycin, spectinomycin, lincomycin, or enrofloxacin depended on the species but was not equal for the three species. The type strains of M. bovis and M. dispar were more susceptible to various antimicrobial agents, including tetracyclines, than the field strains. This finding might indicate that M. bovis and M. dispar strains are becoming resistant to these agents. Antimicrobial agents that are effective in vitro against all three mycoplasma species can be considered for treating mycoplasma infections in pneumonic calves. Therefore, tylosin, kitasamycin, and tiamulin may be preferred over oxytetracycline and chlortetracycline.
ter Laak, E A; Noordergraaf, J H; Verschure, M H
The purpose of this study was to determine the susceptibility of various strains of Mycoplasma bovis, Mycoplasma dispar, and Ureaplasma diversum, which are prevalent causes of pneumonia in calves, to 16 antimicrobial agents in vitro. The MICs of the antimicrobial agents were determined by a serial broth dilution method for 16 field strains and the type strain of M. bovis, for 19 field strains and the type strain of M. dispar, and for 17 field strains of U. diversum. Final MICs for M. bovis and M. dispar were read after 7 days and final MICs for U. diversum after 1 to 2 days. All strains tested were susceptible to tylosin, kitasamycin, and tiamulin but were resistant to nifuroquine and streptomycin. Most strains of U. diversum were intermediately susceptible to oxytetracycline but fully susceptible to chlortetracycline; most strains of M. bovis and M. dispar, however, were resistant to both agents. Strains of M. dispar and U. diversum were susceptible to doxycycline and minocycline, but strains of M. bovis were only intermediately susceptible. Susceptibility or resistance to chloramphenicol, spiramycin, spectinomycin, lincomycin, or enrofloxacin depended on the species but was not equal for the three species. The type strains of M. bovis and M. dispar were more susceptible to various antimicrobial agents, including tetracyclines, than the field strains. This finding might indicate that M. bovis and M. dispar strains are becoming resistant to these agents. Antimicrobial agents that are effective in vitro against all three mycoplasma species can be considered for treating mycoplasma infections in pneumonic calves. Therefore, tylosin, kitasamycin, and tiamulin may be preferred over oxytetracycline and chlortetracycline. PMID:8452363
Comparison of Agar Dilution, Disk Diffusion, MicroScan, and Vitek Antimicrobial Susceptibility Testing Methods to Broth Microdilution for Detection of Fluoroquinolone-Resistant Isolates of the Family Enterobacteriaceae
Steward, Christine D.; Stocker, Sheila A.; Swenson, Jana M.; O’Hara, Caroline M.; Edwards, Jonathan R.; Gaynes, Robert P.; McGowan, John E.; Tenover, Fred C.
Fluoroquinolone resistance appears to be increasing in many species of bacteria, particularly in those causing nosocomial infections. However, the accuracy of some antimicrobial susceptibility testing methods for detecting fluoroquinolone resistance remains uncertain. Therefore, we compared the accuracy of the results of agar dilution, disk diffusion, MicroScan Walk Away Neg Combo 15 conventional panels, and Vitek GNS-F7 cards to the accuracy of the results of the broth microdilution reference method for detection of ciprofloxacin and ofloxacin resistance in 195 clinical isolates of the family Enterobacteriaceae collected from six U.S. hospitals for a national surveillance project (Project ICARE [Intensive Care Antimicrobial Resistance Epidemiology]). For ciprofloxacin, very major error rates were 0% (disk diffusion and MicroScan), 0.9% (agar dilution), and 2.7% (Vitek), while major error rates ranged from 0% (agar dilution) to 3.7% (MicroScan and Vitek). Minor error rates ranged from 12.3% (agar dilution) to 20.5% (MicroScan). For ofloxacin, no very major errors were observed, and major errors were noted only with MicroScan (3.7% major error rate). Minor error rates ranged from 8.2% (agar dilution) to 18.5% (Vitek). Minor errors for all methods were substantially reduced when results with MICs within ±1 dilution of the broth microdilution reference MIC were excluded from analysis. However, the high number of minor errors by all test systems remains a concern. PMID:9986809
Ivančić, Vesna; Mastali, Mitra; Percy, Neil; Gornbein, Jeffrey; Babbitt, Jane T.; Li, Yang; Landaw, Elliot M.; Bruckner, David A.; Churchill, Bernard M.; Haake, David A.
We describe the first direct testing of the antimicrobial susceptibilities of bacterial pathogens in human clinical fluid samples by the use of ATP bioluminescence. We developed an ATP bioluminescence assay that eliminates somatic sources of ATP to selectively quantify the bacterial load in clinical urine specimens with a sensitivity of <1,000 CFU per milliliter. There was a log-log relationship between light emission and the numbers of CFU in clinical urine specimens. A clinical study was performed to evaluate the accuracy of the ATP bioluminescence assay for determination of the antimicrobial susceptibilities of uropathogens in clinical urine specimens tested in a blinded manner. ATP bioluminescent bacterial density quantitation was used to determine the inoculation volume in growth medium with and without antibiotics. After incubation at 37°C for 120 min, the ATP bioluminescence assay was repeated to evaluate the uropathogen response to antibiotics. The ability of the ATP bioluminescence assay to discriminate between antimicrobial susceptibility and resistance was determined by comparison of the results obtained by the ATP bioluminescence assay with the results obtained by standard clinical microbiology methods. Receiver operator characteristic curves were used to determine the optimal threshold for discriminating between susceptibility and resistance. Susceptibility and resistance were correctly predicted in 87% and 95% of cases, respectively, for an overall unweighted accuracy of 91%, when the results were stratified by antibiotic. For samples in which the pathogen was susceptible, the accuracy improved to 95% when the results for samples with less than a 25-fold increase in the amount of bacterial ATP in the medium without antibiotics were excluded. These data indicate that a rapid bioluminescent antimicrobial susceptibility assay may be useful for the management of urinary tract infections. PMID:18272708
Ivancic, Vesna; Mastali, Mitra; Percy, Neil; Gornbein, Jeffrey; Babbitt, Jane T; Li, Yang; Landaw, Elliot M; Bruckner, David A; Churchill, Bernard M; Haake, David A
We describe the first direct testing of the antimicrobial susceptibilities of bacterial pathogens in human clinical fluid samples by the use of ATP bioluminescence. We developed an ATP bioluminescence assay that eliminates somatic sources of ATP to selectively quantify the bacterial load in clinical urine specimens with a sensitivity of <1,000 CFU per milliliter. There was a log-log relationship between light emission and the numbers of CFU in clinical urine specimens. A clinical study was performed to evaluate the accuracy of the ATP bioluminescence assay for determination of the antimicrobial susceptibilities of uropathogens in clinical urine specimens tested in a blinded manner. ATP bioluminescent bacterial density quantitation was used to determine the inoculation volume in growth medium with and without antibiotics. After incubation at 37 degrees C for 120 min, the ATP bioluminescence assay was repeated to evaluate the uropathogen response to antibiotics. The ability of the ATP bioluminescence assay to discriminate between antimicrobial susceptibility and resistance was determined by comparison of the results obtained by the ATP bioluminescence assay with the results obtained by standard clinical microbiology methods. Receiver operator characteristic curves were used to determine the optimal threshold for discriminating between susceptibility and resistance. Susceptibility and resistance were correctly predicted in 87% and 95% of cases, respectively, for an overall unweighted accuracy of 91%, when the results were stratified by antibiotic. For samples in which the pathogen was susceptible, the accuracy improved to 95% when the results for samples with less than a 25-fold increase in the amount of bacterial ATP in the medium without antibiotics were excluded. These data indicate that a rapid bioluminescent antimicrobial susceptibility assay may be useful for the management of urinary tract infections.
Kim, L M; Gray, Jeffery T; Harmon, Barry G; Jones, Richard D; Fedorka-Cray, Paula J
Concerns regarding an apparent association between the use of antimicrobial feed additives (AFAs) in food animal production and a concomitant increase in antimicrobial drug resistance among zoonotic enteropathogens have provided the impetus to propose cessation of their use. While AFAs have been used in food animal production for nearly 50 years, the future use of AFAs will require an understanding of the effects of different classes of antimicrobials on the antimicrobial resistance of commensal flora. The present study examines the effect of three AFAs (apramycin, carbadox, and chlortetracycline) on the antimicrobial susceptibility of Escherichia coli in growing piglets and on animal performance. Three replicate trials were conducted using growing piglets fed standard diets with and without antimicrobial feed additives (AFAs). Fecal samples were cultured selectively for E. coli at regular intervals from all piglets from birth to market and antimicrobial susceptibility testing of E. coli isolates was performed using a replica-plate screening method and a broth microdilution method. While resistance to tetracycline in E. coli varied widely by sample, group, and trial, a significant increase in the percentage of resistant isolates was observed in piglets receiving AFAs when compared to controls (p < 0.0001). Resistance to apramycin increased in E. coli from piglets fed apramycin when compared to controls (p < 0.0001). However, upon removal of apramycin, resistance in E. coli declined to baseline levels by day 75. Piglets receiving AFAs demonstrated improved feed efficiency during phase 4 (p < 0.001), and higher average daily gains in phases 3 and 4 (p < 0.0001). This study suggests that antimicrobial resistance to AFAs in E. coli is drug-dependent and that some antimicrobials may be suitable for continued use in feeds during specified growth periods without concern for persistence of resistant E. coli populations.
Cavanagh, Jorunn Pauline; Wolden, Runa; Heise, Philipp; Esaiassen, Eirin; Klingenberg, Claus; Aarag Fredheim, Elizabeth G
The primary aim of this study was to determine antimicrobial resistance in coagulase-negative staphylococci (CoNS) from healthy adults in the community. Healthy adults (n = 114) were swabbed on six body sites; both armpits, both knee pits and both sides of the groin. Species determination was performed using Matrix Assisted Laser Desorption Ionization - Time of Flight (MALDI-TOF) and susceptibility testing for 11 relevant antimicrobials was performed by the disc diffusion method and minimal inhibitory concentration gradient test. In total, 693 CoNS isolates were identified. Susceptibility testing was done on 386 isolates; one CoNS from each species found on each participant from the different body sites. The prevalence of antimicrobial resistance in the CoNS isolates were; erythromycin (24.6%), fusidic acid (19.9%), tetracycline (11.4%), clindamycin (7.8%), gentamicin (6.2%) and cefoxitin (4.1%). Multidrug resistance was observed in 5.2% of the isolates. Staphylococcus epidermidis and S. hominis were the first and second most prevalent species on all three body sites. We conclude that CoNS isolates from healthy adults in the community have a much lower prevalence of antimicrobial resistance than reported in nosocomial CoNS isolates. Still, we believe that levels of resistance in community CoNS should be monitored as the consumption of antimicrobials in primary care in Norway is increasing.
Goudarzi, Mehdi; Heidary, Mohsen; Azad, Mehdi; Fazeli, Maryam; Goudarzi, Hossein
Aim: The purpose of this study was to determine the antibiotic susceptibility pattern and distribution of integron in H. pylori isolates collected from patients referred to private health care centers in Tehran, Iran. Background: Antibiotic resistance is the main reason for failure of Helicobacter pylori therapy. Integrons as genetic reservoirs play main roles in the dissemination of antimicrobial resistance gene. Methods: During a 12-month cross-sectional study period, 65 H. pylori isolates were recovered from 124 biopsy specimens. Isolates were subjected to susceptibility testing using by Epsilometer test according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guideline. PCR was used to detect different types of integrons. Results: Antimicrobial susceptibility testing revealed that 73.8% of isolates were resistant to metronidazole, 43.1% to clarithromycin, 29.2% to tetracycline, 27.7% to amoxicillin, 23.1% to rifampicin and 13.4% to levofloxacin. Frequency of multidrug resistance among H. pylori isolates was 26.1%. The most predominant resistance profiles among our isolates were included resistance to clarithromycin and metronidazole (20%). Class 1 and 2 integrons were detected in 8 (12.3%) and 15 (23.1%) of the isolates, respectively. Conclusions: The high prevalence of multidrug resistance and frequency of class 2 integron in this survey can be a warning for clinicians. Continuous surveillance is necessary for the development of new treatment protocols to prevent the treatment failures and also further spread of resistant isolates. PMID:28224028
Rodríguez-Lozano, Jesús; de Malet, Ana; Cano, María Eliecer; de la Rubia, Luis; Wallmann, Reinhard; Martínez-Martínez, Luis; Calvo, Jorge
Cumulative susceptibility reports are a valuable tool for the empirical treatment of urinary tract infections, especially in the current context of increasing resistance rates. Our objective was to analyze the antimicrobial susceptibility of bacterial isolates in urine cultures of pediatric patients during a five-year period. Retrospective study of urine cultures from 2011 to 2015. Identification and antimicrobial susceptibility tests were performed using the Vitek-2 system (BioMérieux(®)) and categorized according to EUCAST criteria. Antimicrobial susceptibility data were analyzed by gender and age groups (neonates, 1 month to 5 years, 5-15 years) before being compared with data obtained from patients over the age of 15 years. During the study period, 17164 urine cultures were processed from 7924 patients under 16 years of age. Antimicrobial susceptibility rates in these patients were: ampicillin 36.3%, amoxicillin/clavulanic acid 75.3%, cefuroxime 83.2%, co-trimoxazole 68.9%, ciprofloxacin 85.3%, fosfomycin 85.5%, nitrofurantoin 84.4% and 3rd generation cephalosporins 89-91%. Aminoglycosides (>92%) and carbapenems (95%) maintained the highest susceptibility rates. The prevalence of ESBL-producing isolates was significantly lower in children under the age of 16 years (1.5% vs. 4.1%). In patients under the age of 16 years, Escherichia coli isolates in girls were significantly more sensitive (p<0.0001) to ampicillin (41% vs. 30%) and amoxicillin/clavulanic acid (82% vs. 72%) than in boys. The compilation of cumulative susceptibility reports disaggregated by age or gender reveals significant differences. In our setting, cefuroxime may be considered the first-line empirical treatment in pediatric patients. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.
Ström, G; Halje, M; Karlsson, D; Jiwakanon, J; Pringle, M; Fernström, L-L; Magnusson, U
Intensification of livestock production seen in many low- and middle-income countries is often believed to be associated with increased use of antimicrobials, and may hence contribute to the emergence of antimicrobial resistance. The aim of this study was to map antimicrobial use on small- (n = 25) and medium-scale (n = 27) pig farms in north-eastern Thailand, and to compare antimicrobial susceptibility of commensal Escherichia coli isolated from sows on these farms. Information regarding pig husbandry and antimicrobial treatment regimens was obtained by the use of semi-structured questionnaires. Faecal samples were collected from three healthy sows at each farm, and Escherichia coli was cultured and analysed for antimicrobial susceptibility using the broth microdilution method. Multilevel regression models were used to compare antimicrobial susceptibility between isolates from small- and medium-scale farms. All farms included in the study administered antimicrobials to their sows. Small-scale farmers most commonly (64%) decided themselves when to give antimicrobials and the majority (60%) bought the medicines at the local store or pharmacy, whereas farmers on medium-scale farms always discussed antimicrobial treatment with a veterinarian. Medium-scale farms used a greater diversity of antimicrobials than small-scale farms and did also administer antimicrobials in feed to a higher extent. High levels of antimicrobial resistance to several critically important antimicrobials for human medicine (including ciprofloxacin, streptomycin and ampicillin) were found in isolates from both small- and medium-scale farms. Resistance levels were significantly (P < 0.05) higher in isolates from medium-scale farms for several of the antimicrobials tested, as well as the level of multidrug-resistance (P = 0.026). The routines regarding access and administration of antimicrobials differed between the small- and medium-scale farms. Although the level of antimicrobial
Bodur, Hürrem; Balaban, Neriman; Aksaray, Sebahat; Yetener, Vedat; Akinci, Esragül; Colpan, Aylin; Erbay, Ayse
41 Brucella strains isolated from blood and cerebrospinal fluid cultures were identified to species level and biotypes detected. All of the isolates were Brucella melitensis: 2 strains of B. melitensis biotype-1 and 39 strains of B. melitensis biotype-3. In vitro activities of these strains were detected by the E test method. According to the 90% minimal inhibitory concentration (MIC90) values, the most active agent was doxycycline (MIC90 0.064 microg/ml), followed by ciprofloxacin (MIC90 0.25 microg/ml), trimethoprim-sulfamethoxazole and ceftriaxone (MIC90 0.38 microg/ml). Rifampin exhibited the highest MIC90 value (0.75 microg/ml).
Dutta, Subarna; Haq, Sabah; Hasan, Mohammad Rokibul; Haq, Jalaluddin Ashraful
Melioidosis an infectious disease, caused by a Gram negative bacterium called Burkholderia pseudomallei, is endemic in Bangladesh. This organism is sensitive to limited number of antimicrobial agents and need prolonged treatment. There is no comprehensive data on the antimicrobial susceptibility profile of B. pseudomallei isolated in Bangladesh over last several years. The present study aimed to determine the antimicrobial susceptibility pattern of B. pseudomallei isolated in a tertiary care hospital of Dhaka city from 2009 to 2015. All B. pseudomallei isolated from melioidosis patients over a period of 7 years (2009-2015) in the Department of Microbiology of a 725-bed tertiary care referral hospital in Dhaka city, Bangladesh were included in the study. B. pseudomallei was identified by Gram stain, culture, specific biochemical tests, serology and PCR using specific primers constructed from 16s rRNA region of B. pseudomallei. Antimicrobial susceptibility to specific agents was determined by disk diffusion and minimum inhibitory concentration methods. A total of 20 isolates of B. pseudomallei which were isolated from patients coming from different geographic locations of Bangladesh were included in the study. All the isolates were uniformly sensitive (100%) to ceftazidime, imipenem, piperacillin-tazobactam, amoxicillin-clavulanic acid and tetracycline by both disk diffusion and MIC methods. Two strains were resistant to trimethoprim-sulfamethoxazole by disk diffusion method but were sensitive by MIC method. The MIC50 and MIC90 values of the above antimicrobial agents were almost similar. All the isolates were resistant to amikacin by both MIC and disk diffusion methods. The results of the study suggest that B. pseudomallei prevalent in Bangladesh were still susceptible to all recommended antimicrobial agents used for the treatment of melioidosis. However, regular monitoring is needed to detect any emergence of resistance and shifting of MIC50 and MIC90 values.
Zalacain, A; Obrador, C; Martinez, J P; Viñas, M; Vinuesa, T
Due to the increase of choices relative to antifungals, there is a need to improve the standardization of in vitro methods used to determine the antifungal susceptibility of fungal pathogens. Our study evaluated the in vitro susceptibility of filamentous fungi isolated from patients with toenail onychomycosis against itraconazole, ciclopirox, eberconazole, fluconazole and terbinafine. The minimum inhibitory concentration (MIC) of these antifungal agents was determined with 100 isolates, including dermatophytes (70 strains) and non-dermatophyte molds (30 strains). The susceptibility of fungal isolates was measured by using a technique modified for dermatophytes (0.5 × 10(3)-0.5 × 10(4) conidia/ml as inocula) which followed the procedures described by the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antimicrobial Susceptibility Testing (AFST-EUCAST) and the Clinical and Laboratory Standard Institute (CLSI M38-A). MIC ranges were 0.016-8.0 μg/ml for itraconazole, ciclopirox and eberconazole, 0.063-32.0 μg/ml for fluonazole, and 0.004-2.0 μg/ml for terbinafine. In vitro susceptibility tests indicated that eberconazole has a broad antimicrobial profile, including dermatophytes, as well as other filamentous fungi. Terbinafine was active (0.016-0.250 μg/ml) against dermatophytes.
Jenkins, Stephen G.; Schuetz, Audrey N.
Antimicrobial susceptibility testing (AST) is indicated for pathogens contributing to an infectious process that warrants antimicrobial therapy if susceptibility to antimicrobials cannot be predicted reliably based on knowledge of their identity. Such tests are most frequently used when the etiologic agents are members of species capable of demonstrating resistance to commonly prescribed antibiotics. Some organisms have predictable susceptibility to antimicrobial agents (ie, Streptococcus pyogenes to penicillin), and empirical therapy for these organisms is typically used. Therefore, AST for such pathogens is seldom required or performed. In addition, AST is valuable in evaluating the activity of new and experimental compounds and investigating the epidemiology of antimicrobial resistant pathogens. Several laboratory methods are available to characterize the in vitro susceptibility of bacteria to antimicrobial agents. When the nature of the infection is unclear and the culture yields mixed growth or usual microbiota (wherein the isolates usually bear little relationship to the actual infectious process), AST is usually unnecessary and results may, in fact, be dangerously misleading. Phenotypic methods for detection of specific antimicrobial resistance mechanisms are increasingly being used to complement AST (ie, inducible clindamycin resistance among several gram-positive bacteria) and to provide clinicians with preliminary direction for antibiotic selection pending results generated from standardized AST (ie, β-lactamase tests). In addition, molecular methods are being developed and incorporated by microbiology laboratories into resistance detection algorithms for rapid, sensitive assessment of carriage states of epidemiologically and clinically important pathogens, often directly from clinical specimens (ie, presence of vancomycin-resistant enterococci in fecal specimens). PMID:22386185
Fraga, Edmir Geraldo; Nicodemo, Antonio Carlos; Sampaio, Jorge Luiz Mello
Clostridium difficile is a leading cause of diarrhea in hospitalized patients worldwide. While metronidazole and vancomycin are the most prescribed antibiotics for the treatment of this infection, teicoplanin, tigecycline and nitazoxanide are alternatives drugs. Knowledge on the antibiotic susceptibility profiles is a basic step to differentiate recurrence from treatment failure due to antimicrobial resistance. Because C. difficile antimicrobial susceptibility is largely unknown in Brazil, we aimed to determine the profile of C. difficile strains cultivated from stool samples of inpatients with diarrhea and a positive toxin A/B test using both agar dilution and disk diffusion methods. All 50 strains tested were sensitive to metronidazole according to CLSI and EUCAST breakpoints with an MIC90 value of 2μg/mL. Nitazoxanide and tigecycline were highly active in vitro against these strains with an MIC90 value of 0.125μg/mL for both antimicrobials. The MIC90 were 4μg/mL and 2μg/mL for vancomycin and teicoplanin, respectively. A resistance rate of 8% was observed for moxifloxacin. Disk diffusion can be used as an alternative to screen for moxifloxacin resistance, nitazoxanide, tigecycline and metronidazole susceptibility, but it cannot be used for testing glycopeptides. Our results suggest that C. difficile strains from São Paulo city, Brazil, are susceptible to metronidazole and have low MIC90 values for most of the current therapeutic options available in Brazil.
Daly, Meighan; Diegel, Kelly L; Fitzgerald, Scott D; Schooley, Angie; Berry, Dale E; Kaneene, John B
The state of Michigan has recognized the presence of Mycobacterium bovis in its free-ranging white-tailed deer population since 1994. This endemic infection is primarily located in a 12-county area in the northeastern lower peninsula of Michigan. A statewide surveillance and eradication program of the disease has been in effect since 1994. Worldwide, Mycobacterium tuberculosis complex organisms have a known predilection toward development of antimicrobial resistance. The objective of this study was to investigate the antimicrobial susceptibility of M. bovis isolates from white-tailed deer in Michigan and detect any changes in susceptibility over time. M. bovis isolates from 2 fall hunting seasons (1999 and 2004) were used in this study. The fall season of 2004 marked the first documented case of direct transmission of M. bovis from a wild deer to a human in Michigan. Since M. bovis is a zoonotic disease, knowledge of susceptibility can expedite treatment options in humans. M. bovis isolates were obtained from 58 deer, 4 coyotes, 3 cattle, 2 raccoons, and 1 human case from the 2 years combined. Methods of susceptibility testing included 1% proportion agar plates and Bactec radiometric broth testing. M. bovis was found to be uniformly resistant to the antibiotic pyrazinamide; this resistance is common to all M. bovis isolates. No other antimicrobial resistance was found in any of the tested M. bovis isolates, which may be, in part, attributed to the lack of any significant treatment pressure in wildlife.
Declercq, A M; Boyen, F; Van den Broeck, W; Bossier, P; Karsi, A; Haesebrouck, F; Decostere, A
Flavobacterium columnare is the causative agent of columnaris disease in diverse fish species worldwide. Although columnaris is an important disease, the antimicrobial susceptibility pattern of F. columnare is not well studied. Thus, the purpose of this study was to test the in vitro antimicrobial susceptibility of 97 F. columnare isolates collected worldwide between 1987 and 2011 from 17 fish species. The broth microdilution technique was utilized for reliable testing of these fastidious organisms. None of the isolates displayed acquired resistance to florfenicol, gentamicin, ormetoprim-sulfadimethoxine and trimethoprim-sulfamethoxazole. Acquired resistance to chloramphenicol was detected in 1%, to nitrofuran in 5%, to oxytetracycline in 11% and to enrofloxacin, flumequine and oxolinic acid in 10%, 16% and 16% of the isolates, respectively, as reflected by a bimodal or trimodal distribution of their minimum inhibitory concentrations (MICs). One isolate showed acquired resistance towards several antimicrobial agents including erythromycin. Another isolate revealed acquired resistance towards - amongst others - ampicillin. The isolates displaying acquired resistance originated from ornamental fish species or Vietnamese catfish, except for two isolates coming from wild channel catfish in which acquired resistance was encountered towards oxytetracycline only. Fifty per cent of the resistant isolates from ornamental fish were shown to have acquired resistance against three classes of antimicrobial agents, assigning these isolates as multiple resistant. These data might indicate less prudent use of antimicrobials especially in ornamental fish species. © 2012 Blackwell Publishing Ltd.
Suleman, Muhammad; Prysliak, Tracy; Windeyer, Claire; Perez-Casal, Jose
Mycoplasma bovis is a pathogen globally affecting cattle and bison herds, causing pneumonia, arthritis, mastitis, abortions, and other symptoms, leading to huge economic losses. Many studies have been done regarding the antimicrobial susceptibility of M. bovis isolated from cattle, but no such study is available for isolates recovered from bison. For the first time, in vitro susceptibilities of 40 M. bovis clinical isolates collected from bison herds in Canada are reported here. Minimal inhibitory concentration (MIC) values were determined using Sensititre® plates. The most effective MIC50 and MIC90 were for spectinomycin (1 and >64 μg/mL), tiamulin (1 and >32 μg/mL), and tulathromycin (16 and 64 μg/mL), whereas tetracyclines, fluoroquinolones, and florfenicol failed to inhibit growth of M. bovis bison isolates. Isolates were nonsusceptible to tetracyclines (100%), fluoroquinolones (97.5%), and tilmicosin (100%), whereas the highest susceptibility of bison clinical isolates was seen with spectinomycin (95%) and tulathromycin (67.5%). Two lung isolates (Mb283 and 348) were found resistant to both spectinomycin and tulathromycin. These results show a marked difference in antimicrobial susceptibility of bison isolates as compared with previously reported and laboratory reference cattle isolates, emphasizing the necessity of testing antimicrobial susceptibility of M. bovis bison isolates and to generate better therapeutic regime for improved recovery chances for infected bison herds across North America.
Baserisalehi, M; Al-Mahdi, A Y; Kapadnis, B P
Environmental samples were subjected to determine frequency of occurrence of pathogenic campylobacters in the environment. The antimicrobial susceptibility of the isolates was tested to evaluate the level of antibiotic sensitive campylobacters in the environment of investigation. In all, 70 Campylobacter isolates were obtained from water and domestic animal faeces samples using Kapadnis-Baseri device and antimicrobial susceptibility of them was determined by disc diffusion test and E- test. The results indicated that all the isolates of Campylobacter were sensitive to ciprofloxacin and resistant to cefotaxime, cephalexin and ampicillin. Lowest MIC values were observed for ciprofloxacin and gentamicin (2 microg/mL) and highest MIC values for ampicillin and chloramphinicol (256 microg/mL). In general, pathogenic Campylobacter spp. were prevalent in large numbers in the environment, however, they were sensitive to ciprofloxacin.
Kreizinger, Zsuzsa; Sulyok, Kinga Mária; Makrai, László; Rónai, Zsuzsanna; Fodor, László; Jánosi, Szilárd; Gyuranecz, Miklós
The susceptibility of 29 Bacillus anthracis strains, collected in Hungary between 1933 and 2014, was tested to 10 antibiotics with commercially available minimum inhibitory concentration (MIC) test strips. All strains were susceptible to amoxicillin, ciprofloxacin, clindamycin, doxycycline, gentamicin, penicillin, rifampicin, and vancomycin. Intermediate susceptibility to erythromycin and cefotaxime was detected in 17.2% (5/29) and 58.6% (17/29) of the strains, respectively. Correlations were not observed between the isolation date, location, host species, genotype, and antibiotic susceptibility profile of strains.
Antimicrobial susceptibility testing is recommended to determine which antimicrobial agents should be considered for treating a bacterial pathogen. Many bacteria that cause disease in aquatic animals require growth conditions that vary substantially from routine terrestrial pathogens. It has thus ...
To determine if Campylobacter isolation method influenced antimicrobial susceptibility results, the minimum inhibitory concentrations (MIC) of nine antimicrobials were compared for 291 pairs of Campylobacter isolates recovered from chicken carcass rinse samples using direct plating and an enrichment...
Bunner, Christine A; Norby, Bo; Bartlett, Paul C; Erskine, Ronald J; Downes, Frances P; Kaneene, John B
To determine and compare levels and patterns of antimicrobial resistance among Escherichia coli isolated from pigs on farms that did not use antimicrobial agents versus pigs produced under conventional methods. Cross-sectional study. Sample Population-35 antimicrobial-free and 60 conventional swine farms. Farms were visited once, and fecal samples were collected from 15 finisher pigs if available. One E coli isolate from each sample was tested for susceptibility pattern to 14 antimicrobial agents by use of microbroth dilution. E coli isolates were recovered from 1,381 (97.1%) of 1,422 fecal samples. Herd size was significantly larger for conventional swine farms. Resistance to ceftriaxone, ciprofloxacin, or nalidixic acid was not observed on any of the 95 farms. Three isolates from 2 conventional farms were resistant to ceftiofur. Conventional farms had significantly higher levels of resistance to ampicillin, sulfamethoxazole, tetracycline, and chloramphenicol, compared with antimicrobial-free farms. Fourteen percent of E coli isolates were susceptible or had intermediate resistance to all the tested antimicrobial agents. The 3 most frequent patterns of multiple resistance were streptomycin-tetracycline, sulfamethoxazole-tetracycline, and kanamycin-streptomycin-sulfamethoxazole-tetracycline. Cessation of antimicrobial use did not appear to result in an immediate reduction in antimicrobial resistance in swine farms. Prospective studies of long-term antimicrobial usage and cessation are needed to estimate the extent to which food animal production may be contributing to antimicrobial drug resistance and might provide a direct measure of the rates of reversibility of antimicrobial drug resistance that might be achieved by curtailing antimicrobial usage.
Peng, Hui-ming; Weng, Xi-sheng; Zhai, Ji-liang; Bian, Yan-yan; Lin, Jin; Jin, Jin; Qian, Wen-wei; Zhao, Li-juang
To describe the microbiology, antimicrobial susceptibility of patients proven prosthetic joint infection (PJI) after primary total knee arthroplasty (TKA)and to provide reference for the diagnosis and treatment of this complication. The medical data of the patients with infected knee arthroplasty, who were managed with revision surgery between January 1995 to December 2011 were reviewed. Twenty-nine cases were identified and majority of the patients were female (23/29). Diagnosis of PJI after primary TKA was between 1 week and 10 years (average 24.3 months). The microbiology and antimicrobial susceptibility were analyzed. The overall positive rate of cultures was 65.5% (19/29). The most common organisms identified were Coagulase-negative Staphylococcus (CNS) (7/19) and Staphylococcus Aureus (SA) (5/19). Rare pathogens of Mycobacterium (2/19) and fungi (1/19) were also identified. Vancomycin was the most effective antibiotics with overall sensitivity rates of 100%.Resistant and rare pathogens were all in type IV infection. Gram-positive bacterias are the main pathogen, resistant and rare pathogens should be payed attention to. Antibiotic treatment for infected TKA should be based on the results of drug susceptibility. Vancomycin allows infected knee arthroplasties before the result.
Verlinden, Marc; Boyen, Filip; Pasmans, Frank; Garmyn, An; Haesebrouck, Freddy; Martel, An
A broth microdilution method was used to determine the antimicrobial susceptibility of 20 Brachyspira intermedia isolates obtained from different layer flocks in Belgium and The Netherlands between 2008 and 2010. The antimicrobial agents used were tylosin, tilmicosin, tiamulin, valnemulin, doxycycline, and lincomycin. The minimal inhibitory concentration (MIC) distribution patterns of tylosin, tilmicosin, lincomycin, and doxycycline were bimodal, demonstrating acquired resistance against doxycycline in three strains, against the macrolides in two strains, and against lincomycin in one strain. The MICs of tiamulin and valnemulin showed a monomodal distribution, but with tailing toward the higher MIC values, possibly suggesting low-level acquired resistance in six isolates. Sequencing revealed a G1058C mutation in the 16S rRNA gene in all doxycycline-resistant strains. The strain resistant to tylosin, tilmicosin, and lincomycin had an A2058T mutation in the 23S rRNA gene.
Kawai, Kazuhiro; Higuchi, Hidetoshi; Iwano, Hidetomo; Iwakuma, Akihiro; Onda, Ken; Sato, Reiichiro; Hayashi, Tomohito; Nagahata, Hajime; Oshida, Toshio
Mycoplasma spp. are highly contagious pathogens and intramammary Mycoplasma infection is a serious issue for the dairy industry. As there is no effective vaccine for Mycoplasma infection, control depends on good husbandry and chemo-antibiotic therapy. In this study, antimicrobial susceptibility of Mycoplasma strains recently isolated from cases of bovine mastitis in Japan was evaluated by minimum inhibitory concentration (MIC). All Mycoplasma bovis strains were sensitive to pirlimycin, danofloxacin and enrofloxacin, but not kanamycin, oxytetracycline, tilmicosin or tylosin. M. californicum and M. bovigenitalium strains were sensitive to pirlimycin, danofloxacin, enrofloxacin, oxytetracycline, tilmicosin and tylosin, but not to kanamycin. This is the first report to describe the MIC of major antimicrobial agents for Mycoplasma species isolated from bovine mastitis in Japan.
Gerchman, Irena; Levisohn, Sharon; Mikula, Inna; Lysnyansky, Inna
Monitoring of susceptibility to antibiotics in field isolates of pathogenic bovine mycoplasmas is important for appropriate choice of treatment. Our study compared in vitro susceptibility profiles of Mycoplasma bovis clinical strains, isolated during 2005-2007 from Israeli and imported calves. Minimal inhibitory concentration (MIC) values were determined for macrolides by the microbroth dilution test, for aminoglycosides by commercial Etest, and for fluoroquinolones and tetracyclines by both methods. Notably, although correlation between the methods was generally good, it was not possible to determine the MIC endpoint for enrofloxacin-resistant strains (MIC > or =2.5 microg/ml in the microtest) by Etest. Comparison of antibiotic susceptibility profiles between local and imported M. bovis strains revealed that local strains were significantly more resistant to macrolides than most isolates from imported animals, with MIC(50) of 128 microg/ml vs. 2 microg/ml for tilmicosin and 8 microg/ml vs. 1 microg/ml for tylosin, respectively. However, local strains were more susceptible than most imported strains to fluoroquinolones and spectinomycin. Difference in susceptibility to tetracycline, doxycycline and oxytetracycline between local and imported strains was expressed in MIC(90) values for imported strains in the susceptible range compared to intermediate susceptibility for local strains. The marked difference in susceptibility profiles of M. bovis strains isolated from different geographical regions seen in this study emphasizes the necessity for performing of the antimicrobial susceptibility testing periodically and on a regional basis.
Yıldız, Ömer; Çoban, Ahmet Yılmaz; Şener, Aslı Gamze; Coşkuner, Seher Ayten; Bayramoğlu, Gülçin; Güdücüoğlu, Hüseyin; Özyurt, Mustafa; Tatman-Otkun, Müşerref; Karabiber, Nihal; Özkütük, Nuri; Aktepe, Orhan; Öncü, Serkan; Arslan, Uğur; Bozdoğan, Bülent
Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important nosocomial pathogens and is also emerging in Turkish hospitals. The aim of this study was to determine the antimicrobial susceptibility profiles of MRSA isolated from Turkish hospitals. A total of 397 MRSA strains isolated from 12 hospitals in Turkey were included to present study. Antimicrobial susceptibilities were tested using agar dilution method. Presence of ermA, ermB, ermC, msrA, tetM, tetK, linA and aac-aph genes were studied by PCR. All strains were susceptible to vancomycin and linezolid. The susceptibility rates for fusidic acid, lincomycin, erythromycin, tetracyclin, gentamycin, kanamycin, and, ciprofloxacin were 91.9%, 41.1%, 27.2%, 11.8%, 8.5%, 8.3% and 6.8%, respectively. Lincomycin inactivation was positive for 3 isolates. Of 225 erythromycin resistant isolates 48 had ermA, 20 had ermC, and 128 had ermA-C. PCR was negative for 15 strains. Of 3 isolates with lincomycin inactivation one had linA and msrA. Of 358 gentamycin resistant isolates 334 had aac-aph and 24 were negatives. Among 350 tetracyclin resistant isolates 314 had tetM. Of 36 tetM negative isolates 10 had tetK. MRSA isolates from Turkish hospitals were multiresistant to antimicrobials. Quinolone and gentamycin resistance levels were high and macrolide and lincosamide resistance were relatively low. Susceptibility rates for fusidic asid were high. Linezolide and vancomycin resistance are not emerged. The most common resistance genes were ermA, tetM and aac-aph. Evolution of antimicrobial susceptibilities and resistance genes profiles of MRSA isolates should be surveyed at regional and national level for accurate treatment of patients and to control dissemination of resistance genes.
Wang, Qing-Yong; Li, Rong-Hai; Zheng, Lu-Qing; Shang, Xiao-Hong
The aim of this study was to estimate the prevalence and antimicrobial susceptibility of Ureaplasma urealyticum and Mycoplasma hominis among female outpatients treated for genital infection at a Chinese hospital from January 1, 2009 to December 31, 2013. Samples from 6051 female outpatients were analyzed using Mycoplasma Identification and Antimicrobial Susceptibility Testing (ID/AST). The overall prevalence of U. urealyticum was higher than the prevalence of single M. hominis infection (31.2% vs 0.7%) and coinfections (31.2% vs. 1.9%). The percentage of U. urealyticum and/or M. hominis detected in the 30-39 year age group was greater than in the other age groups. More than 94.6% of the U. urealyticum isolates, 100% of the M. hominis isolates, and 84.3% of the isolates from coinfections were susceptible to doxycycline, minocycline, and tetracycline. More than 69.2% of the U. urealyticum isolates were susceptible to azithromycin, erythromycin, clarithromycin, and roxithromycin, but > 95.6% of the M. hominis isolates and 89.6% of the isolates from coinfections were resistant to these antibiotics. Acetylspiramycin, sparfloxacin, levofloxacin, ciprofloxacin, and ofloxacin were inactive against more than one-half of the isolates. More than 75.6% of the M. hominis isolates were susceptible to spectinomycin, but > 87.1% of the U. urealyticum and 93.3% of the coinfection isolates were resistant to this antibiotic. Isolates from three coinfections were completely resistant to the 14 antibiotics. The determination of antimicrobial susceptibility of these mycoplasma species is often crucial for optimal antimicrobial therapy of infected outpatients. Copyright © 2014. Published by Elsevier B.V.
Validation of Vitek 2 nonfermenting gram-negative cards and Vitek 2 version 4.02 software for identification and antimicrobial susceptibility testing of nonfermenting gram-negative rods from patients with cystic fibrosis.
Otto-Karg, Ines; Jandl, Stefanie; Müller, Tobias; Stirzel, Beate; Frosch, Matthias; Hebestreit, Helge; Abele-Horn, Marianne
Accurate identification and antimicrobial susceptibility testing (AST) of nonfermenters from cystic fibrosis patients are essential for appropriate antimicrobial treatment. This study examined the ability of the newly designed Vitek 2 nonfermenting gram-negative card (NGNC) (new gram-negative identification card; bioMérieux, Marcy-l'Etoile, France) to identify nonfermenting gram-negative rods from cystic fibrosis patients in comparison to reference methods and the accuracy of the new Vitek 2 version 4.02 software for AST compared to the broth microdilution method. Two hundred twenty-four strains for identification and 138 strains for AST were investigated. The Vitek 2 NGNC identified 211 (94.1%) of the nonfermenters correctly. Among morphologically atypical microorganisms, five strains were misidentified and eight strains were determined with low discrimination, requiring additional tests which raised the correct identification rate to 97.8%. Regarding AST, the overall essential agreement of Vitek 2 was 97.6%, and the overall categorical agreement was 92.9%. Minor errors were found in 5.1% of strains, and major and very major errors were found in 1.6% and 0.3% of strains, respectively. In conclusion, the Vitek NGNC appears to be a reliable method for identification of morphologically typical nonfermenters and is an improvement over the API NE system and the Vitek 2 GNC database version 4.01. However, classification in morphologically atypical nonfermenters must be interpreted with care to avoid misidentification. Moreover, the new Vitek 2 version 4.02 software showed good results for AST and is suitable for routine clinical use. More work is needed for the reliable testing of strains whose MICs are close to the breakpoints.
Validation of Vitek 2 Nonfermenting Gram-Negative Cards and Vitek 2 Version 4.02 Software for Identification and Antimicrobial Susceptibility Testing of Nonfermenting Gram-Negative Rods from Patients with Cystic Fibrosis▿
Otto-Karg, Ines; Jandl, Stefanie; Müller, Tobias; Stirzel, Beate; Frosch, Matthias; Hebestreit, Helge; Abele-Horn, Marianne
Accurate identification and antimicrobial susceptibility testing (AST) of nonfermenters from cystic fibrosis patients are essential for appropriate antimicrobial treatment. This study examined the ability of the newly designed Vitek 2 nonfermenting gram-negative card (NGNC) (new gram-negative identification card; bioMérieux, Marcy-l'Ètoile, France) to identify nonfermenting gram-negative rods from cystic fibrosis patients in comparison to reference methods and the accuracy of the new Vitek 2 version 4.02 software for AST compared to the broth microdilution method. Two hundred twenty-four strains for identification and 138 strains for AST were investigated. The Vitek 2 NGNC identified 211 (94.1%) of the nonfermenters correctly. Among morphologically atypical microorganisms, five strains were misidentified and eight strains were determined with low discrimination, requiring additional tests which raised the correct identification rate to 97.8%. Regarding AST, the overall essential agreement of Vitek 2 was 97.6%, and the overall categorical agreement was 92.9%. Minor errors were found in 5.1% of strains, and major and very major errors were found in 1.6% and 0.3% of strains, respectively. In conclusion, the Vitek NGNC appears to be a reliable method for identification of morphologically typical nonfermenters and is an improvement over the API NE system and the Vitek 2 GNC database version 4.01. However, classification in morphologically atypical nonfermenters must be interpreted with care to avoid misidentification. Moreover, the new Vitek 2 version 4.02 software showed good results for AST and is suitable for routine clinical use. More work is needed for the reliable testing of strains whose MICs are close to the breakpoints. PMID:19710272
Izzo, Mm; Mohler, Vl; House, Jk
OBJECTIVE To identify the common serotypes and antimicrobial resistance patterns of Salmonella spp. associated with diarrhoea in Australian dairy calves under the age of 6 weeks. DESIGN Cross-sectional study. METHODS Faecal samples were collected from outbreaks of diarrhoea in dairy and dairy beef calves less than 6 weeks old. Samples were screened for Salmonella using standard enrichment culture techniques. The antimicrobial susceptibility to 12 commonly used veterinary and human antimicrobials was assessed using the Kirby-Bauer disk diffusion method and the susceptibility profiles of dairy and dairy beef properties were compared using Fisher's exact test. RESULTS Salmonella ser. Dublin, S. ser. Typhimurium and S. ser. Bovismorbificans were the three most common salmonella serotypes isolated. The majority of properties had one serotype. Most of the Salmonella isolates were not resistant to any of the antimicrobials tested. No resistance was seen to amikacin and nalidixic acid, and only one isolate was resistant to ceftiofur or amoxicillin-clavulanic acid. The most common antimicrobial resistance was to streptomycin, ampicillin or combination sulfonamides. Multi-drug resistance was detected in S. ser. Anatum, S. ser. Bovismorbificans, S. ser. Muenster, S. ser. Newport and S. ser. Typhimurium. Isolates from dairy beef properties were more likely to be resistant to ampicillin, kanamycin, neomycin, sulfamethoxazole/trimethoprim and tetracycline (P < 0.05) and were more likely to exhibit multi-drug resistance. CONCLUSION The prevalence of antimicrobial resistance in Salmonella isolates from dairy calves in Australia is low compared with that reported overseas. From a human health perspective, resistance to antimicrobials used in the treatment of human salmonellosis was infrequent.
Performance of the Vitek 2 system software version 5.03 in the bacterial identification and antimicrobial susceptibility test: evaluation study of clinical and reference strains of Gram-positive cocci.
Paim, Thiago Galvão da Silva; Cantarelli, Vlademir Vicente; d'Azevedo, Pedro Alves
The genera Enterococcus, Staphylococcus and Streptococcus are recognized as important Gram-positive human pathogens. The aim of this study was to evaluate the performance of Vitek 2 in identifying Gram-positive cocci and their antimicrobial susceptibilities. One hundred four isolates were analyzed to determine the accuracy of the automated system for identifying the bacteria and their susceptibility to oxacillin and vancomycin. The system correctly identified 77.9% and 97.1% of the isolates at the species and genus levels, respectively. Additionally, 81.8% of the Vitek 2 results agreed with the known antimicrobial susceptibility profiles. Vitek 2 correctly identified the commonly isolated strains; however, the limitations of the method may lead to ambiguous findings.
Timonin, M E; Poissant, J; McLoughlin, P D; Hedlin, C E; Rubin, J E
The feral horses of Sable Island are a geographically isolated population located ∼160 km off the east coast of Nova Scotia, Canada. Because these horses have no contact with domestic animals, have minimal contact with people, and have never received antimicrobials, they offer a unique opportunity to study the dissemination of antimicrobial resistance in unmanaged populations. As part of an ongoing multidisciplinary and individual-based monitoring program, we collected feces from 508 geolocalized horses (92% of the total population) between July and September 2014. We selectively cultured Escherichia coli on MacConkey and CHROMagar ESBL media. Antimicrobial susceptibilities were determined, and organisms resistant to β-lactam antimicrobials were screened for β-lactamase genes by PCR. Escherichia coli was recovered from 146 (28.7%) individuals, and the majority of isolates (97%) were susceptible to all drugs tested. Resistance to tetracycline was most common, including organisms isolated from 4 (2.7%) of the colonized horses. A single isolate resistant to ampicillin, ceftriaxone, and ceftiofur was identified, which possessed the CTX-M-1 gene. Our findings demonstrate that although antimicrobial resistance is not common in this remote population, clinically relevant resistance genes are present.
Chappelle, E. W.; Picciolo, G. L.; Vellend, H.; Tuttle, S. A.; Barza, M. J.; Weinstein, L. (Inventor)
The susceptibility of bacteria, particularly those derived from body fluids, to antimicrobial agents is determined in terms of an ATP index measured by culturing a bacterium in a growth medium. The amount of ATP is assayed in a sample of the cultured bacterium by measuring the amount of luminescent light emitted when the bacterial ATP is reacted with a luciferase-luciferin mixture. The sample of the cultured bacterium is subjected to an antibiotic agent. The amount of bacterial adenosine triphosphate is assayed after treatment with the antibiotic by measuring the luminescent light resulting from the reaction. The ATP index is determined from the values obtained from the assay procedures.
Marchand-Austin, Alex; Rawte, Prasad; Toye, Baldwin; Jamieson, Frances B; Farrell, David J; Patel, Samir N
The local epidemiology of antimicrobial susceptibility patterns in anaerobic bacteria is important in guiding the empiric treatment of infections. However, susceptibility data are very limited on anaerobic organisms, particularly among non-Bacteroides organisms. To determine susceptibility profiles of clinically-significant anaerobic bacteria in Ontario Canada, anaerobic isolates from sterile sites submitted to Public Health Ontario Laboratory (PHOL) for identification and susceptibility testing were included in this study. Using the E-test method, isolates were tested for various antimicrobials including, penicillin, cefoxitin, clindamycin, meropenem, piperacillin-tazobactam and metronidazole. The MIC results were interpreted based on guidelines published by Clinical and Laboratory Standards Institute. Of 2527 anaerobic isolates submitted to PHOL, 1412 were either from sterile sites or bronchial lavage, and underwent susceptibility testing. Among Bacteroides fragilis, 98.2%, 24.7%, 1.6%, and 1.2% were resistant to penicillin, clindamycin, piperacillin-tazobactam, and metronidazole, respectively. Clostridium perfringens was universally susceptible to penicillin, piperacillin-tazobactam, and meropenem, whereas 14.2% of other Clostridium spp. were resistant to penicillin. Among Gram-positive anaerobes, Actinomyces spp., Parvimonas micra and Propionibacterium spp. were universally susceptible to β-lactams. Eggerthella spp., Collinsella spp., and Eubacterium spp. showed variable resistance to penicillin. Among Gram-negative anaerobes, Fusobacterium spp., Prevotella spp., and Veillonella spp. showed high resistance to penicillin but were universally susceptible to meropenem and piperacillin-tazobactam. The detection of metronidazole resistant B. fragilis is concerning as occurrence of these isolates is extremely rare. These data highlight the importance of ongoing surveillance to provide clinically relevant information to clinicians for empiric management of
Fernandez, R C; Weiss, A A
We examined the susceptibilities of Bordetella pertussis strains to several antimicrobial peptides by determining the concentration required to inhibit or kill 50% of the bacterial population. The peptides are ranked in decreasing potency as follows: cecropin B > cecropin A >> melittin > cecropin P1 > (ala8,13,18)-magainin II amide > mastoparan = defensin HNP1 > protamine > or = magainin II = magainin I. By using a radial diffusion assay to compare susceptibilities between strains, wild-type B. pertussis BP338 was more resistant than the avirulent bvg mutant strain BP347 and the brk mutant strain BPM2041 to killing by cecropin P1. In contrast, compared with the wild type, the avirulent BP347 strain was highly resistant to killing by protamine and defensin HNP1. PMID:8849226
Aarestrup, F M; Nielsen, E M; Madsen, M; Engberg, J
The MICs of 16 antimicrobial agents were determined for 202 Campylobacter jejuni isolates, 123 Campylobacter coli isolates, and 6 Campylobacter lari isolates from humans and food animals in Denmark. The C. jejuni isolates originated from humans (75), broilers (95), cattle (29), and pigs (3); the C. coli isolates originated from humans (7), broilers (17), and pigs (99); and the C. lari isolates originated from broilers (5) and cattle (1). All isolates were susceptible to apramycin, neomycin, and gentamicin. Only a few C. jejuni isolates were resistant to one or more antimicrobial agents. Resistance to tetracycline was more common among C. jejuni isolates from humans (11%) than among C. jejuni isolates from animals (0 to 2%). More resistance to streptomycin was found among C. jejuni isolates from cattle (10%) than among those from humans (4%) or broilers (1%). A greater proportion of C. coli than of C. jejuni isolates were resistant to the other antimicrobial agents tested. Isolates were in most cases either coresistant to tylosin, spiramycin, and erythromycin or susceptible to all three antibiotics. More macrolide-resistant isolates were observed among C. coli isolates from swine (79%) than among C. coli isolates from broilers (18%) and humans (14%). Twenty-four percent of C. coli isolates from pigs were resistant to enrofloxacin, whereas 29% of C. coli isolates from humans and none from broilers were resistant. More resistance to streptomycin was observed among C. coli isolates from swine (48%) than among C. coli isolates from broilers (6%) or humans (0%). The six C. lari isolates were susceptible to all antimicrobial agents except ampicillin and nalidixic acid. This study showed that antimicrobial resistance was found only at relatively low frequencies among C. jejuni and C. lari isolates. Among C. coli isolates, especially from swine, there was a high level of resistance to macrolides and streptomycin. Furthermore, this study showed differences in the resistance
Comparison of the Vitek 2 Antifungal Susceptibility System with the Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) Broth Microdilution Reference Methods and with the Sensititre YeastOne and Etest Techniques for In Vitro Detection of Antifungal Resistance in Yeast Isolates ▿ ‖
Cuenca-Estrella, Manuel; Gomez-Lopez, Alicia; Alastruey-Izquierdo, Ana; Bernal-Martinez, Leticia; Cuesta, Isabel; Buitrago, Maria J.; Rodriguez-Tudela, Juan L.
The commercial technique Vitek 2 system for antifungal susceptibility testing of yeast species was evaluated. A collection of 154 clinical yeast isolates, including amphotericin B- and azole-resistant organisms, was tested. Results were compared with those obtained by the reference procedures of both the CLSI and the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Two other commercial techniques approved for clinical use, the Etest and the Sensititre YeastOne, were included in the comparative exercise as well. The average essential agreement (EA) between the Vitek 2 system and the reference procedures was >95%, comparable with the average EAs observed between the reference procedures and the Sensititre YeastOne and Etest. The EA values were >97% for Candida spp. and stood at 92% for Cryptococcus neoformans. Intraclass correlation coefficients (ICC) between the commercial techniques and the reference procedures were statistically significant (P < 0.01). Percentages of very major errors were 2.6% between Vitek 2 and the EUCAST technique and 1.6% between Vitek 2 and the CLSI technique. The Vitek 2 MIC results were available after 14 to 18 h of incubation for all Candida spp. (average time to reading, 15.5 h). The Vitek 2 system was shown to be a reliable technique to determine antifungal susceptibility testing of yeast species and a more rapid and easier alternative for clinical laboratories than the procedures developed by either the CLSI or EUCAST. PMID:20220169
Comparison of the Vitek 2 antifungal susceptibility system with the clinical and laboratory standards institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) Broth Microdilution Reference Methods and with the Sensititre YeastOne and Etest techniques for in vitro detection of antifungal resistance in yeast isolates.
Cuenca-Estrella, Manuel; Gomez-Lopez, Alicia; Alastruey-Izquierdo, Ana; Bernal-Martinez, Leticia; Cuesta, Isabel; Buitrago, Maria J; Rodriguez-Tudela, Juan L
The commercial technique Vitek 2 system for antifungal susceptibility testing of yeast species was evaluated. A collection of 154 clinical yeast isolates, including amphotericin B- and azole-resistant organisms, was tested. Results were compared with those obtained by the reference procedures of both the CLSI and the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Two other commercial techniques approved for clinical use, the Etest and the Sensititre YeastOne, were included in the comparative exercise as well. The average essential agreement (EA) between the Vitek 2 system and the reference procedures was >95%, comparable with the average EAs observed between the reference procedures and the Sensititre YeastOne and Etest. The EA values were >97% for Candida spp. and stood at 92% for Cryptococcus neoformans. Intraclass correlation coefficients (ICC) between the commercial techniques and the reference procedures were statistically significant (P<0.01). Percentages of very major errors were 2.6% between Vitek 2 and the EUCAST technique and 1.6% between Vitek 2 and the CLSI technique. The Vitek 2 MIC results were available after 14 to 18 h of incubation for all Candida spp. (average time to reading, 15.5 h). The Vitek 2 system was shown to be a reliable technique to determine antifungal susceptibility testing of yeast species and a more rapid and easier alternative for clinical laboratories than the procedures developed by either the CLSI or EUCAST.
Prüller, Sandra; Rensch, Ulrike; Meemken, Diana; Kaspar, Heike; Kopp, Peter A.; Klein, Günter; Kehrenberg, Corinna
Bordetella bronchiseptica causes infections of the respiratory tract in swine and other mammals and is a precursor for secondary infections with Pasteurella multocida. Treatment of B. bronchiseptica infections is conducted primarily with antimicrobial agents. Therefore it is essential to get an overview of the susceptibility status of these bacteria. The aim of this study was to comparatively analyse broth microdilution susceptibility testing according to CLSI recommendations with an incubation time of 16 to 20 hours and a longer incubation time of 24 hours, as recently proposed to obtain more homogenous MICs. Susceptibility testing against a panel of 22 antimicrobial agents and two fixed combinations was performed with 107 porcine isolates from different farms and regions in Germany and 43 isolates obtained from companion animals in Germany and other European countries. Isolates with increased MICs were investigated by PCR assays for the presence of resistance genes. For ampicillin, all 107 porcine isolates were classified as resistant, whereas only a single isolate was resistant to florfenicol. All isolates obtained from companion animals showed elevated MICs for β-lactam antibiotics and demonstrated an overall low susceptibility to cephalosporines. Extension of the incubation time resulted in 1–2 dilution steps higher MIC50 values of porcine isolates for seven antimicrobial agents tested, while isolates from companion animals exhibited twofold higher MIC50/90 values only for tetracycline and cefotaxime. For three antimicrobial agents, lower MIC50 and MIC90 values were detected for both, porcine and companion animal isolates. Among the 150 isolates tested, the resistance genes blaBOR-1 (n = 147), blaOXA-2, (n = 4), strA and strB (n = 17), sul1 (n = 10), sul2 (n = 73), dfrA7 (n = 3) and tet(A) (n = 8) were detected and a plasmid localisation was identified for several of the resistance genes. PMID:26275219
Prüller, Sandra; Rensch, Ulrike; Meemken, Diana; Kaspar, Heike; Kopp, Peter A; Klein, Günter; Kehrenberg, Corinna
Bordetella bronchiseptica causes infections of the respiratory tract in swine and other mammals and is a precursor for secondary infections with Pasteurella multocida. Treatment of B. bronchiseptica infections is conducted primarily with antimicrobial agents. Therefore it is essential to get an overview of the susceptibility status of these bacteria. The aim of this study was to comparatively analyse broth microdilution susceptibility testing according to CLSI recommendations with an incubation time of 16 to 20 hours and a longer incubation time of 24 hours, as recently proposed to obtain more homogenous MICs. Susceptibility testing against a panel of 22 antimicrobial agents and two fixed combinations was performed with 107 porcine isolates from different farms and regions in Germany and 43 isolates obtained from companion animals in Germany and other European countries. Isolates with increased MICs were investigated by PCR assays for the presence of resistance genes. For ampicillin, all 107 porcine isolates were classified as resistant, whereas only a single isolate was resistant to florfenicol. All isolates obtained from companion animals showed elevated MICs for β-lactam antibiotics and demonstrated an overall low susceptibility to cephalosporines. Extension of the incubation time resulted in 1-2 dilution steps higher MIC50 values of porcine isolates for seven antimicrobial agents tested, while isolates from companion animals exhibited twofold higher MIC50/90 values only for tetracycline and cefotaxime. For three antimicrobial agents, lower MIC50 and MIC90 values were detected for both, porcine and companion animal isolates. Among the 150 isolates tested, the resistance genes blaBOR-1 (n = 147), blaOXA-2, (n = 4), strA and strB (n = 17), sul1 (n = 10), sul2 (n = 73), dfrA7 (n = 3) and tet(A) (n = 8) were detected and a plasmid localisation was identified for several of the resistance genes.
Wang, Jann-Tay; Chen, Pei-Chen; Chang, Shan-Chwen; Shiau, Yih-Ru; Wang, Hui-Ying; Lai, Jui-Fen; Huang, I-Wen; Tan, Mei-Chen; Lauderdale, Tsai-Ling Yang
Longitudinal nationwide data on antimicrobial susceptibility in Proteus mirabilis from different sources are rare. The effects of the revised Clinical and Laboratory Standards Institute (CLSI) β-lactam breakpoints on susceptibility rates and on detecting extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase-producers in this species are also seldom evaluated. The present study analyzed data from the Taiwan Surveillance of Antimicrobial Resistance program to address these issues. Isolates were collected biennially between 2002 and 2012 from 25 to 28 hospitals in Taiwan. Minimum inhibitory concentrations (MIC) were determined by reference broth microdilution method. All isolates with aztreonam, ceftazidime, or cefotaxime MIC ≥ 2 mg/L were checked for the presence of ESBL by CLSI confirmatory test and subjected to ESBL and AmpC β-lactamases gene detection by PCR. Univariate and multivariate analyses were performed. Between 2002 and 2012, a total of 1157 P. mirabilis were studied. Susceptibility to cefotaxime, ceftazidime, and ciprofloxacin decreased significantly during the past decade, from 92.6% to 81.7%, 100% to 95.2%, and 80.1% to 53.8%, respectively (P < 0.01). The revised CLSI breakpoints had significant impact on susceptibility to cefazolin (2009 vs. current breakpoints, 71.9% vs. 0.9%) and imipenem (99.8% vs. 55.1%) (P < 0.001 for both). However, using the 2014 cefazolin breakpoints for urinary tract infections, 81.2% of the urine isolates were susceptible. Susceptibilities of isolates from different specimen types were mostly similar but outpatient isolates were more susceptible than inpatient isolates. The overall prevalence of ESBL- and AmpC- producers was 8.2% and 4.7%, respectively, but AmpC carriage increased significantly over the years (from 0 to 7.0%, P < 0.001). ESBL and AmpC β-lactamase-producers were more likely to be found in elderly and ICU patients. The predominant ESBL and AmpC β-lactamase genes were CTX-M- and CMY
Haruna, M; Sasaki, Y; Murakami, M; Ikeda, A; Kusukawa, M; Tsujiyama, Y; Ito, K; Asai, T; Yamada, Y
Campylobacter was isolated from 67 (47.2%) of 142 broiler flocks between September 2009 and February 2010. The prevalence of Campylobacter in broiler flocks was significantly lower during January and February than it was from September to December. Campylobacter colonization was more common in flocks that were not provided with a disinfected water supply, which was consistent with the findings of a previous study. The prevalence of antimicrobial drug-resistant Campylobacter spp. was investigated, and the minimum inhibitory concentrations of eight antimicrobial agents were determined for 122 Campylobacter jejuni isolates and 46 Campylobacter coli isolates from broiler flocks between 2007 and 2010. In this study, 29.5% (36/122) of C. jejuni isolates and 41.3% (19/46) of C. coli isolates were resistant to enrofloxacin (ERFX), whereas all isolates were susceptible to erythromycin. Furthermore, the ERFX-resistant isolates were tested for susceptibility to other classes of antimicrobial agents, and 55.6% (20/36) of ERFX-resistant C. jejuni isolates and 47.4% (9/19) of ERFX-resistant C. coli isolates were resistant to at least one of aminobenzyl penicillin, dihydrostreptomycin and oxytetracycline. To avoid an impact of antimicrobial drug-resistant Campylobacter spp. on the efficacy of antimicrobial treatment for human campylobacteriosis, prudent use of antimicrobial agents is a requisite. The use of antimicrobial agents should be accompanied by various approaches such as prevention of Campylobacter colonization in broiler flocks with the aim of lowering the occurrence of Campylobacter infection in humans.
Habets, Michelle G. J. L.; Rozen, Daniel E.; Brockhurst, Michael A.
Streptococcus pneumoniae is a facultative pathogen inhabiting the nasopharynx of humans where it is exposed to a range of antimicrobial peptides (AMPs) of the innate immune response. It is possible therefore that the susceptibility of strains to AMPs plays a role in determining their ability to colonize, and furthermore, that AMPs could mediate competitive interactions between co-colonizing genotypes. However, little is known about patterns of natural variation in AMP susceptibility of S. pneumoniae, and it is unclear whether the susceptibilities of an isolate to multiple human AMPs are correlated. We tested this by characterizing the susceptibility of 31 S. pneumoniae natural isolates to human neutrophil peptide (HNP-1) (α-defensin) and LL-37 (cathelicidin). We observed significant variation in susceptibility between isolates to both AMPs, and in the majority of isolates, susceptibilities to HNP-1 and LL-37 were uncorrelated. Clinical isolates were more susceptible to AMPs than were carriage isolates. The polysaccharide capsule of S. pneumoniae is thought to protect cells against AMPs. However, serotype alone could not explain the observed variation in susceptibility suggesting that genetic background plays an equally important role. We tested directly whether AMPs could mediate competition between isolates using competition experiments in the presence and absence of AMPs. These experiments demonstrated that AMPs could indeed reverse the outcome of competition between selected isolates. AMP-mediated competition could therefore contribute to the maintenance of intraspecific genetic diversity in S. pneumoniae. PMID:22764166
Yamamoto, T; Nair, G B; Albert, M J; Parodi, C C; Takeda, Y
Vibrio cholerae O139 (173 strains) and O1 (221 strains) were tested for their in vitro susceptibilities to 39 antimicrobial agents. Both O139 and O1 strains were highly susceptible to azithromycin, cephems, minocycline, penems, and newer fluoroquinolones. O139 strains (94.8%), O1 Indian El Tor strains (97%), and Bangladeshi El Tor strains (50%) were highly resistant to streptomycin, sulfamethoxazole, and trimethoprim and moderately resistant to chloramphenicol and furazolidone, in sharp contrast to O1 Peruvian El Tor and O1 classical strains. Some Bangladeshi El Tor strains (43.3%) showed tetracycline resistance as well. PMID:7695314
Paterna, A; Sánchez, A; Gómez-Martín, A; Corrales, J C; De la Fe, C; Contreras, A; Amores, J
This study examined the susceptibility to several antimicrobials of 28 isolates of Mycoplasma agalactiae obtained from goats in a region (southeastern Spain) where contagious agalactia is endemic. For each isolate, the minimum inhibitory concentration (MIC) against 12 antimicrobials of the quinolone, macrolide, aminoglycoside, and tetracycline families was determined. The antimicrobials with the lowest MIC were enrofloxacin, ciprofloxacin, tylosin, and doxycycline, all with MIC90 (concentration at which growth of 90% of the isolates is inhibited) <1 µg/mL. Norfloxacin (a quinolone) showed a wide MIC range (0.1-12.8 µg/mL), suggesting a resistance mechanism toward this antimicrobial that was not elicited by enrofloxacin or ciprofloxacin (the other quinolones tested). Erythromycin showed the highest MIC90 such that its use against Mycoplasma agalactiae is not recommended. Finally, Mycoplasma agalactiae isolates obtained from goat herds with clinical symptoms of contagious agalactia featured higher MIC90 and MIC50 (concentration at which growth of 50% of the isolates is inhibited) values for many of the antimicrobials compared with isolates from asymptomatic animals. The relationship between the extensive use of antimicrobials in herds with clinical contagious agalactia and variations in MIC requires further study.
Eng, Nelson F; Ybazeta, Gustavo; Chapman, Katrina; Fraleigh, Nya L; Letto, Rebecca; Altman, Eleonora; Diaz-Mitoma, Francisco
BACKGROUND: Helicobacter pylori plays a significant role in gastritis and ulcers. It is a carcinogen as defined by the WHO, and infection can result in adenocarcinomas and mucosa-associated lymphoid tissue lymphomas. In Canada, rates of antimicrobial resistance are relatively unknown, with very few studies conducted in the past 15 years. OBJECTIVE: To examine rates of resistance in Sudbury, Ontario, compare antimicrobial susceptibility methods and attempt to determine the molecular basis of antibiotic resistance. METHODS: Patients attending scheduled visits at Health Sciences North (Sudbury, Ontario) provided gastric biopsy samples on a volunteer basis. In total, 20 H pylori isolates were collected, and antimicrobial susceptibility testing (on amoxicillin, tetracycline, metronidazole, ciprofloxacin, levofloxacin and clarithromycin) was conducted using disk diffusion and E-test methods. Subsequently, genomic DNA from these isolates was sequenced to detect mutations associated with antimicrobial resistance. RESULTS: Sixty-five percent of the isolates were found to be resistant to at least one of the listed antibiotics according to E-test. Three isolates were found to be resistant to ≥3 of the above-mentioned antibiotics. Notably, 25% of the isolates were found to be resistant to both metronidazole and clarithromycin, two antibiotics that are normally prescribed as part of first-line regimens in the treatment of H pylori infections in Canada and most of the world. Among the resistant strains, the sequences of 23S ribosomal RNA and gyrA, which are linked to clarithromycin and ciprofloxacin/levofloxacin resistance, respectively, revealed the presence of known point mutations associated with antimicrobial resistance. CONCLUSIONS: In general, resistance to metronidazole, ciprofloxacin/levofloxacin and clarithromycin has increased since the studies in the early 2000s. These results suggest that surveillance programs of H pylori antibiotic resistance may need to be
Gums, John G
The spread of resistance to many antimicrobial agents in various microbial species has been highlighted by the World Health Organisation and many government agencies around the world. The reasons for this increase and spread are complex and are discussed. A number of surveillance studies has monitored the increase in resistance among isolates of Streptococcus pneumoniae to various important classes of antimicrobials. These results are discussed with particular reference to penicillins, macrolides and fluoroquinolones. Although there is evidence that in vitro resistance to macrolides and more recently to fluoroquinolones may be associated with a reduced clinical efficacy, there is no such clear association with resistance to beta-lactams and lack of clinical efficacy in non-meningeal infections. Resistance or susceptibility to an antimicrobial agent is based on breakpoints and these are set in the US by the National Committee of Clinical and Laboratory Standards. In response to these recent clinical studies showing that non-meningeal pneumococcal infections with strains classified as resistant in vitro still responded well to treatment with various beta-lactams, new breakpoints have been set. Results are presented showing that using these breakpoints, the levels of resistance to the third generation cephalosporins, ceftriaxone and cefotaxime against a range of non-meningeal pneumococcal isolates were lower than those obtained using the previous breakpoints. The excellent pharmacokinetic and pharmacodynamic properties of these agents are believed to contribute to their good activity in the clinic.
Agnoletti, Fabrizio; Ferro, Tiziana; Guolo, Angela; Marcon, Barbara; Cocchi, Monia; Drigo, Ilenia; Mazzolini, Elena; Bano, Luca
Rabbit meat breeding may be heavily affected by enterotoxaemia due to Clostridium spiroforme. Data on its antimicrobial susceptibility are insufficient, presumably because of difficulties in cultivating and identifying the pathogen. Our aim is therefore to provide this information to veterinary practitioners by focusing on a panel of therapeutics used in intensive rabbit units. Lincomycin was also checked in order to investigate the origin of resistance to macrolides. Minimal inhibitory concentrations (MICs) were determined with the agar dilution method according to the CLSI M11-A7 protocol (2007). MIC(50) and MIC(90) were, respectively, 64 and 64microg/ml for tiamulin, 32 and 32microg/ml for norfloxacin, 0.063 and 0.125microg/ml for amoxicillin, and 8 and 16microg/ml for doxycycline. MIC(50) and MIC(90) were 256microg/ml for sulphadimethoxine, spiramycin and lincomycin. Our results have shown that intrinsic or acquired antimicrobial resistances are diffuse in the C. spiroforme population and suggest focusing on prevention rather than on treatment of clostridial overgrowth, by reducing risk factors and using antimicrobials prudently.
Cedeno, J.R.; Krogstad, D.J.
The growth of Entamoeba histolytica in microtiter plates in vitro in a variety of environments with reduced oxygen tensions is reported. With 3% O/sub 2/, 3% CO/sub 2/, and 94% N/sub 2/, the parasite growth in microtiter plates was identical to that in screw-capped culture tubes, as measured by (/sup 3/H)thymidine incorporation and by quantitative parasite counts. There were no significant differences between the drug concentrations necessary to inhibit parasite growth by 50% based on (/sup 3/H)thymidine incorporation vs those defined by quantitative parasite counts for the 15 antimicrobial agents tested (including seven drugs used for the treatment of amebiasis). This technique provides a reproducible method to quantitate the activity of potential antiamebic agents in vitro. The isotopic method should be of particular value in defining the metabolism of the parasite and effects of antimicrobial agents on it, whereas the morphologic method may be more valuable for workers with limited resources available to them.
Maasjost, J; Mühldorfer, K; Cortez de Jäckel S; Hafez, H M
Between 2010 and 2011, 145 Enterococcus isolates (Enterococcus faecalis, n = 127; Enterococcus faecium, n = 18) were collected during routine bacteriologic diagnostics from broilers, layers, and fattening turkeys in Germany showing various clinical signs. The susceptibility to 24 antimicrobial agents was investigated by broth microdilution test to determine minimum inhibitory concentrations (MICs). All E. faecalis isolates (n = 127) were susceptible to the beta-lactam antibiotics ampicillin, amoxicillin-clavulanic acid, and penicillin. Corresponding MIC with 50% inhibition (MIC50) and MIC with 90% inhibition (MIC90) values of these antimicrobial agents were at the lower end of the test range (≤ 4 μg/ml). In addition, no vancomycin-resistant enterococci (VRE) were found. High resistance rates were identified in both Enterococcus species for lincomycin (72%-99%) and tetracycline (67%-82%). Half or more than half of Enterococcus isolates were resistant to gentamicin (54%-72%) and the macrolide antibiotics erythromycin (44%-61%) and tylosin-tartate (44%-56%). Enterococcus faecalis isolated from fattening turkeys showed the highest prevalence of antimicrobial resistance compared to other poultry production systems. Eighty-nine out of 145 Enterococcus isolates were resistant to three or more antimicrobial classes. Again, turkeys stood out with 42 (8 1%) multiresistant isolates. The most-frequent resistance patterns of E. faecalis were gentamicin, lincomycin, and tetracycline in all poultry production systems.
Supré, K; Lommelen, K; De Meulemeester, L
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.
Direct Identification and Antimicrobial Susceptibility Testing of Bacteria From Positive Blood Culture Bottles by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry and the Vitek 2 System
Jo, Sung Jin; Park, Kang Gyun; Han, Kyungja; Park, Dong Jin
Background We evaluated the reliability and accuracy of the combined use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) bacterial identification and Vitek 2 antimicrobial susceptibility testing (AST) for bacteria from positive blood culture bottles. Methods Direct identification and AST were performed in parallel to the standard methods in monomicrobial positive blood culture bottles. In total, 254 isolates grown on aerobic and/or anaerobic bottles were identified with MALDI-TOF Vitek MS (bioMérieux, France), and 1,978 microorganism/antimicrobial agent combinations were assessed. For isolates from anaerobic bottles, an aliquot of the culture broth was centrifuged, washed, and filtered through a nylon mesh. For isolates from aerobic/pediatric bottles, a lysis step using 9.26% ammonium chloride solution and 2% saponin solution was included. Results The overall correct identification rate was 81.8% (208/254) and that for gram-positive/gram-negative isolates was 73.9%/92.6%, respectively, and it was 81.8%, 87.6%, and 57.9% for isolates from aerobic, anaerobic, and pediatric bottles, respectively. Identification was not possible in 45 cases, and most of these isolates were streptococci (N=14) and coagulase-negative staphylococci (N=11). Misidentification occurred only in one case. Compared with standard methods, direct AST showed 97.9% (1,936/1,978) agreement with very major error of 0.25%, major error of 0.05%, and minor error of 1.8%. Conclusions This simple and cost-effective sample preparation method gives reliable results for the direct identification and AST of bacteria. For the identification of streptococci and coagulase-negative staphylococci, the method should be further improved. PMID:26709258
Wu, Qian; Xi, Meili; Lv, Xiaoying; Xu, Yunfeng; Feng, Yuqing; Li, Qiong; Yang, Qinnan; Xia, Xiaodong
The aim of this study was to determine the prevalence and antimicrobial susceptibility of Escherichia coli in retail whole chicken in the People 9 s Republic of China. Five hundred seventy-six raw whole chicken samples, randomly purchased from 146 farmers' markets or supermarkets in four provinces from March through December 2010, were analyzed for E. coli contamination, and the E. coli isolates were further tested for the presence of virulence genes and antimicrobial susceptibility. The overall positive rate for E. coli in retail chicken was 69.1%. E. coli prevalence was the highest in Beijing (86.8%), followed by Henan province (78.5%), Shaanxi province (65.3%), and the lowest prevalence was found in Sichuan province (45.8%). Among 398 isolates recovered, only the eae gene was detected in one isolate; no other virulence genes were detected. Resistance was most common to tetracycline (84.4%), followed by nalidixic acid (74.1%), ampicillin (71.1%), trimethoprim-sulfamethoxazole (70.1%), amoxicillin-clavulanic acid (68.8%), and streptomycin (58.5%). Lower resistance was detected to chloramphenicol (43.7%), kanamycin (42.7%), ciprofloxacin (30.2%), gentamicin (29.4%), cefoperazone (13.6%), amikacin (12.6%), gatifloxacin (8%), and cefoxitin (7.8%). Only 3.8% of the isolates were susceptible to all tested antimicrobials. Six percent of the isolates displayed resistance to one antimicrobial, 6.3% to two, and 83.9% to three or more of the antimicrobials. Our findings indicate that retail chicken in China was commonly contaminated with E. coli, and many E. coli strains exhibited multiple drug resistance. The implementation of good manufacturing practices throughout the poultry production chain is necessary to reduce E. coli contamination in retail chicken, and the prudent use of antibiotics is imperative in poultry production in China.
Osaili, Tareq M; Alaboudi, Akram R; Al-Akhras, Rani R
A total of 140 broiler flocks presented for slaughtering at Amman slaughterhouse were tested for Campylobacter spp. via collection of cloacal swabs from live birds, feathered skin samples at prescalding, and skin samples at postscalding (62°C or 57°C scalding temperature), postevisceration, and postchilling. The results indicated that 40% of the flocks tested by cloacal swabs, 34% at prescalding, 32% at post 57°C scalding, and 32% postevisceration were harboring Campylobacter jejuni. None of the skin samples collected from dressed birds at postscalding (62°C) or postwashing-chilling steps (regardless of scalding temperature) revealed the presence of C. jejuni. Thirty eight isolates were tested for susceptibility to ten antimicrobials by using the microbroth dilution method. Almost 50% of the isolates were multidrug resistant to 9 or 10 out of the ten tested antimicrobials. The other half of tested isolates were sensitive to erythromycin, tetracycline, doxycyclin, chlortetracycline, ciprofloxacin, enorfloxacin, gentamycin, tilmicosin, amoxicillin, and trimethoprim.
The efficacy of antimicrobial treatments to eliminate or control biological growth in the indoor environment can easily be tested on nonporous surfaces. However, the testing of antimicrobial efficacy on porous surfaces, such as those found in the indoor environment [i.e., gypsum ...
The efficacy of antimicrobial treatments to eliminate or control biological growth in the indoor environment can easily be tested on nonporous surfaces. However, the testing of antimicrobial efficacy on porous surfaces, such as those found in the indoor environment [i.e., gypsum ...
Mateus-Vargas, Rafael H; Atanassova, Viktoria; Reich, Felix; Klein, Günter
The increasing number of antimicrobial resistant Enterobacteriaceae both in veterinary and human medicine, the dissemination of these bacteria in several environments and their possible repercussions on human health is causing concern. Game meat is usually seen as free of antimicrobial resistant bacteria. The objective of this study was to evaluate the current antimicrobial susceptibility status in generic Escherichia coli isolated from packed frozen game meat from a game handling establishment in Germany. A total of 229 E. coli isolates were obtained from cuts of red deer, roe deer and wild boar. The susceptibility to 12 antimicrobial agents was evaluated by a broth microdilution method according to ISO 20776-1:2006. Minimal Inhibitory Concentration (MIC) values were compared to breakpoints and cut-off values published by the EUCAST. Isolates showing MICs above the reference values were further studied for associated resistance determinants and phylogrouping by PCR. Overall, 16 E. coli isolates (7.0%) showed resistance (microbiological or clinical) to at least one antimicrobial agent tested. Clinical resistance was recorded to ampicillin (5/229) and chloramphenicol (4/229), whereas the MIC of 9 isolates exceeded the epidemiological cut-off value for doxycycline. One of the ampicillin-resistant isolates showed resistance to the β-lactam antibiotic derivatives tested, cephalosporines and aztreonam. Three of 9 non-wild-type isolates for doxycycline were positive for tet (B) genes. The ß-lactam-resistant isolate was found to harbour blaCTX-M-1 gene. These data show a low prevalence of resistant E. coli in packed game meat compared to studies on conventional meat. Although isolates obtained in this study may also be originating from the processing environment and not necessarily from animals, based on our results, it is important to monitor the development of antimicrobial resistance in game animals and products in order to identify future threats for the
Wei, Ming; Wang, Peng; Qu, Jiuxin; Li, Ran; Liu, Yongzhe; Gu, Li; Yang, Chunxia
The aim of this study was to determine the antibiotic susceptibility of 28 clinical isolates of Nocardia species isolated from Beijing Chao-Yang Hospital, for reducing the insufficiency of information on antimicrobial activities of Nocardia clinical isolates in specific species in China. Molecular diagnosis of Nocardia species was performed using partial 16S rRNA and rpoB gene sequences. Antimicrobial susceptibility testing by broth microdilution was performed according to the Clinical and Laboratory Standards Institute recommendations. The species distribution (n) was N. cyriacigeorgica (13), N. farcinica (6), N. beijingensis (3), N. abscessus (2), N. wallacei (2), N. otitidiscaviarum (1), N. nova (1). The susceptibility rates to trimethoprim-sulfamethoxazole, linezolid, amikacin, imipenem, tobramycin, ceftriaxone and cefotaxime were100%, 100%, 92.86%, 75.00%, 67.86%, 67.86% and 64.29% respectively, while the resistance rates to both ciprofloxacin and clarithromycin were 71.43%. N. cyriacigeorgica was the most frequently isolated Nocardia species. All clinical isolates showed very low susceptibility to ciprofloxacin and clarithromycin, and complete susceptibility to both trimethoprim-sulfamethoxazole, linezolid, which can be the primary choice for the treatment of Nocardia infections in China. Copyright © 2017. Published by Elsevier Ltd.
Novak, Anita; Rubic, Zana; Dogas, Varja; Goic-Barisic, Ivana; Radic, Marina; Tonkic, Marija
Anaerobic bacteria play a significant role in many endogenous polymicrobial infections. Since antimicrobial resistance among anaerobes has increased worldwide, it is useful to provide local susceptibility data to guide empirical therapy. The present study reports recent data on the susceptibility of clinically relevant anaerobes in a University Hospital Centre (UHC) Split, Croatia. A total of 63 Gram-negative and 59 Gram-positive anaerobic clinical isolates from various body sites were consecutively collected from January to December 2013. Antimicrobial susceptibility testing was performed using standardized methods and interpreted using EUCAST criteria. Patient's clinical and demographic data were recorded by clinical microbiologist. Among 35 isolates of Bacteroides spp., 97.1% were resistant to penicillin (PCN), 5.7% to amoxicillin/clavulanic acid (AMC), 8.6% to piperacillin/tazobactam (TZP), 29.0% to clindamycin (CLI) and 2.9% to metronidazole (MZ). Percentages of susceptible strains to imipenem (IPM), meropenem (MEM) and ertapenem (ETP) were 94.3. Resistance of other Gram-negative bacilli was 76.0% to PCN, 8.0% to AMC, 12.0% to TZP, 28.0% to CLI and 8% to MZ. All other Gram-negative strains were fully susceptible to MEM and ETP, while 96.0% were susceptible to IPM. Clostridium spp. isolates were 100% susceptible to all tested antibiotics except to CLI (two of four tested isolates were resistant). Propionibacterium spp. showed resistance to CLI in 4.3%, while 100% were resistant to MZ. Among other Gram-positive bacilli, 18.2% were resistant to PCN, 9.1% to CLI and 54.5% to MZ, while 81.8% of isolates were susceptible to carbapenems. Gram-positive cocci were 100% susceptible to all tested antimicrobials except to MZ, where 28.6% of resistant strains were recorded. Abdomen was the most common source of isolates (82.5%). The most prevalent types of infection were abscess (22.1%), sepsis (14.8%), appendicitis (13.9%) and peritonitis (6.6%). Twenty four patients (19
Ceelen, Liesbeth; Decostere, Annemie; Devriese, Luc A; Ducatelle, Richard; Haesebrouck, Freddy
The in vitro activity of 13 antimicrobial agents against 23 Helicobacter pullorum strains from poultry (21) and human (two) origin, and one human H. canadensis strain was tested by the agar dilution method. With the H. pullorum strains, monomodal distributions of Minimum Inhibitory Concentrations (MICs) were seen with lincomycin, doxycycline, gentamicin, tobramycin, erythromycin, tylosin, metronidazole, and enrofloxacin in concentration ranges considered as indicating susceptibility in other bacteria. The normal susceptibility level for nalidixic acid was situated at or slightly above the MIC breakpoints proposed for Campylobacteriaceae. Ampicillin, ceftriaxone, and sulphamethoxazole-trimethoprim showed poor activity against H. pullorum. For the H. canadensis strain, a similar susceptibility pattern was seen, except for nalidixic acid and enrofloxacin, whose MIC of >512 and 8 microg/ml, respectively, indicated resistance of this agent. With spectinomycin, a bimodal distribution of the MICs was noted for the tested strains; eight H. pullorum isolates originating from one flock showed acquired resistance (MIC>512 microg/ml).
during susceptibility testing: Escherichia coli 25922, Staphylococcus au reus 25923, Brucella abortus 2308, Brucella melitensis rev- I, and Bmcel/a canis ...2011, American Society for Microbiology. All Rights Reserved. Antin1icrobial Susceptibility of Brucella melitensis Isolates in Peru 9 Ryan C. Maves,1...48 human Brucella melitensis biotype 1 strains from Peru between 2000 and 2006. MICs of isolates to doxycycline, azithromycin, gentamicin, rifampin
Abraham, Sam; Groves, Mitchell D; Trott, Darren J; Chapman, Toni A; Turner, Bernadette; Hornitzky, Michael; Jordan, David
Salmonella enterica is a zoonotic pathogen causing a variety of diseases in humans and animals. Many countries are reporting an increase in the prevalence of multidrug-resistant (MDR) S. enterica in food animals. The aim of this study was to determine whether S. enterica isolated from livestock in New South Wales, Australia, have similar resistance traits to those reported internationally. Salmonella enterica (n=165) from clinical infections in food animals between 2007 and 2011 were serotyped and tested for susceptibility to 18 antimicrobials. Also, 22 antimicrobial resistance genes (ARGs), 3 integrons and 18 plasmid replicon types were screened for using PCR. Most isolates (66.1%) remained susceptible to all antimicrobials; 8.5% of the isolates were resistant to four or more antimicrobials. Antimicrobials with the highest prevalence of resistance were sulfafurazole (28.5%), ampicillin (17.0%), tetracycline (15.8%) and trimethoprim (8.5%). There was no resistance to fluoroquinolones or third-generation cephalosporins. The most common ARGs were blaTEM (15.2%), sul2 (10.3%), tetB (9.1%), tetA (5.5%), aphA1 (4.8%) and dhfrV (4.8%). Class 1 integrons (7.9%) and IncFIIA (69.7%) were the most commonly detected integron and plasmid replicon types, respectively. Class 1 integrons were positively associated with MDR phenotypes and ARG carriage (P≤0.001). Internationally prominent MDR serovars associated with severe disease in humans (e.g. AmpC-positive Salmonella Newport) were not detected. Overall, the comparatively favourable resistance status of S. enterica in Australian livestock represents minimal public health risk associated with MDR strains and supports a conservative approach to the registration of antimicrobial drug classes in food-producing animals. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.
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
Bartie, K L; Devine, D A; Wilson, M J; Lewis, M A O
To determine the susceptibility of strains of the Streptococcus milleri group (SMG) to commercially available antimicrobial peptides. Thirty strains of SMG from a range of sources were assessed for their susceptibility to 10 antimicrobial peptides of either human, animal or insect origin, using a double layer diffusion assay. The majority of the test strains were sensitive to the amidated peptides, mastoparan (100%; n = 30), magainin 2 amide (95%; n = 21) and indolicin (91%; n = 23). Some strains were susceptible to cecropin B (30%; n = 30) and histatin (10%; n = 30), whilst no activity was observed for the defensins HNP-1 and HNP-2, histatin 8, cecropin P1 and magainin 2. The majority of strains were resistant to the human derived peptides. The ability to resist such peptides may be a factor in the colonisation of the oral cavity and the survival and initiation of infection in the pulp and root canal environment. Interestingly, the present study indicated that amidated and alpha helical peptides exhibit antimicrobial activity against SMG. Structural modification of these peptides may allow a targeted approach for the development of these substances as preventative or therapeutic agents.
Gutiérrez-Martín, César B; del Blanco, Noemí García; Blanco, Mónica; Navas, Jesús; Rodríguez-Ferri, Elías F
A total of 229 Spanish Actinobacillus pleuropneumoniae isolates recovered from diseased pigs with pleuropneumonia from 1997 to 2004 was tested for their susceptibility to 11 antimicrobials in a broth microdilution method. All the isolates were susceptible to florfenicol and most of them to cephalothin; however, a high rate of resistance was observed to tetracycline. A bimodal or multimodal distribution of isolates over the MIC range were observed for penicillins, tetracycline, trimethoprim, sulfisoxazole and nalidixic acid, suggesting the development of acquired resistance. Eight resistance patterns were established, and 21.1% of the isolates were resistant to at least two antimicrobials. In addition, a considerable increase in the resistance to tetracyclines was observed during the last decade in Spain, when compared with other A. pleuropneumoniae strains isolated during 1987-1988 (Gutiérrez, C.B., Píriz, S., Vadillo, S., Rodríguez Ferri, E.F., 1993. In vitro susceptibility of Actinobacillus pleuropneumoniae strains to 42 antimicrobial agents. Am. J. Vet. Res. 54, 546-550); this finding was also observed for gentamicin in minor percentage.
Dargatz, David A; Marshall, Katherine L; Fedorka-Cray, Paula J; Erdman, Matthew M; Kopral, Christine A
Salmonella is a major cause of foodborne illness and can cause clinical disease in animals. Understanding the on-farm ecology of Salmonella will be helpful in decreasing the risk of foodborne transmission. An objective of this study was to determine the prevalence of Salmonella among fecal samples collected on sheep operations in the United States. Another objective was to compare the use of composite fecal samples with fecal samples collected from individual sheep as a tool for screening sheep flocks for Salmonella. Sheep fecal samples (individual and composite) were collected on operations in 22 states. Salmonella isolates were characterized with regard to species, serotype, and antimicrobial susceptibility profile. Most operations (72.1%) had at least one positive sample and overall 26.9% of samples were positive. The percentage of positive samples varied by animal age class. Composite and individual samples gave similar results. The majority of the isolates (94%) were Salmonella enterica subspecies diarizonae serotype 61:-:1,5,7. Nearly all of the isolates (91.2%) tested for antimicrobial susceptibility were susceptible to all antimicrobials in the panel. The findings suggest that salmonellae typically associated with foodborne disease transmission are infrequently found on sheep operations in the United States.
Blau, D M; McCluskey, B J; Ladely, S R; Dargatz, D A; Fedorka-Cray, P J; Ferris, K E; Headrick, M L
Salmonella serotypes are important foodborne pathogens of humans that can be acquired through consumption of contaminated meat and dairy products. Salmonella infection also can be a significant animal health issue. As part of a national study of U.S. dairy operations conducted between March and September 2002, fecal samples were collected from representative cows in 97 dairy herds in 21 states and were cultured to determine the prevalence of Salmonella shedding. Salmonella was recovered from the feces of at least one cow in 30.9% of the herds. Overall, 7.3% of fecal samples were culture positive for Salmonella. The three most frequently recovered serotypes were Salmonella Meleagridis (24.1%), Salmonella Montevideo (11.9%), and Salmonella Typhimurium (9.9%). The susceptibilities of Salmonella isolates recovered were determined using a panel of 16 antimicrobial drugs. Salmonella isolates recovered from dairy cows had relatively little resistance to these antimicrobial agents; 83.0% of the isolates were susceptible to all antimicrobials tested. This study provides updated information on the prevalence and susceptibility patterns of Salmonella in dairy herds and on cow and herd characteristics. These data contribute to our understanding of the ecology of Salmonella in the dairy farm environment.
Novoa-Farías, O; Frati-Munari, A C; Peredo, M A; Flores-Juárez, S; Novoa-García, O; Galicia-Tapia, J; Romero-Carpio, C E
Bacterial resistance may hamper the antimicrobial management of acute gastroenteritis. Bacterial susceptibility to rifaximin, an antibiotic that achieves high fecal concentrations (up to 8,000μg/g), has not been evaluated in Mexico. To determine the susceptibility to rifaximin and other antimicrobial agents of enteropathogenic bacteria isolated from patients with acute gastroenteritis in Mexico. Bacterial strains were analyzed in stool samples from 1,000 patients with diagnosis of acute gastroenteritis. The susceptibility to rifaximin (RIF) was tested by microdilution (<100, <200, <400 and <800μg/ml) and susceptibility to chloramphenicol (CHL), trimethoprim-sulfamethoxazole (T-S), neomycin (NEO), furazolidone (FUR), fosfomycin (FOS), ampicillin (AMP) and ciprofloxacin (CIP) was tested by agar diffusion at the concentrations recommended by the Clinical & Laboratory Standards Institute and the American Society for Microbiology. Isolated bacteria were: enteropathogenic Escherichia coli (E. coli) (EPEC) 531, Shigella 120, non-Typhi Salmonella 117, Aeromonas spp. 80, enterotoxigenic E. coli (ETEC) 54, Yersinia enterocolitica 20, Campylobacter jejuni 20, Vibrio spp. 20, Plesiomonas shigelloides 20, and enterohemorrhagic E. coli (EHEC 0:157) 18. The overall cumulative susceptibility to RIF at <100, <200, <400, and <800μg/ml was 70.6, 90.8, 99.3, and 100%, respectively. The overall susceptibility to each antibiotic was: AMP 32.2%, T-S 53.6%, NEO 54.1%, FUR 64.7%, CIP 67.3%, CLO 73%, and FOS 81.3%. The susceptibility to RIF <400 and RIF <800μg/ml was significantly greater than with the other antibiotics (p<0.001). Resistance of enteropathogenic bacteria to various antibiotics used in gastrointestinal infections is high. Rifaximin was active against 99-100% of these enteropathogens at reachable concentrations in the intestine with the recommended dose. Copyright © 2015 Asociación Mexicana de Gastroenterología. Published by Masson Doyma México S.A. All rights reserved.
Background Though important in the context of food microbiology and as potential pathogens in immuno-compromised humans, bacterial isolates belonging to the genus Pediococcus are best known for their association with contamination of ethanol fermentation processes (beer, wine, or fuel ethanol). Use of antimicrobial compounds (e.g., hop-compounds, Penicillin) by some industries to combat Pediococcus contaminants is long-standing, yet knowledge about the resistance of pediococci to antimicrobial agents is minimal. Here we examined Pediococcus isolates to determine whether antibiotic resistance is associated with resistance to hops, presence of genes known to correlate with beer spoilage, or with ability to grow in beer. Results Lactic acid bacteria susceptibility test broth medium (LSM) used in combination with commercially available GPN3F antimicrobial susceptibility plates was an effective method for assessing antimicrobial susceptibility of Pediococcus isolates. We report the finding of Vancomycin-susceptible Pediococcus isolates from four species. Interestingly, we found that hop-resistant, beer-spoilage, and beer-spoilage gene-harbouring isolates had a tendency to be more susceptible, rather than more resistant, to antimicrobial compounds. Conclusion Our findings indicate that the mechanisms involved in conferring hop-resistance or ability to spoil beer by Pediococcus isolates are not associated with resistance to antibiotics commonly used for treatment of human infections. Also, Vancomycin-resistance was found to be isolate-specific and not intrinsic to the genus as previously believed. PMID:19735560
Sousa, E L R; Gomes, B P F A; Jacinto, R C; Zaia, A A; Ferraz, C C R
The aim of this investigation was to identify microorganisms from root canals with periapical abscesses and assess the susceptibility of specific anaerobic bacteria to selected antimicrobials and their β-lactamase production. Sixty root canals were microbiologically investigated. The susceptibility of Anaerococcus prevotii, Fusobacterium necrophorum, F. nucleatum, Parvimonas micra, and Prevotella intermedia/nigrescens to antimicrobials was evaluated with the Etest, whereas β-lactamase production was assessed with nitrocefin. A total of 287 different bacterial strains were recovered, including 201 strict anaerobes. The most frequently strict isolated anaerobes were A. prevotii, P. micra, and F. necrophorum. The selected bacteria were susceptible to all the tested antibiotics, except A. prevotii and Fusobacterium species to azithromycin and erythromycin, as well as A. prevotii and F. necrophorum to metronidazole. None of the microorganisms produced β-lactamase. Gram-positive anaerobic bacteria predominated in the root canals with periapical abscesses. All microorganisms tested were susceptible to benzylpenicillin, amoxicillin, amoxicillin + clavulanate, cefaclor, and clindamycin, producing no β-lactamase.
Moore, Catrin E.; Sona, Soeng; Poda, Sar; Putchhat, Hor; Kumar, Varun; Sopheary, Sun; Stoesser, Nicole; Bousfield, Rachel; Day, Nicholas; Parry, Christopher M.
Background: Bacterial resistance to commonly used antimicrobials is an increasing problem in Asia but information concerning the antimicrobial susceptibility of bacteria causing urinary tract infections (UTIs) in children is limited. Methods: This was a 5-year retrospective study of children with suspected UTI attending a paediatric hospital in north-west Cambodia. Urines with a positive culture containing a single organism with a count of >105 colony-forming units (CFU)/ml were considered diagnostic of infection. The organism was identified and the resistance pattern (using CLSI guidelines) and presence of an extended-spectrum β-lactamase (ESBL) phenotype was determined. Results: In total, there were 217 episodes of infection, 210 (97%) with Gram-negative bacteria. Escherichia coli was the most common infecting isolate with high levels of resistance to most oral antibiotics, except nitrofurantoin. Nearly half of the E. coli (44%) were extended-spectrum cephalosporin (ESC)-resistant with the proportion increasing significantly over the 5-year period. ESC-resistant E. coli were more likely to be multi-drug-resistant and 91% demonstrated an ESBL phenotype. Conclusion: The data highlight the importance of microbiological surveillance of UTIs in children, particularly in areas where there are known to be multiply resistant organisms. PMID:25704569
Owen, Joseph R; Noyes, Noelle; Young, Amy E; Prince, Daniel J; Blanchard, Patricia C; Lehenbauer, Terry W; Aly, Sharif S; Davis, Jessica H; O'Rourke, Sean M; Abdo, Zaid; Belk, Keith; Miller, Michael R; Morley, Paul; Van Eenennaam, Alison L
Extended laboratory culture and antimicrobial susceptibility testing timelines hinder rapid species identification and susceptibility profiling of bacterial pathogens associated with bovine respiratory disease, the most prevalent cause of cattle mortality in the United States. Whole-genome sequencing offers a culture-independent alternative to current bacterial identification methods, but requires a library of bacterial reference genomes for comparison. To contribute new bacterial genome assemblies and evaluate genetic diversity and variation in antimicrobial resistance genotypes, whole-genome sequencing was performed on bovine respiratory disease-associated bacterial isolates (Histophilus somni, Mycoplasma bovis, Mannheimia haemolytica, and Pasteurella multocida) from dairy and beef cattle. One hundred genomically distinct assemblies were added to the NCBI database, doubling the available genomic sequences for these four species. Computer-based methods identified 11 predicted antimicrobial resistance genes in three species, with none being detected in M. bovis While computer-based analysis can identify antibiotic resistance genes within whole-genome sequences (genotype), it may not predict the actual antimicrobial resistance observed in a living organism (phenotype). Antimicrobial susceptibility testing on 64 H. somni, M. haemolytica, and P. multocida isolates had an overall concordance rate between genotype and phenotypic resistance to the associated class of antimicrobials of 72.7% (P < 0.001), showing substantial discordance. Concordance rates varied greatly among different antimicrobial, antibiotic resistance gene, and bacterial species combinations. This suggests that antimicrobial susceptibility phenotypes are needed to complement genomically predicted antibiotic resistance gene genotypes to better understand how the presence of antibiotic resistance genes within a given bacterial species could potentially impact optimal bovine respiratory disease treatment
Moodley, Arshnee; Damborg, Peter; Nielsen, Søren Saxmose
Staphylococcus pseudintermedius is a commensal and a common opportunistic pathogen causing mainly infections of the integumentary system in dogs. The recent emergence of multidrug-resistant S. pseudintermedius isolates, in particular methicillin-resistant strains (MRSP) is a threat to small animal health and highlights the need for antimicrobial resistance surveillance to detect trends and potentially perform timeous interventions. We systematically reviewed 202 published articles to investigate temporal changes in antimicrobial resistance in clinical and commensal S. pseudintermedius isolated from dogs in 27 countries between 1980 and 2013. Resistance to the most common antimicrobials tested for in published studies and important for the treatment of staphylococcal infections in dogs were assessed separately for methicillin resistant (MRSP) and methicillin susceptible (MSSP) isolates. Stratified by MSSP and MRSP, no significant increases in antimicrobial resistance were observed over time, except for the penicillinase-labile penicillins (penicillin and ampicillin) among MSSP. However, in recent years, a few studies have reported higher-level of resistance to amikacin, gentamicin and enrofloxacin amongst MSSP. The review highlights inconsistencies between studies as a result of several factors, for example the use of different antimicrobial susceptibility testing methods and interpretation criteria. We recommend that data on susceptibility in important companion animal pathogens are collected and presented in a more harmonized way to allow more precise comparison of susceptibility patterns between studies. One way to accomplish this would be through systematic surveillance either at the country-level or at a larger scale across countries e.g. EU level.
Sánchez-Bautista, Antonia; Coy, Javier; García-Shimizu, Patricia; Rodríguez, Juan Carlos
Implementation of the breakpoints established in the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines in comparison with those of the Clinical and Laboratory Standards Institute (CLSI) means that the criteria for interpreting the susceptibility of some antimicrobials have been modified, resulting in changes in the reports of accumulated antibiotic susceptibility. The effect of applying EUCAST breakpoints in 10,359 clinical isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus spp. was analysed. By applying EUCAST breakpoints, most antimicrobial susceptibility percentages did not change or changed very slightly. However, a decrease in aminoglycoside susceptibility was observed in Gram-negative bacilli, mainly for amikacin and Pseudomonas aeruginosa (23.2%), although only 5.7% were completely resistant; a notably decrease in the percentage of isolates susceptible to aztreonam was also observed. There was also a marked increase in the number of Staphylococcus aureus strains resistant to clindamycin (51.5%) and aminoglycosides (gentamicin 43.1%). Switching from CLSI to EUCAST criteria in some pathogens alters the percentages of resistance to several antimicrobials, and therefore the local epidemiology of the resistance. These changes should be implemented by a multidisciplinary group in order to analyse the influence of the new data on the empirical treatment protocols of each centre. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.
Newman, Mercy J.; Addo, Kwesi K.; Addo, Phyllis
Background. The current definitive treatment of Buruli ulcer with antibiotics makes the issue of antimicrobial drug resistance an unavoidable one. This is as a result of drug misuse by health personnel and patients' noncompliance to treatment regimen. Monitoring of these factors and screening for new effective antimicrobials are crucial to effective management of Buruli ulcer disease. This study therefore investigated the inhibitory activity of some antibiotics against isolates of Mycobacterium ulcerans. Methods. Activity of eight antibiotics was tested against twelve M. ulcerans isolates (2 reference strains and 10 clinical isolates). The anti-M. ulcerans activities were determined by the agar dilution method and the minimum inhibitory concentrations (MICs) were determined by the agar proportion method. Results. All antimicrobials investigated had activity against M. ulcerans isolates tested. The MICs ranged from 0.16 μg/mL to 2.5 μg/mL. Azithromycin recorded the highest inhibitory activity at a mean MIC of 0.39 μg/mL, whilst clofazimine a second-line antileprosy drug, recorded the lowest at a mean MIC of 2.19 μg/mL. Among the four antituberculosis drugs, rifampicin had the highest activity with a mean MIC of 0.81 μg/mL. Conclusion. Azithromycin could be considered as a lucrative alternative to existing treatment methods for inhibiting M. ulcerans in Ghana. PMID:28392809
Baron, Sandrine; Granier, Sophie A.; Larvor, Emeline; Jouy, Eric; Cineux, Maelan; Wilhelm, Amandine; Gassilloud, Benoit; Le Bouquin, Sophie; Kempf, Isabelle; Chauvin, Claire
The importance of the role of environment in the dissemination of antimicrobial resistant bacteria is now well recognized. Thus, bacterial indicators to monitor the phenomena are required. The Aeromonas genus is autochthonous in the aquatic environment and easy to detect in any water type, such as freshwater, or wastewater. These microorganisms are also causing infections in humans and animals (including fish). Furthermore, as Aeromonas spp. is able to acquire antimicrobial resistance mechanisms, it is candidate for indicator bacteria to follow antimicrobial resistance dissemination in aquatic environments. Unfortunately, to date, interpretation criteria for Aeromonas spp. for antimicrobial susceptibility tests are scarce in the literature. No epidemiological cut-off values for Aeromonas are currently available at EUCAST to interpret Minimum Inhibitory Concentrations (MIC). The only interpretation criteria available are clinical breakpoints from CLSI that are adapted from Enterobacteriaceae. Based on the results of MIC distributions obtained for a collection of environmental isolates of Aeromonas, this study aimed at proposing tentative epidemiological cut-off values (COWT) for Aeromonas spp. assessing whether the genus is an acceptable level of definition. Thus, 233 isolates collected from 16 rivers were identified at species level using Maldi-Tof (Bruker). Eleven different species were identified, the most abundant were A. bestiarum (n = 54), A. salmonicida (n = 45), A. sobria (n = 41), and A. eucrenophila (n = 37). 96-well micro-plates containing different concentrations of 15 antimicrobials, namely cefotaxime, ceftazidime, chloramphenicol, colistin, enrofloxacin, erythromycin, florfenicol, flumequine, gentamicin, nalidixic acid, oxolinic acid, streptomycin, temocillin, tetracycline, and trimethoprim-sulfamethoxazole, were prepared. The broth micro-dilution method was used to determine the antimicrobial susceptibility of each isolate. The estimation of COWT
Hashemi-Shahraki, Abodolrazagh; Heidarieh, Parvin; Bostanabad, Saeed Zaker; Hashemzadeh, Mohamad; Feizabadi, Mohamad Mehdi; Schraufnagel, Dean; Mirsaeidi, Mehdi
The aim of this multicenter study was to determine the genetic diversity and antibiotic susceptibility of clinically isolated Nocardia species. One hundred twenty-seven patients with nocardiosis were randomly selected from 5 provinces of Iran. Molecular diagnosis of Nocardia species was performed using multilocus sequence analysis of gyrase B of the β subunit of DNA topoisomerase (gyrB), and 16S rRNA and subunit A of SecA preproteintranslocase (secA1). Antimicrobial susceptibility testing was performed following the Clinical and Laboratory Standards Institute recommendations. Thirty-five N. cyriacigeorgica, 30 N. asteroides, 26 N. farcinica, 12 N. otitidiscaviarum, and 10 N. abscessus cultures were studied. All isolates were susceptible to linezolid. All isolates of N. cyriacigeorgica, N. asteroides, N. abscessus, and N. otitidiscaviarum were susceptible to trimethoprim-sulfamethoxazole, while 8% of N. farcinica isolates were resistant to this drug. All N. otitidiscaviarum isolates were highly resistant to imipenem, but N. cyriacigeorgica, N. asteroides, N. farcinica, and N. abscessus were only moderate resistant. The susceptibility patterns vary with different species of Nocardia. Resistance to trimethoprim-sulfamethoxazole in Iran is low and this drug should be first line therapy, unless drug susceptibility testing shows resistance. Linezolid also covers Nocardia well and could be a second line agent.
Jung, Jette S; Hamacher, Christina; Gross, Birgit; Sparbier, Katrin; Lange, Christoph; Kostrzewa, Markus; Schubert, Sören
With the increasing prevalence of multidrug-resistant Gram-negative bacteria, rapid identification of the pathogen and its individual antibiotic resistance is crucial to ensure adequate antiinfective treatment at the earliest time point. Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry for the identification of bacteria directly from the blood culture bottle has been widely established; however, there is still an urgent need for new methods that permit rapid resistance testing. Recently, a semiquantitative MALDI-TOF mass spectrometry-based method for the prediction of antibiotic resistance was described. We evaluated this method for detecting nonsusceptibility against two β-lactam and two non-β-lactam antibiotics. A collection of 30 spiked blood cultures was tested for nonsusceptibility against gentamicin and ciprofloxacin. Furthermore, 99 patient-derived blood cultures were tested for nonsusceptibility against cefotaxime, piperacillin-tazobactam, and ciprofloxacin in parallel with MALDI-TOF mass spectrometry identification from the blood culture fluid. The assay correctly classified all isolates tested for nonsusceptibility against gentamicin and cefotaxime. One misclassification for ciprofloxacin nonsusceptibility and five misclassifications for piperacillin-tazobactam nonsusceptibility occurred. Identification of the bacterium and prediction of nonsusceptibility was possible within approximately 4 h.
El-Adawy, Hosny; Ahmed, Marwa F E; Hotzel, Helmut; Tomaso, Herbert; Tenhagen, Bernd-Alois; Hartung, Joerg; Neubauer, Heinrich; Hafez, Hafez M
The popularity of food produced from animals kept under an organic regimen has increased in recent years. In Germany, turkey meat consumption has increased. Despite several studies assessing the susceptibility of campylobacters to various antibiotics in poultry, no sufficient data exists regarding the antimicrobial resistance of campylobacters in organic-reared turkeys. This study provides information about antibiotic resistance in Campylobacter isolated from turkeys reared on organic farms in Germany. Ninety-six Campylobacter strains (41 C. jejuni and 55 C. coli) were isolated from different free-range turkey flocks. In vitro antimicrobial sensitivity testing was done using a broth microdilution test, and the presence of resistance genes to antibiotics (ciprofloxacin, tetracycline) was investigated. All Campylobacter isolates from organic turkeys (n = 96) were phenotypically sensitive to gentamicin, erythromycin, streptomycin, and chloramphenicol. In this study, the antibiotic susceptibilities of C. jejuni to ciprofloxacin, tetracycline, and naladixic acid were 56.0%, 51.3%, and 56.0%, respectively. In contrast, 44.0%, 73.0%, and 74.6% of C. coli isolates were resistant to tetracycline, ciprofloxacin, and nalidixic acid, respectively. Replacement of the Thr-86→Ile in the gyrA gene, and the presence of the tet(O) gene were the mainly identified resistance mechanisms against fluoroquinolones and tetracycline, respectively.These results also reinforce the need to develop strategies and implement specific control procedures to reduce the development of antimicrobial resistance.
Tassew, Haimanot; Asrat, Daniel
Introduction. Campylobacter is one of the leading bacterial causes of food-borne disease. The prevalence of Campylobacter species resistant to antimicrobial agents is increasing. This study is intended to determine prevalence and antimicrobial susceptibility patterns of Campylobacter species among under-five children with diarrhea. Methodology. A cross-sectional study was conducted among 227 under-five children with diarrhea from July to October 2012 at Jimma town. Isolation and identification of Campylobacter species were performed using standard bacteriological techniques. Antimicrobial susceptibility test was performed following standard protocol. Chi-square and Fisher's exact tests were used for analysis. Results. From 227 under-five children, 16.7% were positive for Campylobacter spp.; isolates, C. jejuni, C. coli, and C. lari, accounted for 71.1%, 21.1%, and 7.9%, respectively. Higher rate of resistance was observed to ampicillin 76.3%, trimethoprim-sulfamethoxazole (68.4%), tetracycline (39.5%), chloramphenicol (31.6%), clindamycin (26.3%), and doxycycline (23.7%). Erythromycin, ciprofloxacin, gentamicin, norfloxacin, and nalidixic acid were effective for more than 80% of the isolates. Multiple drug resistance was observed among 78.9% of all the three spp. Conclusions. Isolation rate of Campylobacter spp. was high. C. lari was reported for the first time at this study area. Higher rate of resistance was observed to the commonly used drugs. PMID:26904735
Jansson, Désirée S; Pringle, Märit
In vitro antimicrobial susceptibility to tylosin, valnemulin, tiamulin, doxycycline, lincomycin and ampicillin was investigated by broth dilution in 48 Brachyspira spp. isolates from commercial laying hens (n=30) and free-living wild mallards (Anas platyrhynchos) (n=18). Presumed pathogens (Brachyspira alvinipulli, Brachyspira intermedia, Brachyspira pilosicoli), commensals (Brachyspira murdochii, Brachyspira innocens, "Brachyspira pulli"), and isolates of undetermined species affiliation were included. The laying hens had not been exposed to therapeutic levels of antimicrobials for at least 50 weeks before sampling, and low levels of environmental antimicrobial exposure were presumed in mallards. No isolates with decreased susceptibility to tylosin, valnemulin, tiamulin or doxycycline were found. Decreased susceptibility to lincomycin (minimum inhibitory concentration 16 µg/ml) was detected in two isolates (Brachyspira sp.) from laying hens. Five isolates showed decreased susceptibility to ampicillin (minimum inhibitory concentration 16 to >32 µg/ml), including two "B. pulli" and one B. alvinipulli from laying hens, and isolates of B. pilosicoli and "B. pulli" from mallards. Decreased susceptibility to ampicillin was associated with β-lactamase activity in four isolates. A new variant of a class D β-lactamase gene designated bla (oxa-192) was identified in a B. pilosicoli isolate of mallard origin. This is the first time the genetic basis for antimicrobial resistance is described in Brachyspira spp. from a free-living wild bird. Isolates displaying decreased susceptibility to ampicillin were accompanied by fully susceptible isolates of the same species or other genotypes within three laying hen flocks. This underlines the need for performing antimicrobial susceptibility tests on single clones/genotypes, and to analyse multiple isolates from the same flock.
Riesenberg, Anne; Kaspar, Heike; Feßler, Andrea T; Werckenthin, Christiane; Schwarz, Stefan
Due to the importance of antimicrobial susceptibility testing (AST) for veterinary diagnostics, a standardised protocol for AST of Rhodococcus equi by broth microdilution has recently been developed and approved by the Clinical and Laboratory Standards Institute (CLSI). The aim of the present study was to test this protocol in an interlaboratory comparative study for its fitness for use in routine laboratory diagnostics. All of the 18 participating laboratories determined the minimum inhibitory concentrations (MIC) of two R. equi strains against 24 antimicrobial agents. The modal MIC values were determined and the acceptable ranges were set as the modal MIC ±1 dilution step. The R. equi field strain Rh110 showed a slightly better performance than the type strain R. equi ATCC(®) 25729. For the different antimicrobial agents tested, the percentage of MIC values within the acceptable ranges varied from 75.9 to 100% for R. equi ATCC(®) 25729, and from 85.2 to 100% for R. equi Rh110. The most homogeneous MIC results (i.e. modal MIC ±1 dilution step) were obtained for oxacillin and vancomycin, while the most divergent results were seen with cefotaxime and ceftiofur. Using a success rate of at least 80% of the strain-specific MICs being within the acceptable ranges as an arbitrary cut-off, only one of the participating laboratories failed to reach this cut-off value for one of the two R. equi strains. Thus, we consider the new protocol fit for use in routine AST of R. equi. Copyright © 2015 Elsevier B.V. All rights reserved.
Project #OPE-FY16-0001, August 26, 2015. The OIG’s objective is to determine whether the Antimicrobial Testing Program ensures the efficacy of EPA-registered hospital sterilants, disinfectants and tuberculocides.
Soares, Taíssa Cook Siqueira; Paes, Antonio Carlos; Megid, Jane; Ribolla, Paulo Eduardo Martins; Paduan, Karina dos Santos; Gottschalk, Marcelo
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
Deiss, Frédérique; Funes-Huacca, Maribel E; Bal, Jasmin; Tjhung, Katrina F; Derda, Ratmir
To detect antibiotic-resistant bacteria in areas remote from microbiology laboratories, we designed portable culture devices performing an analogue of the Kirby-Bauer disk diffusion test inside patterned papers embedded in tape. We quantified the antibiotic susceptibility of several strains of Escherichia coli and Salmonella typhimurium by measuring blue-colored zones of inhibited growth.
van Hout, Jobke; Heuvelink, Annet; Gonggrijp, Maaike
The objective of the present study was to analyse the in vitro antimicrobial susceptibility of Streptococcus suis isolates from post-mortem samples from pigs in the Netherlands. S. suis isolates originated from diagnostic submissions of pigs sent to the Pathology Department of GD Animal Health, from April 2013 till June 2015. Minimal inhibitory concentrations (MICs) of in total 15 antimicrobials were assessed by broth microdilution following CLSI recommendations. MIC50 and MIC90 values were determined and MICs were interpreted as susceptible, intermediate and resistant using CLSI veterinary breakpoints (when available). Emergence of resistance among S. suis (n=1163) derived from clinical submissions of pigs appeared to be limited. Resistance to ampicillin, ceftiofur, clindamycin, enrofloxacin, florfenicol, penicillin, trimethoprim/sulfamethoxazole and tetracycline was 0.3%, 0.5%, 48.1%, 0.6%, 0.1%, 0.5%, 3.0%, and 78.4%, respectively. Cross-resistance between penicillin and ampicillin appeared to be incomplete. MIC values of erythromycin, clindamycin, neomycin, penicillin and tilmicosin for isolates originating from grower/finisher pigs were significantly more often lower than the MIC values of isolates from suckling/weaned piglets. It has to be kept in mind that these results represent only part of the Dutch pig population and it can be discussed whether this is a representative sample. Interpretation of the MIC results of (clinically relevant) antimicrobials tested for treatment of S. suis infection is strongly hampered by the lack of CLSI-defined veterinary clinical breakpoints that are animal species- and body site-specific. Therefore, and to conduct a clinically reliable monitoring of antimicrobial susceptibility of veterinary pathogens, more species- and organ-specific veterinary breakpoints are urgently needed.
Zhang, Sean X; Rawte, Prasad; Brown, Shirley; Lo, Steven; Siebert, Heather; Pong-Porter, Sylvia; Low, Donald E; Jamieson, Frances B
Both the CLSI agar dilution method and Trek Sensititre broth microdilution panel for Streptococcus pneumoniae antimicrobial susceptibility testing were evaluated against the reference CLSI broth microdilution method using the most recently published CLSI breakpoints. While agar dilution was not an optimal method, the commercial panel appeared to be an acceptable method, with minor errors encountered for ceftriaxone, penicillin, and meropenem.
Picciolo, G. L.; Chappelle, E. W.; Deming, J. W.; Shrock, C. G.; Vellend, H.; Barza, M. J.; Weinstein, L. (Inventor)
A method is described for the quick determination of the susceptibilities of various unidentified bacteria contained in an aqueous physiological fluid sample, particularly urine, to one or more antibiotics. A bacterial adenosine triphosphate (ATP) assay is carried out after the elimination of non-bacterial ATP to determine whether an infection exists. If an infection does exist, a portion of the sample is further processed, including subjecting parts of the portion to one or more antibiotics. Growth of the bacteria in the parts are determined, again by an ATP assay, to determine whether the unidentified bacteria in the sample are susceptible to the antibiotic or antibiotics under test.
Di Giulio, Mara; Di Campli, Emanuela; Di Bartolomeo, Soraya; Cataldi, Valentina; Marzio, Leonardo; Grossi, Laurino; Ciccaglione, Antonio Francesco; Nostro, Antonia; Cellini, Luigina
Helicobacter pylori expresses an increased resistance in respect to antimicrobials currently used in therapy. The aim of this study was to evaluate the antimicrobial profiles of H. pylori isolates to nine conventional antibiotics used in a Central Region (Abruzzo) of Italy. Biopsies were taken from antrum and fundus of 112 adult and 3 children with Urea Breath Test positive with dyspeptic symptoms and analyzed for H. pylori culture and antibacterial activity. Antimicrobial susceptibility tests were performed for clarithromycin, metronidazole, levofloxacin, moxifloxacin, ciprofloxacin, tetracycline, amoxicillin, ampicillin, and rifabutin by a modified agar dilution susceptibility test. Bacterial culture was successful in 100 out of 115 patients. Helicobacter pylori strains were isolated from 98 antrum and 83 fundus samples. The rate of recovery of H. pylori strains was 90.50% (181/200). The percentages of resistance were as follows: clarithromycin 72.44% antrum, 72.28% fundus; metronidazole 34.69% antrum, 42.16% fundus; levofloxacin 42.85% antrum, 53.01% fundus; moxifloxacin 37.35% antrum, 46.57% fundus; ciprofloxacin 39.47% antrum, 44.28% fundus; tetracycline 2.63% antrum, 2.85% fundus; amoxicillin 1.02% antrum, 1.20% fundus; ampicillin 0% antrum and fundus and rifabutin 0% antrum, 1.20% fundus. A total of 35 subjects harbored multi-resistant strains. This study underlines the high rate of resistance to clarithromycin, metronidazole and quinolones, which may reflect an overuse of them. Culture and susceptibility test, should be performed to prevent the emergence of multi-resistance and to assess an efficacious regimen.
Aarestrup, Frank M; Hasman, Henrik
A total of 569 different bacterial isolates (156 Salmonella, 202 E. coli, 43 S. aureus, 38 S. hyicus, 52 E. faecalis, 78 E. faecium) were tested for susceptibility to copper sulphate, benzalkonium chloride, hydrogen peroxide and chlorhexidine using MIC determinations. A total of 442 isolates were also tested for susceptibility to formaldehyde and 177 isolates for susceptibility to zinc chloride. Enterococcal isolates formed a bimodal distribution of MICs to copper sulphate, whereas the other bacterial species formed one large population. Otherwise the isolates formed one large population of susceptibilities to the different antimicrobial agents. Large variations were observed in the susceptibility of the different bacterial species to the different compounds. Staphylococci were in general very susceptible to all antimicrobial compounds tested. The Salmonella isolates were in general less susceptible to copper sulphate, benzalkonium chloride and chlorhexidine followed by E. coli and the Gram-positive species. The opposite was the case for zinc chloride. All isolates were very susceptible to H(2)O(2) with MICs ranging from 0.002 to 0.016%, and to formaldehyde with MICs at 0.003 and 0.006%. This study showed that Danish bacterial isolates from livestock so far have not or have only to a limited degree developed resistance to antimicrobial compounds commonly used for disinfection. Acquired copper resistance was only found in enterococci. There were large differences in the intrinsic susceptibility of the different bacterial species to these compounds, and Salmonella especially seems intrinsically less susceptible than the other bacterial species, which might have human health implications.
Medleau, L; Long, R E; Brown, J; Miller, W H
Specimens obtained from pyogenic skin lesions of 210 dogs were culturally examined for staphylococci. A total of 215 isolates of staphylococci were biotyped, using the biochemical tests contained in a commercial staphylococcal identification system. Of 201 coagulase-positive isolates, 197 were identified as Staphylococcus intermedius, 3 as S aureus, and 1 as S hyicus. Of 14 coagulase-negative isolates, 5 were identified as S epidermidis, 5 as S xylosus, 3 as S simulans, and 1 as S hominis. Antimicrobial susceptibility tests were done on all staphylococcal isolates, using the standard disk-diffusion method. Staphylococcus intermedius isolates were susceptible to cephalothin, methicillin, and gentamicin. Resistance to ampicillin, penicillin G, and tetracycline was frequent. Antibiotic resistance was not associated with the depth of skin infection. Resistance to ampicillin, penicillin, tetracycline, and trimethoprim-sulfamethoxazole was not associated with previous antibiotic use. Increased resistance to chloramphenicol, clindamycin, and erythromycin was associated with previous antibiotic therapy. Antimicrobial susceptibilities of the other Staphylococcus species isolated are reported, but the small numbers of these species precluded making meaningful comparison with S intermedius.
Geornaras, I; von Holy, A
The broth microdilution method was used to determine the activities of selected antimicrobial agents used in the South African poultry industry (danofloxacin, neomycin, chlortetracycline, oxytetracycline, tylosin and colistin) and vancomycin against bacterial isolates previously obtained from carcasses and selected equipment surfaces and environmental sources associated with poultry processing. The antimicrobial susceptibilities of 38 isolates of Staphylococcus (S.) aureus, 25 Listeria (L.) innocua, 18 L. monocytogenes, and 62 isolates belonging to six Salmonella (Salm.) serotypes (Salm. agona, Salm. blockley, Salm. enteritidis, Salm. isangi, Salm. reading and Salm. typhimurium) were determined. The most active antimicrobial agent against all the isolates tested was danofloxacin with minimum inhibitory concentrations (MICs) for 90% of the isolates (MIC90) not exceeding 0.25 and 2 microg/ml for gram-negative and gram-positive isolates, respectively. Conversely, high MICs were recorded for all the isolates tested against chlortetracycline and oxytetracycline (MIC90 range of 32 to > 512 microg/ml), except for the L. monocytogenes and Salm. enteritidis isolates (MIC range of < or = 0.5-4 microg/ml). Neomycin was found to be active against S. aureus, L. innocua, L. monocytogenes, Salm. enteritidis and Salm. isangi isolates, with MICs not exceeding 8 microg/ml. MIC ranges for tylosin and vancomycin, which were only tested against the gram-positive isolates, were from 1 to > 512 microg/ml and from 1 to 4 microg/ml, respectively. The MIC range for the remaining antimicrobial agent, colistin, which was only tested against the Salmonella isolates, was 0.5-16 microg/ml. The lack of MIC breakpoints for the antimicrobial agents used in the poultry industry did not allow for definite conclusions as to the level of resistant bacteria associated with poultry carcasses and the processing environment in this study.
McBain, Andrew J.; Ledder, Ruth G.; Moore, Louise E.; Catrenich, Carl E.; Gilbert, Peter
Quaternary ammonium compounds (QACs) are widely used as adjuncts to hygiene in domestic cleaning products. Current concern that the increased use of such biocides in consumer products might contribute to the emergence of antibiotic resistance has led us to examine the effects of a QAC-containing domestic cleaning fluid on the population dynamics and antimicrobial susceptibility of domestic sink drain biofilm communities. QAC susceptibilities of numerically dominant, culturable drain bacteria (15 genera, 17 species) were determined in vitro before and after repeated QAC exposure (14 passages). A fully characterized drain microcosm was then exposed to short-term (12 days) and long-term (3 months) dosing with a QAC-containing domestic detergent (QD). QAC exposure of isolated cultures caused both increases (three species) and circa twofold decreases (six species) in QAC susceptibility. The susceptibility of Ralstonia sp. was considerably decreased following 14 consecutive QAC passages. Control drain microcosm biofilms maintained dynamic stability, as evidenced by culture and denaturing gradient gel electrophoresis (DGGE) analysis. Bacterial population densities were largely unaffected during short-term exposure to use levels of QD, although 50% QD caused circa 10-fold viability reductions. DGGE analysis supported these observations; identified the major microcosm genera as Pseudomonas, Pseudoalteromonas, Erwinia, and Enterobacter, and showed that aeromonads increased in abundance under 10 to 50% QD. Long-term exposure of the microcosms to QD did not significantly alter the pattern of antimicrobial susceptibility. These data demonstrate the recalcitrance of domestic drain biofilms toward QAC and that although repeated QAC exposure of drain isolates in pure culture results in susceptibility change in some test bacteria, such changes do not necessarily occur within complex communities. PMID:15184143
Savage, Rachel D.; Fowler, Robert A.; Rishu, Asgar H.; Bagshaw, Sean M.; Cook, Deborah; Dodek, Peter; Hall, Richard; Kumar, Anand; Lamontagne, François; Lauzier, François; Marshall, John; Martin, Claudio M.; McIntyre, Lauralyn; Muscedere, John; Reynolds, Steven; Stelfox, Henry T.; Daneman, Nick
Background: Surveillance of antimicrobial resistance is vital to guiding empirical treatment of infections. Collating and reporting routine data on clinical isolate testing may offer more timely information about resistance patterns than traditional surveillance network methods. Methods: Using routine microbiology testing data collected from the Bacteremia Antibiotic Length Actually Needed for Clinical Effectiveness retrospective cohort study, we conducted a descriptive secondary analysis among critically ill patients in whom bloodstream infections had been diagnosed in 14 intensive care units (ICUs) in Canada. The participating sites were located within tertiary care teaching hospitals and represented 6 provinces and 10 cities. More than 80% of the study population was accrued from 2011-2013. We assessed the epidemiologic features of the infections and corresponding antimicrobial susceptibility profiles. Susceptibility testing was done according to Clinical Laboratory Standards Institute guidelines at accredited laboratories. Results: A total of 1416 pathogens were isolated from 1202 patients. The most common organisms were Escherichia coli (217 isolates [15.3%]), Staphylococcus aureus (175 [12.4%]), coagulase-negative staphylococci (117 [8.3%]), Klebsiella pneumoniae (86 [6.1%]) and Streptococcus pneumoniae (85 [6.0%]). The contribution of individual pathogens varied by site. For 13 ICUs, gram-negative susceptibility rates were high for carbapenems (95.4%), tobramycin (91.2%) and piperacillin-tazobactam (90.0%); however, the proportion of specimens susceptible to these agents ranged from 75.0%-100%, 66.7%-100% and 75.0%-100%, respectively, across sites. Fewer gram-negative bacteria were susceptible to fluoroquinolones (84.5% [range 64.1%-97.2%]). A total of 145 patients (12.1%) had infections caused by highly resistant microorganisms, with significant intersite variation (range 2.6%-24.0%, χ2 = 57.50, p < 0.001). Interpretation: We assessed the epidemiologic
Silva, Sanrrangers Sales; Ribeiro, Maximilo de Oliveira; Gomes, Francisco Isaac Fernandes; Chaves, Hellíada Vasconcelos; Silva, Antonio Alfredo Rodrigues e; Zanin, Iriana Carla Junqueira; Barbosa, Francisco Cesar Barroso
ABSTRACT Aspiration of oral bacteria leads to cardiac and respiratory infectious diseases and dentures can act as a reservoir for pathogenic microorganisms. Objective: To determine the occurrence and the in vitro antimicrobial susceptibility of enteric rods and pseudomonads from the denture biofilm of 52 subjects at the Center for Dental Specialties of Sobral/ Ceara, Brazil. Material and Methods: Denture biofilm was collected and samples plated on MacConkey agar. The isolated bacterial colonies were identified using the BBL Crystal enteric/non-fermenter system. Antibiotic bacterial susceptibility was assessed by the disc diffusion method of amoxicillin, amoxicillin/clavulanic acid, doxycycline, tetracycline, tobramycin, imipenem, cefotaxime, and ciprofloxacin. The Minimum Inhibitory Concentration (MIC) of cefotaxime, tobramycin, doxycycline, imipenem, and ciprofloxacin was determined for 40 species by E-test. Results: 34 subjects (65.4%) harbored enteric rods in their prostheses. Klebsiella pneumoniae (26.5%), Escherichia coli (23.5%), and Enterobacter aerogenes (23.5%) were the most prevalent species. All organisms were susceptible to ciprofloxacin and most species were resistant to amoxicillin or amoxicillin/clavulanic acid, demonstrating variable sensitivity patterns to other antimicrobials. However, the MIC showed the emergence of strains with reduced sensitivity to ciprofloxacin (MIC90≥3 μg/ mL) and cefotaxime (MIC90≥2 μg/mL). Conclusion: The findings show high prevalence of nosocomial diseases-related bacterial species and low susceptibility to antimicrobial drugs. Therefore, these results imply caution against the indiscriminate use of broad spectrum antibiotics in dental practice. PMID:27812616
Otth, Laura; Wilson, Myra; Fernández, Heriberto; Otth, Carola; Toledo, Claudio; Cárcamo, Victoria; Rivera, Paula; Ruiz, Luis
Helicobacter pylori colonizes more than 50% of the world population thus, it is considered an important cause of gastric cancer. The aim of this study was to determine the isolation frequency of H. pylori in Southern Chile from patients with symptomatology compatible with gastritis or gastric ulcer and to correlate these findings with demographic parameters of infected patients and the susceptibility profiles of the isolated strains to the antimicrobial drugs used in the eradication treatments. A total of 240 patients were enrolled in the study. Each gastric biopsy was homogenized and seeded onto blood agar plates containing a selective antibiotics mixture (DENT supplement). Plates were incubated at 37° C in a microaerophilic environment for five days. The susceptibility profiles to amoxicillin, ciprofloxacin, clarithromycin, tetracycline and metronidazole were determined using the E-test method. H. pylori was isolated from 99 patients (41.3%) with slightly higher frequency in female (42% positive cultures) than male (40.2% positive cultures). With regard to age and educational level, the highest isolation frequencies were obtained in patients between 21–30 (55%) and 41–50 (52.6%) years old, and patients with secondary (43.9%) and university (46.2%) educational levels. Nineteen (21.6%) strains showed resistance to at least one antimicrobial drug. Tetracycline was the most active antimicrobial in vitro, whereas metronidazole was the less active. One strain (5.3%) showed resistance to amoxicillin, clarithomycin and metronidazole, simultaneously. PMID:24031652
Couto, Natacha; Belas, Adriana; Tilley, Paula; Couto, Isabel; Gama, Luís T; Kadlec, Kristina; Schwarz, Stefan; Pomba, Constança
The aim of this study was to evaluate the biocide and antimicrobial susceptibility of methicillin-resistant staphylococcal isolates from horses. Fourteen methicillin-resistant staphylococci (MRS) were subjected to an extensive genotype characterization, including SCCmec, dru, spa, PFGE and MLST typing. Antimicrobial susceptibility testing was performed and resistance genes were detected by PCR. Minimum bactericidal concentrations (MBCs) of four biocides [chlorhexidine acetate (CHA), benzalkonium chloride (BAC), triclosan (TCL) and glutaraldehyde (GLA)] were determined following the recommendations of document NF EN 1040. The presence of qac and sh-fabI genes was investigated by PCR. Several antimicrobial resistance patterns and genes were detected. When MRS strains were exposed for a longer period of time, a lower concentration of the biocide was needed to achieve lethality. TCL had the lowest MBC values. All MBC values were lower than the recommended in-use concentrations for veterinary medicine. S. haemolyticus and S. cohnii subsp. cohnii carried plasmid-borne qacA and sh-fabI or qacB and a qacH-like genes, respectively. Biocides appear to be a reliable antiseptic option against MRS, since even in the presence of bacterial efflux mechanisms, the recommended concentration is much higher than the in vitro MBC.
Rodriguez-Rivera, Lorraine D; Cummings, Kevin J; Loneragan, Guy H; Rankin, Shelley C; Hanson, Devin L; Leone, William M; Edrington, Thomas S
Dairy cattle are a reservoir of several Salmonella serovars that are leading causes of human salmonellosis. The objectives of this study were to estimate the environmental prevalence of Salmonella on dairy farms in Texas and to characterize the antimicrobial susceptibility of the isolates. Eleven dairy farms throughout Texas were sampled from August through October 2013, using a cross-sectional approach. Samples were collected from four locations within each farm (hospital pen, maternity pen, cow housing area, and calf housing area), and feces were collected from cull cows as available. Environmental and fecal samples were processed for Salmonella, and isolates were tested for susceptibility to 15 antimicrobial agents. Serovar characterization was performed on a subset of these isolates. Salmonella was isolated from 67.0% (236/352) of the environmental samples and 64.2% (43/67) of the cull cow fecal samples. Environmental samples from the maternity pen were significantly more likely to be Salmonella positive than samples from the cow and calf housing areas. Multidrug resistance was evident in 11.9% (27/226) of environmental isolates and 19.5% (8/41) of fecal isolates. Salmonella isolates from the calf housing area and maternity pen were significantly more likely to be multidrug resistant (MDR) than isolates from the cow housing area. The most common serovars found among the MDR isolates were Newport, Muenchen, and Typhimurium. These results help provide a focus for efforts to mitigate the burden of antimicrobial-resistant Salmonella at the preharvest level.
Otth, Laura; Wilson, Myra; Fernández, Heriberto; Otth, Carola; Toledo, Claudio; Cárcamo, Victoria; Rivera, Paula; Ruiz, Luis
Helicobacter pylori colonizes more than 50% of the world population thus, it is considered an important cause of gastric cancer. The aim of this study was to determine the isolation frequency of H. pylori in Southern Chile from patients with symptomatology compatible with gastritis or gastric ulcer and to correlate these findings with demographic parameters of infected patients and the susceptibility profiles of the isolated strains to the antimicrobial drugs used in the eradication treatments. A total of 240 patients were enrolled in the study. Each gastric biopsy was homogenized and seeded onto blood agar plates containing a selective antibiotics mixture (DENT supplement). Plates were incubated at 37° C in a microaerophilic environment for five days. The susceptibility profiles to amoxicillin, ciprofloxacin, clarithromycin, tetracycline and metronidazole were determined using the E-test method. H. pylori was isolated from 99 patients (41.3%) with slightly higher frequency in female (42% positive cultures) than male (40.2% positive cultures). With regard to age and educational level, the highest isolation frequencies were obtained in patients between 21-30 (55%) and 41-50 (52.6%) years old, and patients with secondary (43.9%) and university (46.2%) educational levels. Nineteen (21.6%) strains showed resistance to at least one antimicrobial drug. Tetracycline was the most active antimicrobial in vitro, whereas metronidazole was the less active. One strain (5.3%) showed resistance to amoxicillin, clarithomycin and metronidazole, simultaneously.
Bandelj, P; Golob, M; Ocepek, M; Zdovc, I; Vengust, M
A significant risk factor for developing Clostridium difficile infection (CDI) in humans and animals is associated with the antimicrobial use. It has often been hypothesized that farm animals could be the source for human infection with Clostridium difficile (CD). In the European Union, family-run dairy farms are the predominant farming model, which are more interlinked within the community compared to large-scale intensive dairy or beef farms. Therefore, it is important to investigate antimicrobial susceptibility patterns of CD in such environment. A total of 159 CD isolates from 20 family dairy farms were tested with a customized broth microdilution plate for their antimicrobial resistance. Seventeen antimicrobials were selected (amoxicillin, ceftriaxone, clindamycin, daptomycin, erythromycin, fusidic acid, imipenem, levofloxacin, linezolid, metronidazole, moxifloxacin, oxacillin, rifampicin, tetracycline, tigecycline, trimethoprim/sulfamethoxazole and vancomycin), which are commonly used for treatment of CDI in veterinary and human medicine, or were previously applied in CD epidemiological studies. Antimicrobials, which are used for treatment of CDI in humans (metronidazole, vancomycin, fusidic acid, tigecycline, linezolid) inhibited CD growth in vitro. Most CD isolates were resistant to erythromycin (93.1%), daptomycin (69.2%) and clindamycin (46.5%). High multiple-resistance was found in CD ribotype 012 (n = 5, 100%), some CD SLO 060 (n = 4, 25%) and one CD 033 (n = 1, 1.1%). High multiple-resistance in this study was linked with CD ribotypes and not with the origin of CD. The low prevalence of these ribotypes (6.3%; 10/159) indicates that family-run dairy farms are an unlikely source of CD with multiple-resistance to antimicrobials.
Piriz, S; Cuenca, R; Valle, J; Vadillo, S
The agar dilution method was used to determine the inhibitory activities of 28 antimicrobial agents against 35 strains of the genus Peptostreptococcus, 4 strains of the species Peptococcus niger, 20 strains of the species Megasphaera elsdenii, 7 strains from the species Acidaminococcus fermentans, 8 strains of the genus Clostridium, 11 strains of the genus Eubacterium, and 1 strain of the species Propionibacterium acidipropionici, all of which were isolated from 125 clinical cases of ovine foot rot between January 1987 and December 1988. The three unreidopenicillins studied proved to be the most active antimicrobial agents, with a high percentage of strains being susceptible at a concentration of 64 micrograms/ml. Penicillin G, ampicillin, and the three cephalosporins studied also had good activity. Fosfomycin showed a high degree of activity among the 116 anaerobic bacteria tested. PMID:1590689
Paterna, A; Tatay-Dualde, J; Amores, J; Prats-van der Ham, M; Sánchez, A; de la Fe, C; Contreras, A; Corrales, J C; Gómez-Martín, Á
The minimum inhibitory concentration (MIC) and minimum mycoplasmacidal concentration (MMC) of 17 antimicrobials against 41 Spanish caprine isolates of Mycoplasma mycoides subsp. capri (Mmc) obtained from different specimens (milk, external auricular canal and semen) were determined using a liquid microdilution method. For half of the isolates, the MIC was also estimated for seven of the antimicrobials using an epsilometric test (ET), in order to compare both methods and assess the validity of ET. Mutations in genes gyrA, gyrB, parC and parE conferring fluoroquinolone resistance, which have been recently described in Mmc, were investigated using PCR. The anatomical origin of the isolate had no effect on its antimicrobial susceptibility. Moxifloxacin and doxycycline had the lowest MIC values. The rest of the fluoroquinolones studied (except norfloxacin), together with tylosin and clindamycin, also had low MIC values, although the MMC obtained for clindamycin was higher than for the other antimicrobials. For all the aminoglycosides, spiramycin and erythromycin, a notable level of resistance was observed. The ET was in close agreement with broth microdilution at low MICs, but not at intermediate or high MICs. The analysis of the genomic sequences revealed the presence of an amino acid substitution in codon 83 of the gene gyrA, which has not been described previously in Mmc. Copyright © 2016 Elsevier Ltd. All rights reserved.
Lettini, A A; Vo Than, T; Marafin, E; Longo, A; Antonello, K; Zavagnin, P; Barco, L; Mancin, M; Cibin, V; Morini, M; Dang Thi Sao, M; Nguyen Thi, T; Pham Trung, H; Le, L; Nguyen Duc, T; Ricci, A
This study was conducted to estimate the prevalence of Salmonella spp. and their antimicrobial susceptibilities on poultry and swine farms, sampled in 2 regions in Central Vietnam. A total of 67 poultry farms and 46 swine farms were sampled in a period of 5 months (from September 2012 to January 2013). Salmonella spp. was prevalent in 46.3% and 71.7% of poultry and swine farms, respectively. Altogether, 99 non-typhoidal Salmonella were isolated and the most common serovars were Salmonella Weltevreden (19%), followed by Salmonella Typhimurium (12%) and Salmonella 4,,12:i:- (11%). Overall, 71 of 99 (72%) Salmonella isolates were resistant to at least one of the 14 antimicrobial agents tested. Both in poultry and swine farms, high levels of resistance were observed for ampicillin, chloramphenicol, ciprofloxacin, sulphamethoxazole and tetracycline. The presence of Salmonella isolates from poultry and swine farms which were resistant to different classes of antimicrobials suggests that alternative control measures to antimicrobials should be implemented. Moreover, an effective policy should be promoted to encourage a prudent use of these agents in animal farming in Vietnam. © 2016 Blackwell Verlag GmbH.
Suzuki, Masaru; Miyaki, Masaru; Sekine, Kazuhiko; Kurihara, Tomohiro; Abe, Shinya; Aikawa, Naoki; Shinagawa, Nagao
Our goal was to analyze minimum inhibitory concentration (MIC) data for Staphylococcus aureus isolated from surgical infections (SIs) and to look for correlations among the clinically available antimicrobials that were tested. Clinical isolates from SIs were collected by a multicenter surveillance group involving 34 institutions in Japan. During the period April 1998 to March 2007, 312 strains of S. aureus [71 methicillin susceptible (MSSA) and 241 methicillin resistant (MRSA)] were consecutively obtained from these institutions. MIC data for 18 clinically available antimicrobial agents [ABPC, CEZ, CTM, CMX, CPR, FMOX, CFPM, CZOP, IPM, MEMP, GM, ABK, MINO, CLDM, FOM, LVFX, VCM, and TEIC (abbreviations defined in Tables 2 and 3)] against these isolates was analyzed using a principal component analysis (PCA). PCA revealed that four principal components explained 71.1% of the total variance. The first component consisted of major contributions from MEPM and IPM. The second component consisted of major contributions from MINO. These two-first axes, which were strong and explained 54.2% of the total variance, were able to classify the clinical isolates into four clusters. Furthermore, the proportion of the four clusters provided the characteristics of the S. aureus that were clinically isolated at each institute. PCA is a clinically applicable method for analyzing MIC patterns. Such analyses might contribute to the establishment of a practical classification of antimicrobial agents and to the identification of the characteristic antimicrobial resistance patterns at each institute.
Gieseker, Charles M; Crosby, Tina C; Mayer, Tamara D; Bodeis, Sonya M; Stine, Cynthia B
Flavobacterium columnare and F. psychrophilum are major fish pathogens that cause diseases that may require antimicrobial therapy. Choice of appropriate treatment is dependent upon determining the antimicrobial susceptibility of isolates. Therefore we optimized methods for broth microdilution testing of F. columnare and F. psychrophilum to facilitate standardizing an antimicrobial susceptibility test. We developed adaptations to make reproducible broth inoculums and confirmed the proper incubation time and media composition. We tested the stability of potential quality-control bacteria and compared test results between different operators. Log phase occurred at 48 h for F. columnare and 72-96 h for F. psychrophilum, confirming the test should be incubated at 28°C for approximately 48 h and at 18°C for approximately 96 h, respectively. The most consistent susceptibility results were achieved with plain, 4-g/L, dilute Mueller-Hinton broth supplemented with dilute calcium and magnesium. Supplementing the broth with horse serum did not improve growth. The quality-control strains, Escherichia coli ATCC 25922 and Aeromonas salmonicida subsp. salmonicida ATCC 33658, yielded stable minimal inhibitory concentrations (MIC) against all seven antimicrobials tested after 30 passes at 28°C and 15 passes at 18°C. In comparison tests, most MICs of the isolates agreed 100% within one drug dilution for ampicillin, florfenicol, and oxytetracycline. The agreement was lower with the ormetoprim-sulfdimethoxine combination, but there was at least 75% agreement for all but one isolate. These experiments have provided methods to help standardize antimicrobial susceptibility testing of these nutritionally fastidious aquatic bacteria. Received June 24, 2015; accepted October 2, 2015.
Mégraud, Francis; Lehours, Philippe
The discovery of Helicobacter pylori in 1982 was the starting point of a revolution concerning the concepts and management of gastroduodenal diseases. It is now well accepted that the most common stomach disease, peptic ulcer disease, is an infectious disease, and all consensus conferences agree that the causative agent, H. pylori, must be treated with antibiotics. Furthermore, the concept emerged that this bacterium could be the trigger of various malignant diseases of the stomach, and it is now a model for chronic bacterial infections causing cancer. Most of the many different techniques involved in diagnosis of H. pylori infection are performed in clinical microbiology laboratories. The aim of this article is to review the current status of these methods and their application, highlighting the important progress which has been made in the past decade. Both invasive and noninvasive techniques will be reviewed. PMID:17428887
Norman, Keri N; Scott, Harvey M; Harvey, Roger B; Norby, Bo; Hume, Michael E
Clostridium difficile can be a major problem in hospitals because the bacterium primarily affects individuals with an altered intestinal flora; this largely occurs through prolonged antibiotic use. Proposed sources of increased community-acquired infections are food animals and retail meats. The objective of this study was to compare the antimicrobial resistance patterns of C. difficile isolated from a closed, integrated population of humans and swine to increase understanding of the bacterium in these populations. Swine fecal samples were collected from a vertically flowing swine population consisting of farrowing, nursery, breeding, and grower/finisher production groups. Human wastewater samples were collected from swine worker and nonworker occupational group cohorts. Antimicrobial susceptibility testing was performed on 523 C. difficile strains from the population using the commercially available agar diffusion Epsilometer test (Etest(®)) for 11 different antimicrobials. All of the swine and human strains were susceptible to amoxicillin/clavulanic acid, piperacillin/tazobactam, and vancomycin. In addition, all of the human strains were susceptible to chloramphenicol. The majority of the human and swine strains were resistant to cefoxitin and ciprofloxacin. Statistically significant differences in antimicrobial susceptibility were found among the swine production groups for ciprofloxacin, tetracycline, amoxicillin/clavulanic acid, and clindamycin. No significant differences in antimicrobial susceptibility were found across human occupational group cohorts. We found that 8.3% of the swine strains and 13.3% of the human strains exhibited resistance to metronidazole. The finding of differences in susceptibility patterns between human and swine strains of C. difficile provides evidence that transmission between host species in this integrated population is unlikely.
Shadomy, Smith; Carver, Melinda
The reliability of the standardized 30-μg cephalothin disk and that of an experimental 30-μg cefaclor disk in predicting probable clinical susceptibility to cefaclor were compared. Quantitative determinations of cefaclor susceptibility were measured by the World Health Organization International Collaborative Study agar dilution procedure; diffusion disk tests were performed by the standardized U.S. Food and Drug Administration disk test. The cephalothin disk erred in predicting probable susceptibility in 52% of isolates of Enterococcus spp. resistant to 16 μg or less of cefaclor per ml; the cefaclor disk did not. The cephalothin disk erred in correctly predicting susceptibility in only 20% of cefaclor-susceptible isolates of Enterobacter spp.; the cefaclor disk correctly predicted susceptibility for 70%. These results indicate the need for further evaluation of a separate cefaclor disk for use in susceptibility testing with this new cephalosporin. PMID:646345
Drigo, Ilenia; Mazzolini, Elena; Bacchin, Cosetta; Tonon, Elena; Puiatti, Cinzia; Bano, Luca; Spigaglia, Patrizia; Barbanti, Fabrizio; Agnoletti, Fabrizio
Clostridium difficile is an important cause of enteric disease in humans and animals. Recent studies demonstrated a genetic overlap between C. difficile isolated from animals and humans suggesting animals as possible reservoir for human pathogenic strains. This study was a preliminary investigation on the occurrence of C. difficile in rabbits raised in industrial holdings for food production and aimed to characterise isolates and estimate their antimicrobial susceptibility. C. difficile isolates were characterized by toxin profiles, toxinotyping and PCR-ribotyping. The MICs of six antibiotics were determined using E-test. Between 2007 and 2013, 285 industrial holdings (representing 40% of the national census) submitted rabbits to our laboratory for diagnostic purposes, among these holdings, groups of three to five post-weaned rabbits were sampled once by convenience. 1279 samples of caecal content were collected. The overall isolation rate of C. difficile from the enteric specimen was 3% (38/1279), with no difference among animals affected or not by enteric disorders. Among isolates 66% (25/38) were toxigenic. Sixteen different PCR-ribotypes (RTs) were identified. Among the toxigenic strains RT-014/020, RT-078 and RT-012 were found in at least three rabbit holdings. According to the ECOFF threshold, 82% (31/38) C. difficile isolates displayed a reduced susceptibility to at least one and 18% (7/38) to three tested antimicrobials. Rabbits are colonized by heterogeneous C. difficile ribotypes many of which are commonly isolated in humans. One third of isolates displayed a reduced susceptibility to MTZ, the first choice antimicrobial for human CDI treatment. According to our findings rabbits are a potential source of C. difficile for humans.
White, Brian K.; Mende, Katrin; Weintrob, Amy C.; Beckius, Miriam L.; Zera, Wendy C.; Lu, Dan; Bradley, William; Tribble, David R.; Schnaubelt, Elizabeth R.; Murray, Clinton K.
Data from recent conflicts related to war wounds and obligate anaerobes are limited. We define the epidemiology and antimicrobial susceptibility of obligate anaerobes from Iraq and Afghanistan casualties (6/2009–12/2013), as well as their association with clinical outcomes. Susceptibility against eleven antibiotics (7 classes) was tested. Overall, 59 patients had 119 obligate anaerobes identified (83 were first isolates). Obligate anaerobes were isolated 7–13 days post-injury, primarily from lower extremity wounds (43%), and were largely Bacteroides spp. (42%) and Clostridium spp. (19%). Patients with pelvic wounds were more likely to have Bacteroides spp. and concomitant resistant gram-negative aerobes. Seventy-three percent of isolates were resistant to ≥1 antimicrobials. Bacteroides spp. demonstrated the most resistance (16% of first isolates). Patients with resistant isolates had similar outcomes to those with susceptible strains. Serial recovery of isolates occurred in 15% of patients and was significantly associated with isolation of Bacteroides spp., along with resistant gram-negative aerobes. PMID:26607420
da Silva Barros, Maria Elisabete; de Assis Santos, Daniel; Soares Hamdan, Júnia
Trichophyton rubrum isolates were used in susceptibility testing for azoles by E-test. Voriconazole was the most and fluconazole was the less-active drug. Our results are in agreement with susceptibility data observed by researchers that used others' methodologies. E-test seems to be a reliable methodology to susceptibility-testing for T. rubrum.
Kuang, Xiuhua; Hao, Haihong; Dai, Menghong; Wang, Yulian; Ahmad, Ijaz; Liu, Zhenli; Zonghui, Yuan
Salmonella spp. can indirectly infect humans via transfer from animals and animal-derived food products, and thereby cause potentially fatal diseases. Therefore, gaining an understanding of Salmonella infection in farm animals is increasingly important. The aim of this study was to identify the distribution of serotypes in Salmonella samples isolated from chickens (n = 837), pigs (n = 930), and dairy cows (n = 418) in central China (Henan, Hubei, and Hunan provinces) in 2010-2011, and investigate the susceptibility of strains to antimicrobial agents. Salmonella isolates were identified by PCR amplification of the invA gene, serotypes were determined by using a slide agglutination test for O and H antigens, and susceptibility to 24 antimicrobials was tested using the agar dilution method. In total, 248 Salmonella strains were identified: 105, 105, and 38 from chickens, dairy cows, and pigs, respectively. Additionally, 209 strains were identified in diseased pigs from the Huazhong Agricultural University veterinary hospital. Among these 457 strains, the dominant serotypes were Typhimurium in serogroup B, IIIb in serogroup C, and Enteritidis in serogroup D. In antimicrobial susceptibility tests, 41.14% of Salmonella spp. were susceptible to all antimicrobial agents, 48.14% were resistant to at least one, and 34.72% were resistant to more than three classes. Strains were highly resistant to sulfamethoxazole-trimethoprim (39.61%), nalidixic acid (39.17%), doxycycline (28.22%), and tetracycline (27.58%). Resistance to cephalosporins and fluoroquinolones ranged from 5.25 to 7.44% and 19.04 to 24.51%, respectively. Among penicillin-resistant and cephalosporin-resistant strains, 25 isolates produced extended-spectrum β-lactamases (ESBLs). The multidrug-resistant and ESBL-producing Salmonella strains identified in healthy animals here will present a challenge for veterinary medicine and farm animal husbandry, and could also pose a threat to public health. The level of
Marques, M B; Brookings, E S; Moser, S A; Sonke, P B; Waites, K B
The in vitro susceptibilities of 69 nosocomial Acinetobacter isolates were determined by the broth microdilution method. Fourteen (20%) isolates were resistant to at least two aminoglycosides and two extended-spectrum penicillins. Nine antimicrobial combinations were then tested for synergy against these 14 isolates by checkerboard titration: imipenem with ciprofloxacin, amikacin, and tobramycin and ampicillin-sulbactam, piperacillin-tazobactam, and ticarcillin-clavulanate with amikacin and tobramycin. Synergy was detected with one or more antimicrobial combinations against 9 of 14 (64%) isolates, partial synergy was detected with one or more combinations against all 14 isolates, and an additive effect alone was observed with two different combinations against two isolates. No antagonism was detected with any combination. Imipenem plus either amikacin or tobramycin resulted in a synergistic or partial synergistic response against all 14 isolates. Specific combinations showing synergy against A. baumannii isolates were imipenem with tobramycin (four isolates), imipenem with amikacin (three isolates), ampicillin-sulbactam with tobramycin (six isolates), ampicillin-sulbactam with amikacin (three isolates), and ticarcillin-clavulanate with tobramycin (one isolate). Genotyping by randomly amplified polymorphic DNA analysis showed that 9 of the 14 isolates were of one strain, 4 isolates were of a second strain, and the remaining isolate was of a different strain. Eight of 14 (57%) patients infected with resistant A. baumannii isolates died. Only 3 of 14 patients had received a therapeutic regimen which was tested for synergy. Clinical studies are needed to determine the significance of these findings. PMID:9145838
Sánchez, Juan Gabriel Bueno; Kouznetsov, Vladimir V.
The emergence of multidrug-resistant strains of Mycobacterium tuberculosis underscores the need of continuous developments on new and efficient methods to determine the susceptibility of isolates of M. tuberculosis in the search for novel antimicrobial agents. Natural products constitute an important source of new drugs, but design and implementation of antimycobacterial susceptibility testing methods are necessary for evaluate the different extracts and compounds. A number of biological assay methodologies are in current use, ranging from the classical disk diffusion and broth dilution assay format, to radiorespirometric (BACTEC), dye-based, and fluorescent/luminescence reporter assays. This review presents an analysis on the in vitro susceptibility testing methods developed for determinate antitubercular activity in natural products and related compounds (semi-synthetic natural products and natural products-derived compounds) and the criteria to select the adequate method for determination of biological activity of new natural products. PMID:24031490
Gilardi, G. L.
Antimicrobial susceptibility data regarding nonfermentative, gram-negative bacteria (Pseudomonas, Alcaligenes, Acinetobacter, Moraxella, Flavobacterium) are presented showing that the antibiograms of most species examined can be used as an important auxillary aid in their differentiation. PMID:5132093
Coles, Mada; Poole, Doris; Lund, Lorraine; Page, Robert
Abstract The in vitro susceptibility of a total of 1819 bacterial isolates from canine and 103 isolates from feline otitis externa cases to 13 antimicrobial drugs over a 5-year period was evaluated. Among topically used drugs, 90% of isolates were susceptible to gentamicin. Susceptibility of Pseudomonas aeruginosa to gentamicin was 85%, and to polymyxin B 100%. For isolates other than the Pseudomonas sp., susceptibility was highest to amoxicillin-clavulanic acid. PMID:16604982
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, June 2005, p. 2571–2572 Vol. 49, No. 6 0066-4804/05/$08.000 doi:10.1128/AAC.49.6.2571–2572.2005 Copyright...2005, American Society for Microbiology. All Rights Reserved. Posttreatment Changes in Escherichia coli Antimicrobial Susceptibility Rates among... antimicrobial resistance of Escherichia coli among deployed U.S. military personnel being treated for diarrhea were evaluated. Stool samples were collected
Mayorga, Melissa; Rodríguez-Cavallini, Evelyn; López-Ureña, Diana; Barquero-Calvo, Elías; Quesada-Gómez, Carlos
The etiology of veterinary infectious diseases has been the focus of considerable research, yet relatively little is known about the causative agents of anaerobic infections. Susceptibility studies have documented the emergence of antimicrobial resistance and indicate distinct differences in resistance patterns related to veterinary hospitals, geographic regions, and antibiotic-prescribing regimens. The aim of the present study was to identify the obligate anaerobic bacteria from veterinary clinical samples and to determinate the in vitro susceptibility to eight antimicrobials and their resistance-associated genes. 81 clinical specimens obtained from food-producing animals, pets and wild animals were examined to determine the relative prevalence of obligate anaerobic bacteria, and the species represented. Bacteroides spp, Prevotella spp and Clostridium spp represented approximately 80% of all anaerobic isolates. Resistance to metronidazole, clindamycin, tetracycline and fluoroquinolones was found in strains isolated from food-producing animals. Ciprofloxacin, enrofloxacin and cephalotin showed the highest resistance in all isolates. In 17%, 4% and 14% of tetracycline-resistant isolates, the resistance genes tetL, tetM and tetW were respectively amplified by PCR whereas in 4% of clindamycin-resistant strains the ermG gene was detected. 26% of the isolates were positive for cepA, while only 6% harbored the cfxA (resistance-conferring genes to beta-lactams). In this study, the obligate anaerobic bacteria from Costa Rica showed a high degree of resistance to most antimicrobials tested. Nevertheless, in the majority of cases this resistance was not related to the resistance acquired genes usually described in anaerobes. It is important to address and regulate the use of antimicrobials in the agricultural industry and the empirical therapy in anaerobic bacterial infections in veterinary medicine, especially since antibiotics and resistant bacteria can persist in the
Wexler, H M
The demand for susceptibility testing of anaerobes has increased, yet consensus as to procedure and interpretation in this area has not been achieved. While routine testing of anaerobic isolates is not needed, certain isolates in specific clinical settings should be tested. Also, laboratories may monitor their local antibiograms by doing periodic surveillance batch testing. The National Committee for Clinical Laboratory Standards has published a protocol of methods approved for susceptibility testing of anaerobic bacteria. Both agar and broth microdilution are included; however, the broth disk elution method is no longer approved by the National Committee for Clinical Laboratory Standards because of method-related interpretive errors. A number of newer methods are undergoing evaluation and seem promising. Clinicians and microbiologists reviewing susceptibility reports should be aware of sources of variability in the test results. Variables in susceptibility testing of anaerobes include the media and methods used, organisms chosen for testing, breakpoints chosen for interpretation, antibiotic, and determination of endpoint. Clustering of MICs around the breakpoint may lead to significant variability in test results. Adherence of testing laboratories to approved methods and careful descriptions of the method and the breakpoints used for interpretation would facilitate interlaboratory comparisons and allow problems of emerging resistance to be noted. A variety of resistance mechanisms occurs in anaerobic bacteria, including the production of beta-lactamase and other drug-inactivating enzymes, alteration of target proteins, and inability of the drug to penetrate the bacterial wall. Antimicrobial resistance patterns in the United States and abroad are described. PMID:1747863
EPA is announcing the availability for public comment of two proposed test methods and associated testing guidance for evaluating antimicrobial pesticides against two biofilm bacteria, Pseudomonas aeruginosa and Staphylococcus aureus.
Jacob, Megan E; Fox, James Trent; Reinstein, Shelby L; Nagaraja, T G
Organic and natural food production systems are increasing in popularity, at least partially because consumers perceive that these niche markets provide healthier and safer food products. One major difference between these niche markets and conventional production systems is the use of antimicrobials. Because antimicrobial agents exert selective pressures for antimicrobial resistance, relating antimicrobial susceptibility of foodborne bacteria to niche market production systems is of interest. Other differences between production systems might also influence the susceptibility of foodborne pathogens. The objective of this review is to compare the impact of food animal production systems on the antimicrobial susceptibility of common foodborne bacterial pathogens. Studies comparing the susceptibility of such pathogens were diverse in terms of geographic location, procedures, species of bacteria, and antimicrobials evaluated; thus, it was difficult to draw conclusions. The literature is highly variable in terms of production type and practices and susceptibility associations, although few studies have compared truly organic and conventional practices. When statistical associations were found between production type and minimum inhibitory concentrations or percentage of isolates resistant for a particular pathogen, the isolates from conventionally reared animals/products were more commonly resistant than the comparison group (organic, antibiotic free, etc.). Therefore, further studies are needed to better assess public health consequences of antimicrobial resistance and food animal production systems, specifically organic or natural versus conventional.
Rubin, Joseph E; Ball, Katherine R; Chirino-Trejo, Manuel
This study characterized the antimicrobial susceptibility of 221 Staphylococcus aureus isolated from various species, and 60 canine Staphylococcus pseudintermedius isolated from 1986 through 2000 at the Western College of Veterinary Medicine (WCVM). Resistance of S. aureus was most common to penicillin (31%) and tetracycline (14%); resistance of S. pseudintermedius to penicillin was present in 8% and to tetracycline in 34% of isolates. Resistance to trimethoprim/sulfamethoxazole was only seen among S. pseudintermedius, and there was no resistance to amoxicillin/clavulanate, ampicillin/sulbactam, cephalothin, amikacin, gentamicin, enrofloxacin, chloramphenicol, or rifampin among any isolate. Inducible clindamycin resistance was found in both S. aureus and S. pseudintermedius, highlighting the need for careful interpretation of culture and susceptibility test results. There were significant differences in the minimum inhibitory concentrations of penicillin, ciprofloxacin, enrofloxacin, clindamycin, erythromycin, chloramphenicol, and tetracycline between avian, bovine, equine, and porcine isolates.
Guérin-Faublée, V; Flandrois, J P; Broye, E; Tupin, F; Richard, Y
Actinomyces pyogenes induces suppurative diseases in ruminants and many other animal species. Most of the earlier antimicrobial susceptibility data has been obtained by disk diffusion techniques. Minimal inhibitory concentrations (MIC) of 22 antibiotics for 103 strains of A pyogenes of animal origin were determined by agar dilution test (Mueller-Hinton agar supplemented with 5% sheep blood). All the strains were susceptible to penicillin G, amoxicillin, methicillin, cephalothin, cefoperazone, pristinamycin, kanamycin, gentamicin, spectinomycin, chloramphenicol, vancomycin, novobiocin and rifampin. Fifty-nine percent were resistant to streptomycin, 67% to tetracycline, doxycycline and minocycline, 12% to erythromycin, spiramycin and lincomycin. Most of the strains resistant to macrolides and lincosamides exhibited a constitutive MLS(B)-like phenotype. In the cultural conditions used, it was not possible to determine accurate MIC of fucidic acid and pefloxacin.
Gutiérrez, C B; Rodríguez Barbosa, J I; Tascón, R I; Costa, L; Riera, P; Rodríguez Ferri, E F
Seventy-one isolates of Actinobacillus pleuropneumoniae isolated from the lungs of pigs in outbreaks of pleuropneumonia in Spain were serotyped by indirect haemagglutination. Serotype 4 (42.2 per cent), serotype 7 (22.5 per cent) and serotype 2 (12.8 per cent) were predominant, whereas serotypes 1, 3, 6, 8, 9, 12 and untypable isolates were present only in small numbers. Serotypes 1, 2, 4 and 7 originated mainly from cases of acute pleuropneumonia, whereas serotypes 3, 6, 8, 9 and 12 were associated with chronically infected herds. The susceptibility of the isolates to 20 antimicrobial agents was determined by agar disc diffusion. Most were susceptible to cefuroxime, cefaclor, cefazolin, kanamycin, tobramycin, gentamicin, oxolinic acid, ciprofloxacin, enoxacin, thiamphenicol, colistin and trimethoprim/sulphamethoxazole. Marked resistance was found with amoxicillin, ticarcillin, oxytetracycline, doxycycline and metronidazole. Rifampicin, fosfomycin and tiamulin were the agents most effective against the isolates tested.
Alcaide, Fernando; Esteban, Jaime; González-Martin, Julià; Palacios, Juan-José
Mycobacteria are a large group of microorganisms, multiple species of which are major causes of morbidity and mortality, such as tuberculosis and leprosy. At present, the emergence and spread of multidrug-resistant strains of Mycobacterium tuberculosis complex are one of the most serious health problems worldwide. Furthermore, in contrast to M. tuberculosis and Mycobacterium leprae, non-tuberculous mycobacteria (NTM) are more frequently isolated and, in many cases, treatment is based on drug susceptibility testing. This article is a review of the different methods to determine the in vitro drug susceptibility of M. tuberculosis complex and the most relevant NTM isolates. The molecular techniques currently used for rapid detection of resistance of clinical specimens are also analysed. Copyright © 2016 Elsevier España, S.L.U. y Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.
Lamm, Catherine G; Love, Brenda C; Krehbiel, Clint R; Johnson, Nicholas J; Step, Douglas L
A retrospective study was performed to compare the treatment regimens in feedlot cattle that died with bovine respiratory disease (BRD) to the antimicrobial susceptibility patterns of the microorganisms isolated from lungs. Forty-three cattle submitted by the Willard Sparks Beef Research Center (WSBRC) to the Oklahoma Animal Disease Diagnostic Laboratory for postmortem examination during 2007 had bronchopneumonia (acute = 16, subacute = 5, or chronic = 22). Lungs from cattle were cultured aerobically (40 cattle) and for Mycoplasma spp. (34 cattle). Susceptibility panels were performed. At least 1 BRD pathogen (Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Mycoplasma bovis, or Arcanobacterium pyogenes) was isolated from 39 cattle, and 77% (30/39) had multiple organisms recovered. Mycoplasmal infections were common (25/34) and a major component of mixed infections (24/25). The majority (60%) of the M. haemolytica, P. multocida, and H. somni isolates were resistant to tetracycline. Most of the H. somni isolates (67%) were susceptible to tilmicosin (Ti), enrofloxacin (En), ceftiofur (Ce), and florfenicol, despite extensive treatment with Ti, En, and Ce (75% of isolates were from cattle that received each antimicrobial once). Most of the M. haemolytica (65%) and P. multocida (79%) isolates were susceptible to En and Ce, despite antemortem treatment of cattle with these antimicrobials. Hence, the current study reports a discrepancy between the antemortem treatment of clinical BRD and the susceptibility patterns of the bacteria isolated from lungs postmortem. Based on these findings, factors other than antimicrobial resistance are playing a role in the death of feedlot cattle with BRD.
Vay, Carlos; Cittadini, Roxana; Barberis, Claudia; Hernán Rodríguez, Carlos; Perez Martínez, Herminia; Genero, Fabiana; Famiglietti, Angela
Non-enterococcal Gram-positive bacteria that are intrinsically vancomycin-resistant have been infrequently isolated in association with serious infections. However, well-documented infections have lately been reported with increasing frequency. Because these organisms may be pathogens, we tested the MICs of 19 antimicrobial agents by the agar dilution method for predicting susceptibility. The activity of these antimicrobial agents was assessed against 28 strains (Lactobacillus rhamnosus, 6; Lactobacillus acidophilus, 1; Lactobacillus casei, 1; Lactobacillus fermentum, 2; Lactobacillus brevis, 1; Lactobacillus plantarum, 1; Weissella confusa, 2; Leuconostoc mesenteroides, 7; Leuconostoc lactis, 4; Pediococcus acidilactici, 2; Pediococcus pentosaceus, 1), isolated from clinical specimens in an Argentinian university hospital from 1997 to 2003. The MICs of penicillin for 67% of the Lactobacillus strains and 100% of the Leuconostoc spp. and Pediococcus spp. strains tested were in the 0.25-2 microg/mL range. Erythromycin was the most active antimicrobial overall. Multiresistance was observed in 2 strains (Lactobacillus rhamnosus, 1; Lactobacillus plantarum, 1).
Kuang, Dai; Zhang, Jianmin; Meng, Jianghong; Yang, Xiaowei; Jin, Huiming; Shi, Weimin; Luo, Kaijian; Tao, Yan; Pan, Haijian; Xu, Xuebin; Ren, Tao
Salmonella enterica serotype Agona (Salmonella Agona) has been among the top 10 serotypes that cause human diarrheal diseases in China. A total of 95 Salmonella Agona (67 from humans, and 28 from animals, food of animal origins, and environmental sources) recovered in Shanghai, China from 2005 to 2011 were subjected to antimicrobial susceptibility testing and molecular subtyping using pulsed-field gel electrophoresis (PFGE). Approximately 68.4% of the Salmonella Agona isolates were pansusceptible to 15 antimicrobial agents tested, and 4 isolates (4.21%) were resistant to at least 3 antimicrobials. PFGE analysis resulted in 41 unique patterns, of which 4 major PFGE patterns (X3, X4, X5, and X6) were grouped together at 96.1% similarity. Isolates of the four patterns included those from food (pork, beef, and chicken) and humans. Our findings showed that the same clones of Salmonella Agona were recovered from human patients and food, and that food of animal origin was potentially a major vehicle of Salmonella Agona in human salmonellosis in Shanghai.
Purpose The goal of this study was to characterize the patterns of antimicrobial resistance and virulence genes in samples of Staphylococcus aureus (S. aureus) isolated from periodontitis patients. Methods From July 2015 to August 2015, oral saliva was collected from a total of 112 patients diagnosed with periodontitis, including 80 outpatients in dental hospitals and 32 patients in dental clinics located in Seoul and Cheonan. The samples were subjected to a susceptibility test to evaluate the prevalence of antimicrobial resistance, and the pathogenic factors and antimicrobial resistance factors in the DNA of S. aureus were analyzed using polymerase chain reaction. Results A susceptibility test against 15 antimicrobial agents showed that 88% of cultures were resistant to ampicillin, 88% to penicillin, and 2% to oxacillin. Resistance to at least two drugs was observed in 90% of cultures, and the most common pattern of multidrug resistance was to ampicillin and penicillin. Enterotoxins were detected in 65.9% of samples. The cell hemolysin gene hld was detected in 100% of cultures and hla was detected in 97.6% of samples. All strains resistant to penicillin and ampicillin had the blaZ gene. The aph(3′)IIIa gene, which encodes an aminoglycoside modifying enzyme, was detected in 46.3% of samples. Conclusions In the treatment of oral S. aureus infections, it is important to identify the pathogenic genes and the extent of antimicrobial resistance. Furthermore, it is necessary to study patterns of antimicrobial resistance and cross-infection in the context of periodontological specialties in which antimicrobials are frequently used, such as maxillofacial surgery, where the frequency of antimicrobial use for minor procedures such as implant placement is increasing. PMID:26734493
Kirkcaldy, Robert D; Harvey, Alesia; Papp, John R; Del Rio, Carlos; Soge, Olusegun O; Holmes, King K; Hook, Edward W; Kubin, Grace; Riedel, Stefan; Zenilman, Jonathan; Pettus, Kevin; Sanders, Tremeka; Sharpe, Samera; Torrone, Elizabeth
Gonorrhea is the second most commonly reported notifiable disease in the United States; 350,062 gonorrhea cases were reported in 2014. Sexually transmitted infections caused by Neisseria gonorrhoeae are a cause of pelvic inflammatory disease in women, which can lead to serious reproductive complications including tubal infertility, ectopic pregnancy, and chronic pelvic pain. Prevention of sequelae and of transmission to sexual partners relies largely on prompt detection and effective antimicrobial treatment. However, treatment has been compromised by the absence of routine antimicrobial susceptibility testing in clinical care and evolution of antimicrobial resistance to the antibiotics used to treat gonorrhea. 2014. The Gonococcal Isolate Surveillance Project (GISP) was established in 1986 as a sentinel surveillance system to monitor trends in antimicrobial susceptibilities of N. gonorrhoeae strains in the United States. Each month, N. gonorrhoeae isolates are collected from up to the first 25 men with gonococcal urethritis attending each of the participating sexually transmitted disease (STD) clinics at 27 sites. The number of participating sites has varied over time (21-30 per year). Selected demographic and clinical data are abstracted from medical records. Isolates are tested for antimicrobial susceptibility using agar dilution at one of five regional laboratories. A total of 5,093 isolates were collected in 2014. Of these, 25.3% were resistant to tetracycline, 19.2% to ciprofloxacin, and 16.2% to penicillin (plasmid-based, chromosomal, or both). Reduced azithromycin susceptibility (Azi-RS) (defined as minimum inhibitory concentration [MIC] ≥2.0 µg/mL) increased from 0.6% in 2013 to 2.5% in 2014. The increase occurred in all geographic regions, but was greatest in the Midwest, and among all categories of sex of sex partners (men who have sex with men [MSM], men who have sex with men and women [MSMW], and men who have sex with women [MSW]). No Azi-RS isolates
Stock, Ingo; Rahman, Motiur; Sherwood, Kimberley Jane; Wiedemann, Bernd
Bangladeshi diarrheagenic Hafnia alvei-like strains have been described recently as the new species Escherichia albertii (Int J Syst Evolut Microbiol. 2003;53:807-810). The natural susceptibility of 21 E. albertii and 76 H. alvei strains to 69 antimicrobial agents was examined, applying a microdilution procedure in IsoSensitest broth (for all the strains) and cation-adjusted Mueller-Hinton broth (for some strains). Examining the phenotypic features of both taxa with commercial identification systems and conventional tests, a database for an accurate biochemical separation of E. albertii from H. alvei was also established. Both taxa were naturally sensitive or sensitive and of intermediate susceptibility to aminoglycosides, acylureidopenicillins, ticarcillin, several cephalosporins, carbapenems, aztreonam, quinolones, folate pathway inhibitors, and nitrofurantoin. They were naturally resistant to tetracycline, penicillin G, oxacillin, all macrolides except for azithromycin, lincosamides, streptogramins, glycopeptides, rifampicin, and fusidic acid. Taxon-related differences in natural susceptibility affecting clinical assessment criteria were seen with doxycycline, minocycline, aminopenicillins, some cephalosporins, azithromycin, and fosfomycin. E. albertii was more susceptible than H. alvei to these agents and was naturally sensitive to all beta-lactams (except for penicillin G and oxacillin), azithromycin, and fosfomycin. H. alvei was naturally resistant or of intermediate susceptibility to all tetracyclines, amoxicillin, amoxicillin-clavulanate, ampicillin-sulbactam, narrow-spectrum cephalosporins, azithromycin, and fosfomycin. Motile malonate-negative Hafnia strains (indicating genospecies 2 of the H. alvei complex) were less susceptible to some cephalosporins than nonmotile, malonate-positive hafniae (indicating genospecies 1). Proline deaminase, hydroxyproline amidase, tripeptidase, chitinase, Voges-Proskauer reaction, and assimilation of histidine as well as
Schwarz, Stefan; Alesík, Eva; Grobbel, Mirjam; Lübke-Becker, Antina; Werckenthin, Christiane; Wieler, Lothar H; Wallmann, Jürgen
A total of 92 canine/feline Pasteurella multocida strains form respiratory tract infections or infections of skin/ear/mouth as well as 42 canine/feline Bordetella bronchiseptica strains from respiratory tract infections were investigated for their susceptibility to antimicrobial agents. While the P. multocida strains were susceptible to all antimicrobial agents tested - except sulfonamides -, a considerable number of the B. bronchiseptica strains was resistant or exhibited high MIC values against a number of antimicrobial agents including penicillin G, oxacillin, cefazolin, ceftiofur, cefquinome, sulfamethoxazole, and trimethoprim/sulfamethoxazole.
Campigotto, Aaron; Muller, Matthew P; Taggart, Linda R; Haj, Reem; Leung, Elizabeth; Nadarajah, Jeya; Matukas, Larissa M
Cumulative susceptibility test data (CSTD) are used to guide empirical antimicrobial therapy and to track trends in antibiotic resistance. The Clinical and Laboratory Standards Institute recommends reporting CSTD at least annually and sets the minimum number of isolates per reported organism at 30. To comply, many hospitals combine data from multiple intensive care units (ICUs); however, this may not be appropriate to guide empirical therapy because of variations in patient populations. In this study, susceptibility data for two different ICUs at a tertiary care hospital in Toronto, Canada, were used to create a traditional CSTD report, which combined data from different ICUs, and a rolling-average CSTD report, which pooled 2 years of data for each ICU separately. For simplicity, data for only the most common Gram-negative organisms (Escherichia coli,Pseudomonas aeruginosa) and the most relevant antibiotics (ciprofloxacin, piperacillin-tazobactam) were examined. With the rolling-average method, significant differences in susceptibility were seen between the ICUs in 50% of the organism-antimicrobial combinations. Furthermore, the 3% median year-over-year difference in susceptibilities seen for the 16 organism-antibiotic combinations by using the traditional method was lower than the 14% median difference seen for the 20 between-ICU within-year comparisons obtained using the rolling-average method. Changes in our selection of empirical antibiotics resulted from this revised approach, and our results suggest that pooling data from ICUs with different patient populations may not be appropriate. A rolling-average method may be an appropriate strategy for the creation of individual-unit CSTD reports.
Campigotto, Aaron; Muller, Matthew P.; Taggart, Linda R.; Haj, Reem; Leung, Elizabeth; Nadarajah, Jeya
Cumulative susceptibility test data (CSTD) are used to guide empirical antimicrobial therapy and to track trends in antibiotic resistance. The Clinical and Laboratory Standards Institute recommends reporting CSTD at least annually and sets the minimum number of isolates per reported organism at 30. To comply, many hospitals combine data from multiple intensive care units (ICUs); however, this may not be appropriate to guide empirical therapy because of variations in patient populations. In this study, susceptibility data for two different ICUs at a tertiary care hospital in Toronto, Canada, were used to create a traditional CSTD report, which combined data from different ICUs, and a rolling-average CSTD report, which pooled 2 years of data for each ICU separately. For simplicity, data for only the most common Gram-negative organisms (Escherichia coli, Pseudomonas aeruginosa) and the most relevant antibiotics (ciprofloxacin, piperacillin-tazobactam) were examined. With the rolling-average method, significant differences in susceptibility were seen between the ICUs in 50% of the organism-antimicrobial combinations. Furthermore, the 3% median year-over-year difference in susceptibilities seen for the 16 organism-antibiotic combinations by using the traditional method was lower than the 14% median difference seen for the 20 between-ICU within-year comparisons obtained using the rolling-average method. Changes in our selection of empirical antibiotics resulted from this revised approach, and our results suggest that pooling data from ICUs with different patient populations may not be appropriate. A rolling-average method may be an appropriate strategy for the creation of individual-unit CSTD reports. PMID:26791365
Kádár, Béla; Kocsis, Béla; Kristof, Katalin; Tóth, Ákos; Szabó, Dóra
In this study susceptibility to different antimicrobial peptides was investigated on colistin-susceptible and colistin-resistant identical pulsotype strains of KPC-2 producing Klebsiella pneumoniae ST258 as well as colistin-susceptible and colistin-resistant Enterobacter asburiae strains isolated from clinical samples. In our test, bacteria were exposed to 50 mg/ml lactoferrin, lysozyme and protamine - cationic antimicrobial peptides belonging to innate immune system and having structural similarity to polymyxins - in separate reactions. After 18 hours incubation of colonies were counted. 40% of colistin-resistant K. pneumoniae strains and 97% of colistin-susceptible counterpart strains were lysed by protamine whereas 87% and 100% colony forming unit decrease by lysozyme was seen, respectively. In the case of colistin-resistant E. asburiae strains 1 log10 cell count increase were observed after treatment with lysozyme and 1.56 log10 after lactoferrin exposure compared to the initial number whereas the colistin-susceptible showed no relevant cell count increase. Our findings suggest that acquired colistin-resistance in Enterobacteriaceae is associated with tolerance against antimicrobial peptides.
Marie, J; Morvan, H; Berthelot-Hérault, F; Sanders, P; Kempf, I; Gautier-Bouchardon, A V; Jouy, E; Kobisch, M
The susceptibility of 135 Streptococcus suis strains isolated from pigs (n = 110) and from humans (n = 25) to 13 antimicrobial agents was studied by microdilution and disc diffusion methods using Mueller-Hinton Agar II (MH) supplemented with either defibrinated sheep blood (MHSB) or horse serum (MHHS). Results were similar for both methods used except for penicillin G whose zone diameters were reduced with MHSB compared with MHHS. When MH was supplemented with sheep blood, 39% of S. suis strains classified as penicillin susceptible by MHHS microdilution showed intermediate susceptibility. Nearly all strains were susceptible to penicillin G (except by disc diffusion in MHSB), amoxicillin, ceftiofur, florfenicol, gentamicin and bacitracin. The least active antimicrobial agents were doxycycline and macrolides/lincosamides. High-level resistance (MIC > 500 mg/L or zone diameters < 10 mm) to streptomycin and kanamycin was detected in only a few strains. The virulence of strains did not seem to be related to antimicrobial resistance because no statistical difference was reported between the proportion of resistant strains of S. suis isolated from pigs with meningitis, septicaemia and arthritis, and those from tonsils and nasal cavities. However, significant differences were found in the proportions of macrolide- or doxycycline-resistant strains between S. suis serotype 2 and other serotypes. The results of antibiotic susceptibility testing presented in this study indicate that beta-lactams can be used in empirical treatment of human and pig S. suis infections in France.
Mastitis occurs in numerous species. Antimicrobial agents are used for treatment of infectious mastitis in dairy cattle, other livestock, companion animals, and humans. Mastitis is an economically important disease of dairy cattle and most mastitis research has focused on epidemiology and control of bovine mastitis. Antibiotic treatment of clinical and subclinical mastitis in dairy cattle is an established component of mastitis control programs. Research on the treatment of clinical and subclinical mastitis in other dairy species such as sheep and goats has been less frequent, although the general principles of mastitis therapy in small ruminants are similar to those of dairy cattle. Research on treatment of clinical mastitis in humans is limited and as for other species empirical treatment of mastitis appears to be common. While antimicrobial susceptibility testing is recommended to direct treatment decisions in many clinical settings, the use of susceptibility testing for antibiotic selection for mastitis treatments of dairy cattle has been challenged in a number of publications. The principle objective of this review is to summarize the literature evaluating the question, "Does antimicrobial susceptibility predict treatment outcome for intramammary infections caused by common bacterial pathogens?" This review also addresses current issues related to antimicrobial use and treatment decisions for mastitis in dairy cattle. Information on treatment of mastitis in other species, including humans, is included although research appears to be limited. Issues related to study design, gaps in current knowledge and opportunities for future research are identified for bovine mastitis therapy.
Wexler, H M; Molitoris, E; Jashnian, F; Finegold, S M
Antimicrobial susceptibility tests were performed on brucella laked blood agar with 340 isolates and 14 antimicrobial agents by the standard agar dilution technique and the spiral gradient technique in which antibiotic concentrations were established by diffusion from the agar surface. For comparison, spiral gradient MICs were determined by calculating antimicrobial concentrations at growth endpoints and rounding up to the next twofold incremental concentration. The cumulative percentage of strains susceptible at the breakpoint determined from spiral gradient data was within 10%, generally, of the percentage of strains susceptible at the breakpoint determined from agar dilution data. The overall agreement between the two techniques (within one doubling dilution) was 90.6%. The spiral gradient agar dilution technique is a reasonable alternative to the conventional agar dilution technique for susceptibility testing of anaerobic bacteria. Images PMID:1929262
Swenson, J M; Facklam, R R; Thornsberry, C
Eighty-five strains of vancomycin-resistant gram-positive bacteria from three genera, Leuconostoc, Pediococcus, and Lactobacillus, were tested to determine susceptibility to 24 antimicrobial agents by broth microdilution and to 10 agents by disk diffusion. The MICs of vancomycin and teicoplanin ranged from 64 to greater than 512 micrograms/ml; however, the MICs of daptomycin, a new lipopeptide, were all less than or equal to 0.25 micrograms/ml. None of the organisms were resistant to imipenem, minocycline, chloramphenicol, gentamicin, or daptomycin. The MICs of penicillin were in the moderately susceptible range for all but three strains. Susceptibility to the other agents varied by genus and, in some cases, by species. When disk diffusion results were compared with MICs for drugs recommended for streptococci by the National Committee for Clinical Laboratory Standards, Villanova, Pa., few very major or major errors were obtained, but the number of minor errors was 19.3%. Therefore, we recommended that MIC testing be used instead of disk diffusion testing for these organisms. PMID:2344161
Knupp de Souza, Daniele Maria; Diniz, Claudio Galuppo; Filho, Didier Silveira Castellano; Andrade de Oliveira, Laura Maria; Coelho, Débora Martins; Talha, Luciana De Souza; Nascimento, Thiago César do; Ferreira-Machado, Alessandra Barbosa; Silva, Vânia Lúcia da
Bacterial vaginosis (BV) is a syndrome related to Gardnerella vaginalis and is characterized by an imbalance in the vaginal microbiota. This work focused on the evaluation of antimicrobial susceptibility patterns and the occurrence of the vaginolysin (vly) gene in G. vaginalis isolated from BV and non-BV patients. The vaginal secretions were collected randomly and processed for G. vaginalis isolation. The isolates were presumptively identified by β-hemolysis and oxidase and catalase tests. Polymerase chain reaction (PCR) was performed to confirm bacterial identity and to detect the vly gene. Antimicrobial susceptibility patterns were determined. Of 89 patients, G. vaginalis was isolated from 42 (37 BV and 5 non-BV), and 204 isolates were selected (179 from BV and 25 non-BV). The vly gene was detected in all G. vaginalis isolated from non-BV women and in 98.3% of the bacteria from BV patients. High resistance was observed for ampicillin (54.4%), metronidazole (59.8%), tinidazole (60.3%) and secnidazole (71.6%). Further studies are needed to better address the role of G. vaginalis and the vly gene in BV pathogenesis.
Palaniappan, Kavitha; Holley, Richard A
Plant-derived antibacterial compounds may be of value as a novel means for controlling antibiotic resistant zoonotic pathogens which contaminate food animals and their products. Individual activity of natural antimicrobials (eugenol, thymol, carvacrol, cinnamaldehyde, allyl isothiocyanate (AIT)) and activity when paired with an antibiotic was studied using broth microdilution and checkerboard methods. In the latter assays, fractional inhibitory concentration (FIC) values were calculated to characterize interactions between the inhibitors. Bacteria tested were chosen because of their resistance to at least one antibiotic which had a known genetic basis. Substantial susceptibility of these bacteria toward the natural antimicrobials and a considerable reduction in the minimum inhibitory concentrations (MIC's) of the antibiotics were noted when paired combinations of antimicrobial and antibiotic were used. In the interaction study, thymol and carvacrol were found to be highly effective in reducing the resistance of Salmonella Typhimurium SGI 1 (tet A) to ampicillin, tetracycline, penicillin, bacitracin, erythromycin and novobiocin (FIC<0.4) and resistance of Streptococcus pyogenes ermB to erythromycin (FIC<0.5). With Escherichia coli N00 666, thymol and cinnamaldehyde were found to have a similar effect (FIC<0.4) in reducing the MIC's of ampicillin, tetracycline, penicillin, erythromycin and novobiocin. Carvacrol, thymol (FIC<0.3) and cinnamaldehyde (FIC<0.4) were effective against Staphylococcus aureus blaZ and in reducing the MIC's of ampicillin, penicillin and bacitracin. Allyl isothiocyanate (AIT) was effective in reducing the MIC of erythromycin (FIC<0.3) when tested against S. pyogenes. Fewer combinations were found to be synergistic when the decrease in viable population (log DP) was calculated. Together, fractional inhibitory concentrations < or = 0.5 and log DP<-1 indicated synergistic action between four natural antimicrobials and as many as three antibiotics
Maciel, Jonas Fernandes; Matter, Letícia Beatriz; Trindade, Michele Martins; Camillo, Giovana; Lovato, Maristela; de Ávila Botton, Sônia; Castagna de Vargas, Agueda
In this study an avian colisepticemia outbreak was investigated. Two isolates from a chicken with colisepticemia were characterized for antimicrobial susceptibility and virulence factors profile. For this purpose 7 antimicrobial and 29 genes (fimH, hrlA/hek, iha, papC, sfa/focCD, tsh, mat, tia, gimB, ibeA, chuA, fyuA, ireA, iroN, irp2, iucD, sitD. chr., sitD. ep., iss, neuC, ompA, traT, astA, hlyA, sat, vat, pic, malX, cvi/cva) were tested. The outbreak happened in a hick chicken breeding located in the northwestern region of Rio Grande do Sul state in South of Brazil and caused 28.3% (102 deads of a total of 360 chickens) of mortality rate. Escherichia coli isolates obtained from the avian spleen and liver belong to the same phylogenetic group A and present resistance to all antimicrobials tested (ampicillin, tetracycline, gentamicin, neomycin, sulfa + trimethoprim, enrofloxacin, and norfloxacin). Both isolates harbor virulence factors related to adhesion (fimH, papC, mat), invasion (tia), iron acquisition system (iroN) and serum resistance (iss, ompA, traT), showing that these groups are important for Avian Pathogenic E. coli (APEC). However, they present different virulence profiles for some genes, whereas liver-isolate carries more hrlA/hek (adhesin), gimB (invasin), sitD ep. (iron acquisition system), sat (toxin) and hylA (toxin) genes, the spleen-isolate harbors fyuA (iron acquisition system) gene. Here, we highlight a coinfection by different strains of APEC in the same animal with colisepticemia, the great antimicrobial resistance of these bacterial isolates and the genetic traits that modulate the virulence for high mortality rate of chickens for human consumption. Copyright © 2016 Elsevier Ltd. All rights reserved.
Homogeneity of antimicrobial policy, yet heterogeneity of antimicrobial resistance: antimicrobial non-susceptibility among 108,717 clinical isolates from primary, secondary and tertiary care patients in London.
Moore, Luke S P; Freeman, Rachel; Gilchrist, Mark J; Gharbi, Myriam; Brannigan, Eimear T; Donaldson, Hugo; Livermore, David M; Holmes, Alison H
We examined the 4 year trend in antimicrobial susceptibilities and prescribing across levels of care at two London teaching hospitals and their multisite renal unit, and for the surrounding community. Laboratory and pharmacy information management systems were interrogated, with antimicrobial use and susceptibilities analysed between hospitals, within hospitals and over time. A total of 108,717 isolates from 71,687 patients were identified, with significant differences (at P < 0.05) in antimicrobial susceptibility between and within hospitals. Across the 4 years, rates of ESBL-/AmpC-producing Enterobacteriaceae ranged from 6.4% to 10.7% among community isolates, 17.8% to 26.9% at ward level and 25.2% to 52.5% in critical care. Significant variations were also demonstrated in glycopeptide-resistant enterococci (ward level 6.2%-17.4%; critical care 21.9%-56.3%), MRSA (ward level 18.5%-38.2%; critical care 12.5%-47.9%) and carbapenem-resistant Pseudomonas spp. (ward level 8.3%-16.9%; critical care 19.9%-53.7%). Few instances of persistently higher resistance were seen between the hospitals in equivalent cohorts, despite persistently higher antimicrobial use in Hospital 1 than Hospital 2. We found significant fluctuations in non-susceptibility year on year across the cohorts, but with few persistent trends. The marked heterogeneity of antimicrobial susceptibilities between hospitals, within hospitals and over time demands detailed, standardized surveillance and appropriate benchmarking to identify possible drivers and effective interventions. Homogeneous antimicrobial policies are unlikely to continue to be suitable as individual hospitals join hospital networks, and policies should be tailored to local resistance rates, at least at the hospital level, and possibly with finer resolution, particularly for critical care. © The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy.
Kuper, Kristi M; Coyle, Elizabeth A; Wanger, Audrey
Antifungal susceptibility testing is not as commonly performed as antibacterial susceptibility testing. The methodology for detecting antifungal resistance is newer and requires different testing supplies that may not be readily available in a clinical laboratory setting. Breakpoints for molds are lacking. Yeast breakpoints are available for most antifungals but are continually updated based on epidemiologic surveillance. Reliable and reproducible antifungal susceptibility testing methods, as well as more research on the role of susceptibility testing in patient care, are necessary in order to provide the clinician with information that can be translated into positive clinical outcomes at the bedside. There are nuances with current testing methods that, if unrecognized, could lead to misinterpretation of results and inappropriate antifungal selection. Clinicians who have an understanding of qualitative and quantitative methods, automated susceptibility testing systems, and other commercial tests can successfully engage this knowledge to improve antifungal use and patient outcomes. This primer describes the common antifungal susceptibility tests used in the clinical microbiology laboratory and reviews literature related to the impact of appropriate drug selection, timing, fungal resistance mechanisms, pharmacokinetics, and pharmacodynamics on clinical outcomes. Both conventional and modern testing methods are discussed. © 2012 Pharmacotherapy Publications, Inc.
Mirajkar, Nandita S.; Davies, Peter R.
Outbreaks of swine dysentery, caused by Brachyspira hyodysenteriae and the recently discovered “Brachyspira hampsonii,” have reoccurred in North American swine herds since the late 2000s. Additionally, multiple Brachyspira species have been increasingly isolated by North American diagnostic laboratories. In Europe, the reliance on antimicrobial therapy for control of sw