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Sample records for acquired resistance mechanisms

  1. Mechanisms of polymyxin resistance: acquired and intrinsic resistance in bacteria

    PubMed Central

    Olaitan, Abiola O.; Morand, Serge; Rolain, Jean-Marc

    2014-01-01

    Polymyxins are polycationic antimicrobial peptides that are currently the last-resort antibiotics for the treatment of multidrug-resistant, Gram-negative bacterial infections. The reintroduction of polymyxins for antimicrobial therapy has been followed by an increase in reports of resistance among Gram-negative bacteria. Some bacteria, such as Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii, develop resistance to polymyxins in a process referred to as acquired resistance, whereas other bacteria, such as Proteus spp., Serratia spp., and Burkholderia spp., are naturally resistant to these drugs. Reports of polymyxin resistance in clinical isolates have recently increased, including acquired and intrinsically resistant pathogens. This increase is considered a serious issue, prompting concern due to the low number of currently available effective antibiotics. This review summarizes current knowledge concerning the different strategies bacteria employ to resist the activities of polymyxins. Gram-negative bacteria employ several strategies to protect themselves from polymyxin antibiotics (polymyxin B and colistin), including a variety of lipopolysaccharide (LPS) modifications, such as modifications of lipid A with phosphoethanolamine and 4-amino-4-deoxy-L-arabinose, in addition to the use of efflux pumps, the formation of capsules and overexpression of the outer membrane protein OprH, which are all effectively regulated at the molecular level. The increased understanding of these mechanisms is extremely vital and timely to facilitate studies of antimicrobial peptides and find new potential drugs targeting clinically relevant Gram-negative bacteria. PMID:25505462

  2. Mechanisms of acquired resistance to androgen receptor targeting drugs in castration resistant prostate cancer

    PubMed Central

    Chism, David D.; De Silva, Dinuka; Whang, Young E.

    2014-01-01

    After initial response to androgen receptor targeting drugs abiraterone or enzalutamide, most patients develop progressive disease and therefore, castration resistant prostate cancer (CRPC) remains a terminal disease. Multiple mechanisms underlying acquired resistance have been postulated. Intratumoral androgen synthesis may resume after abiraterone treatment. A point mutation in the ligand binding domain of androgen receptor may confer resistance to enzalutamide. Emergence of androgen receptor splice variants lacking the ligand binding domain may mediate resistance to abiraterone and enzalutamide. Steroid receptors such as glucocorticoid receptor may substitute for androgen receptor. Drugs with novel mechanisms of action or combination therapy, along with biomarkers for patient selection, may be needed to improve the therapy of CRPC. PMID:24927631

  3. ABCB1 as predominant resistance mechanism in cells with acquired SNS-032 resistance

    PubMed Central

    Rothweiler, Florian; Voges, Yvonne; Balónová, Barbora; Blight, Barry A.; Cinatl, Jindrich

    2016-01-01

    The CDK inhibitor SNS-032 had previously exerted promising anti-neuroblastoma activity via CDK7 and 9 inhibition. ABCB1 expression was identified as major determinant of SNS-032 resistance. Here, we investigated the role of ABCB1 in acquired SNS-032 resistance. In contrast to ABCB1-expressing UKF-NB-3 sub-lines resistant to other ABCB1 substrates, SNS-032-adapted UKF-NB-3 (UKF-NB-3rSNS- 032300nM) cells remained sensitive to the non-ABCB1 substrate cisplatin and were completely re-sensitized to cytotoxic ABCB1 substrates by ABCB1 inhibition. Moreover, UKF-NB-3rSNS-032300nM cells remained similarly sensitive to CDK7 and 9 inhibition as UKF-NB-3 cells. In contrast, SHEPrSNS-0322000nM, the SNS-032-resistant sub-line of the neuroblastoma cell line SHEP, displayed low level SNS-032 resistance also when ABCB1 was inhibited. This discrepancy may be explained by the higher SNS-032 concentrations that were used to establish SHEPrSNS-0322000nM cells, since SHEP cells intrinsically express ABCB1 and are less sensitive to SNS-032 (IC50 912 nM) than UKF-NB-3 cells (IC50 153 nM). In conclusion, we show that ABCB1 expression represents the primary (sometimes exclusive) resistance mechanism in neuroblastoma cells with acquired resistance to SNS-032. Thus, ABCB1 inhibitors may increase the SNS-032 efficacy in ABCB1-expressing cells and prolong or avoid resistance formation. PMID:27517323

  4. Distinct mechanisms contribute to acquired cisplatin resistance of urothelial carcinoma cells

    PubMed Central

    Höhn, Annika; Krüger, Katharina; Skowron, Margaretha A.; Bormann, Stefanie; Schumacher, Lena; Schulz, Wolfgang A.; Hoffmann, Michèle J.; Niegisch, Günter; Fritz, Gerhard

    2016-01-01

    Cisplatin (CisPt) is frequently used in the therapy of urothelial carcinoma (UC). Its therapeutic efficacy is limited by inherent or acquired drug resistance. Here, we comparatively investigated the CisPt-induced response of two different parental urothelial carcinoma cell lines (RT-112, J-82) with that of respective drug resistant variants (RT-112R, J-82R) obtained upon month-long CisPt selection. Parental RT-112 cells were ~2.5 fold more resistant to CisPt than J-82 cells and showed a different expression pattern of CisPt-related resistance factors. CisPt resistant RT-112R and J-82R variants revealed a 2–3-fold increased CisPt resistance as compared to their corresponding parental counterparts. Acquired CisPt resistance was accompanied by morphological alterations resembling epithelial mesenchymal transition (EMT). RT-112R cells revealed lower apoptotic frequency and more pronounced G2/M arrest following CisPt exposure than RT-112 cells, whereas no differences in death induction were observed between J-82 and J-82R cells. CisPt resistant J-82R cells however were characterized by a reduced formation of CisPt-induced DNA damage and related DNA damage response (DDR) as compared to J-82 cells. Such difference was not observed between RT-112R and RT-112 cells. J-82R cells showed an enhanced sensitivity to pharmacological inhibition of checkpoint kinase 1 (Chk1) and, moreover, could be re-sensitized to CisPt upon Chk1 inhibition. Based on the data we suggest that mechanisms of acquired CisPt resistance of individual UC cells are substantially different, with apoptosis- and DDR-related mechanisms being of particular relevance. Moreover, the findings indicate that targeting of Chk1 might be useful to overcome acquired CisPt resistance of certain subtypes of UC. PMID:27191498

  5. MECHANISMS OF ACQUIRED RESISTANCE TO ENDOCRINE THERAPY IN HORMONE-DEPENDENT BREAST CANCER CELLS1

    PubMed Central

    Yue, Wei; Fan, Ping; Wang, Jiping; Li, Yuebai; Santen, Richard J.

    2007-01-01

    Acquired resistance is a major problem limiting the clinical benefit of endocrine therapy. To investigate the mechanisms involved, two in vitro models were developed from MCF-7 cells. Long-term culture of MCF-7 cells in estrogen deprived medium (LTED) mimics aromatase inhibition in patients. Continued exposure of MCF-7 to tamoxifen represents a model of acquired resistance to antiestrogens (TAM-R). Long-term estrogen deprivation results in sustained activation of the ERK MAP kinase and the PI3 kinase/mTOR pathways. Using a novel Ras inhibitor, farnesylthiosalicylic acid (FTS), to achieve dual inhibition of the pathways, we found that the mTOR pathway plays the primary role in mediation of proliferation of LTED cells. In contrast to the LTED model, there is no sustained activation of ERK MAPK but enhanced responsiveness to rapid stimulation induced by E2 and TAM in TAM-R cells. An increased amount of ERα formed complexes with EGFR and c-Src in TAM-R cells, which apparently resulted from extra-nuclear redistribution of ERα. Blockade of c-Src activity drove ERα back to the nucleus and reduced ERα-EGFR interaction. Prolonged blockade of c-Src activity restored sensitivity of TAM-R cells to tamoxifen. Our results suggest that different mechanisms are involved in acquired endocrine resistance and the necessity for individualized treatment of recurrent diseases. PMID:17616457

  6. Mutational and acquired carbapenem resistance mechanisms in multidrug resistant Pseudomonas aeruginosa clinical isolates from Recife, Brazil

    PubMed Central

    Cavalcanti, Felipe Lira de Sá; Mirones, Cristina Rodríguez; Paucar, Elena Román; Montes, Laura Álvarez; Leal-Balbino, Tereza Cristina; de Morais, Marcia Maria Camargo; Martínez-Martínez, Luis; Ocampo-Sosa, Alain Antonio

    2015-01-01

    An investigation was carried out into the genetic mechanisms responsible for multidrug resistance in nine carbapenem-resistant Pseudomonas aeruginosaisolates from different hospitals in Recife, Brazil. Susceptibility to antimicrobial agents was determined by broth microdilution. Polymerase chain reaction (PCR) was employed to detect the presence of genes encoding β-lactamases, aminoglycoside-modifying enzymes (AMEs), 16S rRNA methylases, integron-related genes and OprD. Expression of genes coding for efflux pumps and AmpC cephalosporinase were assessed by quantitative PCR. The outer membrane proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The blaSPM-1, blaKPC-2 and blaGES-1 genes were detected in P. aeruginosaisolates in addition to different AME genes. The loss of OprD in nine isolates was mainly due to frameshift mutations, premature stop codons and point mutations. An association of loss of OprD with the overexpression of MexAB-OprM and MexXY-OprM was observed in most isolates. Hyper-production of AmpC was also observed in three isolates. Clonal relationship of the isolates was determined by repetitive element palindromic-PCR and multilocus sequence typing. Our results show that the loss of OprD along with overexpression of efflux pumps and β-lactamase production were responsible for the multidrug resistance in the isolates analysed. PMID:26676375

  7. Mutational and acquired carbapenem resistance mechanisms in multidrug resistant Pseudomonas aeruginosa clinical isolates from Recife, Brazil.

    PubMed

    Cavalcanti, Felipe Lira de Sá; Mirones, Cristina Rodríguez; Paucar, Elena Román; Montes, Laura Álvarez; Leal-Balbino, Tereza Cristina; Morais, Marcia Maria Camargo de; Martínez-Martínez, Luis; Ocampo-Sosa, Alain Antonio

    2015-12-01

    An investigation was carried out into the genetic mechanisms responsible for multidrug resistance in nine carbapenem-resistant Pseudomonas aeruginosa isolates from different hospitals in Recife, Brazil. Susceptibility to antimicrobial agents was determined by broth microdilution. Polymerase chain reaction (PCR) was employed to detect the presence of genes encoding β-lactamases, aminoglycoside-modifying enzymes (AMEs), 16S rRNA methylases, integron-related genes and OprD. Expression of genes coding for efflux pumps and AmpC cephalosporinase were assessed by quantitative PCR. The outer membrane proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The blaSPM-1, blaKPC-2 and blaGES-1 genes were detected in P. aeruginosa isolates in addition to different AME genes. The loss of OprD in nine isolates was mainly due to frameshift mutations, premature stop codons and point mutations. An association of loss of OprD with the overexpression of MexAB-OprM and MexXY-OprM was observed in most isolates. Hyper-production of AmpC was also observed in three isolates. Clonal relationship of the isolates was determined by repetitive element palindromic-PCR and multilocus sequence typing. Our results show that the loss of OprD along with overexpression of efflux pumps and β-lactamase production were responsible for the multidrug resistance in the isolates analysed.

  8. Antibacterial mechanisms of rhodomyrtone against important hospital-acquired antibiotic-resistant pathogenic bacteria.

    PubMed

    Leejae, Sukanlaya; Taylor, Peter William; Voravuthikunchai, Supayang Piyawan

    2013-01-01

    The antibacterial mechanisms of rhodomyrtone, a member of the acylphloroglucinols isolated from Rhodomyrtus tomentosa leaves, against important hospital-acquired antibiotic-resistant pathogenic bacteria were assessed. The results indicated that rhodomyrtone exhibited pronounced antibacterial activity against key antibiotic-resistant pathogens including epidemic meticillin-resistant Staphylococcus aureus (EMRSA), vancomycin-intermediate S. aureus and vancomycin-resistant enterococcal strains. The strains EMRSA-16, Enterococcus faecalis ATCC 29212 and VRE-3 demonstrated a significant decrease in survival ability after treatment with rhodomyrtone at 1× (0.5 µg ml(-1)), 2×, 4× and 8× MIC for 24 h. Moreover, the compound was observed in the cytoplasmic fraction of rhodomyrtone-treated S. aureus, and only a very fine band of the compound was seen following separation of the cell-wall and cell-membrane fractions of the treated cells. In addition, exposure of S. aureus to rhodomyrtone at 4×, 2× and 1× MIC for 24 h produced no significant effect on the bacterial cell membrane and cell lysis, suggesting that neither of these is the main target of rhodomyrtone action in these organisms. Stepwise isolation of the bacterial cells with increasing resistance to rhodomyrtone was not induced in either S. aureus or EMRSA-16 after 45 passages on Luria-Bertani agar supplemented with rhodomyrtone. In addition, in vitro toxicity of rhodomyrtone at 128× MIC on human erythrocytes was not observed. These results provide evidence to support therapeutic challenges of rhodomyrtone against Gram-positive pathogens.

  9. Understanding and overcoming the mechanisms of primary and acquired resistance to abiraterone and enzalutamide in castration resistant prostate cancer.

    PubMed

    Buttigliero, Consuelo; Tucci, Marcello; Bertaglia, Valentina; Vignani, Francesca; Bironzo, Paolo; Di Maio, Massimo; Scagliotti, Giorgio Vittorio

    2015-12-01

    In recent years, in castration resistant prostate cancer (CRPC), several new drugs have been approved that prolong overall survival, including enzalutamide and abiraterone, two new-generation hormonal therapies. Despite the demonstrated benefit of these agents, not all patients with CRPC are responsive to treatment, the gain in median progression-free survival with these therapies compared to standard of care is, rather disappointingly, still less than six months and the appearance of acquired resistance is almost universal. Approximately one third of patients treated with abiraterone and 25% of those treated with enzalutamide show primary resistance to these agents. Even if the mechanisms of resistance to these agents are not fully defined, many hypotheses are emerging, including systemic and intratumoral androgen biosynthesis up-regulation, androgen receptor (AR) gene mutations and amplifications, alteration of pathways involved in cross-talk with AR signaling, glucocorticoid receptor overexpression, neuroendocrine differentiation, immune system deregulation and others. The aim of this paper is to review currently available data about mechanisms of resistance to abiraterone and enzalutamide, and to discuss how these mechanisms could be potentially overcome through novel therapeutic agents.

  10. Characterization of fecal vancomycin-resistant enterococci with acquired and intrinsic resistance mechanisms in wild animals, Spain.

    PubMed

    Lozano, Carmen; Gonzalez-Barrio, David; Camacho, Maria Cruz; Lima-Barbero, Jose Francisco; de la Puente, Javier; Höfle, Ursula; Torres, Carmen

    2016-11-01

    The objectives were to evaluate the presence of vancomycin-resistant enterococci with acquired (VRE-a) and intrinsic (VRE-i) resistance mechanisms in fecal samples from different wild animals, and analyze their phenotypes and genotypes of antimicrobial resistance. A total of 348 cloacal/rectal samples from red-legged partridges (127), white storks (81), red kites (59), and wild boars (81) (June 2014/February 2015) were inoculated in Slanetz-Bartley agar supplemented with vancomycin (4 μg/mL). We investigated the susceptibility to 12 antimicrobials and the presence of 19 antimicrobial resistance and five virulence genes. In addition, we performed multilocus sequence typing, detection of IS16 and studied Tn1546 structure. One VRE-a isolate was identified in one wild boar. This isolate was identified as Enterococcus faecium, harbored vanA gene included into Tn1546 (truncated with IS1542/IS1216), and belonged to the new ST993. This isolate contained the erm(A), erm(B), tet(M), dfrG, and dfrK genes. Neither element IS16 nor the studied virulence genes were detected. Ninety-six VRE-i isolates were identified (89 Enterococcus gallinarum and seven Enterococcus casseliflavus), with the following prevalence: red kites (71.2 %), white storks (46.9 %), red-legged partridges (7.9 %), and wild boars (4.9 %). Most E. gallinarum isolates showed resistance to tetracycline (66.3 %) and/or erythromycin (46.1 %). High-level resistance to aminoglycosides was present among our VRE-i isolates: kanamycin (22.9 %), streptomycin (11.5 %), and gentamicin (9.4 %). In general, VRE-i isolates of red kites showed higher rates of resistance for non-glycopeptide agents than those of other animal species. The dissemination of acquired resistance mechanisms in natural environments could have implications in the global spread of resistance with public health implications.

  11. In vitro antimicrobial susceptibility of Alloscardovia omnicolens and molecular mechanisms of acquired resistance.

    PubMed

    Isnard, Christophe; Lienhard, Reto; Reissier, Sophie; Rodriguez, Sonia; Krähenbühl, Joanna; Liassine, Nadia; Guérin, François; Cattoir, Vincent

    2016-03-01

    All the 31 isolates of Alloscardovia omnicolens exhibited low MICs for β-lactams, glycopeptides, linezolid, tetracyclines, and cotrimoxazole. One strain showed MICs ≥256μg/mL for both erythromycin and clindamycin with a single point mutation in 23S rRNA. One strain likely had acquired fluoroquinolone resistance associated with a unique mutation in ParC.

  12. Bayesian model of signal rewiring reveals mechanisms of gene dysregulation in acquired drug resistance in breast cancer

    PubMed Central

    Azad, A. K. M.; Keith, Jonathan M.

    2017-01-01

    . Our results suggest many signaling pathway structures are compromised in acquired resistance, and V-structures of aberrant signaling within/among those pathways may provide further insights into the bypass mechanism of targeted inhibition. PMID:28288164

  13. Bayesian model of signal rewiring reveals mechanisms of gene dysregulation in acquired drug resistance in breast cancer.

    PubMed

    Azad, A K M; Lawen, Alfons; Keith, Jonathan M

    2017-01-01

    . Our results suggest many signaling pathway structures are compromised in acquired resistance, and V-structures of aberrant signaling within/among those pathways may provide further insights into the bypass mechanism of targeted inhibition.

  14. Acquired BRAF inhibitor resistance: a multicenter meta-analysis of the spectrum and frequencies, clinical behavior, and phenotypic associations of resistance mechanisms

    PubMed Central

    Johnson, Douglas B.; Menzies, Alexander M.; Zimmer, Lisa; Eroglu, Zeynep; Ye, Fei; Zhao, Shilin; Rizos, Helen; Sucker, Antje; Scolyer, Richard A.; Gutzmer, Ralf; Gogas, Helen; Kefford, Richard F.; Thompson, John F.; Becker, Jürgen C.; Berking, Carola; Egberts, Friederike; Loquai, Carmen; Goldinger, Simone M.; Pupo, Gulietta M.; Hugo, Willy; Kong, Xiangju; Garraway, Levi A.; Sosman, Jeffrey A.; Ribas, Antoni; Lo, Roger S.; Long, Georgina V.; Schadendorf, Dirk

    2015-01-01

    Background Acquired resistance to BRAF inhibitors (BRAFi) is a near-universal phenomenon caused by numerous genetic and non-genetic alterations. In this study, we evaluated the spectrum, onset, pattern of progression, and subsequent clinical outcomes associated with specific mechanisms of resistance. Methods We compiled clinical and genetic data from 100 patients with 132 tissue samples obtained at progression on BRAFi therapy from 3 large, previously published studies of BRAFi resistance. These samples were subjected to whole exome sequencing and/or PCR-based genetic testing. Results Among 132 samples, putative resistance mechanisms were identified in 58%, including NRAS or KRAS mutations (20%), BRAF splice variants (16%), BRAFV600E/K amplifications (13%), MEK1/2 mutations (7%), and non-MAPK pathway alterations (11%). Marked heterogeneity was observed within tumors and patients; 18 of 19 patients (95%) with >1 progression biopsy had distinct/unknown drivers of resistance between samples. NRAS mutations were associated with vemurafenib use (p=0.045) and intracranial metastases (p=0.036), and MEK1/2 mutations correlated with hepatic progression (p=0.011). Progression-free survival and overall survival were similar across resistance mechanisms. The median survival after disease progression was 6.9 months, and responses to subsequent BRAF and MEK inhibition were uncommon (2 of 15; 13%). Post-progression outcomes did not correlate with specific acquired BRAFi resistance mechanisms. Conclusions This is the first study to systematically characterize the clinical implications of particular acquired BRAFi resistance mechanisms in patients with BRAF-mutant melanoma largest study to compile the landscape of resistance. Despite marked heterogeneity of resistance mechanisms within patients, NRAS mutations correlated with vemurafenib use and intracranial disease involvement. PMID:26608120

  15. In Vitro Activity of ASP2397 against Aspergillus Isolates with or without Acquired Azole Resistance Mechanisms

    PubMed Central

    Jensen, Rasmus Hare; Cuenca-Estrella, Manuel

    2015-01-01

    ASP2397 is a new compound with a novel and as-yet-unknown target different from that of licensed antifungal agents. It has activity against Aspergillus and Candida glabrata. We compared its in vitro activity against wild-type and azole-resistant A. fumigatus and A. terreus isolates with that of amphotericin B, itraconazole, posaconazole, and voriconazole. Thirty-four isolates, including 4 wild-type A. fumigatus isolates, 24 A. fumigatus isolates with alterations in CYP51A TR/L98H (5 isolates), M220 (9 isolates), G54 (9 isolates), and HapE (1 isolate), and A. terreus isolates (2 wild-type isolates and 1 isolate with an M217I CYP51A alteration), were analyzed. EUCAST E.Def 9.2 and CLSI M38-A2 MIC susceptibility testing was performed. ASP2397 MIC50 values (in milligrams per liter, with MIC ranges in parentheses) determined by EUCAST and CLSI were 0.5 (0.25 to 1) and 0.25 (0.06 to 0.25) against A. fumigatus CYP51A wild-type isolates and were similarly 0.5 (0.125 to >4) and 0.125 (0.06 to >4) against azole-resistant A. fumigatus isolates, respectively. These values were comparable to those for amphotericin B, which were 0.25 (0.125 to 0.5) and 0.25 (0.125 to 0.25) against wild-type isolates and 0.25 (0.125 to 1) and 0.25 (0.125 to 1) against isolates with azole resistance mechanisms, respectively. In contrast, MICs for the azole compounds were elevated and highest for itraconazole: >4 (1 to >4) and 4 (0.5 to >4) against isolates with azole resistance mechanisms compared to 0.125 (0.125 to 0.25) and 0.125 (0.06 to 0.25) against wild-type isolates, respectively. ASP2397 was active against A. terreus CYP51A wild-type isolates (MIC 0.5 to 1), whereas MICs of both azole and ASP2397 were elevated for the mutant isolate. ASP2397 displayed in vitro activity against A. fumigatus and A. terreus isolates which was independent of the presence or absence of azole target gene resistance mutations in A. fumigatus. The findings are promising at a time when azole-resistant A. fumigatus

  16. Ubenimex attenuates acquired sorafenib resistance in renal cell carcinoma by inhibiting Akt signaling in a lipophagy associated mechanism

    PubMed Central

    Liu, Shuai; Gao, Mingwei; Wang, Xiaoqing; Ding, Sentai; Lv, Jiaju; Gao, Dexuan; Wang, Zhiyang; Niu, Zhihong

    2016-01-01

    Sorafenib is used as first line treatment of renal cell carcinoma (RCC) due to the poor sensitivity to radiotherapy and chemotherapy of this malignancy; however, acquired resistance limits the application of sorafenib and its analogues. In this study, we explored a new strategy to overcome acquired resistance to sorafenib. The RCC cell lines 786-O and ACHN were cultured in presence of increasing concentrations of sorafenib to generate sorafenib-resistant cell lines, 786-O-R and ACHN-R. Interestingly, treatment with ubenimex (0.25 mg/ml) and 3-MA (2 mM) restored the sensitivity of resistant cell lines to sorafenib, indicating the involvement of autophagy in acquired resistance. High levels of autophagy flux were observed in resistant cells, and the opposite effects of ubenimex and 3-MA suggested a complex role for autophagy. While 3-MA abolished protection in sorafenib-resistant cells, ubenimex induced uncontrolled autophagy and autophagic cell death. Lipophagy, characterized by a lipid droplet cargo, was observed in RCC tissues and cells. In sorafenib-resistant cells, ubenimex inhibited the Akt signaling pathway that regulates autophagy. In summary, lipophagy participates in sorafenib-resistance of RCC, which could be reversed by interventions targeting the Akt pathway. PMID:27816967

  17. Acquired Antibiotic Resistance Genes: An Overview

    PubMed Central

    van Hoek, Angela H. A. M.; Mevius, Dik; Guerra, Beatriz; Mullany, Peter; Roberts, Adam Paul; Aarts, Henk J. M.

    2011-01-01

    In this review an overview is given on antibiotic resistance (AR) mechanisms with special attentions to the AR genes described so far preceded by a short introduction on the discovery and mode of action of the different classes of antibiotics. As this review is only dealing with acquired resistance, attention is also paid to mobile genetic elements such as plasmids, transposons, and integrons, which are associated with AR genes, and involved in the dispersal of antimicrobial determinants between different bacteria. PMID:22046172

  18. Natural and acquired macrolide resistance in mycobacteria.

    PubMed

    Doucet-Populaire, F; Buriánková, K; Weiser, J; Pernodet, J-L

    2002-12-01

    The genus Mycobacterium contains two of the most important human pathogens, Mycobacterium tuberculosis and Mycobacterium leprae, the etiologic agents of tuberculosis and leprosy, respectively. Other mycobacteria are mostly saprophytic organisms, living in soil and water, but some of them can cause opportunistic infections. The increasing incidence of tuberculosis as well as infections with non-tuberculous mycobacteria (NTM) in AIDS patients has renewed interest in molecular mechanisms of drug resistance in these pathogens. Mycobacteria show a high degree of intrinsic resistance to most common antibiotics. For instance, species from the M. tuberculosis complex (MTC) are intrinsically resistant to macrolides. Nevertheless, some semi-synthetic macrolides as the erythromycin derivatives clarithromycin, azithromycin and most recently the ketolides, are active against NTM, particularly Mycobacterium avium, and some of them are widely used for infection treatment. However, shortly after the introduction of these new drugs, resistant strains appeared due to mutations in the macrolide target, the ribosome. The mycobacterial cell wall with its specific composition and structure is considered to be a major factor in promoting the natural resistance of mycobacteria to various antibiotics. However, to explain the difference in macrolide sensitivity between the MTC and NTM, the synergistic contribution of a specific resistance mechanism might be required, in addition to possible differences in cell wall permeability. This mini-review summarizes the current knowledge on the natural and acquired macrolide resistance in mycobacteria, gives an overview of potential mechanisms implicated in the intrinsic resistance and brings recent data concerning a macrolide resistance determinant in the MTC.

  19. Tunable-combinatorial Mechanisms of Acquired Resistance Limit the Efficacy of BRAF/MEK Co-targeting but Result in Melanoma Drug Addiction

    PubMed Central

    Moriceau, Gatien; Hugo, Willy; Hong, Aayoung; Shi, Hubing; Kong, Xiangju; Yu, Clarissa C.; Koya, Richard C.; Samatar, Ahmed A.; Khanlou, Negar; Braun, Jonathan; Ruchalski, Kathleen; Seifert, Heike; Larkin, James; Dahlman, Kimberly B.; Johnson, Douglas B.; Algazi, Alain; Sosman, Jeffrey A.; Ribas, Antoni; Lo, Roger S.

    2014-01-01

    SUMMARY Combined BRAF and MEK targeted therapy improves upon BRAF inhibitor (BRAFi) therapy but is still beset by acquired resistance. We show that melanomas acquire resistance to combined BRAF and MEK inhibition by augmenting or combining mechanisms of single-agent BRAFi resistance. These double-drug resistance-associated genetic configurations significantly altered molecular interactions underlying MAPK pathway reactivation. V600EBRAF, expressed at supra-physiological levels because of V600EBRAF ultra-amplification, dimerized with and activated CRAF. In addition, MEK mutants enhanced interaction with over-expressed V600EBRAF via a regulatory interface at R662 of V600EBRAF. Importantly, melanoma cell lines selected for resistance to BRAFi+MEKi, but not those to BRAFi alone, displayed robust drug addiction, providing a potentially exploitable therapeutic opportunity. PMID:25600339

  20. HER2 amplification: a potential mechanism of acquired resistance to EGFR inhibition in EGFR-mutant lung cancers that lack the second-site EGFRT790M mutation.

    PubMed

    Takezawa, Ken; Pirazzoli, Valentina; Arcila, Maria E; Nebhan, Caroline A; Song, Xiaoling; de Stanchina, Elisa; Ohashi, Kadoaki; Janjigian, Yelena Y; Spitzler, Paula J; Melnick, Mary Ann; Riely, Greg J; Kris, Mark G; Miller, Vincent A; Ladanyi, Marc; Politi, Katerina; Pao, William

    2012-10-01

    EGF receptor (EGFR)-mutant lung cancers eventually become resistant to treatment with EGFR tyrosine kinase inhibitors (TKI). The combination of EGFR-TKI afatinib and anti-EGFR antibody cetuximab can overcome acquired resistance in mouse models and human patients. Because afatinib is also a potent HER2 inhibitor, we investigated the role of HER2 in EGFR-mutant tumor cells. We show in vitro and in vivo that afatinib plus cetuximab significantly inhibits HER2 phosphorylation. HER2 overexpression or knockdown confers resistance or sensitivity, respectively, in all studied cell line models. FISH analysis revealed that HER2 was amplified in 12% of tumors with acquired resistance versus only 1% of untreated lung adenocarcinomas. Notably, HER2 amplification and EGFR(T790M) were mutually exclusive. Collectively, these results reveal a previously unrecognized mechanism of resistance to EGFR-TKIs and provide a rationale to assess the status and possibly target HER2 in EGFR-mutant tumors with acquired resistance to EGFR-TKIs.

  1. Signal regulators of systemic acquired resistance

    PubMed Central

    Gao, Qing-Ming; Zhu, Shifeng; Kachroo, Pradeep; Kachroo, Aardra

    2015-01-01

    Salicylic acid (SA) is an important phytohormone that plays a vital role in a number of physiological responses, including plant defense. The last two decades have witnessed a number of breakthroughs related to biosynthesis, transport, perception and signaling mediated by SA. These findings demonstrate that SA plays a crictical role in both local and systemic defense responses. Systemic acquired resistance (SAR) is one such SA-dependent response. SAR is a long distance signaling mechanism that provides broad spectrum and long-lasting resistance to secondary infections throughout the plant. This unique feature makes SAR a highly desirable trait in crop production. This review summarizes the recent advances in the role of SA in SAR and discusses its relationship to other SAR inducers. PMID:25918514

  2. Acquired savolitinib resistance in non-small cell lung cancer arises via multiple mechanisms that converge on MET-independent mTOR and MYC activation

    PubMed Central

    Castriotta, Lillian; Ladd, Brendon; Markovets, Aleksandra; Beran, Garry; Ren, Yongxin; Zhou, Feng; Adam, Ammar; Zinda, Michael; Reimer, Corinne; Qing, Weiguo; Su, Weiguo; Clark, Edwin; D'Cruz, Celina M.; Schuller, Alwin G.

    2016-01-01

    Lung cancer is the most common cause of cancer death globally with a significant, unmet need for more efficacious treatments. The receptor tyrosine kinase MET has been implicated as an oncogene in numerous cancer subtypes, including non-small cell lung cancer (NSCLC). Here we explore the therapeutic potential of savolitinib (volitinib, AZD6094, HMPL-504), a potent and selective MET inhibitor, in NSCLC. In vitro, savolitinib inhibits MET phosphorylation with nanomolar potency, which correlates with blockade of PI3K/AKT and MAPK signaling as well as MYC down-regulation. In vivo, savolitinib causes inhibition of these pathways and significantly decreases growth of MET-dependent xenografts. To understand resistance mechanisms, we generated savolitinib resistance in MET-amplified NSCLC cell lines and analyzed individual clones. We found that upregulation of MYC and constitutive mTOR pathway activation is a conserved feature of resistant clones that can be overcome by knockdown of MYC or dual mTORC1/2 inhibition. Lastly, we demonstrate that mechanisms of resistance are heterogeneous, arising via a switch to EGFR dependence or by a requirement for PIM signaling. This work demonstrates the efficacy of savolitinib in NSCLC and characterizes acquired resistance, identifying both known and novel mechanisms that may inform combination strategies in the clinic. PMID:27472392

  3. Resistance mechanisms

    PubMed Central

    Cag, Yasemin; Caskurlu, Hulya; Fan, Yanyan; Cao, Bin

    2016-01-01

    By definition, the terms sepsis and septic shock refer to a potentially fatal infectious state in which the early administration of an effective antibiotic is the most significant determinant of the outcome. Because of the global spread of resistant bacteria, the efficacy of antibiotics has been severely compromised. S. pneumonia, Escherichia coli (E. coli), Klebsiella, Acinetobacter, and Pseudomonas are the predominant pathogens of sepsis and septic shock. It is common for E. coli, Klebsiella, Acinetobacter and Pseudomonas to be resistant to multiple drugs. Multiple drug resistance is caused by the interplay of multiple resistance mechanisms those emerge via the acquisition of extraneous resistance determinants or spontaneous mutations. Extended-spectrum beta-lactamases (ESBLs), carbapenemases, aminoglycoside-modifying enzymes (AMEs) and quinolone resistance determinants are typically external and disseminate on mobile genetic elements, while porin-efflux mechanisms are activated by spontaneous modifications of inherited structures. Porin and efflux mechanisms are frequent companions of multiple drug resistance in Acinetobacter and P. aeruginosa, but only occasionally detected among E. coli and Klebsiella. Antibiotic resistance became a global health threat. This review examines the major resistance mechanisms of the leading microorganisms of sepsis. PMID:27713884

  4. Targets for Combating the Evolution of Acquired Antibiotic Resistance.

    PubMed

    Culyba, Matthew J; Mo, Charlie Y; Kohli, Rahul M

    2015-06-16

    Bacteria possess a remarkable ability to rapidly adapt and evolve in response to antibiotics. Acquired antibiotic resistance can arise by multiple mechanisms but commonly involves altering the target site of the drug, enzymatically inactivating the drug, or preventing the drug from accessing its target. These mechanisms involve new genetic changes in the pathogen leading to heritable resistance. This recognition underscores the importance of understanding how such genetic changes can arise. Here, we review recent advances in our understanding of the processes that contribute to the evolution of antibiotic resistance, with a particular focus on hypermutation mediated by the SOS pathway and horizontal gene transfer. We explore the molecular mechanisms involved in acquired resistance and discuss their viability as potential targets. We propose that additional studies into these adaptive mechanisms not only can provide insights into evolution but also can offer a strategy for potentiating our current antibiotic arsenal.

  5. Targets for Combating the Evolution of Acquired Antibiotic Resistance

    PubMed Central

    2015-01-01

    Bacteria possess a remarkable ability to rapidly adapt and evolve in response to antibiotics. Acquired antibiotic resistance can arise by multiple mechanisms but commonly involves altering the target site of the drug, enzymatically inactivating the drug, or preventing the drug from accessing its target. These mechanisms involve new genetic changes in the pathogen leading to heritable resistance. This recognition underscores the importance of understanding how such genetic changes can arise. Here, we review recent advances in our understanding of the processes that contribute to the evolution of antibiotic resistance, with a particular focus on hypermutation mediated by the SOS pathway and horizontal gene transfer. We explore the molecular mechanisms involved in acquired resistance and discuss their viability as potential targets. We propose that additional studies into these adaptive mechanisms not only can provide insights into evolution but also can offer a strategy for potentiating our current antibiotic arsenal. PMID:26016604

  6. The evolution of resistance through costly acquired immunity.

    PubMed Central

    Boots, Michael; Bowers, Roger G.

    2004-01-01

    We examine the evolutionary dynamics of resistance to parasites through acquired immunity. Resistance can be achieved through the innate mechanisms of avoidance of infection and reduced pathogenicity once infected, through recovery from infection and through remaining immune to infection: acquired immunity. We assume that each of these mechanisms is costly to the host and find that the evolutionary dynamics of innate immunity in hosts that also have acquired immunity are quantitatively the same as in hosts that possess only innate immunity. However, compared with resistance through avoidance or recovery, there is less likely to be polymorphism in the length of acquired immunity within populations. Long-lived organisms that can recover at intermediate rates faced with fast-transmitting pathogens that cause intermediate pathogenicity (mortality of infected individuals) are most likely to evolve long-lived acquired immunity. Our work emphasizes that because whether or not acquired immunity is beneficial depends on the characteristics of the disease, organisms may be selected to only develop acquired immunity to some of the diseases that they encounter. PMID:15209105

  7. Mechanisms of intrinsic resistance and acquired susceptibility of Pseudomonas aeruginosa isolated from cystic fibrosis patients to temocillin, a revived antibiotic

    PubMed Central

    Chalhoub, Hussein; Pletzer, Daniel; Weingart, Helge; Braun, Yvonne; Tunney, Michael M.; Elborn, J. Stuart; Rodriguez-Villalobos, Hector; Plésiat, Patrick; Kahl, Barbara C.; Denis, Olivier; Winterhalter, Mathias; Tulkens, Paul M.; Van Bambeke, Françoise

    2017-01-01

    The β-lactam antibiotic temocillin (6-α-methoxy-ticarcillin) shows stability to most extended spectrum β-lactamases, but is considered inactive against Pseudomonas aeruginosa. Mutations in the MexAB-OprM efflux system, naturally occurring in cystic fibrosis (CF) isolates, have been previously shown to reverse this intrinsic resistance. In the present study, we measured temocillin activity in a large collection (n = 333) of P. aeruginosa CF isolates. 29% of the isolates had MICs ≤ 16 mg/L (proposed clinical breakpoint for temocillin). Mutations were observed in mexA or mexB in isolates for which temocillin MIC was ≤512 mg/L (nucleotide insertions or deletions, premature termination, tandem repeat, nonstop, and missense mutations). A correlation was observed between temocillin MICs and efflux rate of N-phenyl-1-naphthylamine (MexAB-OprM fluorescent substrate) and extracellular exopolysaccharide abundance (contributing to a mucoid phenotype). OpdK or OpdF anion-specific porins expression decreased temocillin MIC by ~1 two-fold dilution only. Contrarily to the common assumption that temocillin is inactive on P. aeruginosa, we show here clinically-exploitable MICs on a non-negligible proportion of CF isolates, explained by a wide diversity of mutations in mexA and/or mexB. In a broader context, this work contributes to increase our understanding of MexAB-OprM functionality and help delineating how antibiotics interact with MexA and MexB. PMID:28091521

  8. Acquired resistance to gemcitabine and cross-resistance in human pancreatic cancer clones.

    PubMed

    Yoneyama, Hiroshi; Takizawa-Hashimoto, Asako; Takeuchi, Osamu; Watanabe, Yukiko; Atsuda, Koichiro; Asanuma, Fumiki; Yamada, Yoshinori; Suzuki, Yukio

    2015-01-01

    The efficacy of gemcitabine (GEM), a standard treatment agent for pancreatic cancer, is insufficient because of primary or acquired resistance to this drug. Patients with tumors intrinsically sensitive to GEM gradually acquire resistance and require a shift to second agents, which are associated with the risk of cross-resistance. However, whether cross-resistance is actually present has long been disputed. Using six GEM-resistant and four highly GEM-resistant clones derived from the pancreatic cancer cell line BxPC-3, we determined the resistance of each clone and parent cell line to GEM and four anticancer agents (5-FU, CDDP, CPT-11, and DTX). The GEM-resistant clones had different resistances to GEM and other agents, and did not develop a specific pattern of cross-resistance. This result shows that tumor cells are heterogeneous. However, all highly GEM-resistant clones presented overexpression of ribonucleotide reductase subunit M1 (RRM1), a target enzyme for metabolized GEM, and showed cross-resistance with 5-FU. The expression level of RRM1 was high; therefore, resistance to GEM was high. We showed that a tumor cell acquired resistance to GEM, and cross-resistance developed in one clone. These results suggest that only cells with certain mechanisms for high-level resistance to GEM survive against selective pressure applied by highly concentrated GEM. RRM1 may be one of the few factors that can induce high resistance to GEM and a suitable therapeutic target for GEM-resistant pancreatic cancer.

  9. Deficient BIM Expression as a Mechanism of Intrinsic and Acquired Resistance to Targeted Therapies in EGFR-Mutant and ALK-Positive Lung Cancers

    DTIC Science & Technology

    2015-08-01

    EGFR- Mutant and ALK-Positive Lung Cancers PRINCIPAL INVESTIGATOR: Lecia Sequist MD. CONTRACTING ORGANIZATION: Massachusetts General Hospital Boston...and Acquired Resistance to Targeted Therapies in EGFR- Mutant and ALK-Positive Lung Cancers 5b. GRANT NUMBER W81XWH-13-1-0227 5c. PROGRAM ELEMENT...to a specific kinase, inhibition of that kinase often leads to cell growth arrest and apoptosis. For example, EGFR mutant and EML4-ALK lung cancers

  10. Deficient BIM Expression as a Mechanism of Intrinsic and Acquired Resistance to Targeted Therapies in EGFR-Mutant and ALK-Positive Lung Cancers

    DTIC Science & Technology

    2015-08-01

    EGFR- Mutant and ALK-Positive Lung Cancers PRINCIPAL INVESTIGATOR: Jeffrey Engelman MD PhD. CONTRACTING ORGANIZATION: Massachusetts General Hospital...Intrinsic and Acquired Resistance to Targeted Therapies in EGFR- Mutant and ALK-Positive Lung Cancers 5b. GRANT NUMBER W81XWH-13-1-0226 5c. PROGRAM...to a specific kinase, inhibition of that kinase often leads to cell growth arrest and apoptosis. For example, EGFR mutant and EML4-ALK lung cancers

  11. Free radicals mediate systemic acquired resistance.

    PubMed

    Wang, Caixia; El-Shetehy, Mohamed; Shine, M B; Yu, Keshun; Navarre, Duroy; Wendehenne, David; Kachroo, Aardra; Kachroo, Pradeep

    2014-04-24

    Systemic acquired resistance (SAR) is a form of resistance that protects plants against a broad spectrum of secondary infections. However, exploiting SAR for the protection of agriculturally important plants warrants a thorough investigation of the mutual interrelationships among the various signals that mediate SAR. Here, we show that nitric oxide (NO) and reactive oxygen species (ROS) serve as inducers of SAR in a concentration-dependent manner. Thus, genetic mutations that either inhibit NO/ROS production or increase NO accumulation (e.g., a mutation in S-nitrosoglutathione reductase [GSNOR]) abrogate SAR. Different ROS function additively to generate the fatty-acid-derived azelaic acid (AzA), which in turn induces production of the SAR inducer glycerol-3-phosphate (G3P). Notably, this NO/ROS→AzA→G3P-induced signaling functions in parallel with salicylic acid-derived signaling. We propose that the parallel operation of NO/ROS and SA pathways facilitates coordinated regulation in order to ensure optimal induction of SAR.

  12. Deficient BIM Expression as a Mechanism of Intrinsic and Acquired Resistance to Targeted Therapies in EGFR-Mutant and ALK-Positive Lung Cancers

    DTIC Science & Technology

    2014-08-01

    depressed   in  patients’  specimens  following  acquired...second-­‐generation  ALK  inhibitors.   2C.  Current  objectives:  Determine  if  BIM  levels  are   depressed  (or  BIM  has...whether  resistant  lines  have  a   depressed  apoptotic  response  to  second-­‐line  targeted   therapies  by

  13. Molecular mechanisms of antibiotic resistance.

    PubMed

    Blair, Jessica M A; Webber, Mark A; Baylay, Alison J; Ogbolu, David O; Piddock, Laura J V

    2015-01-01

    Antibiotic-resistant bacteria that are difficult or impossible to treat are becoming increasingly common and are causing a global health crisis. Antibiotic resistance is encoded by several genes, many of which can transfer between bacteria. New resistance mechanisms are constantly being described, and new genes and vectors of transmission are identified on a regular basis. This article reviews recent advances in our understanding of the mechanisms by which bacteria are either intrinsically resistant or acquire resistance to antibiotics, including the prevention of access to drug targets, changes in the structure and protection of antibiotic targets and the direct modification or inactivation of antibiotics.

  14. Adaptive and Acquired Resistance to EGFR Inhibitors Converge on the MAPK Pathway

    PubMed Central

    Ma, Pengfei; Fu, Yujie; Chen, Minjiang; Jing, Ying; Wu, Jie; Li, Ke; Shen, Ying; Gao, Jian-Xin; Wang, Mengzhao; Zhao, Xiaojing; Zhuang, Guanglei

    2016-01-01

    Both adaptive and acquired resistance significantly limits the efficacy of the epidermal growth factor receptor (EGFR) kinase inhibitors. However, the distinct or common mechanisms of adaptive and acquired resistance have not been fully characterized. Here, through systematic modeling of erlotinib resistance in lung cancer, we found that feedback reactivation of MAPK signaling following erlotinib treatment, which was dependent on the MET receptor, contributed to the adaptive resistance of EGFR inhibitors. Interestingly, acquired resistance to erlotinib was also associated with the MAPK pathway activation as a result of CRAF or NRAS amplification. Consequently, combined inhibition of EGFR and MAPK impeded the development of both adaptive and acquired resistance. These observations demonstrate that adaptive and acquired resistance to EGFR inhibitors can converge on the same pathway and credential cotargeting EGFR and MAPK as a promising therapeutic approach in EGFR mutant tumors. PMID:27279914

  15. Mechanisms of drug resistance: quinolone resistance

    PubMed Central

    Hooper, David C.; Jacoby, George A.

    2015-01-01

    Quinolone antimicrobials are synthetic and widely used in clinical medicine. Resistance emerged with clinical use and became common in some bacterial pathogens. Mechanisms of resistance include two categories of mutation and acquisition of resistance-conferring genes. Resistance mutations in one or both of the two drug target enzymes, DNA gyrase and DNA topoisomerase IV, are commonly in a localized domain of the GyrA and ParE subunits of the respective enzymes and reduce drug binding to the enzyme-DNA complex. Other resistance mutations occur in regulatory genes that control the expression of native efflux pumps localized in the bacterial membrane(s). These pumps have broad substrate profiles that include quinolones as well as other antimicrobials, disinfectants, and dyes. Mutations of both types can accumulate with selection pressure and produce highly resistant strains. Resistance genes acquired on plasmids can confer low-level resistance that promotes the selection of mutational high-level resistance. Plasmid-encoded resistance is due to Qnr proteins that protect the target enzymes from quinolone action, one mutant aminoglycoside-modifying enzyme that also modifies certain quinolones, and mobile efflux pumps. Plasmids with these mechanisms often encode additional antimicrobial resistances and can transfer multidrug resistance that includes quinolones. Thus, the bacterial quinolone resistance armamentarium is large. PMID:26190223

  16. Mechanisms of drug resistance: quinolone resistance.

    PubMed

    Hooper, David C; Jacoby, George A

    2015-09-01

    Quinolone antimicrobials are synthetic and widely used in clinical medicine. Resistance emerged with clinical use and became common in some bacterial pathogens. Mechanisms of resistance include two categories of mutation and acquisition of resistance-conferring genes. Resistance mutations in one or both of the two drug target enzymes, DNA gyrase and DNA topoisomerase IV, are commonly in a localized domain of the GyrA and ParE subunits of the respective enzymes and reduce drug binding to the enzyme-DNA complex. Other resistance mutations occur in regulatory genes that control the expression of native efflux pumps localized in the bacterial membrane(s). These pumps have broad substrate profiles that include quinolones as well as other antimicrobials, disinfectants, and dyes. Mutations of both types can accumulate with selection pressure and produce highly resistant strains. Resistance genes acquired on plasmids can confer low-level resistance that promotes the selection of mutational high-level resistance. Plasmid-encoded resistance is due to Qnr proteins that protect the target enzymes from quinolone action, one mutant aminoglycoside-modifying enzyme that also modifies certain quinolones, and mobile efflux pumps. Plasmids with these mechanisms often encode additional antimicrobial resistances and can transfer multidrug resistance that includes quinolones. Thus, the bacterial quinolone resistance armamentarium is large.

  17. Intrinsic, adaptive and acquired antimicrobial resistance in Gram-negative bacteria.

    PubMed

    Arzanlou, Mohsen; Chai, Wern Chern; Venter, Henrietta

    2017-02-28

    Gram-negative bacteria are responsible for a large proportion of antimicrobial-resistant infections in humans and animals. Among this class of bacteria are also some of the most successful environmental organisms. Part of this success is their adaptability to a variety of different niches, their intrinsic resistance to antimicrobial drugs and their ability to rapidly acquire resistance mechanisms. These mechanisms of resistance are not exclusive and the interplay of several mechanisms causes high levels of resistance. In this review, we explore the molecular mechanisms underlying resistance in Gram-negative organisms and how these different mechanisms enable them to survive many different stress conditions.

  18. Acquired resistance of Mycobacterium tuberculosis to bedaquiline.

    PubMed

    Andries, Koen; Villellas, Cristina; Coeck, Nele; Thys, Kim; Gevers, Tom; Vranckx, Luc; Lounis, Nacer; de Jong, Bouke C; Koul, Anil

    2014-01-01

    Bedaquiline (BDQ), an ATP synthase inhibitor, is the first drug to be approved for treatment of multi-drug resistant tuberculosis in decades. In vitro resistance to BDQ was previously shown to be due to target-based mutations. Here we report that non-target based resistance to BDQ, and cross-resistance to clofazimine (CFZ), is due to mutations in Rv0678, a transcriptional repressor of the genes encoding the MmpS5-MmpL5 efflux pump. Efflux-based resistance was identified in paired isolates from patients treated with BDQ, as well as in mice, in which it was confirmed to decrease bactericidal efficacy. The efflux inhibitors verapamil and reserpine decreased the minimum inhibitory concentrations of BDQ and CFZ in vitro, but verapamil failed to increase the bactericidal effect of BDQ in mice and was unable to reverse efflux-based resistance in vivo. Cross-resistance between BDQ and CFZ may have important clinical implications.

  19. Augmented HR Repair Mediates Acquired Temozolomide Resistance in Glioblastoma.

    PubMed

    Gil Del Alcazar, Carlos Rodrigo; Todorova, Pavlina Krasimirova; Habib, Amyn A; Mukherjee, Bipasha; Burma, Sandeep

    2016-10-01

    Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults and is universally fatal. The DNA alkylating agent temozolomide is part of the standard-of-care for GBM. However, these tumors eventually develop therapy-driven resistance and inevitably recur. While loss of mismatch repair (MMR) and re-expression of MGMT have been shown to underlie chemoresistance in a fraction of GBMs, resistance mechanisms operating in the remaining GBMs are not well understood. To better understand the molecular basis for therapy-driven temozolomide resistance, mice bearing orthotopic GBM xenografts were subjected to protracted temozolomide treatment, and cell lines were generated from the primary (untreated) and recurrent (temozolomide-treated) tumors. As expected, the cells derived from primary tumors were sensitive to temozolomide, whereas the cells from the recurrent tumors were significantly resistant to the drug. Importantly, the acquired resistance to temozolomide in the recurrent lines was not driven by re-expression of MGMT or loss of MMR but was due to accelerated repair of temozolomide-induced DNA double-strand breaks (DSB). Temozolomide induces DNA replication-associated DSBs that are primarily repaired by the homologous recombination (HR) pathway. Augmented HR appears to underpin temozolomide resistance in the recurrent lines, as these cells were cross-resistant to other agents that induced replication-associated DSBs, exhibited faster resolution of damage-induced Rad51 foci, and displayed higher levels of sister chromatid exchanges (SCE). Furthermore, in light of recent studies demonstrating that CDK1 and CDK2 promote HR, it was found that CDK1/2 inhibitors countered the heightened HR in recurrent tumors and sensitized these therapy-resistant tumor cells to temozolomide.

  20. Dominant mechanisms of primary resistance differ from dominant mechanisms of secondary resistance to targeted therapies.

    PubMed

    Asić, Ksenija

    2016-01-01

    The effectiveness of targeted therapies is currently limited, as almost all patients eventually acquire resistance within year/year and a half from therapy initiation and a small subset of a patients fail to respond at all, demonstrating intrinsic resistance. The aim of this review was to determine the potential common features and differences between the mechanisms of intrinsic and acquired resistance to targeted therapies by analyzing established resistance-generating alterations for ten FDA-approved targeted drugs. The frequency of alterations underlying intrinsic and acquired resistance shows distinctive pattern, where dominant mechanisms of intrinsic resistance include aberrations of signals downstream or upstream of the targeted protein and dominant mechanisms of acquired resistance refer to lesions in the target itself or alterations of signals at target-level that can mimic or compensate for target function. It appears that during the evolution of acquired resistance, the tumor cell is inclined to preserve the same oncogene addiction on a targeted protein it had prior to drug administration. On the other hand, intrinsic resistance develops early in tumorogenesis and is based on randomly selected mutated signals between targeted and non-targeted signaling pathways, leading to the acquisition of cancer hallmarks. In general, there is an overlap between the mechanisms of intrinsic and acquired resistance, but the occurrence frequency and distribution of alterations underlying intrinsic and acquired resistance to targeted therapies are significantly different. Focus should be placed on different group of genes in pursuing predictive markers for intrinsic and acquired resistance to targeted therapies.

  1. A Research-Inspired Laboratory Sequence Investigating Acquired Drug Resistance

    ERIC Educational Resources Information Center

    Taylor, Elizabeth Vogel; Fortune, Jennifer A.; Drennan, Catherine L.

    2010-01-01

    Here, we present a six-session laboratory exercise designed to introduce students to standard biochemical techniques in the context of investigating a high impact research topic, acquired resistance to the cancer drug Gleevec. Students express a Gleevec-resistant mutant of the Abelson tyrosine kinase domain, the active domain of an oncogenic…

  2. Acquired resistance of pancreatic cancer cells to cisplatin is multifactorial with cell context-dependent involvement of resistance genes

    PubMed Central

    Mezencev, R; Matyunina, L V; Wagner, G T; McDonald, J F

    2016-01-01

    Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal of malignancies, in large measure, due to the propensity of PDAC cells to acquire resistance to chemotherapeutic agents. A better understanding of the molecular basis of acquired resistance is a major focus of contemporary PDAC research. We report here the results of a study to independently develop cisplatin resistance in two distinct parental PDAC cell lines, AsPC1 and BxPC3, and to subsequently examine the molecular mechanisms associated with the acquired resistance. Cisplatin resistance in both resistant cell lines was found to be multifactorial and to be associated with mechanisms related to drug transport, drug inactivation, DNA damage response, DNA repair and the modulation of apoptosis. Our results demonstrate that the two resistant cell lines employed alternative molecular strategies in acquiring resistance dictated, in part, by pre-existing molecular differences between the parental cell lines. Collectively, our findings indicate that strategies to inhibit or reverse acquired resistance of PDAC cells to cisplatin, and perhaps other chemotherapeutic agents, may not be generalized but will require individual molecular profiling and analysis to be effective. PMID:27910856

  3. Trypanosoma congolense: Natural and Acquired Resistance in the Bovine

    DTIC Science & Technology

    1980-08-01

    of Immune or natural and acquired Immunity In cattle to partially Immune dams (Whiteside 1962). trypanosomiasis . It has been postulated Certain breeds...of cattle also appear to be that young animals are more resistant to naturally resistant to trypanosome infection trypanosomiasis than adults (Fiennes...1970), Murray el al. (1979). Attempts to induce immunity to trypanosomiasis under field I Reprint requests should be addressed to B. T, conditions

  4. PeaT1-induced systemic acquired resistance in tobacco follows salicylic acid-dependent pathway.

    PubMed

    Zhang, Wei; Yang, Xiufen; Qiu, Dewen; Guo, Lihua; Zeng, Hongmei; Mao, Jianjun; Gao, Qiufeng

    2011-04-01

    Systemic acquired resistance (SAR) is an inducible defense mechanism which plays a central role in protecting plants from pathogen attack. A new elicitor, PeaT1 from Alternaria tenuissima, was expressed in Escherichia coil and characterized with systemic acquired resistance to tobacco mosaic virus (TMV). PeaT1-treated plants exhibited enhanced systemic resistance with a significant reduction in number and size of TMV lesions on wild tobacco leaves as compared with control. The quantitative analysis of TMV CP gene expression with real-time quantitative PCR showed there was reduction in TMV virus concentration after PeaT1 treatment. Similarly, peroxidase (POD) activity and lignin increased significantly after PeaT1 treatment. The real-time quantitative PCR revealed that PeaT1 also induced the systemic accumulation of pathogenesis-related gene, PR-1a and PR-1b which are the markers of systemic acquired resistance (SAR), NPR1 gene for salicylic acid (SA) signal transduction pathway and PAL gene for SA synthesis. The accumulation of SA and the failure in development of similar level of resistance as in wild type tobacco plants in PeaT1 treated nahG transgenic tobacco plants indicated that PeaT1-induced resistance depended on SA accumulation. The present work suggested that the molecular mechanism of PeaT1 inducing disease resistance in tobacco was likely through the systemic acquired resistance pathway mediated by salicylic acid and the NPR1 gene.

  5. Primary and acquired resistance to PD-1/PD-L1 blockade in cancer treatment.

    PubMed

    Wang, Qiaohong; Wu, Xia

    2017-05-01

    PD-1/PD-L1 blockade appears to be a very promising immunotherapy with significant clinical benefits and durable responses in multiple tumor types. However, the effectual clinical benefits of PD-1/PD-L1 blockade are hampered by a high rate of primary resistance, where patients do not respond to PD-1/PD-L1 blockade initially. And more distressingly, most patients eventually develop acquired resistance after an initial response to PD-1/PD-L1 blockade. The mechanisms underlying primary and acquired resistance to PD-1/PD-L1 blockade have remained ambiguous. This review documents in detail the current understanding of the mechanisms through which resistance to anti-PD1/PD-L1 therapy occurs. The mechanisms underlying primary resistance to PD-1/PD-L1 blockade contain several immunoregulatory factors affecting tumor-specific immune responses within the immune microenvironment, co-enrichment of a group of 26 transcriptomic signatures (named innate anti-PD-1 resistance (IPRES) signatures) and cancer-cell-autonomous cues. The mechanism attributable to acquired resistance harbors evolution of neoantigen landscape, mutations of JAK and β-2-microglobulin, and epigenetic stability of exhausted T cells. At last, the promising therapeutic strategies to sensitize the resistant patients are also briefly discussed.

  6. Non-genomic and Immune Evolution of Melanoma Acquiring MAPKi Resistance

    PubMed Central

    Hugo, Willy; Shi, Hubing; Sun, Lu; Piva, Marco; Song, ChunYing; Kong, Xiangju; Moriceau, Gatien; Hong, Aayoung; Dahlman, Kimberly B.; Johnson, Douglas B.; Sosman, Jeffrey A.; Ribas, Antoni; Lo, Roger S.

    2015-01-01

    SUMMARY Clinically acquired resistance to MAPK inhibitor (MAPKi) therapies for melanoma cannot be fully explained by genomic mechanisms and may be accompanied by co-evolution of intra-tumoral immunity. We sought to discover non-genomic mechanisms of acquired resistance and dynamic immune compositions by a comparative, transcriptomic-methylomic analysis of patient-matched melanoma tumors biopsied before therapy and during disease progression. Transcriptomic alterations across resistant tumors were highly recurrent, in contrast to mutations, and were frequently correlated with differential methylation of tumor cell-intrinsic CpG sites. We identified in the tumor cell compartment supra-physiologic c-MET up-expression, infra-physiologic LEF1 down-expression, and YAP1 signature enrichment as drivers of acquired resistance. Importantly, high intra-tumoral cytolytic T-cell inflammation prior to MAPKi therapy preceded CD8 T-cell deficiency/exhaustion and loss of antigen-presentation in half of disease-progressive melanomas, suggesting cross-resistance to salvage anti-PD-1/PD-L1 immunotherapy. Thus, melanoma acquires MAPKi-resistance with highly dynamic and recurrent non-genomic alterations and co-evolving intra-tumoral immunity. PMID:26359985

  7. Non-genomic and Immune Evolution of Melanoma Acquiring MAPKi Resistance.

    PubMed

    Hugo, Willy; Shi, Hubing; Sun, Lu; Piva, Marco; Song, Chunying; Kong, Xiangju; Moriceau, Gatien; Hong, Aayoung; Dahlman, Kimberly B; Johnson, Douglas B; Sosman, Jeffrey A; Ribas, Antoni; Lo, Roger S

    2015-09-10

    Clinically acquired resistance to MAPK inhibitor (MAPKi) therapies for melanoma cannot be fully explained by genomic mechanisms and may be accompanied by co-evolution of intra-tumoral immunity. We sought to discover non-genomic mechanisms of acquired resistance and dynamic immune compositions by a comparative, transcriptomic-methylomic analysis of patient-matched melanoma tumors biopsied before therapy and during disease progression. Transcriptomic alterations across resistant tumors were highly recurrent, in contrast to mutations, and were frequently correlated with differential methylation of tumor cell-intrinsic CpG sites. We identified in the tumor cell compartment supra-physiologic c-MET up-expression, infra-physiologic LEF1 down-expression and YAP1 signature enrichment as drivers of acquired resistance. Importantly, high intra-tumoral cytolytic T cell inflammation prior to MAPKi therapy preceded CD8 T cell deficiency/exhaustion and loss of antigen presentation in half of disease-progressive melanomas, suggesting cross-resistance to salvage anti-PD-1/PD-L1 immunotherapy. Thus, melanoma acquires MAPKi resistance with highly dynamic and recurrent non-genomic alterations and co-evolving intra-tumoral immunity.

  8. Antimicrobial Resistance and Clinical Outcomes in Nursing Home-Acquired Pneumonia, Compared to Community-Acquired Pneumonia

    PubMed Central

    Kang, Yun-Seong; Ryoo, Soo Ryeong; Byun, Seung Joo; Jeong, Yun-Jeong; Oh, Jin Young

    2017-01-01

    Purpose Patients with nursing home-acquired pneumonia (NHAP) should be treated as hospital-acquired pneumonia (HAP) according to guidelines published in 2005. However, controversy still exists on whether the high mortality of NHAP results from multidrug resistant pathogens or underlying disease. We aimed to outline differences and factors contributing to mortality between NHAP and community-acquired pneumonia (CAP) patients. Materials and Methods We retrospectively evaluated patients aged 65 years or older with either CAP or NHAP from 2008 to 2014. Patients with healthcare-associated pneumonia other than NHAP or HAP were excluded. Results Among 317 patients, 212 patients had CAP and 105 had NHAP. Patients with NHAP had higher mortality, more frequently used a ventilator, and had disease of higher severity than CAP. The incidences of aspiration, tube feeding, and poor functional status were higher in NHAP. Twenty three out of 54 NHAP patients and three out of 62 CAP patients had multidrug resistant pathogens (p<0.001). Eleven patients with NHAP died at discharge, compared to 7 patients with CAP (p=0.009). However, there was no association between mortality rate and presence of multidrug-resistant pathogens. The number of involved lobes on chest X-ray [odds ratio (OR)=1.708; 95% confidence interval (CI), 1.120 to 2.605] and use of mechanical ventilation (OR=9.537; 95% CI, 1.635 to 55.632) were significantly associated with in-hospital mortality. Conclusion Patients with NHAP had higher mortality than patients with CAP. The excess mortality among patients with NHAP and CAP was related to disease severity but not to the presence of multidrug resistant pathogens. PMID:27873512

  9. Systemic acquired resistance delays race shifts to major resistance genes in bell pepper.

    PubMed

    Romero, A M; Ritchie, D F

    2004-12-01

    ABSTRACT The lack of durability of host plant disease resistance is a major problem in disease control. Genotype-specific resistance that involves major resistance (R) genes is especially prone to failure. The compatible (i.e., disease) host-pathogen interaction with systemic acquired resistance (SAR) has been studied extensively, but the incompatible (i.e., resistant) interaction less so. Using the pepper-bacterial spot (causal agent, Xanthomonas axonopodis pv. vesicatoria) pathosystem, we examined the effect of SAR in reducing the occurrence of race-change mutants that defeat R genes in laboratory, greenhouse, and field experiments. Pepper plants carrying one or more R genes were sprayed with the plant defense activator acibenzolar-S-methyl (ASM) and challenged with incompatible strains of the pathogen. In the greenhouse, disease lesions first were observed 3 weeks after inoculation. ASM-treated plants carrying a major R gene had significantly fewer lesions caused by both the incompatible (i.e., hypersensitive) and compatible (i.e., disease) responses than occurred on nonsprayed plants. Bacteria isolated from the disease lesions were confirmed to be race-change mutants. In field experiments, there was a delay in the detection of race-change mutants and a reduction in disease severity. Decreased disease severity was associated with a reduction in the number of race-change mutants and the suppression of disease caused by the race-change mutants. This suggests a possible mechanism related to a decrease in the pathogen population size, which subsequently reduces the number of race-change mutants for the selection pressure of R genes. Thus, inducers of SAR are potentially useful for increasing the durability of genotype-specific resistance conferred by major R genes.

  10. Mechanisms of Antibiotic Resistance

    PubMed Central

    Munita, Jose M.; Arias, Cesar A.

    2015-01-01

    Emergence of resistance among the most important bacterial pathogens is recognized as a major public health threat affecting humans worldwide. Multidrug-resistant organisms have emerged not only in the hospital environment but are now often identified in community settings, suggesting that reservoirs of antibiotic-resistant bacteria are present outside the hospital. The bacterial response to the antibiotic “attack” is the prime example of bacterial adaptation and the pinnacle of evolution. “Survival of the fittest” is a consequence of an immense genetic plasticity of bacterial pathogens that trigger specific responses that result in mutational adaptations, acquisition of genetic material or alteration of gene expression producing resistance to virtually all antibiotics currently available in clinical practice. Therefore, understanding the biochemical and genetic basis of resistance is of paramount importance to design strategies to curtail the emergence and spread of resistance and devise innovative therapeutic approaches against multidrug-resistant organisms. In this chapter, we will describe in detail the major mechanisms of antibiotic resistance encountered in clinical practice providing specific examples in relevant bacterial pathogens. PMID:27227291

  11. Broad-spectrum acquired resistance in barley induced by the Pseudomonas pathosystem shares transcriptional components with Arabidopsis systemic acquired resistance.

    PubMed

    Colebrook, E H; Creissen, G; McGrann, G R D; Dreos, R; Lamb, C; Boyd, L A

    2012-05-01

    Inducible resistance responses play a central role in the defense of plants against pathogen attack. Acquired resistance (AR) is induced alongside defense toward primary attack, providing broad-spectrum protection against subsequent pathogen challenge. The localization and molecular basis of AR in cereals is poorly understood, in contrast with the well-characterized systemic acquired resistance (SAR) response in Arabidopsis. Here, we use Pseudomonas syringae as a biological inducer of AR in barley, providing a clear frame of reference to the Arabidopsis-P. syringae pathosystem. Inoculation of barley leaf tissue with the nonadapted P. syringae pv. tomato avrRpm1 (PstavrRpm1) induced an active local defense response. Furthermore, inoculation of barley with PstavrRpm1 resulted in the induction of broad-spectrum AR at a distance from the local lesion, "adjacent" AR, effective against compatible isolates of P. syringae and Magnaporthe oryzae. Global transcriptional profiling of this adjacent AR revealed similarities with the transcriptional profile of SAR in Arabidopsis, as well as transcripts previously associated with chemically induced AR in cereals, suggesting that AR in barley and SAR in Arabidopsis may be mediated by analogous pathways.

  12. Cellular memory of acquired stress resistance in Saccharomyces cerevisiae.

    PubMed

    Guan, Qiaoning; Haroon, Suraiya; Bravo, Diego González; Will, Jessica L; Gasch, Audrey P

    2012-10-01

    Cellular memory of past experiences has been observed in several organisms and across a variety of experiences, including bacteria "remembering" prior nutritional status and amoeba "learning" to anticipate future environmental conditions. Here, we show that Saccharomyces cerevisiae maintains a multifaceted memory of prior stress exposure. We previously demonstrated that yeast cells exposed to a mild dose of salt acquire subsequent tolerance to severe doses of H(2)O(2). We set out to characterize the retention of acquired tolerance and in the process uncovered two distinct aspects of cellular memory. First, we found that H(2)O(2) resistance persisted for four to five generations after cells were removed from the prior salt treatment and was transmitted to daughter cells that never directly experienced the pretreatment. Maintenance of this memory did not require nascent protein synthesis after the initial salt pretreatment, but rather required long-lived cytosolic catalase Ctt1p that was synthesized during salt exposure and then distributed to daughter cells during subsequent cell divisions. In addition to and separable from the memory of H(2)O(2) resistance, these cells also displayed a faster gene-expression response to subsequent stress at >1000 genes, representing transcriptional memory. The faster gene-expression response requires the nuclear pore component Nup42p and serves an important function by facilitating faster reacquisition of H(2)O(2) tolerance after a second cycle of salt exposure. Memory of prior stress exposure likely provides a significant advantage to microbial populations living in ever-changing environments.

  13. Characterization of In Vivo acquired resistance of Mycoplasma hyopneumoniae to macrolides and lincosamides.

    PubMed

    Stakenborg, Tim; Vicca, Jo; Butaye, Patrick; Maes, Dominiek; Minion, F Chris; Peeters, Johan; De Kruif, Aart; Haesebrouck, Freddy

    2005-01-01

    Macrolides and related antibiotics are used to control mycoplasma infections in the pig industry worldwide. Some porcine mycoplasmas, however, survive these treatments by acquiring resistance. The mechanism of acquired resistance to macrolides and lincosamides was studied in more detail for Mycoplasma hyopneumoniae by comparing both the phenotype and genotype of a resistant field isolate to five susceptible isolates. The MICs were significantly higher for the resistant strain for all antibiotics tested. The MICs for the 16-membered macrolide tylosin ranged from 8 to 16 microg for the resistant strain and from 0.03 to 0.125 microg/ml for the five susceptible strains. The MICs for the 15-membered macrolides and lincosamides were higher than 64 microg/ml for the resistant strain while only 0.06 to 0.5 microg/ml for the susceptible strains. Mycoplasma hyopneumoniae strains are intrinsically resistant to the 14-membered macrolides due to a G 2057 A transition (E. coli numbering) in their 23S rDNA. Therefore, high MICs were observed for all strains, although the MICs for the resistant strain were clearly increased. An additional, acquired A 2058 G point mutation was found in the 23S rRNA gene of the resistant strain. No differences linked to resistance were found in the ribosomal proteins L4 and L22. The present study showed that 23S rRNA mutations resulting in resistance to macrolides and lincosamides as described in other Mycoplasma spp. also occur under field conditions in M. hyopneumoniae.

  14. Increased sensitivity to platinum drugs of cancer cells with acquired resistance to trabectedin

    PubMed Central

    Colmegna, B; Uboldi, S; Frapolli, R; Licandro, S A; Panini, N; Galmarini, C M; Badri, Nadia; Spanswick, V J; Bingham, J P; Kiakos, Konstantinos; Erba, E; Hartley, J A; D'Incalci, M

    2015-01-01

    Background: In order to investigate the mechanisms of acquired resistance to trabectedin, trabectedin-resistant human myxoid liposarcoma (402-91/T) and ovarian carcinoma (A2780/T) cell lines were derived and characterised in vitro and in vivo. Methods: Resistant cell lines were obtained by repeated exposures to trabectedin. Characterisation was performed by evaluating drug sensitivity, cell cycle perturbations, DNA damage and DNA repair protein expression. In vivo experiments were performed on A2780 and A2780/T xenografts. Results: 402-91/T and A2780/T cells were six-fold resistant to trabectedin compared with parental cells. Resistant cells were found to be hypersensitive to UV light and did not express specific proteins involved in the nucleotide excision repair (NER) pathway: XPF and ERCC1 in 402-91/T and XPG in A2780/T. NER deficiency in trabectedin-resistant cells was associated with the absence of a G2/M arrest induced by trabectedin and with enhanced sensitivity (two-fold) to platinum drugs. In A2780/T, this collateral sensitivity, confirmed in vivo, was associated with an increased formation of DNA interstrand crosslinks. Conclusions: Our finding that resistance to trabectedin is associated with the loss of NER function, with a consequent increased sensitivity to platinum drugs, provides the rational for sequential use of these drugs in patients who have acquired resistance to trabectedin. PMID:26633559

  15. Effects of YM155 on survivin levels and viability in neuroblastoma cells with acquired drug resistance

    PubMed Central

    Voges, Yvonne; Michaelis, Martin; Rothweiler, Florian; Schaller, Torsten; Schneider, Constanze; Politt, Katharina; Mernberger, Marco; Nist, Andrea; Stiewe, Thorsten; Wass, Mark N; Rödel, Franz; Cinatl, Jindrich

    2016-01-01

    Resistance formation after initial therapy response (acquired resistance) is common in high-risk neuroblastoma patients. YM155 is a drug candidate that was introduced as a survivin suppressant. This mechanism was later challenged, and DNA damage induction and Mcl-1 depletion were suggested instead. Here we investigated the efficacy and mechanism of action of YM155 in neuroblastoma cells with acquired drug resistance. The efficacy of YM155 was determined in neuroblastoma cell lines and their sublines with acquired resistance to clinically relevant drugs. Survivin levels, Mcl-1 levels, and DNA damage formation were determined in response to YM155. RNAi-mediated depletion of survivin, Mcl-1, and p53 was performed to investigate their roles during YM155 treatment. Clinical YM155 concentrations affected the viability of drug-resistant neuroblastoma cells through survivin depletion and p53 activation. MDM2 inhibitor-induced p53 activation further enhanced YM155 activity. Loss of p53 function generally affected anti-neuroblastoma approaches targeting survivin. Upregulation of ABCB1 (causes YM155 efflux) and downregulation of SLC35F2 (causes YM155 uptake) mediated YM155-specific resistance. YM155-adapted cells displayed increased ABCB1 levels, decreased SLC35F2 levels, and a p53 mutation. YM155-adapted neuroblastoma cells were also characterized by decreased sensitivity to RNAi-mediated survivin depletion, further confirming survivin as a critical YM155 target in neuroblastoma. In conclusion, YM155 targets survivin in neuroblastoma. Furthermore, survivin is a promising therapeutic target for p53 wild-type neuroblastomas after resistance acquisition (neuroblastomas are rarely p53-mutated), potentially in combination with p53 activators. In addition, we show that the adaptation of cancer cells to molecular-targeted anticancer drugs is an effective strategy to elucidate a drug's mechanism of action. PMID:27735941

  16. Community-Acquired Methicillin-Resistant Pyogenic Liver Abscess

    PubMed Central

    Cherian, Joel; Singh, Rahul; Varma, Muralidhar; Vidyasagar, Sudha; Mukhopadhyay, Chiranjay

    2016-01-01

    Pyogenic liver abscesses are rare with an incidence of 0.5% to 0.8% and are mostly due to hepatobiliary causes (40% to 60%). Most are polymicrobial with less than 10% being caused by Staphylococcus aureus. Of these, few are caused by methicillin-resistant Staphylococcus aureus (MRSA) and fewer still by a community-acquired strain. Here we present a case study of a patient with a community-acquired MRSA liver abscess. The patient presented with fever since 1 month and tender hepatomegaly. Blood tests revealed elevated levels of alkaline phosphatase, C-reactive protein, erythrocyte sedimentation rate, and neutrophilic leukocytosis. Blood cultures were sterile. Ultrasound of the abdomen showed multiple abscesses, from which pus was drained and MRSA isolated. Computed tomography of the abdomen did not show any source of infection, and an amebic serology was negative. The patient was started on vancomycin for 2 weeks, following which he became afebrile and was discharged on oral linezolid for 4 more weeks. Normally a liver abscess is treated empirically with ceftriaxone for pyogenic liver abscess and metronidazole for amebic liver abscess. However, if the patient has risk factors for a Staphylococcal infection, it is imperative that antibiotics covering gram-positive organisms be added while waiting for culture reports. PMID:27540556

  17. Exocytosis of polyubiquitinated proteins in bortezomib-resistant leukemia cells: a role for MARCKS in acquired resistance to proteasome inhibitors

    PubMed Central

    Franke, Niels E.; Kaspers, Gertjan L.; Assaraf, Yehuda G.; van Meerloo, Johan; Niewerth, Denise; Kessler, Floortje L.; Poddighe, Pino J.; Kole, Jeroen; Smeets, Serge J.; Ylstra, Bauke; Bi, Chonglei; Chng, Wee Joo; Horton, Terzah M.; Menezes, Rene X.; Musters, Renée J.P.; Zweegman, Sonja; Jansen, Gerrit; Cloos, Jacqueline

    2016-01-01

    PSMB5 mutations and upregulation of the β5 subunit of the proteasome represent key determinants of acquired resistance to the proteasome inhibitor bortezomib (BTZ) in leukemic cells in vitro. We here undertook a multi-modality (DNA, mRNA, miRNA) array-based analysis of human CCRF-CEM leukemia cells and BTZ-resistant subclones to determine whether or not complementary mechanisms contribute to BTZ resistance. These studies revealed signatures of markedly reduced expression of proteolytic stress related genes in drug resistant cells over a broad range of BTZ concentrations along with a high upregulation of myristoylated alanine-rich C-kinase substrate (MARCKS) gene expression. MARCKS upregulation was confirmed on protein level and also observed in other BTZ-resistant tumor cell lines as well as in leukemia cells with acquired resistance to other proteasome inhibitors. Moreover, when MARCKS protein expression was demonstrated in specimens derived from therapy-refractory pediatric leukemia patients (n = 44), higher MARCKS protein expression trended (p = 0.073) towards a dismal response to BTZ-containing chemotherapy. Mechanistically, we show a BTZ concentration-dependent association of MARCKS protein levels with the emergence of ubiquitin-containing vesicles in BTZ-resistant CEM cells. These vesicles were found to be extruded and taken up in co-cultures with proteasome-proficient acceptor cells. Consistent with these observations, MARCKS protein associated with ubiquitin-containing vesicles was also more prominent in clinical leukemic specimen with ex vivo BTZ resistance compared to BTZ-sensitive leukemia cells. Collectively, we propose a role for MARCKS in a novel mechanism of BTZ resistance via exocytosis of ubiquitinated proteins in BTZ-resistant cells leading to quenching of proteolytic stress. PMID:27542283

  18. Primary, Adaptive, and Acquired Resistance to Cancer Immunotherapy.

    PubMed

    Sharma, Padmanee; Hu-Lieskovan, Siwen; Wargo, Jennifer A; Ribas, Antoni

    2017-02-09

    Cancer immunotherapy can induce long lasting responses in patients with metastatic cancers of a wide range of histologies. Broadening the clinical applicability of these treatments requires an improved understanding of the mechanisms limiting cancer immunotherapy. The interactions between the immune system and cancer cells are continuous, dynamic, and evolving from the initial establishment of a cancer cell to the development of metastatic disease, which is dependent on immune evasion. As the molecular mechanisms of resistance to immunotherapy are elucidated, actionable strategies to prevent or treat them may be derived to improve clinical outcomes for patients.

  19. Myeloid cells that impair immunotherapy are restored in melanomas which acquire resistance to BRAF inhibitors.

    PubMed

    Steinberg, Shannon M; Shabaneh, Tamer; Zhang, Peisheng; Martyanov, Viktor; Li, Zhenghui; Malik, Brian; Wood, Tammara; Boni, Andrea; Molodtsov, Aleksey; Angeles, Christina V; Curiel, Tyler J; Whitfield, Michael; Turk, Mary Jo

    2017-02-15

    Acquired resistance to BRAFV600E inhibitors (BRAFi) in melanoma remains a common clinical obstacle, as is the case for any targeted drug therapy that can be developed given the plastic nature of cancers. While there has been significant focus on the cancer cell-intrinsic properties of BRAFi resistance, the impact of BRAFi resistance on host immunity has not been explored. Here we provide preclinical evidence that resistance to BRAFi in an autochthonous mouse model of melanoma is associated with restoration of myeloid-derived suppressor cells (MDSC) in the tumor microenvironment initially reduced by BRAFi treatment. In contrast to restoration of MDSC, levels of T regulatory cells remained reduced in BRAFi-resistant tumors. Accordingly, tumor gene expression signatures specific for myeloid cell chemotaxis and homeostasis reappeared in BRAFi-resistant tumors. Notably, MDSC restoration relied upon MAPK pathway reactivation and downstream production of the myeloid attractant CCL2 in BRAFi-resistant melanoma cells. Strikingly, while combination checkpoint blockade (anti-CTLA-4 + anti-PD-1) was ineffective against BRAFi-resistant melanomas, the addition of MDSC depletion/blockade (anti-Gr-1 + CCR2 antagonist) prevented outgrowth of BRAFi-resistant tumors. Our results illustrate how extrinsic pathways of immunosuppression elaborated by melanoma cells dominate the tumor microenvironment and highlight the need to target extrinsic as well as intrinsic mechanisms of drug resistance.

  20. Activation of Alternate Prosurvival Pathways Accounts for Acquired Sunitinib Resistance in U87MG Glioma Xenografts

    PubMed Central

    Lv, Hua; Mazloom, Amin R.; Xu, Huilei; Ma'ayan, Avi; Gallo, James M.

    2012-01-01

    Acquired drug resistance represents a major obstacle to using sunitinib for the treatment of solid tumors. Here, we examined the cellular and molecular alterations in tumors that are associated with acquired brain tumor resistance to sunitinib by using an in vivo model. U87MG tumors obtained from nude mice that received sunitinib (40 mg/kg/day) for 30 days were classified into sunitinib-sensitive and -resistant groups based on tumor volume and underwent targeted gene microarray and protein array analyses. The expression of several angiogenesis-associated genes was significantly modulated in sunitinib-treated tumors compared with those in control tumors (p < 0.05), whereas no significant differences were observed between sunitinib-sensitive and -resistant tumors (p > 0.05). Tumor vasculature based on microvessel density, neurogenin 2 chondroitin sulfate proteoglycan density, and α-smooth muscle actin density was also similar in sunitinib-treatment groups (p > 0.05). The moderate increase in unbound sunitinib tumor-to-plasma area-under-the-curve ratio in sunitinib-resistant mice was accompanied by up-regulated ATP-binding cassette G2 expression in tumor. The most profound difference between the sunitinib-sensitive and -resistant groups was found in the expression of several phosphorylated proteins involved in intracellular signaling. In particular, phospholipase C-γ1 phosphorylation in sunitinib-resistant tumors was up-regulated by 2.6-fold compared with that in sunitinib-sensitive tumors (p < 0.05). In conclusion, acquired sunitinib resistance in U87MG tumors is not associated with revascularization in tumors, but rather with the activation of alternate prosurvival pathways involved in an escape mechanism facilitating tumor growth and possibly insufficient drug uptake in tumor cells caused by an up-regulated membrane efflux transporter. PMID:22869928

  1. Radiation-resistant acquired immunity of vaccinated mice to Schistosoma mansoni

    SciTech Connect

    Aitken, R.; Coulson, P.S.; Dixon, B.; Wilson, R.A.

    1987-11-01

    Vaccination of mice with attenuated cercariae of Schistosoma mansoni induces specific acquired resistance to challenge infection. This resistance is immunologically-mediated, possibly via a delayed-type hypersensitivity. Studies of parasite migration have shown that the protective mechanism operates most effectively in the lungs of vaccinated mice. We have probed the mechanism by exposing mice to 500 rads of gamma radiation before challenge infection. Our results show that the effector mechanism operative against challenge larvae is resistant to radiation. In contrast, classical immune responses are markedly suppressed by the same treatment. While leukocyte populations in the blood fall dramatically after irradiation, numbers of cells recoverable by bronchoalveolar lavage are unaffected. We suggest that vaccination with attenuated cercariae establishes populations of sensitized cells in the lungs which trigger the mechanism of resistance when challenge schistosomula migrate through pulmonary capillary beds. Although the cells may be partially disabled by irradiation, they remain responsive to worm antigens and thereby capable of initiating the elimination mechanism. This hypothesis would explain the radiation resistance of vaccine-induced immunity to S. mansoni.

  2. Insect eggs induce a systemic acquired resistance in Arabidopsis.

    PubMed

    Hilfiker, Olivier; Groux, Raphaël; Bruessow, Friederike; Kiefer, Karin; Zeier, Jürgen; Reymond, Philippe

    2014-12-01

    Although they constitute an inert stage of the insect's life, eggs trigger plant defences that lead to egg mortality or attraction of egg parasitoids. We recently found that salicylic acid (SA) accumulates in response to oviposition by the Large White butterfly Pieris brassicae, both in local and systemic leaves, and that plants activate a response that is similar to the recognition of pathogen-associated molecular patterns (PAMPs), which are involved in PAMP-triggered immunity (PTI). Here we discovered that natural oviposition by P. brassicae or treatment with egg extract inhibit growth of different Pseudomonas syringae strains in Arabidopsis through the activation of a systemic acquired resistance (SAR). This egg-induced SAR involves the metabolic SAR signal pipecolic acid, depends on ALD1 and FMO1, and is accompanied by a stronger induction of defence genes upon secondary infection. Although P. brassicae larvae showed a reduced performance when feeding on Pseudomonas syringae-infected plants, this effect was less pronounced when infected plants had been previously oviposited. Altogether, our results indicate that egg-induced SAR might have evolved as a strategy to prevent the detrimental effect of bacterial pathogens on feeding larvae.

  3. Emergence of Hospital Acquired Carbapenem Resistant Non-Fermenters in Teaching Institute

    PubMed Central

    Katare, Neeraj; Pandey, Aparna; Bhatambare, Ganesh Shivmurti; Bajpai, Trupti

    2016-01-01

    Introduction Non-Fermenting Gram Negative Bacilli (NFGNB) are emerging now-a-days because of their tendency to colonize various surfaces and inherent resistance to commonly used disinfectants. They are responsible for multi-drug resistant hospital acquired infections. Detection of carbapenem resistance mechanisms is essential for treatment and infection control purpose as can spread to other organisms causing hospital outbreaks. Aim To characterize non-fermenters from various clinical samples and to detect different carbapenem resistance mechanisms in meropenem resistant isolates. Materials and Methods The prospective study was conducted at Sri Aurobindo Medical College and Post Graduate Institute, Indore over a period of one and half year from December 2014 to May 2016. A total of 1310 samples were collected from Ventilator Associated Pneumonia (VAP), Surgical Site Infection (SSI), Urinary Tract Infection (UTI), septicaemia, Lower Respiratory Tract Infection (LRTI) and middle ear infected patients. Non-fermenters were identified by standard microbiological tests. Meropenem resistance was determined by Kirby-Bauer disk diffusion method and resistant isolates were further tested by Modified Hodge test, Combined disc test and AmpC disc test. Results Isolation rate of non-fermenters was 13.82% (181/1310). Colistin, amikacin and imipenem were the antibiotics with maximum sensitivity. Overall meropenem resistance was found to be 44.2% (80/181). Metallo-β-lactamase and AmpC-β-lactamase were produced by 56.82% (25/44) and 72.22% (26/36) of meropenem resistant Pseudomonas and Acinetobacter species respectively. Conclusion Detection of carbapenem resistance mechanisms and implementation of antibiotic policy are needed to prevent the emergence of non-fermenter infections. PMID:28208857

  4. Induction of autophagy counteracts the anticancer effect of cisplatin in human esophageal cancer cells with acquired drug resistance.

    PubMed

    Yu, Le; Gu, Chunping; Zhong, Desheng; Shi, Lili; Kong, Yi; Zhou, Zhitao; Liu, Shuwen

    2014-12-01

    Cisplatin-based chemotherapy frequently resulted in acquired resistance. The underpinning mechanism of such resistance remains obscure especially in relation to autophagic response. This study thus investigated the role of autophagy in the anticancer activity of cisplatin in human esophageal cancer cells with acquired cisplatin resistance. In response to cisplatin treatment, EC109 cells exhibited substantial apoptosis and senescence whereas cisplatin-resistant EC109/CDDP cells exhibited resistance. In this respect, cisplatin increased ERK phosphorylation whose inhibition by MEK inhibitor significantly attenuated the cytotoxic and cytostatic effect of cisplatin. Notably, cisplatin preferentially induces autophagy in EC109/CDDP cells but not in EC109 cells. Moreover, the induction of autophagy was accompanied by the suppression of mTORC1 activity. Abolition of autophagy by pharmacological inhibitors or knockdown of ATG5/7 re-sensitized EC109/CDDP cells. Co-administration of an autophagy inhibitor chloroquine and cisplatin significantly suppressed tumor growth whereas cisplatin monotherapy failed to elicit anticancer activity in nude mice xenografted with EC109/CDDP cells. To conclude, our data implicate autophagic response as a key mechanism of acquired resistance to cisplatin, suggesting that autophagy is a novel target to improve therapy efficiency of cisplatin toward human esophageal cancers with acquired resistance.

  5. The vitamin D receptor and inducible nitric oxide synthase associated pathways in acquired resistance to Cooperia oncophora infection in cattle

    PubMed Central

    2011-01-01

    Cooperia oncophora is an economically important gastrointestinal nematode in ruminants. Acquired resistance to Cooperia oncophora infection in cattle develops rapidly as a result of prior infections. Naïve cattle, when given a primary infection of high-dose infective L3 larvae, develop a strong immunity to subsequent reinfection. Compared to primary infection, reinfection resulted in a marked reduction in worm establishment. In order to understand molecular mechanisms underlying the development of acquired resistance, we characterized the transcriptomic responses of the bovine small intestine to a primary infection and reinfection. A total of 23 pathways were significantly impacted during infection. The vitamin D receptor activation was strongly induced only during reinfection, suggesting that this pathway may play an important role in the development of acquired resistance via its potential roles in immune regulation and intestinal mucosal integrity maintenance. The expression of inducible nitric oxide synthase (NOS2) was strongly induced during reinfection but not during primary infection. As a result, several canonical pathways associated with NOS2 were impacted. The genes involved in eicosanoid synthesis, including prostaglandin synthase 2 (PTGS2 or COX2), remained largely unchanged during infection. The rapid development of acquired resistance may help explain the lack of relative pathogenicity by Cooperia oncophora infection in cattle. Our findings facilitate the understanding of molecular mechanisms underlying the development of acquired resistance, which could have an important implication in vaccine design. PMID:21414188

  6. Multiple means to the same end: the genetic basis of acquired stress resistance in yeast.

    PubMed

    Berry, David B; Guan, Qiaoning; Hose, James; Haroon, Suraiya; Gebbia, Marinella; Heisler, Lawrence E; Nislow, Corey; Giaever, Guri; Gasch, Audrey P

    2011-11-01

    In nature, stressful environments often occur in combination or close succession, and thus the ability to prepare for impending stress likely provides a significant fitness advantage. Organisms exposed to a mild dose of stress can become tolerant to what would otherwise be a lethal dose of subsequent stress; however, the mechanism of this acquired stress tolerance is poorly understood. To explore this, we exposed the yeast gene-deletion libraries, which interrogate all essential and non-essential genes, to successive stress treatments and identified genes necessary for acquiring subsequent stress resistance. Cells were exposed to one of three different mild stress pretreatments (salt, DTT, or heat shock) and then challenged with a severe dose of hydrogen peroxide (H(2)O(2)). Surprisingly, there was little overlap in the genes required for acquisition of H(2)O(2) tolerance after different mild-stress pretreatments, revealing distinct mechanisms of surviving H(2)O(2) in each case. Integrative network analysis of these results with respect to protein-protein interactions, synthetic-genetic interactions, and functional annotations identified many processes not previously linked to H(2)O(2) tolerance. We tested and present several models that explain the lack of overlap in genes required for H(2)O(2) tolerance after each of the three pretreatments. Together, this work shows that acquired tolerance to the same severe stress occurs by different mechanisms depending on prior cellular experiences, underscoring the context-dependent nature of stress tolerance.

  7. Mechanisms of echinocandin antifungal drug resistance

    PubMed Central

    Perlin, David S.

    2015-01-01

    Fungal infections due to Candida and Aspergillus species cause extensive morbidity and mortality, especially among immunosuppressed patients, and antifungal therapy is critical to patient management. Yet only a few drug classes are available to treat invasive fungal diseases, and this problem is compounded by the emergence of antifungal resistance. Echinocandin drugs are the preferred choice to treat candidiasis. They are the first cell wall–active agents and target the fungal-specific enzyme glucan synthase, which catalyzes the biosynthesis of β-1,3-glucan, a key cell wall polymer. Therapeutic failures occur rarely among common Candida species, with the exception of Candida glabrata, which are frequently multidrug resistant. Echinocandin resistance in susceptible species is always acquired during therapy. The mechanism of resistance involves amino acid changes in hot-spot regions of Fks subunits of glucan synthase, which decrease the sensitivity of the enzyme to drug. Cellular stress response pathways lead to drug adaptation, which promote the formation of resistant fks strains. Clinical factors promoting echinocandin resistance include empiric therapy, prophylaxis, gastrointestinal reservoirs, and intra-abdominal infections. A better understanding of the echinocandin resistance mechanism, along with cellular and clinical factors promoting resistance, will promote more effective strategies to overcome and prevent echinocandin resistance. PMID:26190298

  8. Multidrug efflux pumps as main players in intrinsic and acquired resistance to antimicrobials.

    PubMed

    Hernando-Amado, Sara; Blanco, Paula; Alcalde-Rico, Manuel; Corona, Fernando; Reales-Calderón, Jose A; Sánchez, María B; Martínez, José L

    2016-09-01

    Multidrug efflux pumps constitute a group of transporters that are ubiquitously found in any organism. In addition to other functions with relevance for the cell physiology, efflux pumps contribute to the resistance to compounds used for treating different diseases, including resistance to anticancer drugs, antibiotics or antifungal compounds. In the case of antimicrobials, efflux pumps are major players in both intrinsic and acquired resistance to drugs currently in use for the treatment of infectious diseases. One important aspect not fully explored of efflux pumps consists on the identification of effectors able to induce their expression. Indeed, whereas the analysis of clinical isolates have shown that mutants overexpressing these resistance elements are frequently found, less is known on the conditions that may trigger expression of efflux pumps, hence leading to transient induction of resistance in vivo, a situation that is barely detectable using classical susceptibility tests. In the current article we review the structure and mechanisms of regulation of the expression of bacterial and fungal efflux pumps, with a particular focus in those for which a role in clinically relevant resistance has been reported.

  9. Systemic acquired resistance (50 years after discovery): moving from the lab to the field.

    PubMed

    Gozzo, Franco; Faoro, Franco

    2013-12-26

    Induction of plant defense(s) against pathogen challenge(s) has been the object of progressively more intense research in the past two decades. Insights on mechanisms of systemic acquired resistance (SAR) and similar, alternative processes, as well as on problems encountered on moving to their practical application in open field, have been carefully pursued and, as far as possible, defined. In reviewing the number of research works published in metabolomic, genetic, biochemical, and crop protection correlated disciplines, the following outline has been adopted: 1, introduction to the processes currently considered as models of the innate immunity; 2, primary signals, such as salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA), involved with different roles in the above-mentioned processes; 3, long-distance signals, identified from petiole exudates as mobile signaling metabolites during expressed resistance; 4, exogenous inducers, including the most significant chemicals known to stimulate the plant resistance induction and originated from both synthetic and natural sources; 5, fungicides shown to act as stimulators of SAR in addition to their biocidal action; 6, elusive mechanism of priming, reporting on the most recent working hypotheses on the pretranscriptional ways through which treated plants may express resistance upon pathogen attack and how this resistance can be transmitted to the next generation; 7, fitness costs and benefits of SAR so far reported from field application of induced resistance; 8, factors affecting efficacy of induced resistance in the open field, indicating that forces, unrevealed under controlled conditions, may be operative in the field; 9, concluding remarks address the efforts required to apply the strategy of crop resistance induction according to the rules of integrated pest management.

  10. Socioeconomic and behavioral factors leading to acquired bacterial resistance to antibiotics in developing countries.

    PubMed Central

    Okeke, I. N.; Lamikanra, A.; Edelman, R.

    1999-01-01

    In developing countries, acquired bacterial resistance to antimicrobial agents is common in isolates from healthy persons and from persons with community-acquired infections. Complex socioeconomic and behavioral factors associated with antibiotic resistance, particularly regarding diarrheal and respiratory pathogens, in developing tropical countries, include misuse of antibiotics by health professionals, unskilled practitioners, and laypersons; poor drug quality; unhygienic conditions accounting for spread of resistant bacteria; and inadequate surveillance. PMID:10081668

  11. Community-acquired Methicillin-resistant Staphylococcus aureus, Uruguay

    PubMed Central

    Ma, Xiao Xue; Galiana, Antonio; Pedreira, Walter; Mowszowicz, Martin; Christophersen, Inés; Machiavello, Silvia; Lope, Liliana; Benaderet, Sara; Buela, Fernanda; Vicentino, Walter; Albini, María; Bertaux, Olivier; Constenla, Irene; Bagnulo, Homero; Llosa, Luis; Ito, Teruyo

    2005-01-01

    A novel, methicillin-resistant Staphylococcus aureus clone (Uruguay clone) with a non–multidrug-resistant phenotype caused a large outbreak, including 7 deaths, in Montevideo, Uruguay. The clone was distinct from the highly virulent community clone represented by strain MW2, although both clones carried Panton-Valentine leukocidin gene and cna gene. PMID:15963301

  12. Mechanisms of Resistance to Aminoglycoside Antibiotics: Overview and Perspectives

    PubMed Central

    Garneau-Tsodikova, Sylvie

    2015-01-01

    Aminoglycoside (AG) antibiotics are used to treat many Gram-negative and some Gram-positive infections and, importantly, multidrug-resistant tuberculosis. Among various bacterial species, resistance to AGs arises through a variety of intrinsic and acquired mechanisms. The bacterial cell wall serves as a natural barrier for small molecules such as AGs and may be further fortified via acquired mutations. Efflux pumps work to expel AGs from bacterial cells, and modifications here too may cause further resistance to AGs. Mutations in the ribosomal target of AGs, while rare, also contribute to resistance. Of growing clinical prominence is resistance caused by ribosome methyltransferases. By far the most widespread mechanism of resistance to AGs is the inactivation of these antibiotics by AG-modifying enzymes. We provide here an overview of these mechanisms by which bacteria become resistant to AGs and discuss their prevalence and potential for clinical relevance. PMID:26877861

  13. Influence of infection of cotton by Rotylenchulus Reniformis and Meloidogyne Incognita on the production of enzymes involved in systemic acquired resistance.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Systemic acquired resistance (SAR), which results in enhanced defense mechanisms in plants, can be elicited by virulent and avirulent strains of pathogens including nematodes. Recent studies of nematode reproduction strongly suggest that Meloidogyne incognita and Rotylenchulus reniformis induce SAR ...

  14. Anticoagulation therapy for a LVAD patient with acquired warfarin resistance.

    PubMed

    Yoshioka, Daisuke; Toda, Koichi; Hidaka, Takayuki; Yasuda, Soichiro; Saito, Shunsuke; Domae, Keitaro; Sawa, Yoshiki

    2017-03-27

    Anticoagulation therapy with warfarin is essential for postoperative management in patients with left ventricular assist device (LVAD). In this manuscript, we report the case of a patient who developed warfarin resistance after LVAD implantation. Although we administered a novel anticoagulant drug in addition to warfarin and aspirin therapy, the patient developed a major stroke. The patient needed continuous intravenous heparinization until heart transplantation for approximately 2 years. Meticulous management of anticoagulation therapy is essential for a LVAD with warfarin resistance. To our best knowledge, our case is the first case of warfarin resistance in a patient with LVAD.

  15. Acquired Multidrug Antifungal Resistance in Candida lusitaniae during Therapy

    PubMed Central

    Asner, Sandra A.; Giulieri, Stefano; Diezi, Manuel; Marchetti, Oscar

    2015-01-01

    Candida lusitaniae is usually susceptible to echinocandins. Beta-1,3-glucan synthase encoded by FKS genes is the target of echinocandins. A few missense mutations in the C. lusitaniae FKS1 hot spot 1 (HS1) have been reported. We report here the rapid emergence of antifungal resistance in C. lusitaniae isolated during therapy with amphotericin B (AMB), caspofungin (CAS), and azoles for treatment of persistent candidemia in an immunocompromised child with severe enterocolitis and visceral adenoviral disease. As documented from restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analysis, the five C. lusitaniae isolates examined were related to each other. From antifungal susceptibility and molecular analyses, 5 different profiles (P) were obtained. These profiles included the following: profile 1 (P1) (CAS MIC [μg/ml], 0.5; fluconazole [FLC] MIC, 0.25), determined while the patient was being treated with liposomal AMB for 3 months; P2 (FLC MIC [μg/ml], 0.25; CAS MIC, 4), while the patient was being treated with CAS for 2 weeks; P3 (CAS MIC [μg/ml], 0.5; FLC MIC, 32), while the patient was being treated with azoles and CAS initially followed by azoles alone for a week; P4 (CAS MIC [μg/ml], 8; FLC MIC, 8), while the patient was being treated with both drugs for 3 weeks; and P5 (AMB MIC [μg/ml], 0.125; CAS MIC, 8), while the patient was being treated with AMB and FLC for 2 weeks. CAS resistance was associated with resistance not only to micafungin and anidulafungin but also to AMB. Analysis of CAS resistance revealed 3 novel FKS1 mutations in CAS-resistant isolates (S638Y in P2; S631Y in P4; S638P in P5). While S638Y and -P are within HS1, S631Y is in close proximity to this domain but was confirmed to confer candin resistance using a site-directed mutagenesis approach. FLC resistance could be linked with overexpression of major facilitator gene 7 (MFS7) in C. lusitaniae P2 and P4 and was associated with resistance to 5

  16. Activation of the Met kinase confers acquired drug resistance in FGFR-targeted lung cancer therapy.

    PubMed

    Kim, S-M; Kim, H; Yun, M R; Kang, H N; Pyo, K-H; Park, H J; Lee, J M; Choi, H M; Ellinghaus, P; Ocker, M; Paik, S; Kim, H R; Cho, B C

    2016-07-18

    Aberrant fibroblast growth factor receptor (FGFR) activation/expression is a common feature in lung cancer (LC). In this study, we evaluated the antitumor activity of and the mechanisms underlying acquired resistance to two potent selective FGFR inhibitors, AZD4547 and BAY116387, in LC cell lines. The antitumor activity of AZD4547 and BAY1163877 was screened in 24 LC cell lines, including 5 with FGFR1 amplification. Two cell lines containing FGFR1 amplifications, H1581 and DMS114, were sensitive to FGFR inhibitors (IC50<250 nm). Clones of FGFR1-amplified H1581 cells resistant to AZD4547 or BAY116387 (H1581AR and H1581BR cells, respectively) were established. Receptor tyrosine kinase (RTK) array and immunoblotting analyses showed strong overexpression and activation of Met in H1581AR/BR cells, compared with that in the parental cells. Gene set enrichment analysis against the Kyoto Encyclopedia of Genes and Genomes (KEGG) database showed that cytokine-cytokine receptor interaction pathways were significantly enriched in H1581AR/BR cells, with Met contributing significantly to the core enrichment. Genomic DNA quantitative PCR and fluorescent in situ hybridization analyses showed MET amplification in H1581AR, but not in H1581BR, cells. Met amplification drives acquired resistance to AZD4547 in H1581AR cells by activating ErbB3. Combination treatment with FGFR inhibitors and an anaplastic lymphoma kinase (ALK)/Met inhibitor, crizotinib, or Met-specific short interfering RNA (siRNA) synergistically inhibited cell proliferation in both H1581AR and H1581BR cells. Conversely, ectopic expression of Met in H1581 cells conferred resistance to AZD4547 and BAY1163877. Acquired resistance to FGFR inhibitors not only altered cellular morphology, but also promoted migration and invasion of resistant clones, in part by inducing epithelial-to-mesenchymal transition. Taken together, our data suggest that Met activation is sufficient to bypass dependency on FGFR signaling. Concurrent

  17. Vorinostat-induced autophagy switches from a death-promoting to a cytoprotective signal to drive acquired resistance.

    PubMed

    Dupéré-Richer, D; Kinal, M; Ménasché, V; Nielsen, T H; Del Rincon, S; Pettersson, F; Miller, W H

    2013-02-07

    Histone deacetylase inhibitors (HDACi) have shown promising activity against hematological malignancies in clinical trials and have led to the approval of vorinostat for the treatment of cutaneous T-cell lymphoma. However, de novo or acquired resistance to HDACi therapy is inevitable, and their molecular mechanisms are still unclear. To gain insight into HDACi resistance, we developed vorinostat-resistant clones from the hematological cell lines U937 and SUDHL6. Although cross-resistant to some but not all HDACi, the resistant cell lines exhibit dramatically increased sensitivity toward chloroquine, an inhibitor of autophagy. Consistent with this, resistant cells growing in vorinostat show increased autophagy. Inhibition of autophagy in vorinostat-resistant U937 cells by knockdown of Beclin-1 or Lamp-2 (lysosome-associated membrane protein 2) restores sensitivity to vorinostat. Interestingly, autophagy is also activated in parental U937 cells by de novo treatment with vorinostat. However, in contrast to the resistant cells, inhibition of autophagy decreases sensitivity to vorinostat. These results indicate that autophagy can switch from a proapoptotic signal to a prosurvival function driving acquired resistance. Moreover, inducers of autophagy (such as mammalian target of rapamycin inhibitors) synergize with vorinostat to induce cell death in parental cells, whereas the resistant cells remain insensitive. These data highlight the complexity of the design of combination strategies using modulators of autophagy and HDACi for the treatment of hematological malignancies.

  18. Acquired resistance to dasatinib in lung cancer cell lines conferred by DDR2 gatekeeper mutation and NF1 loss.

    PubMed

    Beauchamp, Ellen M; Woods, Brittany A; Dulak, Austin M; Tan, Li; Xu, Chunxiao; Gray, Nathanael S; Bass, Adam J; Wong, Kwok-kin; Meyerson, Matthew; Hammerman, Peter S

    2014-02-01

    The treatment of non-small cell lung cancer has evolved dramatically over the past decade with the adoption of widespread use of effective targeted therapies in patients with distinct molecular alterations. In lung squamous cell carcinoma (lung SqCC), recent studies have suggested that DDR2 mutations are a biomarker for therapeutic response to dasatinib and clinical trials are underway testing this hypothesis. Although targeted therapeutics are typically quite effective as initial therapy for patients with lung cancer, nearly all patients develop resistance with long-term exposure to targeted drugs. Here, we use DDR2-dependent lung cancer cell lines to model acquired resistance to dasatinib therapy. We perform targeted exome sequencing to identify two distinct mechanisms of acquired resistance: acquisition of the T654I gatekeeper mutation in DDR2 and loss of NF1. We show that NF1 loss activates a bypass pathway, which confers ERK dependency downstream of RAS activation. These results indicate that acquired resistance to dasatinib can occur via both second-site mutations in DDR2 and by activation of bypass pathways. These data may help to anticipate mechanisms of resistance that may be identified in upcoming clinical trials of anti-DDR2 therapy in lung cancer and suggest strategies to overcome resistance.

  19. Mechanisms of Drug Resistance: Daptomycin Resistance

    PubMed Central

    Tran, Truc T.; Munita, Jose M.; Arias, Cesar A.

    2016-01-01

    Daptomycin (DAP) is a cyclic lipopeptide with in vitro activity against a variety of Gram-positive pathogens, including multidrug-resistant organisms. Since its introduction in clinical practice in 2003, DAP has become an important key front-line antibiotic for severe or deep-seated infections caused by Gram-positive organisms. Unfortunately, DAP-resistance (R) has been extensively documented in clinically important organisms such as Staphylococcus aureus, Enterococcus spp, and Streptococcus spp. Studies on the mechanisms of DAP-R in Bacillus subtilis and other Gram-positive bacteria indicate that the genetic pathways of DAP resistance are diverse and complex. However, a common phenomenon emerging from these mechanistic studies is that DAP-R is associated with important adaptive changes in cell wall and cell membrane homeostasis with critical changes in cell physiology. Findings related to these adaptive changes have offered novel insights into the genetics and molecular mechanisms of bacterial cell envelope stress response and the manner in which Gram-positive bacteria cope with the antimicrobial peptide attack and protect vital structures of the cell envelope such as the cell membrane. In this review, we will examine the most recent findings related to the molecular mechanisms of resistance to DAP in relevant Gram-positive pathogens and discuss the clinical implications for therapy against these important bacteria. PMID:26495887

  20. Acquired resistance to the 16-membered macrolides tylosin and tilmicosin by Mycoplasma bovis.

    PubMed

    Lerner, Uri; Amram, Eytan; Ayling, Roger D; Mikula, Inna; Gerchman, Irena; Harrus, Shimon; Teff, Dina; Yogev, David; Lysnyansky, Inna

    2014-01-31

    The molecular mechanism of acquired resistance to the 16-membered macrolides tylosin (Ty) and tilmicosin (Tm) was investigated in Mycoplasma bovis field isolates. Sequence analysis of domains II and V of the two 23S rRNA alleles and ribosomal proteins L4 and L22 was performed on 54 M. bovis isolates showing different minimal inhibitory concentrations (MIC). The presence of any one of the point mutations G748A, C752T, A2058G, A2059G or A2059C (Escherichia coli numbering) in one or both alleles of the 23S rRNAs was correlated with decreased susceptibility to Ty (8-1024 μg/ml) and to Tm (32 to >256 μg/ml) in 27/27 and 27/31 M. bovis isolates, respectively. Although a single mutation in domain II or V could be sufficient to cause decreased susceptibility to Ty, our data imply that a combination of mutations in two domains is necessary to achieve higher MICs (≥ 128 μg/ml). The influence of a combination of mutations in two domains II and V on enhancement of resistance to Tm was less clear. In addition, the amino acid (aa) substitution L22-Q90H was found in 24/32 representative M. bovis isolates with different MICs, but no correlation with decreased susceptibility to Ty or Tm was identified. Multiple aa substitutions were also identified in the L4 protein, including at positions 185-186 (positions 64 and 65 in E. coli) which are adjacent to the macrolide-binding site. This is the first description of the molecular mechanism of acquired resistance to the 16-membered macrolides in M. bovis.

  1. Acquired resistance to venetoclax (ABT-199) in t(14;18) positive lymphoma cells.

    PubMed

    Bodo, Juraj; Zhao, Xiaoxian; Durkin, Lisa; Souers, Andrew J; Phillips, Darren C; Smith, Mitchell R; Hsi, Eric D

    2016-10-25

    The chromosomal translocation t(14;18) in follicular lymphoma (FL) is a primary oncogenic event resulting in BCL-2 over-expression. This study investigates activity of the BH3 mimetic venetoclax (ABT-199), which targets BCL-2, and mechanisms of acquired resistance in FL.The sensitivity of FL cells to venetoclax treatment correlated with BCL-2/BIM ratio. Cells with similar expression of anti-apoptotic proteins, but with higher levels of BIM were more sensitive to the treatment. Venetoclax induced dissociation of BCL-2/ BIM complex and a decrease in mitochondrial potential. Interestingly the population of cells that survived venetoclax treatment showed increased p-ERK1/2 and p-BIM (S69), as well as a decrease in total BIM levels. Venetoclax resistant cells initially showed elevated levels of p-AKT and p-Foxo1/3a, a dissociation of BIM/BCL-2/BECLIN1 complex, and a decrease in SQSTM1/p62 level (indicating increased autophagy) together with a slight decline in BIM expression. After stable resistant cell lines were established, a significant reduction of BCL-2 levels and almost total absence of BIM was observed.The acquisition of these resistance phenotypes could be prevented via selective ERK/AKT inhibition or anti-CD20 antibody treatment, thus highlighting possible combination therapies for FL patients.

  2. Interconnection between flowering time control and activation of systemic acquired resistance.

    PubMed

    Banday, Zeeshan Z; Nandi, Ashis K

    2015-01-01

    The ability to avoid or neutralize pathogens is inherent to all higher organisms including plants. Plants recognize pathogens through receptors, and mount resistance against the intruders, with the help of well-elaborated defense arsenal. In response to some localinfections, plants develop systemic acquired resistance (SAR), which provides heightened resistance during subsequent infections. Infected tissues generate mobile signaling molecules that travel to the systemic tissues, where they epigenetically modify expression o a set of genes to initiate the manifestation of SAR in distant tissues. Immune responses are largely regulated at transcriptional level. Flowering is a developmental transition that occurs as a result of the coordinated action of large numbers of transcription factors that respond to intrinsic signals and environmental conditions. The plant hormone salicylic acid (SA) which is required for SAR activation positively regulates flowering. Certain components of chromatin remodeling complexes that are recruited for suppression of precocious flowering are also involved in suppression of SAR in healthy plants. FLOWERING LOCUS D, a putative histone demethylase positively regulates SAR manifestation and flowering transition in Arabidopsis. Similarly, incorporation of histone variant H2A.Z in nucleosomes mediated by PHOTOPERIOD-INDEPENDENT EARLY FLOWERING 1, an ortholog of yeast chromatin remodeling complex SWR1, concomitantly influences SAR and flowering time. SUMO conjugation and deconjugation mechanisms also similarly affect SAR and flowering in an SA-dependent manner. The evidences suggest a common underlying regulatory mechanism for activation of SAR and flowering in plants.

  3. Mechanisms of drug resistance: daptomycin resistance.

    PubMed

    Tran, Truc T; Munita, Jose M; Arias, Cesar A

    2015-09-01

    Daptomycin (DAP) is a cyclic lipopeptide with in vitro activity against a variety of Gram-positive pathogens, including multidrug-resistant organisms. Since its introduction into clinical practice in 2003, DAP has become an important key frontline antibiotic for severe or deep-seated infections caused by Gram-positive organisms. Unfortunately, DAP resistance (DAP-R) has been extensively documented in clinically important organisms such as Staphylococcus aureus, Enterococcus spp., and Streptococcus spp. Studies on the mechanisms of DAP-R in Bacillus subtilis and other Gram-positive bacteria indicate that the genetic pathways of DAP-R are diverse and complex. However, a common phenomenon emerging from these mechanistic studies is that DAP-R is associated with important adaptive changes in cell wall and cell membrane homeostasis with critical changes in cell physiology. Findings related to these adaptive changes have provided novel insights into the genetics and molecular mechanisms of bacterial cell envelope stress response and the manner in which Gram-positive bacteria cope with the antimicrobial peptide attack and protect vital structures of the cell envelope, such as the cell membrane. In this review, we will examine the most recent findings related to the molecular mechanisms of resistance to DAP in relevant Gram-positive pathogens and discuss the clinical implications for therapy against these important bacteria.

  4. Arabidopsis thaliana FLOWERING LOCUS D is required for systemic acquired resistance.

    PubMed

    Singh, Vijayata; Roy, Shweta; Giri, Mrunmay Kumar; Chaturvedi, Ratnesh; Chowdhury, Zulkarnain; Shah, Jyoti; Nandi, Ashis Kumar

    2013-09-01

    Localized infection in plants often induces systemic acquired resistance (SAR), which provides long-term protection against subsequent infections. A signal originating in the SAR-inducing organ is transported to the distal organs, where it stimulates salicylic acid (SA) accumulation and priming, a mechanism that results in more robust activation of defenses in response to subsequent pathogen infection. In recent years, several metabolites that promote long-distance SAR signaling have been identified. However, the mechanism or mechanisms by which plants perceive and respond to the SAR signals are largely obscure. Here, we show that, in Arabidopsis thaliana, the FLOWERING LOCUS D (FLD) is required for responding to the SAR signals leading to the systemic accumulation of SA and enhancement of disease resistance. Although the fld mutant was competent in accumulating the SAR-inducing signal, it was unable to respond to the SAR signal that accumulates in petiole exudates of wild-type leaves inoculated with a SAR-inducing pathogen. Supporting FLD's role in systemic SAR signaling, we observed that dehydroabietinal and azelaic acid, two metabolites that, in wild-type plants, promote SAR-associated systemic accumulation of SA and priming, respectively, were unable to promote SAR in the fld mutant. FLD also participates in flowering, where it functions to repress expression of the flowering repressor FLOWERING LOCUS C (FLC). However, epistasis analysis indicates that FLD's function in SAR is independent of FLC.

  5. Mutations Associated with Acquired Resistance to PD-1 Blockade in Melanoma

    PubMed Central

    Zaretsky, Jesse M.; Garcia-Diaz, Angel; Shin, Daniel S.; Escuin-Ordinas, Helena; Hugo, Willy; Hu-Lieskovan, Siwen; Torrejon, Davis Y.; Abril-Rodriguez, Gabriel; Sandoval, Salemiz; Barthly, Lucas; Saco, Justin; Moreno, Blanca Homet; Mezzadra, Riccardo; Chmielowski, Bartosz; Ruchalski, Kathleen; Shintaku, I. Peter; Sanchez, Phillip J.; Puig-Saus, Cristina; Cherry, Grace; Seja, Elizabeth; Kong, Xiangju; Pang, Jia; Berent-Maoz, Beata; Comin-Anduix, Begoña; Graeber, Thomas G.; Tumeh, Paul C.; Schumacher, Ton N.M.; Lo, Roger S.; Ribas, Antoni

    2016-01-01

    BACKGROUND Approximately 75% of objective responses to anti–programmed death 1 (PD-1) therapy in patients with melanoma are durable, lasting for years, but delayed relapses have been noted long after initial objective tumor regression despite continuous therapy. Mechanisms of immune escape in this context are unknown. METHODS We analyzed biopsy samples from paired baseline and relapsing lesions in four patients with metastatic melanoma who had had an initial objective tumor regression in response to anti–PD-1 therapy (pembrolizumab) followed by disease progression months to years later. RESULTS Whole-exome sequencing detected clonal selection and outgrowth of the acquired resistant tumors and, in two of the four patients, revealed resistance-associated loss-of-function mutations in the genes encoding interferon-receptor–associated Janus kinase 1 (JAK1) or Janus kinase 2 (JAK2), concurrent with deletion of the wild-type allele. A truncating mutation in the gene encoding the antigen-presenting protein beta-2-microglobulin (B2M) was identified in a third patient. JAK1 and JAK2 truncating mutations resulted in a lack of response to interferon gamma, including insensitivity to its antiproliferative effects on cancer cells. The B2M truncating mutation led to loss of surface expression of major histocompatibility complex class I. CONCLUSIONS In this study, acquired resistance to PD-1 blockade immunotherapy in patients with melanoma was associated with defects in the pathways involved in interferon-receptor signaling and in antigen presentation. (Funded by the National Institutes of Health and others.) PMID:27433843

  6. Community-Acquired Methicillin-Resistant "Staphylococcus aureus": Considerations for School Nurses

    ERIC Educational Resources Information Center

    Alex, Aniltta; Letizia, MariJo

    2007-01-01

    Methicillin-resistant "Staphylococcus aureus" (MRSA) is a disease-causing organism that has been present in hospital settings since the 1960s. However, a genetically distinct strain of MRSA, called community-acquired methicillin-resistant "Staphylococcus aureus" (CA-MRSA), has emerged in recent years in community settings among healthy…

  7. Antibiotic Resistance, Virulence, and Genetic Background of Community-Acquired Uropathogenic Escherichia coli from Algeria.

    PubMed

    Yahiaoui, Merzouk; Robin, Frédéric; Bakour, Rabah; Hamidi, Moufida; Bonnet, Richard; Messai, Yamina

    2015-10-01

    The aim of the study was to investigate antibiotic resistance mechanisms, virulence traits, and genetic background of 150 nonrepetitive community-acquired uropathogenic Escherichia coli (CA-UPEC) from Algeria. A rate of 46.7% of isolates was multidrug resistant. bla genes detected were blaTEM (96.8% of amoxicillin-resistant isolates), blaCTX-M-15 (4%), overexpressed blaAmpC (4%), blaSHV-2a, blaTEM-4, blaTEM-31, and blaTEM-35 (0.7%). All tetracycline-resistant isolates (51.3%) had tetA and/or tetB genes. Sulfonamides and trimethoprim resistance genes were sul2 (60.8%), sul1 (45.9%), sul3 (6.7%), dfrA14 (25.4%), dfrA1 (18.2%), dfrA12 (16.3%), and dfrA25 (5.4%). High-level fluoroquinolone resistance (22.7%) was mediated by mutations in gyrA (S83L-D87N) and parC (S80I-E84G/V or S80I) genes. qnrB5, qnrS1, and aac(6')-Ib-cr were rare (5.3%). Class 1 and/or class 2 integrons were detected (40.7%). Isolates belonged to phylogroups B2+D (50%), A+B1 (36%), and F+C+Clade I (13%). Most of D (72.2%) and 38.6% of B2 isolates were multidrug resistant; they belong to 14 different sequence types, including international successful ST131, ST73, and ST69, reported for the first time in the community in Algeria and new ST4494 and ST4529 described in this study. Besides multidrug resistance, B2 and D isolates possessed virulence factors of colonization, invasion, and long-term persistence. The study highlighted multidrug-resistant CA-UPEC with high virulence traits and an epidemic genetic background.

  8. [Quinolones. Nowadays perspectives and mechanisms of resistance].

    PubMed

    Álvarez-Hernández, Diego Abelardo; Garza-Mayén, Gilda Sofía; Vázquez-López, Rosalno

    2015-10-01

    Quinolones are a family of synthetic broad-spectrum antimicrobial drugs whose target is the synthesis of DNA. They directly inhibit DNA replication by interacting with two enzymes; DNA gyrase and topoisomerase IV. They have been widely used for the treatment of several community and hospital acquired infections, in the food processing industry and in the agricultural field, making the increasing incidence of quinolone resistance a frequent problem associated with constant exposition to diverse microorganisms. Resistance may be achieved by three non-exclusive mechanisms; through chromosomic mutations in the Quinolone Resistance-Determining Regions of DNA gyrase and topoisomerase IV, by reducing the intracytoplasmic concentrations of quinolones actively or passively and by Plasmid-Mediated Quinolones-Resistance genes, [Qnr determinant genes of resistance to quinolones, variant gene of the aminoglycoside acetyltransferase (AAC(6')-Ib-c)] and encoding genes of efflux pumps (qepA and oqxAB)]. The future of quinolones is uncertain, however, meanwhile they continue to be used in an irrational way, increasing resistance to quinolones should remain as an area of primary priority for research.

  9. Molecular mechanisms of antibiotic resistance.

    PubMed

    Wright, Gerard D

    2011-04-14

    Over the past decade, resistance to antibiotics has emerged as a crisis of global proportion. Microbes resistant to many and even all clinically approved antibiotics are increasingly common and easily spread across continents. At the same time there are fewer new antibiotic drugs coming to market. We are reaching a point where we are no longer able to confidently treat a growing number of bacterial infections. The molecular mechanisms of drug resistance provide the essential knowledge on new drug development and clinical use. These mechanisms include enzyme catalyzed antibiotic modifications, bypass of antibiotic targets and active efflux of drugs from the cell. Understanding the chemical rationale and underpinnings of resistance is an essential component of our response to this clinical challenge.

  10. (Mechanisms of tolerance and resistance)

    SciTech Connect

    Waters, L.C.

    1990-08-28

    The traveler participated in the Seventh International Congress of Pesticide Chemistry by presenting a poster entitled Studies on the Expression of Insecticide Resistance-Associated Cytochrome P450 in Drosophila Using Cloned DNA'' and as an invited speaker in the Workshop Session on Insecticide Resistance. The Congress covered a wide range of topics, including studies of new syntheic compounds and natural products with crop protecting properties, modes of action of pesticides, mechanisms of pesticide resistance, environmental fate of pesticides and estimates of risk to pesticide exposure. Several presentations on the potential role of cytochrome P450 in resistance to insecticides and herbicides were relevant to our work at ORNL's Biology Division on molecular mechanisms of P450 expression.

  11. Novobiocin Inhibits the Antimicrobial Resistance Acquired through DNA Damage-Induced Mutagenesis in Acinetobacter baumannii

    PubMed Central

    Jara, Luis M.; Pérez-Varela, María; Corral, Jordi; Arch, Marta; Cortés, Pilar; Bou, Germán; Barbé, Jordi

    2015-01-01

    Acinetobacter baumannii, a worldwide emerging nosocomial pathogen, acquires antimicrobial resistances in response to DNA-damaging agents, which increase the expression of multiple error-prone DNA polymerase components. Here we show that the aminocoumarin novobiocin, which inhibits the DNA damage response in Gram-positive bacteria, also inhibits the expression of error-prone DNA polymerases in this Gram-negative multidrug-resistant pathogen and, consequently, its potential acquisition of antimicrobial resistance through DNA damage-induced mutagenesis. PMID:26503651

  12. Mechanisms of antidepressant resistance

    PubMed Central

    El-Hage, Wissam; Leman, Samuel; Camus, Vincent; Belzung, Catherine

    2013-01-01

    Depression is one of the most frequent and severe mental disorder. Since the discovery of antidepressant (AD) properties of the imipramine and then after of other tricyclic compounds, several classes of psychotropic drugs have shown be effective in treating major depressive disorder (MDD). However, there is a wide range of variability in response to ADs that might lead to non response or partial response or in increased rate of relapse or recurrence. The mechanisms of response to AD therapy are poorly understood, and few biomarkers are available than can predict response to pharmacotherapy. Here, we will first review markers that can be used to predict response to pharmacotherapy, such as markers of drug metabolism or blood-brain barrier (BBB) function, the activity of specific brain areas or neurotransmitter systems, hormonal dysregulations or plasticity, and related molecular targets. We will describe both clinical and preclinical studies and describe factors that might affect the expression of these markers, including environmental or genetic factors and comorbidities. This information will permit us to suggest practical recommendations and innovative treatment strategies to improve therapeutic outcomes. PMID:24319431

  13. Community-acquired methicillin-resistant Staphylococcus aureus: an ongoing challenge for WOC nursing.

    PubMed

    Price, Molly

    2010-01-01

    Infection is a common complication of chronic wounds that delays healing. Community-acquired methicillin-resistant Staphylococcus aureus has emerged as a common pathogen and major impediment to healing affected chronic wounds. Community-acquired methicillin-resistant S aureus is virulent, highly communicable, and difficult to eradicate. Treatment options include incision and drainage, debridement, and systemic antimicrobials. Early aggressive wound management and appropriate antibiotic therapy are considered essential to successful treatment. Facility-specific protocols should be developed to minimize the spread of this organism to the general population, with particular attention focused on protecting patients burdened with chronic wounds. This article reviews current knowledge of community-acquired methicillin-resistant S aureus, focusing on its impact on persons with chronic wounds.

  14. Acquired subglottic stenosis caused by methicillin resistant Staphylococcus aureus that produce epidermal cell differentiation inhibitor

    PubMed Central

    Yamada, Y; Sugai, M; Woo, M; Nishida, N; Sugimoto, T

    2001-01-01

    Local infection of the trachea in intubated neonates is one of the main risk factors for development of acquired subglottic stenosis, although its role in the pathogenesis is unclear. Methicillin resistant Staphylococcus aureus (MRSA) is often the cause of critical illness in neonatal patients. Two cases are reported of acquired subglottic stenosis following bacterial infection of the trachea, suggesting an association with the staphylococcal exotoxin, epidermal cell differentiation inhibitor (EDIN). EDIN-producing MRSA were isolated from purulent tracheal secretions from both infants. Acquired subglottic stenosis in both cases was probably caused by delayed wound healing as the result of EDIN inhibition of epithelial cell migration.

 PMID:11124922

  15. Carfilzomib and oprozomib synergize with histone deacetylase inhibitors in head and neck squamous cell carcinoma models of acquired resistance to proteasome inhibitors.

    PubMed

    Zang, Yan; Kirk, Christopher J; Johnson, Daniel E

    2014-09-01

    Acquired resistance to proteasome inhibitors represents a considerable impediment to their effective clinical application. Carfilzomib and its orally bioavailable structural analog oprozomib are second-generation, highly-selective, proteasome inhibitors. However, the mechanisms of acquired resistance to carfilzomib and oprozomib are incompletely understood, and effective strategies for overcoming this resistance are needed. Here, we developed models of acquired resistance to carfilzomib in two head and neck squamous cell carcinoma cell lines, UMSCC-1 and Cal33, through gradual exposure to increasing drug concentrations. The resistant lines R-UMSCC-1 and R-Cal33 demonstrated 205- and 64-fold resistance, respectively, relative to the parental lines. Similarly, a high level of cross-resistance to oprozomib, as well as paclitaxel, was observed, whereas only moderate resistance to bortezomib (8- to 29-fold), and low level resistance to cisplatin (1.5- to 5-fold) was seen. Synergistic induction of apoptosis signaling and cell death, and inhibition of colony formation followed co-treatment of acquired resistance models with carfilzomib and the histone deacetylase inhibitor (HDACi) vorinostat. Synergism was also seen with other combinations, including oprozomib plus vorinostat, or carfilzomib plus the HDACi entinostat. Synergism was accompanied by upregulation of proapoptotic Bik, and suppression of Bik attenuated the synergy. The acquired resistance models also exhibited elevated levels of MDR-1/P-gp. Inhibition of MDR-1/P-gp with reversin 121 partially overcame carfilzomib resistance in R-UMSCC-1 and R-Cal33 cells. Collectively, these studies indicate that combining carfilzomib or oprozomib with HDAC or MDR-1/P-gp inhibitors may be a useful strategy for overcoming acquired resistance to these proteasome inhibitors.

  16. Acquisition of a single EZH2 D1 domain mutation confers acquired resistance to EZH2-targeted inhibitors

    PubMed Central

    Baker, Theresa; Nerle, Sujata; Pritchard, Justin; Zhao, Boyang; Rivera, Victor M.

    2015-01-01

    Although targeted therapies have revolutionized cancer treatment, overcoming acquired resistance remains a major clinical challenge. EZH2 inhibitors (EZH2i), EPZ-6438 and GSK126, are currently in the early stages of clinical evaluation and the first encouraging signs of efficacy have recently emerged in the clinic. To anticipate mechanisms of resistance to EZH2i, we used a forward genetic platform combining a mutagenesis screen with next generation sequencing technology and identified a hotspot of secondary mutations in the EZH2 D1 domain (Y111 and I109). Y111D mutation within the WT or A677G EZH2 allele conferred robust resistance to both EPZ-6438 and GSK126, but it only drove a partial resistance within the Y641F allele. EZH2 mutants required histone methyltransferase (HMT) catalytic activity and the polycomb repressive complex 2 (PRC2) components, SUZ12 and EED, to drive drug resistance. Furthermore, D1 domain mutations not only blocked the ability of EZH2i to bind to WT and A677G mutant, but also abrogated drug binding to the Y641F mutant. These data provide the first cellular validation of the mechanistic model underpinning the oncogenic function of WT and mutant EZH2. Importantly, our findings suggest that acquired-resistance to EZH2i may arise in WT and mutant EZH2 patients through a single mutation that remains targetable by second generation EZH2i. PMID:26360609

  17. Acquired antibiotic resistance among wild animals: the case of Iberian Lynx (Lynx pardinus).

    PubMed

    Sousa, Margarida; Gonçalves, Alexandre; Silva, Nuno; Serra, Rodrigo; Alcaide, Eva; Zorrilla, Irene; Torres, Carmen; Caniça, Manuela; Igrejas, Gilberto; Poeta, Patrícia

    2014-01-01

    The selective pressure generated by the clinical misuse of antibiotics has been the major driving force leading to the emergence of antibiotic resistance among bacteria. Antibiotics or even resistant bacteria are released into the environment and contaminate the surrounding areas. Human and animal populations in contact with these sources are able to become reservoirs of these resistant organisms. Then, due to the convergence between habitats, the contact of wild animals with other animals, humans, or human sources is now more common and this leads to an increase in the exchange of resistance determinants between their microbiota. Indeed, it seems that wildlife populations living in closer proximity to humans have higher levels of antibiotic resistance. Now, the Iberian Lynx (Lynx pardinus) is a part of this issue, being suggested as natural reservoir of acquired resistant bacteria. The emerging public health concern regarding microbial resistance to antibiotics is becoming true: the bacteria are evolving and are now affecting unintentional hosts.

  18. Antimicrobial Resistance Mechanisms among Campylobacter

    PubMed Central

    2013-01-01

    Campylobacter jejuni and Campylobacter coli are recognized as the most common causative agents of bacterial gastroenteritis in the world. Humans most often become infected by ingesting contaminated food, especially undercooked chicken, but also other sources of bacteria have been described. Campylobacteriosis is normally a self-limiting disease. Antimicrobial treatment is needed only in patients with more severe disease and in those who are immunologically compromised. The most common antimicrobial agents used in the treatment of Campylobacter infections are macrolides, such as erythromycin, and fluoroquinolones, such as ciprofloxacin. Tetracyclines have been suggested as an alternative choice in the treatment of clinical campylobacteriosis but in practice are not often used. However, during the past few decades an increasing number of resistant Campylobacter isolates have developed resistance to fluoroquinolones and other antimicrobials such as macrolides, aminoglycosides, and beta-lactams. Trends in antimicrobial resistance have shown a clear correlation between use of antibiotics in the veterinary medicine and animal production and resistant isolates of Campylobacter in humans. In this review, the patterns of emerging resistance to the antimicrobial agents useful in treatment of the disease are presented and the mechanisms of resistance to these drugs in Campylobacter are discussed. PMID:23865047

  19. Antimicrobial resistance mechanisms among Campylobacter.

    PubMed

    Wieczorek, Kinga; Osek, Jacek

    2013-01-01

    Campylobacter jejuni and Campylobacter coli are recognized as the most common causative agents of bacterial gastroenteritis in the world. Humans most often become infected by ingesting contaminated food, especially undercooked chicken, but also other sources of bacteria have been described. Campylobacteriosis is normally a self-limiting disease. Antimicrobial treatment is needed only in patients with more severe disease and in those who are immunologically compromised. The most common antimicrobial agents used in the treatment of Campylobacter infections are macrolides, such as erythromycin, and fluoroquinolones, such as ciprofloxacin. Tetracyclines have been suggested as an alternative choice in the treatment of clinical campylobacteriosis but in practice are not often used. However, during the past few decades an increasing number of resistant Campylobacter isolates have developed resistance to fluoroquinolones and other antimicrobials such as macrolides, aminoglycosides, and beta-lactams. Trends in antimicrobial resistance have shown a clear correlation between use of antibiotics in the veterinary medicine and animal production and resistant isolates of Campylobacter in humans. In this review, the patterns of emerging resistance to the antimicrobial agents useful in treatment of the disease are presented and the mechanisms of resistance to these drugs in Campylobacter are discussed.

  20. Acquired and Native Resistance of Staphylococcus aureus to Cephalexin and Other β-Lactam Antibiotics 1

    PubMed Central

    Kayser, Fritz H.; Benner, E. Jack; Hoeprich, Paul D.

    1970-01-01

    Staphylococcus aureus cells that are initially susceptible to cephalexin can be induced to acquire intrinsic resistance to cephalexin in comparatively few steps. Concomitantly, resistance to cephalothin, oxacillin, and dicloxacillin increases. By population analysis, there is heteroresistance to cephalexin in some strains of S. aureus. Heterogeneity in colonial morphology on prolonged incubation in the presence of subinhibitory concentrations of cephalexin may constitute an expression of such heteroresistance. Images PMID:5201887

  1. Acquired immunity and stochasticity in epidemic intervals impede the evolution of host disease resistance.

    PubMed

    Harding, Karin C; Hansen, B Johan L; Goodman, Simon J

    2005-12-01

    Disease can generate intense selection pressure on host populations, but here we show that acquired immunity in a population subject to repeated disease outbreaks can impede the evolution of genetic disease resistance by maintaining susceptible genotypes in the population. Interference between the life-history schedule of a species and periodicity of the disease has unintuitive effects on selection intensity, and stochasticity in outbreak period further reduces the rate of spread of disease-resistance alleles. A general age-structured population genetic model was developed and parameterized using empirical data for phocine distemper virus (PDV) epizootics in harbor seals. Scenarios with acquired immunity had lower levels of epizootic mortality compared with scenarios without acquired immunity for the first PDV outbreaks, but this pattern was reversed after about five disease cycles. Without acquired immunity, evolution of disease resistance was more rapid, and long-term population size variation is efficiently dampened. Acquired immunity has the potential to significantly influence rapid evolutionary dynamics of a host population in response to age-structured disease selection and to alter predicted selection intensities compared with epidemiological models that do not consider such feedback. This may have important implications for evolutionary population dynamics in a range of human, agricultural, and wildlife disease settings.

  2. Acquired resistance affects male sexual display and female choice in guppies

    PubMed Central

    pez, S. L

    1998-01-01

    Is resistance to parasites related to the expression of male secondary sex characters? Handicap models predict a positive relationship, proposing that males displaying extravagant sex characters may be honestly signalling their resistance to females. However, no current evidence addresses whether individual changes in immunity (acquired resistance) are reflected in sexual traits. In this experiment I use guppies to compare male orange colour, sigmoid display and female preferences for individual males, before and after a primary challenge infection of males. Challenge infections were terminated chemically and fish were given ten days' recovery time before proceeding with the second measurements. The degree of acquired resistance was quantified a posteriori, by exposing males to a secondary infection. Sigmoid display rates and female preference for males differed for males of different resistance groups after challenge infection only. This difference was due to resistant males displaying more than non-resistant ones. No differences were detected in male orange colour, but this may be because colour needs a longer time than ten days to be recovered and adjusted. The results show that the level of acquired resistance affects sexual display and attractiveness in guppies. They suggest that once an effective immunity is built up by a male, he can afford to incur higher costs for sexual characteristics, whereas a male that lacks the ability to build up effective resistance cannot. These costs probably consist of higher energy expenditure and/or higher circulating levels of testosterone, which may be needed to increase display. Priming and effective establishment of an individual's resistance to parasitic infection could eventually result in a higher availability of resources for sexual functions.

  3. Mechanism of resistance to anthracyclines and vinca alkaloids.

    PubMed

    Danø, K; Skovsgaard, T; Nissen, N I; Friche, E; Di Marco, A

    1983-01-01

    Occurrence of cross-resistance between anthracyclines and vinca alkaloids is the rule in experimental tumors with acquired resistance to these drugs. So far, there is no indication that this phenomenon is due to an intracellular mechanism of action common to the two groups of drugs. In nearly all reported studies, acquired experimental resistance and cross-resistance are related to a decreased cellular accumulation of both types of drugs, although other factors also are involved. In Ehrlich ascites tumors, a number of findings at steady-state conditions indicate that the decreased accumulation is dependent on a cellular mechanism for active outward drug transport, which is common to anthracyclines and vinca alkaloids, but changes in inward transport and intracellular binding capacity also contribute. Similar findings have been reported for resistance and cross-resistance in P388 leukemia. Recent results with counteraction of acquired experimental resistance in animal tumors by inhibition of outward drug transport and studies on the effect of different anthracycline derivatives on accumulation of daunomycin in resistant cells are discussed.

  4. Mechanisms of resistance to EGFR-targeted drugs: lung cancer.

    PubMed

    Morgillo, Floriana; Della Corte, Carminia Maria; Fasano, Morena; Ciardiello, Fortunato

    2016-01-01

    Despite the improvement in clinical outcomes derived by the introduction of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs) in the treatment of patients with advanced non-small cell lung cancer (NSCLC) whose tumours harbour EGFR-activating mutations, prognosis remains unfavourable because of the occurrence of either intrinsic or acquired resistance. We reviewed the published literature and abstracts of oral and poster presentations from international conferences addressing EGFR-TKIs resistance mechanisms discovered in preclinical models and in patients with NSCLC. The molecular heterogeneity of lung cancer has several implications in terms of possible mechanisms of either intrinsic or acquired resistance to EGFR-targeted inhibitors. Several mechanisms of resistance have been described to EGFR-TKIs, such as the occurrence of secondary mutation (T790M, C797S), the activation of alternative signalling (Met, HGF, AXL, Hh, IGF-1R), the aberrance of the downstream pathways (AKT mutations, loss of PTEN), the impairment of the EGFR-TKIs-mediated apoptosis pathway (BCL2-like 11/BIM deletion polymorphism) and histological transformation. Although some of the mechanisms of resistance have been identified, much additional information is needed to understand and overcome resistance to EGFR-TKI agents. The majority of resistance mechanisms described are the result of a selection of pre-existing clones; thus, studies on the mechanisms by which subclonal alterations have an impact on tumour biology and influence cancer progression are extremely important in order to define the best treatment strategy.

  5. Resistance mechanisms in Campylobacter jejuni

    PubMed Central

    Iovine, Nicole M.

    2013-01-01

    Campylobacter jejuni is a major cause of food-borne gastroenteritis worldwide. While mortality is low, morbidity imparted by post-infectious sequelae such as Guillain-Barré syndrome, Reiter syndrome/reactive arthritis and irritable bowel syndrome is significant. In addition, the economic cost is high due to lost productivity. Food animals, particularly poultry, are the main reservoirs of C. jejuni. The over-use of antibiotics in the human population and in animal husbandry has led to an increase in antibiotic-resistant infections, particularly with fluoroquinolones. This is problematic because C. jejuni gastroenteritis is clinically indistinguishable from that caused by other bacterial pathogens, and such illnesses are usually treated empirically with fluoroquinolones. Since C. jejuni is naturally transformable, acquisition of additional genes imparting antibiotic resistance is likely. Therefore, an understanding of the antibiotic resistance mechanisms in C. jejuni is needed to provide proper therapy both to the veterinary and human populations. PMID:23406779

  6. Community-acquired methicillin-resistant Staphylococcus aureus: an emerging cause of acute bacterial parotitis.

    PubMed

    Nicolasora, Nelson P; Zacharek, Mark A; Malani, Anurag N

    2009-02-01

    Staphylococcus aureus has long been recognized as a cause of acute bacterial parotitis. A case of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) parotitis is presented, highlighting the emergence of this increasingly important pathogen to cause a wide variety of infections. Also reviewed are the salient clinical and microbiologic features of this novel infection.

  7. EGFR inhibitor and chemotherapy combinations for acquired TKI resistance in EGFR-mutant NSCLC models.

    PubMed

    Laurila, Niina; Koivunen, Jussi P

    2015-07-01

    Acquired resistance to EGFR TKIs is the most important limiting factor for treatment efficiency in EGFR-mutant NSCLC. Although the continuation of EGFR TKI beyond disease progression in combination with chemotherapy is often suggested as a strategy for treating acquired resistance, the optimal treatment sequence for EGFR TKI and chemotherapy is unknown. In the current work, NSCLC cell lines PC9ER, H1975 and HCC827GR, representing the acquired TKI resistance genotypes (T790M, cMET), were exposed to a chemotherapeutic agent, cisplatin or paclitaxel, in combination with EGFR TKIs (erlotinib, WZ4002) in vitro and analysed for cytotoxicity and apoptotic response. The result showed that all the combinations of EGFR TKIs with a chemotherapeutic agent tested had a synergistic effect on cytotoxicity and increased the apoptotic response. The sequences involving a chemotherapeutic agent concurrently with an EGFR TKI or preceding it were the most efficient strategies. Our in vitro models suggest that the combination of an EGFR TKI and chemotherapy is beneficial in cases of acquired EGFR TKI resistance. Furthermore, the sequence of chemotherapy followed by EGFR TKI is significantly more powerful than the reversed order, so that an intercalated approach is likely to be the most active strategy in clinical use and ought to be tested in a randomized clinical trial.

  8. Acquired antimicrobial resistance in the intestinal microbiota of diverse cat populations.

    PubMed

    Moyaert, H; De Graef, E M; Haesebrouck, F; Decostere, A

    2006-08-01

    The aim of this study was to investigate the prevalence of acquired antimicrobial resistance in the resident intestinal microbiota of cats and to identify significant differences between various cat populations. Escherichia coli, Enterococcus faecalis, E. faecium and Streptococcus canis were isolated as faecal indicator bacteria from rectal swabs of 47 individually owned cats, 47 cattery cats and 18 hospitalised cats, and submitted through antimicrobial sensitivity tests. The results revealed that bacteria isolated from hospitalised and/or cattery cats were more frequently resistant than those from individually owned cats. E. coli isolates from hospitalised cats were particularly resistant to ampicillin, tetracycline and sulfonamide. Both enterococci and streptococci showed high resistance to tetracycline and in somewhat lesser extent to erythromycin and tylosin. Most E. faecium isolates were resistant to lincomycin and penicillin. One E. faecalis as well as one E. faecium isolate from hospitalised cats showed 'high-level resistance' (MIC > 500 microg/ml) against gentamicin, a commonly used antimicrobial agent in case of human enterococcal infections. The results of this research demonstrate that the extent of acquired antimicrobial resistance in the intestinal microbiota of cats depends on the social environment of the investigated population. It is obvious that the flora of healthy cats may act as a reservoir of resistance genes.

  9. The Mechanism of Fluid Resistance

    NASA Technical Reports Server (NTRS)

    Vonkarman, T.; Rubach, H.

    1979-01-01

    The mechanism of fluid resistance within the limit of the square law is presented. It was concluded that the investigations should be extended and completed in two directions, namely: by an investigation of stable vortex configurations in space, and by considering the perfect fluid as the limiting case of a viscous fluid and then limiting the law of vortex of formation with the condition that only those fluid particles which were in contact with the surface of the body can receive rotation.

  10. Mechanisms of tumour resistance against chemotherapeutic agents in veterinary oncology.

    PubMed

    Klopfleisch, R; Kohn, B; Gruber, A D

    2016-01-01

    Several classes of chemotherapy drugs are used as first line or adjuvant treatment of the majority of tumour types in veterinary oncology. However, some types of tumour are intrinsically resistant to several anti-cancer drugs, and others, while initially sensitive, acquire resistance during treatment. Chemotherapy often significantly prolongs survival or disease free interval, but is not curative. The exact mechanisms behind intrinsic and acquired chemotherapy resistance are unknown for most animal tumours, but there is increasing knowledge on the mechanisms of drug resistance in humans and a few reports on molecular changes in resistant canine tumours have emerged. In addition, approaches to overcome or prevent chemotherapy resistance are becoming available in humans and, given the overlaps in molecular alterations between human and animal tumours, these may also be relevant in veterinary oncology. This review provides an overview of the current state of research on general chemotherapy resistance mechanisms, including drug efflux, DNA repair, apoptosis evasion and tumour stem cells. The known resistance mechanisms in animal tumours and the potential of these findings for improving treatment efficacy in veterinary oncology are also explored.

  11. Mechanisms of buffer therapy resistance.

    PubMed

    Bailey, Kate M; Wojtkowiak, Jonathan W; Cornnell, Heather H; Ribeiro, Maria C; Balagurunathan, Yoganand; Hashim, Arig Ibrahim; Gillies, Robert J

    2014-04-01

    Many studies have shown that the acidity of solid tumors contributes to local invasion and metastasis. Oral pH buffers can specifically neutralize the acidic pH of tumors and reduce the incidence of local invasion and metastatic formation in multiple murine models. However, this effect is not universal as we have previously observed that metastasis is not inhibited by buffers in some tumor models, regardless of buffer used. B16-F10 (murine melanoma), LL/2 (murine lung) and HCT116 (human colon) tumors are resistant to treatment with lysine buffer therapy, whereas metastasis is potently inhibited by lysine buffers in MDA-MB-231 (human breast) and PC3M (human prostate) tumors. In the current work, we confirmed that sensitive cells utilized a pH-dependent mechanism for successful metastasis supported by a highly glycolytic phenotype that acidifies the local tumor microenvironment resulting in morphological changes. In contrast, buffer-resistant cell lines exhibited a pH-independent metastatic mechanism involving constitutive secretion of matrix degrading proteases without elevated glycolysis. These results have identified two distinct mechanisms of experimental metastasis, one of which is pH-dependent (buffer therapy sensitive cells) and one which is pH-independent (buffer therapy resistant cells). Further characterization of these models has potential for therapeutic benefit.

  12. Polyclonal Secondary FGFR2 Mutations Drive Acquired Resistance to FGFR Inhibition in Patients with FGFR2 Fusion-Positive Cholangiocarcinoma.

    PubMed

    Goyal, Lipika; Saha, Supriya K; Liu, Leah Y; Siravegna, Giulia; Leshchiner, Ignaty; Ahronian, Leanne G; Lennerz, Jochen K; Vu, Phuong; Deshpande, Vikram; Kambadakone, Avinash; Mussolin, Benedetta; Reyes, Stephanie; Henderson, Laura; Sun, Jiaoyuan Elisabeth; Van Seventer, Emily E; Gurski, Joseph M; Baltschukat, Sabrina; Schacher-Engstler, Barbara; Barys, Louise; Stamm, Christelle; Furet, Pascal; Ryan, David P; Stone, James R; Iafrate, A John; Getz, Gad; Porta, Diana Graus; Tiedt, Ralph; Bardelli, Alberto; Juric, Dejan; Corcoran, Ryan B; Bardeesy, Nabeel; Zhu, Andrew X

    2017-03-01

    Genetic alterations in the fibroblast growth factor receptor (FGFR) pathway are promising therapeutic targets in many cancers, including intrahepatic cholangiocarcinoma (ICC). The FGFR inhibitor BGJ398 displayed encouraging efficacy in patients with FGFR2 fusion-positive ICC in a phase II trial, but the durability of response was limited in some patients. Here, we report the molecular basis for acquired resistance to BGJ398 in three patients via integrative genomic characterization of cell-free circulating tumor DNA (cfDNA), primary tumors, and metastases. Serial analysis of cfDNA demonstrated multiple recurrent point mutations in the FGFR2 kinase domain at progression. Accordingly, biopsy of post-progression lesions and rapid autopsy revealed marked inter- and intralesional heterogeneity, with different FGFR2 mutations in individual resistant clones. Molecular modeling and in vitro studies indicated that each mutation led to BGJ398 resistance and was surmountable by structurally distinct FGFR inhibitors. Thus, polyclonal secondary FGFR2 mutations represent an important clinical resistance mechanism that may guide the development of future therapeutic strategies.Significance: We report the first genetic mechanisms of clinical acquired resistance to FGFR inhibition in patients with FGFR2 fusion-positive ICC. Our findings can inform future strategies for detecting resistance mechanisms and inducing more durable remissions in ICC and in the wide variety of cancers where the FGFR pathway is being explored as a therapeutic target. Cancer Discov; 7(3); 252-63. ©2016 AACR.See related commentary by Smyth et al., p. 248This article is highlighted in the In This Issue feature, p. 235.

  13. CIPROFLOXACIN RESISTANCE PATTERN AMONG BACTERIA ISOLATED FROM PATIENTS WITH COMMUNITY-ACQUIRED URINARY TRACT INFECTION

    PubMed Central

    REIS, Ana Carolina Costa; SANTOS, Susana Regia da Silva; de SOUZA, Siane Campos; SALDANHA, Milena Góes; PITANGA, Thassila Nogueira; OLIVEIRA, Ricardo Riccio

    2016-01-01

    SUMMARY Objective: To identify the main bacterial species associated with community-acquired urinary tract infection (UTI) and to assess the pattern of ciprofloxacin susceptibility among bacteria isolated from urine cultures. Methods: We conducted a retrospective study in all the patients with community-acquired UTI seen in Santa Helena Laboratory, Camaçari, Bahia, Brazil during five years (2010-2014). All individuals who had a positive urine culture result were included in this study. Results: A total of 1,641 individuals met the inclusion criteria. Despite the fact that participants were female, we observed a higher rate of resistance to ciprofloxacin in males. The most frequent pathogens identified in urine samples were Escherichia coli, Klebsiella pneumoniae and Staphylococcus saprophyticus. Antimicrobial resistance has been observed mainly for ampicillin, sulfamethoxazole + trimethoprim and ciprofloxacin. Moreover, E. coli has shown the highest rate of ciprofloxacin resistance, reaching 36% of ciprofloxacin resistant strains in 2014. Conclusion: The rate of bacterial resistance to ciprofloxacin observed in the studied population is much higher than expected, prompting the need for rational use of this antibiotic, especially in infections caused by E. coli. Prevention of bacterial resistance can be performed through control measures to limit the spread of resistant microorganisms and a rational use of antimicrobial policy. PMID:27410913

  14. Antimicrobial resistance trends among community-acquired respiratory tract pathogens in Greece, 2009-2012.

    PubMed

    Maraki, Sofia; Papadakis, Ioannis S

    2014-01-01

    The aim of the present study was to determine the antimicrobial resistance trends of respiratory tract pathogens isolated from patients with community-acquired respiratory tract infections (CARTIs) in Crete, Greece, over a 4-year period (2009-2012). A total of 588 community-acquired respiratory pathogens were isolated during the study period. Streptococcus pneumoniae was the most common organism responsible for 44.4% of CARTIs, followed by Haemophilus influenzae (44.2%) and Moraxella catarrhalis (11.4%). Among S. pneumoniae, the prevalence of isolates with intermediate- and high-level resistance to penicillin was 27.2% and 12.3%, respectively. Macrolide resistance slightly decreased from 29.4% over the period 2009-2010 to 28.8% over the period 2011-2012. Multiresistance was observed among 56 (54.4%) penicillin nonsusceptible isolates. A nonsignificant increase in resistance of H. influenzae isolates was noted for β -lactams, cotrimoxazole, and tetracycline. Among the 67 M. catarrhalis tested, 32 produced beta-lactamase and were resistant to ampicillin. Macrolide resistance decreased over the study period. All isolates were susceptible to amoxicillin + clavulanic acid, chloramphenicol, rifampicin, and the fluoroquinolones. Although a decreasing trend in the prevalence of resistance of the three most common pathogens involved in CARTIs was noted, continuous surveillance of antimicrobial susceptibility at the local and national level remains important, in order to guide appropriate empirical antimicrobial therapy.

  15. Amphibians acquire resistance to live and dead fungus overcoming fungal immunosuppression.

    PubMed

    McMahon, Taegan A; Sears, Brittany F; Venesky, Matthew D; Bessler, Scott M; Brown, Jenise M; Deutsch, Kaitlin; Halstead, Neal T; Lentz, Garrett; Tenouri, Nadia; Young, Suzanne; Civitello, David J; Ortega, Nicole; Fites, J Scott; Reinert, Laura K; Rollins-Smith, Louise A; Raffel, Thomas R; Rohr, Jason R

    2014-07-10

    Emerging fungal pathogens pose a greater threat to biodiversity than any other parasitic group, causing declines of many taxa, including bats, corals, bees, snakes and amphibians. Currently, there is little evidence that wild animals can acquire resistance to these pathogens. Batrachochytrium dendrobatidis is a pathogenic fungus implicated in the recent global decline of amphibians. Here we demonstrate that three species of amphibians can acquire behavioural or immunological resistance to B. dendrobatidis. Frogs learned to avoid the fungus after just one B. dendrobatidis exposure and temperature-induced clearance. In subsequent experiments in which B. dendrobatidis avoidance was prevented, the number of previous exposures was a negative predictor of B. dendrobatidis burden on frogs and B. dendrobatidis-induced mortality, and was a positive predictor of lymphocyte abundance and proliferation. These results suggest that amphibians can acquire immunity to B. dendrobatidis that overcomes pathogen-induced immunosuppression and increases their survival. Importantly, exposure to dead fungus induced a similar magnitude of acquired resistance as exposure to live fungus. Exposure of frogs to B. dendrobatidis antigens might offer a practical way to protect pathogen-naive amphibians and facilitate the reintroduction of amphibians to locations in the wild where B. dendrobatidis persists. Moreover, given the conserved nature of vertebrate immune responses to fungi and the fact that many animals are capable of learning to avoid natural enemies, these results offer hope that other wild animal taxa threatened by invasive fungi might be rescued by management approaches based on herd immunity.

  16. Clinical Significance of Community- and Healthcare-Acquired Carbapenem-Resistant Enterobacteriaceae Isolates

    PubMed Central

    Tang, Hung-Jen; Hsieh, Cheng-Fang; Chang, Ping-Chin; Chen, Jyh-Jou; Lin, Yu-Hsiu; Lai, Chih-Cheng; Chao, Chien-Ming; Chuang, Yin-Ching

    2016-01-01

    This study was conducted to investigate the clinical significance, manifestations, microbiological characteristics and outcomes of carbapenem-resistant Enterobacteriaceae (CRE) isolates, and compare the clinical features of community- and healthcare-acquired CRE isolates. A total of 78 patients were identified to have CRE. Klebsiella pneumoniae was the most common pathogens (n = 42, 53.8%), followed by Enterobacter cloacae (n = 24, 30.8%), and Escherichia coli (n = 11, 14.1%). Most of the patients acquired CRE from healthcare settings (n = 55, 70.5%), and other cases got CRE from community settings (n = 23, 29.5%). Nine cases (11.5%) were classified as CRE colonization. Among the remaining 69 cases of CRE infections, pneumonia (n = 28, 40.6%) was the most common type of infections, followed by urinary tract infection (n = 24, 34.8%), and intra-abdominal infection (n = 16, 23.2%). The patients acquired CRE from community settings were more likely to be elderly, female, and had more urinary tract infections than from healthcare settings. In contrast, the patients acquired CRE from healthcare settings had more intra-abdominal infections, intra-abdominal surgery, and presence of indwelling device than from community settings. In conclusion, community-acquired CRE are not rare, and their associated clinical presentations are different from healthcare-acquired CRE. PMID:26999356

  17. Characterization of in vivo-acquired resistance to macrolides of Mycoplasma gallisepticum strains isolated from poultry

    PubMed Central

    2011-01-01

    The macrolide class of antibiotics, including tylosin and tilmicosin, is widely used in the veterinary field for prophylaxis and treatment of mycoplasmosis. In vitro susceptibility testing of 50 strains of M. gallisepticum isolated in Israel during the period 1997-2010 revealed that acquired resistance to tylosin as well as to tilmicosin was present in 50% of them. Moreover, 72% (13/18) of the strains isolated from clinical samples since 2006 showed acquired resistance to enrofloxacin, tylosin and tilmicosin. Molecular typing of the field isolates, performed by gene-target sequencing (GTS), detected 13 molecular types (I-XIII). Type II was the predominant type prior to 2006 whereas type X, first detected in 2008, is currently prevalent. All ten type X strains were resistant to both fluoroquinolones and macrolides, suggesting selective pressure leading to clonal dissemination of resistance. However, this was not a unique event since resistant strains with other GTS molecular types were also found. Concurrently, the molecular basis for macrolide resistance in M. gallisepticum was identified. Our results revealed a clear-cut correlation between single point mutations A2058G or A2059G in domain V of the gene encoding 23S rRNA (rrnA, MGA_01) and acquired macrolide resistance in M. gallisepticum. Indeed, all isolates with MIC ≥ 0.63 μg/mL to tylosin and with MIC ≥ 1.25 μg/mL to tilmicosin possess one of these mutations, suggesting an essential role in decreased susceptibility of M. gallisepticum to 16-membered macrolides. PMID:21810258

  18. Characterization of in vivo-acquired resistance to macrolides of Mycoplasma gallisepticum strains isolated from poultry.

    PubMed

    Gerchman, Irena; Levisohn, Sharon; Mikula, Inna; Manso-Silván, Lucía; Lysnyansky, Inna

    2011-08-02

    The macrolide class of antibiotics, including tylosin and tilmicosin, is widely used in the veterinary field for prophylaxis and treatment of mycoplasmosis. In vitro susceptibility testing of 50 strains of M. gallisepticum isolated in Israel during the period 1997-2010 revealed that acquired resistance to tylosin as well as to tilmicosin was present in 50% of them. Moreover, 72% (13/18) of the strains isolated from clinical samples since 2006 showed acquired resistance to enrofloxacin, tylosin and tilmicosin. Molecular typing of the field isolates, performed by gene-target sequencing (GTS), detected 13 molecular types (I-XIII). Type II was the predominant type prior to 2006 whereas type X, first detected in 2008, is currently prevalent. All ten type X strains were resistant to both fluoroquinolones and macrolides, suggesting selective pressure leading to clonal dissemination of resistance. However, this was not a unique event since resistant strains with other GTS molecular types were also found. Concurrently, the molecular basis for macrolide resistance in M. gallisepticum was identified. Our results revealed a clear-cut correlation between single point mutations A2058G or A2059G in domain V of the gene encoding 23S rRNA (rrnA, MGA_01) and acquired macrolide resistance in M. gallisepticum. Indeed, all isolates with MIC ≥ 0.63 μg/mL to tylosin and with MIC ≥ 1.25 μg/mL to tilmicosin possess one of these mutations, suggesting an essential role in decreased susceptibility of M. gallisepticum to 16-membered macrolides.

  19. A set of NF-κB-regulated microRNAs induces acquired TRAIL resistance in lung cancer.

    PubMed

    Jeon, Young-Jun; Middleton, Justin; Kim, Taewan; Laganà, Alessandro; Piovan, Claudia; Secchiero, Paola; Nuovo, Gerard J; Cui, Ri; Joshi, Pooja; Romano, Giulia; Di Leva, Gianpiero; Lee, Bum-Kyu; Sun, Hui-Lung; Kim, Yonghwan; Fadda, Paolo; Alder, Hansjuerg; Garofalo, Michela; Croce, Carlo M

    2015-06-30

    TRAIL (TNF-related apoptosis-inducing ligand) is a promising anticancer agent that can be potentially used as an alternative or complementary therapy because of its specific antitumor activity. However, TRAIL can also stimulate the proliferation of cancer cells through the activation of NF-κB, but the exact mechanism is still poorly understood. In this study, we show that chronic exposure to subtoxic concentrations of TRAIL results in acquired resistance. This resistance is associated with the increase in miR-21, miR-30c, and miR-100 expression, which target tumor-suppressor genes fundamental in the response to TRAIL. Importantly, down-regulation of caspase-8 by miR-21 blocks receptor interacting protein-1 cleavage and induces the activation of NF-κB, which regulates these miRNAs. Thus, TRAIL activates a positive feedback loop that sustains the acquired resistance and causes an aggressive phenotype. Finally, we prove that combinatory treatment of NF-κB inhibitors and TRAIL is able to revert resistance and reduce tumor growth, with important consequences for the clinical practice.

  20. ZEB1 Mediates Acquired Resistance to the Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer

    PubMed Central

    Yoshida, Takeshi; Song, Lanxi; Bai, Yun; Kinose, Fumi; Li, Jiannong; Ohaegbulam, Kim C.; Muñoz-Antonia, Teresita; Qu, Xiaotao; Eschrich, Steven; Uramoto, Hidetaka; Tanaka, Fumihiro; Nasarre, Patrick; Gemmill, Robert M.; Roche, Joëlle; Drabkin, Harry A.; Haura, Eric B.

    2016-01-01

    Epithelial-mesenchymal transition (EMT) is one mechanism of acquired resistance to inhibitors of the epidermal growth factor receptor-tyrosine kinases (EGFR-TKIs) in non-small cell lung cancer (NSCLC). The precise mechanisms of EMT-related acquired resistance to EGFR-TKIs in NSCLC remain unclear. We generated erlotinib-resistant HCC4006 cells (HCC4006ER) by chronic exposure of EGFR-mutant HCC4006 cells to increasing concentrations of erlotinib. HCC4006ER cells acquired an EMT phenotype and activation of the TGF-β/SMAD pathway, while lacking both T790M secondary EGFR mutation and MET gene amplification. We employed gene expression microarrays in HCC4006 and HCC4006ER cells to better understand the mechanism of acquired EGFR-TKI resistance with EMT. At the mRNA level, ZEB1 (TCF8), a known regulator of EMT, was >20-fold higher in HCC4006ER cells than in HCC4006 cells, and increased ZEB1 protein level was also detected. Furthermore, numerous ZEB1 responsive genes, such as CDH1 (E-cadherin), ST14, and vimentin, were coordinately regulated along with increased ZEB1 in HCC4006ER cells. We also identified ZEB1 overexpression and an EMT phenotype in several NSCLC cells and human NSCLC samples with acquired EGFR-TKI resistance. Short-interfering RNA against ZEB1 reversed the EMT phenotype and, importantly, restored erlotinib sensitivity in HCC4006ER cells. The level of micro-RNA-200c, which can negatively regulate ZEB1, was significantly reduced in HCC4006ER cells. Our results suggest that increased ZEB1 can drive EMT-related acquired resistance to EGFR-TKIs in NSCLC. Attempts should be made to explore targeting ZEB1 to resensitize TKI-resistant tumors. PMID:26789630

  1. Mechanisms of lapatinib resistance in HER2-driven breast cancer.

    PubMed

    D'Amato, Valentina; Raimondo, Lucia; Formisano, Luigi; Giuliano, Mario; De Placido, Sabino; Rosa, Roberta; Bianco, Roberto

    2015-12-01

    Targeted therapies have been approved for various malignancies but the acquisition of resistance remains a substantial challenge in the clinical management of advanced cancers. Twenty-five per cent of breast cancers overexpress ErbB2/HER2, which confers a more aggressive phenotype and is associated with a poor prognosis. HER2-targeting therapies (trastuzumab, pertuzumab, TDM1 and lapatinib) are available, but a significant fraction of HER2-positive breast cancers eventually relapse or progress. This suggests that acquired or intrinsic resistance enables escape from HER2 inhibition. This review focuses on mechanisms of intrinsic/acquired resistance to lapatinib identified in preclinical and clinical studies. A better understanding of these mechanisms could lead to novel predictive markers of lapatinib response and to novel therapeutic strategies for breast cancer patients.

  2. Community Acquired Enterococcal Urinary Tract Infections and Antibiotic Resistance Profile in North India

    PubMed Central

    Goel, Varun; Kumar, Dinesh; Kumar, Rajendra; Mathur, Purva; Singh, Sarman

    2016-01-01

    Background: Urinary tract infections (UTIs) remain a major problem both in hospitalized and outdoor patients. Multidrug-resistant enterococci are emerging as a major nosocomial pathogen with increasing frequency. However, the incidence of community-acquired enterococcal infections and species prevalent in India is not thoroughly investigated. Objectives: This study aims to estimate the burden of community-acquired UTIs seen at a tertiary care hospital and to identify the Enterococcus species isolated from these patients. The study also aims to determine the antibiotic susceptibility pattern with reference to high-level aminoglycosides and vancomycin. Materials and Methods: Semi-quantitative cultures from a total of 22,810 urine samples obtained from patients seen at various Outpatient Departments were analyzed. From them 115 nonduplicate isolates of enterococci were obtained as significant pure growth (>105 cfu/ml) and speciated. Antibiotic susceptibility was performed by Kirby–Bauer disc diffusion method. Vancomycin resistance screening was performed by the vancomycin screen agar method recommended by Clinical and Laboratory Standards Institute and confirmed by determination of minimum inhibitory concentration by agar dilution method. Results: Of 115 enterococcal isolates, 61 were identified as Enterococcus faecalis, 42 as Enterococcus faecium, 3 each as Enterococcus dispar, and Enterococcus pseudoavium. High-level gentamicin resistance (HLGR) was higher in E. faecium (47.6%) than E. faecalis (32.7%) and HLSR also showed the same pattern with 47.6% and 27.9% resistance, respectively. Vancomycin resistant enterococci accounted for 11.3% of the isolates, and out of them 53.8% were E. faecium by agar dilution method. Conclusion: High rate of resistance to antibiotics of penicillin group and aminoglycosides was observed in our tertiary care hospital even in community acquired UTIs. Hence, there is an urgent need for more rational and restricted use of antimicrobials

  3. [A mathematical model for the chemical control of Aedes aegypti (Diptera: Culicidae) having acquired chemical resistance].

    PubMed

    Restrepo-Alape, Leonardo D; Toro-Zapata, Hernán D; Muñoz-Loaiza, Aníbal

    2010-12-01

    Dengue fever is a common vector-borne disease in tropical and subtropical areas. It is transmitted to humans by the bite of an infected female Aedes mosquito. Since no vaccines are currently available which can protect against infection, disease control relies on controlling the mosquito population. This work was aimed at modelling such mosquito's population dynamics regarding chemical control of the adult population and its acquired resistance to chemicals. The model was analysed by using classical dynamic system theory techniques and mosquito growth threshold was determined as this establishes when a particular population may prosper in the environment or when it is likely to disappear. A suitable chemical control strategy was developed from such threshold. Simulations were made in control and non-control scenarios; this determined the degree of control application effectiveness against different levels of acquired resistance.

  4. Community-acquired methicillin resistant Staphylococcus aureus: a new aetiological agent of prostatic abscess

    PubMed Central

    Abreu, Diego; Arroyo, Carlos; Suarez, Ruben; Campolo, Horacio; Izaguirre, Juan; Decía, Ricardo; Machado, Miguel; Carvalhal, Gustavo Franco; Clavijo, Jorge

    2011-01-01

    Prostatic abscess is rare. Its potentially serious course requires a high level of clinical suspicion and prompt and effective treatment. The causative germs are usually either enterobacteria or Enterococcus. The authors highlight the importance of considering epidemiological and clinical aspects in the early diagnosis and treatment. Prostatic abscess due to community-acquired methicillin resistant Staphylococcus has three typical characteristics: skin entry point, periprostatic compromise, and anaemia and low prothrombin. PMID:22696740

  5. Disseminated cryptococcosis and fluconazole resistant oral candidiasis in a patient with acquired immunodeficiency syndrome (AIDS).

    PubMed

    Kothavade, Rajendra J; Oberai, Chetan M; Valand, Arvind G; Panthaki, Mehroo H

    2010-10-28

    Disseminated cryptococcosis and recurrent oral candidiasis was presented in a-heterosexual AIDS patient. Candida tropicalis (C.tropicalis) was isolated from the oral pseudomembranous plaques and Cryptococcus neoformans (C. neoformans) was isolated from maculopapular lesions on body parts (face, hands and chest) and body fluids (urine, expectorated sputum, and cerebrospinal fluid). In vitro drug susceptibility testing on the yeast isolates demonstrated resistance to fluconazole acquired by C. tropicalis which was a suggestive possible root cause of recurrent oral candidiasis in this patient.

  6. Spontaneous Lactobacillus delbrueckii phage-resistant mutants with acquired bile tolerance.

    PubMed

    Guglielmotti, Daniela; Marcó, Mariángeles Briggiler; Vinderola, Celso; de Los Reyes Gavilán, Clara; Reinheimer, Jorge; Quiberoni, Andrea

    2007-11-01

    Three commercial phage-sensitive strains of Lactobacillus delbrueckii (strains Ab(1), YSD V and Ib(3)) and four spontaneous phage-resistant mutants (strains A(7), A(17), V(2) and I(39)) isolated from them, all with a probiotic potential previously demonstrated were studied for their tolerance of bile salts (ox gall). Minimal Inhibitory Concentrations (MICs) ranged from 0.30% to 0.35% (w/v) of ox gall. These strains were exposed to gradually increasing concentrations of ox gall with the aim of isolating bile resistant derivatives. Stable derivatives able to tolerate up to 0.9% of ox gall were obtained from L. delbrueckii Ab(1), as well as from its spontaneous phage-resistant mutants A(7) and A(17). Random Amplified Polymorphic DNA (RAPD-PCR) analysis revealed a strong genetic homology between the ox gall-tolerant derivatives and their respective non-adapted original strains. These derivatives maintained, in general, the phage resistance phenotype of the non-adapted strains, with only one exception (phage-resistant mutant A(7)). After progressive ox gall adaptation, the phage-resistant mutant A(7) also exhibited progressive reversion of the phage resistance phenotype. The derivative with the highest ox gall-acquired tolerance (A(7)(0.9)) became sensitive to the phage, but derivatives with low (A(7)(0.3)) and intermediate (A(7)(0.6)) ox gall-acquired tolerance retained phage resistance. The technological properties of ox gall derivatives were comparable to those of their respective parent strains. However, the cells of the former were smaller than those of the original strains. Finally, the tolerant derivatives grew faster in the presence of ox gall than the parent strains. Our results demonstrated that it was possible to obtain, by a natural selection strategy, probiotic strains with acquired ox gall-tolerance from three (L. delbrueckii Ab(1) and their phage-resistant mutants A(7) and A(17)) of seven tested strains. Since such derivatives keep both phage resistance

  7. Garenoxacin activity against isolates form patients hospitalized with community-acquired pneumonia and multidrug-resistant Streptococcus pneumoniae.

    PubMed

    Jones, Ronald N; Sader, Helio S; Stilwell, Matthew G; Fritsche, Thomas R

    2007-05-01

    Community-acquired pneumonia (CAP) continues to cause significant morbidity worldwide, and the principal bacterial pathogens (Streptococcus pneumoniae and Haemophilus influenzae) have acquired numerous resistance mechanisms over the last few decades. CAP treatment guidelines have suggested the use of broader spectrum agents, such as antipneumococcal fluoroquinolones as the therapy for at-risk patient population. In this report, we studied 3087 CAP isolates from the SENTRY Antimicrobial Surveillance Program (1999-2005) worldwide and all respiratory tract infection (RTI) isolate population of pneumococci (14665 strains) grouped by antibiogram patterns against a new des-F(6)-quinolone, garenoxacin. Results indicated that garenoxacin was highly active against CAP isolates of S. pneumoniae (MIC(90), 0.06 microg/mL) and H. influenzae (MIC(90), < or =0.03 microg/mL). This garenoxacin potency was 8- to 32-fold greater than gatifloxacin, levofloxacin, and ciprofloxacin against the pneumococci and >99.9% of strains were inhibited at < or =1 microg/mL (proposed susceptible breakpoint). Garenoxacin MIC values were not affected by resistances among S. pneumoniae strains to penicillin or erythromycin; however, coresistances were high among the beta-lactams (penicillins and cephalosporins), macrolides, tetracyclines, and trimethoprim/sulfamethoxazole. Analysis of S. pneumoniae isolates with various antimicrobial resistance patterns to 6 drug classes demonstrated that garenoxacin was active against >99.9% (MIC, < or =1 microg/mL) of strains, and the most resistant pneumococci (6-drug resistance, 1051 strains or 7.2% of all isolates) were completely susceptible (100.0% at < or =1 microg/mL) to garenoxacin (MIC(90), 0.06 microg/mL). These results illustrate the high activity of garenoxacin against contemporary CAP isolates and especially against multidrug-resistant (MDR) S. pneumoniae that have created therapeutic dilemmas for all RTI presentations. Garenoxacin appears to be a

  8. Congenital and acquired ADAMTS13 deficiency: Two mechanisms, one patient.

    PubMed

    Ferrari, Barbara; Cairo, Andrea; Pontiggia, Silvia; Mancini, Ilaria; Masini, Luciano; Peyvandi, Flora

    2015-08-01

    Thrombotic thrombocytopenic purpura (TTP) is a life-threatening microangiopathy with a heterogeneous and largely unpredictable course. It is caused by ADAMTS13 deficiency, that can be either congenital or due to anti-ADAMTS13 autoantibodies development. ADAMTS13 deficiency is necessary but not always sufficient to cause acute clinical manifestations and trigger factors may be needed. We report the case of a woman diagnosed with congenital TTP in her adulthood, presenting with anti-ADAMTS13 autoantibodies in acute phase during ticlopidine consumption. Noteworthy, the two ADAMTS13 mutations identified in this patient are novel: one is a splice-site mutation located in intron 11 (c.1308+2_5delTAGG) and the other is a point missense mutation in exon 29 (c.4184T>C leading to p.Leu1395Pro substitution). Since congenital TTP is an extremely rare disease and drug-induced TTP is an uncommon side effect of treatment with ticlopidine, the simultaneous occurrence of both mechanisms of disease in one patient is exceptional. This case represents TTP as a multifactorial disease, with ADAMTS13 genetic abnormality and environmental exposures acting together in determining individual clinical phenotype.

  9. Acquired resistance to the second-generation androgen receptor antagonist enzalutamide in castration-resistant prostate cancer

    PubMed Central

    Kregel, Steven; Chen, James L.; Tom, Westin; Krishnan, Venkatesh; Kach, Jacob; Brechka, Hannah; Fessenden, Tim B.; Isikbay, Masis; Paner, Gladell P.

    2016-01-01

    Enzalutamide (MDV3100) is a second generation Androgen Receptor (AR) antagonist with proven efficacy in the treatment of castration resistant prostate cancer (CRPC). The majority of treated patients, however, develop resistance and disease progression and there is a critical need to identify novel targetable pathways mediating resistance. The purpose of this study was to develop and extensively characterize a series of enzalutamide-resistant prostate cancer cell lines. Four genetically distinct AR-positive and AR-pathway dependent prostate cancer cell lines (CWR-R1, LAPC-4, LNCaP, VCaP) were made resistant to enzalutamide by long-term culture (> 6 months) in enzalutamide. Extensive characterization of these lines documented divergent in vitro growth characteristics and AR pathway modulation. Enzalutamide-resistant LNCaP and CWR-R1 cells, but not LAPC-4 and VCAP cells, demonstrated increased castration-resistant and metastatic growth in vivo. Global gene expression analyses between short-term enzalutamide treated vs. enzalutamide-resistant cells identified both AR pathway and non-AR pathway associated changes that were restored upon acquisition of enzalutamide resistance. Further analyses revealed very few common gene expression changes between the four resistant cell lines. Thus, while AR-mediated pathways contribute in part to enzalutamide resistance, an unbiased approach across several cell lines demonstrates a greater contribution toward resistance via pleiotropic, non-AR mediated mechanisms. PMID:27036029

  10. Bacterial viruses enable their host to acquire antibiotic resistance genes from neighbouring cells

    PubMed Central

    Haaber, Jakob; Leisner, Jørgen J.; Cohn, Marianne T.; Catalan-Moreno, Arancha; Nielsen, Jesper B.; Westh, Henrik; Penadés, José R.; Ingmer, Hanne

    2016-01-01

    Prophages are quiescent viruses located in the chromosomes of bacteria. In the human pathogen, Staphylococcus aureus, prophages are omnipresent and are believed to be responsible for the spread of some antibiotic resistance genes. Here we demonstrate that release of phages from a subpopulation of S. aureus cells enables the intact, prophage-containing population to acquire beneficial genes from competing, phage-susceptible strains present in the same environment. Phage infection kills competitor cells and bits of their DNA are occasionally captured in viral transducing particles. Return of such particles to the prophage-containing population can drive the transfer of genes encoding potentially useful traits such as antibiotic resistance. This process, which can be viewed as ‘auto-transduction', allows S. aureus to efficiently acquire antibiotic resistance both in vitro and in an in vivo virulence model (wax moth larvae) and enables it to proliferate under strong antibiotic selection pressure. Our results may help to explain the rapid exchange of antibiotic resistance genes observed in S. aureus. PMID:27819286

  11. Acquired platinum resistance involves epithelial to mesenchymal transition through ubiquitin ligase FBXO32 dysregulation

    PubMed Central

    Tanaka, Nobuyuki; Miyazaki, Yasumasa; Mikami, Shuji; Niwa, Naoya; Otsuka, Yutaro; Mizuno, Ryuichi; Kikuchi, Eiji; Miyajima, Akira; Sabe, Hisataka; Okada, Yasunori; Suematsu, Makoto; Oya, Mototsugu

    2016-01-01

    To identify the molecules involved in epithelial to mesenchymal transition (EMT) in urothelial carcinoma (UC) after acquisition of platinum resistance, here we examined the changes in global gene expression before and after platinum treatment. Four invasive UC cell lines, T24, 5637, and their corresponding sublines T24PR and 5637PR with acquired platinum resistance, were assessed by microarray, and the ubiquitin E3 ligase FBXO32 was newly identified as a negative regulator of EMT in UC tumors after acquisition of platinum resistance. In vitro and in vivo studies showed an intimate relationship between FBXO32 expression and EMT, demonstrating that FBXO32 dysregulation in T24PR cells results in elevated expression of the mesenchymal molecules SNAIL and vimentin and decreased expression of the epithelial molecule E-cadherin. The association between FBXO32 expression and EMT was further validated using clinical samples. Knockdown of MyoD expression, a specific target of FBXO32 polyubiquitination, revealed upregulation of E-cadherin expression and downregulation of SNAIL and vimentin expression in T24PR cells. Comparative genomic hybridization array analysis demonstrated loss of heterozygosity at 8q24.13 in T24PR cells, which harbors FBXO32. Our findings suggest the importance of the association between EMT and ubiquitin-proteasome regulation when tumors develop acquired platinum resistance. PMID:27812537

  12. Acquired platinum resistance involves epithelial to mesenchymal transition through ubiquitin ligase FBXO32 dysregulation.

    PubMed

    Tanaka, Nobuyuki; Kosaka, Takeo; Miyazaki, Yasumasa; Mikami, Shuji; Niwa, Naoya; Otsuka, Yutaro; Minamishima, Yoji Andrew; Mizuno, Ryuichi; Kikuchi, Eiji; Miyajima, Akira; Sabe, Hisataka; Okada, Yasunori; Uhlén, Per; Suematsu, Makoto; Oya, Mototsugu

    2016-11-03

    To identify the molecules involved in epithelial to mesenchymal transition (EMT) in urothelial carcinoma (UC) after acquisition of platinum resistance, here we examined the changes in global gene expression before and after platinum treatment. Four invasive UC cell lines, T24, 5637, and their corresponding sublines T24PR and 5637PR with acquired platinum resistance, were assessed by microarray, and the ubiquitin E3 ligase FBXO32 was newly identified as a negative regulator of EMT in UC tumors after acquisition of platinum resistance. In vitro and in vivo studies showed an intimate relationship between FBXO32 expression and EMT, demonstrating that FBXO32 dysregulation in T24PR cells results in elevated expression of the mesenchymal molecules SNAIL and vimentin and decreased expression of the epithelial molecule E-cadherin. The association between FBXO32 expression and EMT was further validated using clinical samples. Knockdown of MyoD expression, a specific target of FBXO32 polyubiquitination, revealed upregulation of E-cadherin expression and downregulation of SNAIL and vimentin expression in T24PR cells. Comparative genomic hybridization array analysis demonstrated loss of heterozygosity at 8q24.13 in T24PR cells, which harbors FBXO32. Our findings suggest the importance of the association between EMT and ubiquitin-proteasome regulation when tumors develop acquired platinum resistance.

  13. Acquired resistance to BRAF inhibition in BRAFV600E mutant gliomas

    PubMed Central

    Yao, Tsun-Wen; Zhang, Jie; Prados, Michael; Weiss, William A.; James, C. David; Nicolaides, Theodore

    2017-01-01

    Activating mutation of BRAF is a common finding in pediatric gliomas. As many as 14% of high grade and up to 66% of certain subtypes of low grade pediatric glioma have the BRAFV600E mutation. Small molecule inhibitors that selectively target BRAFV600E are FDA approved for melanoma and have shown significant efficacy in treating BRAFV600E glioma in pre-clinical trials. Despite showing initial anti-tumor activity, acquired drug resistance significantly limits the benefit from being treated with BRAFV600E inhibitors. Here, we have identified molecular responses to BRAFV600E inhibitor treatment in human glioma models that have substantial clinical implications. Specifically, we show that BRAFV600E inhibitor resistant cells upregulate pro-survival mediators such as Wnt, and additionally increase receptor tyrosine kinase activity, including EGFR and Axl, promoting resistance to BRAFV600E inhibition. Our results suggest strategies to circumvent acquired resistance to BRAFV600E inhibitor therapy, and thereby improve outcomes for patients with BRAFV600E gliomas. PMID:27611946

  14. Fluoroquinolone susceptibility testing of Salmonella enterica: detection of acquired resistance and selection of zone diameter breakpoints for levofloxacin and ofloxacin.

    PubMed

    Sjölund-Karlsson, Maria; Howie, Rebecca L; Crump, John A; Whichard, Jean M

    2014-03-01

    Fluoroquinolones (e.g., ciprofloxacin) have become a mainstay for treating severe Salmonella infections in adults. Fluoroquinolone resistance in Salmonella is mostly due to mutations in the topoisomerase genes, but plasmid-mediated quinolone resistance (PMQR) mechanisms have also been described. In 2012, the Clinical and Laboratory Standards Institute (CLSI) revised the ciprofloxacin interpretive criteria (breakpoints) for disk diffusion and MIC test methods for Salmonella. In 2013, the CLSI published MIC breakpoints for Salmonella to levofloxacin and ofloxacin, but breakpoints for assigning disk diffusion results to susceptible (S), intermediate (I), and resistant (R) categories are still needed. In this study, the MICs and inhibition zone diameters for nalidixic acid, ciprofloxacin, levofloxacin, and ofloxacin were determined for 100 clinical isolates of nontyphi Salmonella with or without resistance mechanisms. We confirmed that the new levofloxacin MIC breakpoints resulted in the highest category agreement (94%) when plotted against the ciprofloxacin MICs and that the new ofloxacin MIC breakpoints resulted in 92% category agreement between ofloxacin and ciprofloxacin. By applying the new MIC breakpoints in the MIC zone scattergrams for levofloxacin and ofloxacin, the following disk diffusion breakpoints generated the least number of errors: ≥28 mm (S), 19 to 27 mm (I), and ≤18 mm (R) for levofloxacin and ≥25 mm (S), 16 to 24 mm (I), and ≤15 mm (R) for ofloxacin. Neither the levofloxacin nor the ofloxacin disk yielded good separation of isolates with and without resistance mechanisms. Further studies will be needed to develop a disk diffusion assay that efficiently detects all isolates with acquired resistance to fluoroquinolones.

  15. Evolving trends in Streptococcus pneumoniae resistance: implications for therapy of community-acquired bacterial pneumonia.

    PubMed

    Jones, Ronald N; Jacobs, Michael R; Sader, Helio S

    2010-09-01

    Pneumonia is a major infectious disease associated with significant morbidity, mortality and utilisation of healthcare resources. Streptococcus pneumoniae is the predominant pathogen in community-acquired pneumonia (CAP), accounting for 20-60% of bacterial cases. Emergence of multidrug-resistant S. pneumoniae has become a significant problem in the management of CAP. Although pneumococcal conjugate vaccine usage in children has led to significant decreases in morbidity and mortality due to S. pneumoniae in all age groups, disease management has been further complicated by the unexpected increase in resistant serotypes, such as 19A, in some regions. Until rapid and accurate diagnostic tests become available, initial treatment of CAP will remain empirical. Thus, selection of appropriate antimicrobial therapy for CAP must be based on prediction of the most likely pathogens and their local antimicrobial susceptibility patterns. This article reviews information on antimicrobial resistance patterns amongst S. pneumoniae and implications for managing CAP.

  16. Mechanisms of Resistance to Antibody-Drug Conjugates.

    PubMed

    Loganzo, Frank; Sung, Matthew; Gerber, Hans-Peter

    2016-12-01

    Drug resistance limits the effectiveness of cancer therapies. Despite attempts to develop curative anticancer treatments, tumors evolve evasive mechanisms limiting durable responses. Hence, diverse therapies are used to attack cancer, including cytotoxic and targeted agents. Antibody-drug conjugates (ADC) are biotherapeutics designed to deliver potent cytotoxins to cancer cells via tumor-specific antigens. Little is known about the clinical manifestations of drug resistance to this class of therapy; however, recent preclinical studies reveal potential mechanisms of resistance. Because ADCs are a combination of antibody and small molecule cytotoxin, multifactorial modes of resistance are emerging that are inherent to the structure and function of the ADC. Decreased cell-surface antigen reduces antibody binding, whereas elevated drug transporters such as MDR1 and MRP1 reduce effectiveness of the payload. Inherent to the uniqueness of the ADC, other novel resistance mechanisms are emerging, including altered antibody trafficking, ADC processing, and intracellular drug release. Most importantly, the modular nature of the ADC allows components to be switched and replaced, enabling development of second-generation ADCs that overcome acquired resistance. This review is intended to highlight recent progress in our understanding of ADC resistance, including approaches to create preclinical ADC-refractory models and to characterize their emerging mechanisms of resistance. Mol Cancer Ther; 15(12); 2825-34. ©2016 AACR.

  17. Acquired Genetic Mechanisms of a Multiresistant Bacterium Isolated from a Treatment Plant Receiving Wastewater from Antibiotic Production

    PubMed Central

    Johnning, Anna; Moore, Edward R. B.; Svensson-Stadler, Liselott; Shouche, Yogesh S.; Larsson, D. G. Joakim

    2013-01-01

    The external environment, particularly wastewater treatment plants (WWTPs), where environmental bacteria meet human commensals and pathogens in large numbers, has been highlighted as a potential breeding ground for antibiotic resistance. We have isolated the extensively drug-resistant Ochrobactrum intermedium CCUG 57381 from an Indian WWTP receiving industrial wastewater from pharmaceutical production contaminated with high levels of quinolones. Antibiotic susceptibility testing against 47 antibiotics showed that the strain was 4 to >500 times more resistant to sulfonamides, quinolones, tetracyclines, macrolides, and the aminoglycoside streptomycin than the type strain O. intermedium LMG 3301T. Whole-genome sequencing identified mutations in the Indian strain causing amino acid substitutions in the target enzymes of quinolones. We also characterized three acquired regions containing resistance genes to sulfonamides (sul1), tetracyclines [tet(G) and tetR], and chloramphenicol/florfenicol (floR). Furthermore, the Indian strain harbored acquired mechanisms for horizontal gene transfer, including a type I mating pair-forming system (MPFI), a MOBP relaxase, and insertion sequence transposons. Our results highlight that WWTPs serving antibiotic manufacturing may provide nearly ideal conditions for the recruitment of resistance genes into human commensal and pathogenic bacteria. PMID:24038701

  18. Acquired genetic mechanisms of a multiresistant bacterium isolated from a treatment plant receiving wastewater from antibiotic production.

    PubMed

    Johnning, Anna; Moore, Edward R B; Svensson-Stadler, Liselott; Shouche, Yogesh S; Larsson, D G Joakim; Kristiansson, Erik

    2013-12-01

    The external environment, particularly wastewater treatment plants (WWTPs), where environmental bacteria meet human commensals and pathogens in large numbers, has been highlighted as a potential breeding ground for antibiotic resistance. We have isolated the extensively drug-resistant Ochrobactrum intermedium CCUG 57381 from an Indian WWTP receiving industrial wastewater from pharmaceutical production contaminated with high levels of quinolones. Antibiotic susceptibility testing against 47 antibiotics showed that the strain was 4 to >500 times more resistant to sulfonamides, quinolones, tetracyclines, macrolides, and the aminoglycoside streptomycin than the type strain O. intermedium LMG 3301T. Whole-genome sequencing identified mutations in the Indian strain causing amino acid substitutions in the target enzymes of quinolones. We also characterized three acquired regions containing resistance genes to sulfonamides (sul1), tetracyclines [tet(G) and tetR], and chloramphenicol/florfenicol (floR). Furthermore, the Indian strain harbored acquired mechanisms for horizontal gene transfer, including a type I mating pair-forming system (MPFI), a MOBP relaxase, and insertion sequence transposons. Our results highlight that WWTPs serving antibiotic manufacturing may provide nearly ideal conditions for the recruitment of resistance genes into human commensal and pathogenic bacteria.

  19. Update on HIV-1 acquired and transmitted drug resistance in Africa.

    PubMed

    Ssemwanga, Deogratius; Lihana, Raphael W; Ugoji, Chinenye; Abimiku, Alash'le; Nkengasong, John; Dakum, Patrick; Ndembi, Nicaise

    2015-01-01

    The last ten years have witnessed a significant scale-up and access to antiretroviral therapy in Africa, which has improved patient quality of life and survival. One major challenge associated with increased access to antiretroviral therapy is the development of antiretroviral resistance due to inconsistent drug supply and/or poor patient adherence. We review the current state of both acquired and transmitted drug resistance in Africa over the past ten years (2001-2011) to identify drug resistance associated with the different drug regimens used on the continent and to help guide affordable strategies for drug resistance surveillance. A total of 161 references (153 articles, six reports and two conference abstracts) were reviewed. Antiretroviral resistance data was available for 40 of 53 African countries. A total of 5,541 adult patients from 99 studies in Africa were included in this analysis. The pooled prevalence of drug resistance mutations in Africa was 10.6%, and Central Africa had the highest prevalence of 54.9%. The highest prevalence of nucleoside reverse transcriptase inhibitor mutations was in the west (55.3%) and central (54.8%) areas; nonnucleoside reverse transcriptase inhibitor mutations were highest in East Africa (57.0%) and protease inhibitors mutations highest in Southern Africa (16.3%). The major nucleoside reverse transcriptase inhibitor mutation in all four African regions was M184V. Major nonnucleoside reverse transcriptase inhibitor as well as protease inhibitor mutations varied by region. The prevalence of drug resistance has remained low in several African countries although the emergence of drug resistance mutations varied across countries. Continued surveillance of antiretroviral therapy resistance remains crucial in gauging the effectiveness of country antiretroviral therapy programs and strategizing on effective and affordable strategies for successful treatment.

  20. Cancer cell resistance mechanisms: a mini review.

    PubMed

    Al-Dimassi, S; Abou-Antoun, T; El-Sibai, M

    2014-06-01

    Cancer is a leading cause of death worldwide accounting to 13 % of all deaths. One of the main causes behind the failure of treatment is the development of various therapy resistance mechanisms by the cancer cells leading to the recurrence of the disease. This review sheds a light on some of the mechanisms developed by cancer cells to resist therapy as well as some of the structures involved such as the ABC members' involvement in chemotherapy resistance and MET and survivin overexpression leading to radiotherapy resistance. Understanding those mechanisms will enable scientists to overcome resistance and possibly improve treatment and disease prognosis.

  1. Selinexor is effective in acquired resistance to ibrutinib and synergizes with ibrutinib in chronic lymphocytic leukemia

    PubMed Central

    Hing, Zachary A.; Mantel, Rose; Beckwith, Kyle A.; Guinn, Daphne; Williams, Erich; Smith, Lisa L.; Williams, Katie; Johnson, Amy J.; Lehman, Amy M.; Byrd, John C.; Woyach, Jennifer A.

    2015-01-01

    Despite the therapeutic efficacy of ibrutinib in chronic lymphocytic leukemia (CLL), complete responses are infrequent, and acquired resistance to Bruton agammaglobulinemia tyrosine kinase (BTK) inhibition is being observed in an increasing number of patients. Combination regimens that increase frequency of complete remissions, accelerate time to remission, and overcome single agent resistance are of considerable interest. We previously showed that the XPO1 inhibitor selinexor is proapoptotic in CLL cells and disrupts B-cell receptor signaling via BTK depletion. Herein we show the combination of selinexor and ibrutinib elicits a synergistic cytotoxic effect in primary CLL cells and increases overall survival compared with ibrutinib alone in a mouse model of CLL. Selinexor is effective in cells isolated from patients with prolonged lymphocytosis following ibrutinib therapy. Finally, selinexor is effective in ibrutinib-refractory mice and in a cell line harboring the BTK C481S mutation. This is the first report describing the combined activity of ibrutinib and selinexor in CLL, which represents a new treatment paradigm and warrants further evaluation in clinical trials of CLL patients including those with acquired ibrutinib resistance. PMID:25838351

  2. Protein arginine methyltransferase 1 may be involved in pregnane x receptor-activated overexpression of multidrug resistance 1 gene during acquired multidrug resistant

    PubMed Central

    Li, Tingting; Kong, Ah-Ng Tony; Ma, Zhiqiang; Liu, Haiyan; Liu, Pinghua; Xiao, Yu; Jiang, Xuehua; Wang, Ling

    2016-01-01

    Purpose Pregnane x receptor (PXR) - activated overexpression of the multidrug resistance 1 (MDR1) gene is an important way for tumor cells to acquire drug resistance. However, the detailed mechanism still remains unclear. In the present study, we aimed to investigate whether protein arginine methyl transferase 1(PRMT1) is involved in PXR - activated overexpression of MDR1 during acquired multidrug resistant. Experimental Design Arginine methyltransferase inhibitor 1 (AMI-1) was used to pharmacologically block PRMT1 in resistant breast cancer cells (MCF7/adr). The mRNA and protein levels of MDR1 were detected by real-time PCR and western blotting analysis. Immunofluorescence microscopy and co-immunoprecipitation were used to investigate the physical interaction between PXR and PRMT1. Then, 136 candidate compounds were screened for PRMT1 inhibitors. Lastly, luciferase reporter gene and nude mice bearing resistant breast cancer xenografts were adopted to investigate the anti-tumor effect of PRMT1 inhibitors when combined with adriamycin. Results AMI-1 significantly suppressed the expression of MDR1 in MCF7/adr cells and increased cells sensitivity of MCF7/adr to adriamycin. Physical interaction between PRMT1 and PXR exists in MCF7/adr cells, which could be disrupted by AMI-1. Those results suggest that PRMT1 may be involved in PXR-activated overexpression of MDR1 in resistant breast cancer cells, and AMI-1 may suppress MDR1 by disrupting the interaction between PRMT1 and PXR. Then, five compounds including rutin, isoquercitrin, salvianolic acid A, naproxen, and felodipline were identified to be PRMT1 inhibitors. Finally, those PRMT1 inhibitors were observed to significantly decrease MDR1 promoter activity in vitro and enhance the antitumor effect of adriamycin in nude mice that bearing resistant breast cancer xenografts. Conclusions PRMT1 may be an important co-activator of PXR in activating MDR1 gene during acquired resistance, and PRMT1 inhibitor combined with

  3. Probing the mechanisms of silicon-mediated pathogen resistance.

    PubMed

    Cai, Kunzheng; Gao, Dan; Chen, Jining; Luo, Shiming

    2009-01-01

    Silicon is the second most abundant mineral element in soil, it has important role in alleviating various environmental stresses and enhancing plant resistance against pathogen, but the exact mechanism by which Si mediates pathogen resistance remains unclear. One of the resistance mechanisms is related to silicon deposition in leaf that acts as a physical barrier to hinder pathogen penetration. But more evidence show that silicon can induce defense responses that are functionally similar to systemic acquired resistance, Si-treated plants can significantly increase antioxidant enzyme activities and the production of antifungal compounds such as phenolic metabolism product, phytoalexins and pathogenesis-related proteins etc. Molecular and biochemical detections show that Si can activate the expression of defense-related genes and may play important role in the transduction of plant stress signal such as salicylic acid, jasmonic acid and ethylene.

  4. Pneumococcal antimicrobial resistance: therapeutic strategy and management in community-acquired pneumonia.

    PubMed

    Aspa, Javier; Rajas, Olga; de Castro, Felipe Rodríguez

    2008-02-01

    Streptococcus pneumoniae has been consistently shown to represent the most frequent causative agent of community-acquired pneumonia (CAP) and pneumococcal antibiotic resistance towards different families of antibiotics continues to be a much-debated issue. Microbial resistance causes a great deal of confusion in choosing an empirical treatment for pneumonia and this makes it necessary to know which factors actually determine the real impact of antimicrobial resistance on the outcome of pneumococcal infections. Several different aspects have to be taken into account when analyzing this matter, such as the study design, the condition of the patient at the time of diagnosis, the choice of the initial antimicrobial regimen (combination or monotherapy) and the pharmacokinetic/pharmacodynamic variables of the chosen antibiotic. It is generally accepted that in the treatment of beta-lactam-resistant pneumococcal infections, the use of standard antipneumococcal beta-lactam agents is unlikely to impact negatively on the outcome of CAP when appropriate agents are given in sufficient doses. As a general rule, for infections with penicillin-sensitive strains, penicillin or an aminopenicillin in a standard dosage will be effective; in the cases of strains with intermediate resistance, beta-lactam agents are still considered appropriate treatment although higher dosages are recommended; finally, infections with isolates of high-level penicillin resistance should be treated with alternative agents such as the third-generation cephalosporins or the new antipneumococcal fluoroquinolones. In areas of high prevalence of high-level macrolide resistance, empirical monotherapy with a macrolide is not optimal for the treatment of hospitalised patients with moderate or moderately-severe CAP. Fluoroquinolones are considered to be excellent antibiotics in the treatment of pneumococcal CAP in adults, but their general recommendation has been withheld due to fears of a widespread development

  5. ERK2, but Not ERK1, Mediates Acquired and “De novo” Resistance to Imatinib Mesylate: Implication for CML Therapy

    PubMed Central

    Aceves-Luquero, Clara I.; Agarwal, Anupriya; Callejas-Valera, Juan L.; Arias-González, Laura; Esparís-Ogando, Azucena; del Peso Ovalle, Luis; Bellón-Echeverria, Itxaso; de la Cruz-Morcillo, Miguel A.; Galán Moya, Eva M.; Gimeno, Inmaculada Moreno; Gómez, Juan C.; Deininger, Michael W.; Pandiella, Atanasio; Prieto, Ricardo Sánchez

    2009-01-01

    Resistance to Imatinib Mesylate (IM) is a major problem in Chronic Myelogenous Leukaemia management. Most of the studies about resistance have focused on point mutations on BCR/ABL. However, other types of resistance that do not imply mutations in BCR/ABL have been also described. In the present report we aim to study the role of several MAPK in IM resistance not associate to BCR/ABL mutations. Therefore we used an experimental system of resistant cell lines generated by co-culturing with IM (K562, Lama 84) as well as primary material from resistant and responder patient without BCR/ABL mutations. Here we demonstrate that Erk5 and p38MAPK signaling pathways are not implicated in the acquired resistance phenotype. However, Erk2, but not Erk1, is critical for the acquired resistance to IM. In fact, Bcr/Abl activates preferentially Erk2 in transient transfection in a dose dependent fashion through the c-Abl part of the chimeric protein. Finally, we present evidences demonstrating how constitutive activation of Erk2 is a de novo mechanism of resistance to IM. In summary our data support the use of therapeutic approaches based on Erk2 inhibition, which could be added to the therapeutic armamentarium to fight CML, especially when IM resistance develops secondary to Erk2 activation. PMID:19568437

  6. An intact cuticle in distal tissues is essential for the induction of systemic acquired resistance in plants.

    PubMed

    Xia, Ye; Gao, Qing-Ming; Yu, Keshun; Lapchyk, Ludmila; Navarre, DuRoy; Hildebrand, David; Kachroo, Aardra; Kachroo, Pradeep

    2009-02-19

    Systemic acquired resistance (SAR), initiated by a plant upon recognition of microbial effectors, involves generation of a mobile signal at the primary infection site, which translocates to and activates defense responses in distal tissues via unknown mechanism(s). We find that an acyl carrier protein, ACP4, is required to perceive the mobile SAR signal in distal tissues of Arabidopsis. Although acp4 plants generated the mobile signal, they failed to induce the systemic immunity response. Defective SAR in acp4 plants was not due to impairment in salicylic acid (SA)-, methyl SA-, or jasmonic acid-mediated plant hormone signaling pathways but was associated with the impaired cuticle of acp4 leaves. Other cuticle-impairing genetic mutations or physical removal of the cuticle also compromised SAR. This cuticular requirement was relevant only during mobile signal generation and its translocation to distal tissues. Collectively, these data suggest an active role for the plant cuticle in SAR-related molecular signaling.

  7. Arabidopsis TTR1 causes LRR-dependent lethal systemic necrosis, rather than systemic acquired resistance, to Tobacco ringspot virus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most Arabidopsis ecotypes display tolerance to the Tobacco ringspot virus (TRSV), but a subset of Arabidopsis ecotypes, including Estland (Est), develop lethal systemic necrosis (LSN), which differs from the localized hypersensitive responses (HRs) or systemic acquired resistance (SAR) characteristi...

  8. Long-term persistence of acquired resistance to 5-fluorouracil in the colon cancer cell line SW620

    SciTech Connect

    Tentes, I.K.; Schmidt, W.M.; Krupitza, G.; Steger, G.G.; Mikulits, W.; Kortsaris, A.; Mader, R.M.

    2010-11-15

    Treatment resistance to antineoplastic drugs represents a major clinical problem. Here, we investigated the long-term stability of acquired resistance to 5-fluorouracil (FU) in an in vitro colon cancer model, using four sub-clones characterised by increasing FU-resistance derived from the cell line SW620. The resistance phenotype was preserved after FU withdrawal for 15 weeks ({approx} 100 cell divisions) independent of the established level of drug resistance and of epigenetic silencing. Remarkably, resistant clones tolerated serum deprivation, adopted a CD133{sup +} CD44{sup -} phenotype, and further exhibited loss of membrane-bound E-cadherin together with predominant nuclear {beta}-catenin localisation. Thus, we provide evidence for a long-term memory of acquired drug resistance, driven by multiple cellular strategies (epithelial-mesenchymal transition and selective propagation of CD133{sup +} cells). These resistance phenomena, in turn, accentuate the malignant phenotype.

  9. Infection control implications of heterogeneous resistance mechanisms in carbapenem-resistant Enterobacteriaceae (CRE).

    PubMed

    Goodman, K E; Simner, P J; Tamma, P D; Milstone, A M

    2016-01-01

    The Centers for Disease Control and Prevention (CDC) defines carbapenem-resistant Enterobacteriaceae (CRE) based upon a phenotypic demonstration of carbapenem resistance. However, considerable heterogeneity exists within this definitional umbrella. CRE may mechanistically differ by whether they do or do not produce carbapenemases. Moreover, patients can acquire CRE through multiple pathways: endogenously through antibiotic selective pressure on intestinal microbiota, exogenously through horizontal transmission or through a combination of these factors. Some evidence suggests that non-carbapenemase-producing CRE may be more frequently acquired by antibiotic exposure and carbapenemase-producing CRE via horizontal transmission, but definitive data are lacking. This review examines types of CRE resistance mechanisms, antibiotic exposure and horizontal transmission pathways of CRE acquisition, and the implications of these heterogeneities to the development of evidence-based CRE healthcare epidemiology policies. In our Expert Commentary & Five-Year View, we outline specific nosocomial CRE knowledge gaps and potential methodological approaches for their resolution.

  10. Acquired EGFR C797S mutation mediates resistance to AZD9291 in non-small cell lung cancer harboring EGFR T790M.

    PubMed

    Thress, Kenneth S; Paweletz, Cloud P; Felip, Enriqueta; Cho, Byoung Chul; Stetson, Daniel; Dougherty, Brian; Lai, Zhongwu; Markovets, Aleksandra; Vivancos, Ana; Kuang, Yanan; Ercan, Dalia; Matthews, Sarah E; Cantarini, Mireille; Barrett, J Carl; Jänne, Pasi A; Oxnard, Geoffrey R

    2015-06-01

    Here we studied cell-free plasma DNA (cfDNA) collected from subjects with advanced lung cancer whose tumors had developed resistance to the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) AZD9291. We first performed next-generation sequencing of cfDNA from seven subjects and detected an acquired EGFR C797S mutation in one; expression of this mutant EGFR construct in a cell line rendered it resistant to AZD9291. We then performed droplet digital PCR on serial cfDNA specimens collected from 15 AZD9291-treated subjects. All were positive for the T790M mutation before treatment, but upon developing AZD9291 resistance three molecular subtypes emerged: six cases acquired the C797S mutation, five cases maintained the T790M mutation but did not acquire the C797S mutation and four cases lost the T790M mutation despite the presence of the underlying EGFR activating mutation. Our findings provide insight into the diversity of mechanisms through which tumors acquire resistance to AZD9291 and highlight the need for therapies that are able to overcome resistance mediated by the EGFR C797S mutation.

  11. Non-invasive analysis of acquired resistance to cancer therapy by sequencing of plasma DNA.

    PubMed

    Murtaza, Muhammed; Dawson, Sarah-Jane; Tsui, Dana W Y; Gale, Davina; Forshew, Tim; Piskorz, Anna M; Parkinson, Christine; Chin, Suet-Feung; Kingsbury, Zoya; Wong, Alvin S C; Marass, Francesco; Humphray, Sean; Hadfield, James; Bentley, David; Chin, Tan Min; Brenton, James D; Caldas, Carlos; Rosenfeld, Nitzan

    2013-05-02

    Cancers acquire resistance to systemic treatment as a result of clonal evolution and selection. Repeat biopsies to study genomic evolution as a result of therapy are difficult, invasive and may be confounded by intra-tumour heterogeneity. Recent studies have shown that genomic alterations in solid cancers can be characterized by massively parallel sequencing of circulating cell-free tumour DNA released from cancer cells into plasma, representing a non-invasive liquid biopsy. Here we report sequencing of cancer exomes in serial plasma samples to track genomic evolution of metastatic cancers in response to therapy. Six patients with advanced breast, ovarian and lung cancers were followed over 1-2 years. For each case, exome sequencing was performed on 2-5 plasma samples (19 in total) spanning multiple courses of treatment, at selected time points when the allele fraction of tumour mutations in plasma was high, allowing improved sensitivity. For two cases, synchronous biopsies were also analysed, confirming genome-wide representation of the tumour genome in plasma. Quantification of allele fractions in plasma identified increased representation of mutant alleles in association with emergence of therapy resistance. These included an activating mutation in PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha) following treatment with paclitaxel; a truncating mutation in RB1 (retinoblastoma 1) following treatment with cisplatin; a truncating mutation in MED1 (mediator complex subunit 1) following treatment with tamoxifen and trastuzumab, and following subsequent treatment with lapatinib, a splicing mutation in GAS6 (growth arrest-specific 6) in the same patient; and a resistance-conferring mutation in EGFR (epidermal growth factor receptor; T790M) following treatment with gefitinib. These results establish proof of principle that exome-wide analysis of circulating tumour DNA could complement current invasive biopsy approaches to identify

  12. Community-acquired methicillin-resistant Staphylococcus aureus in a Malaysian tertiary centre.

    PubMed

    Rashid, Zetti Zainol; Bahari, Norazlah; Othman, Amizah; Jaafar, Roslinda; Mohamed, Nurul Azmawati; Jabbari, Idimaz; Sulong, Anita; Hashim, Rohaidah; Ahmad, Norazah

    2013-01-01

    Abstract. Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is a pathogen recognized to be distinct in both phenotype and genotype from hospital-acquired MRSA. We have identified CA-MRSA cases in Universiti Kebangsaan Malaysia Medical Centre, Kuala Lumpur, Malaysia, including their antibiotic susceptibility patterns and genotypic characteristics. Cases were identified during January to December 2009 from routine clinical specimens, where culture and antibiotic susceptibility results yielded pauci-resistant MRSA isolates suspected as being CA-MRSA. The patients' clinical data were collected and their specimens were sent for molecular confirmation and analysis. Five cases of CA-MRSA were identified, which had a multi-sensitive pattern on antibiotic susceptibility tests and were resistant to only penicillin and oxacillin. All cases were skin and soft-tissue infections, including diabetic foot with gangrene, infected scalp hematoma, philtrum abscess in a healthcare worker, thrombophlebitis complicated with abscess and infected bedsore. All five cases were confirmed MRSA by detection of mecA. SCCmec typing (ccr and mec complex) revealed SCCmec type IV for all cases except the infected bedsore case. Panton-Valentine leukocidin gene was positive in all isolates. As clinical features among methicillin-sensitive Staphylococcus aureus, CA-MRSA and "nosocomial CA-MRSA" are indistinct, early recognition is necessary in order to initiate appropriate antibiotics and infection control measures. Continual surveillance of pauci-resistant MRSA and molecular analysis are necessary in order to identify emerging strains as well as their epidemiology and transmission, both in the community and in healthcare setting.

  13. Effect of United States buckwheat honey on antibiotic-resistant hospital acquired pathogens

    PubMed Central

    Hammond, Eric Nee-Armah; Duster, Megan; Musuuza, Jackson Ssentalo; Safdar, Nasia

    2016-01-01

    Introduction Due to an upsurge in antibiotic-resistant infections and lack of therapeutic options, new approaches are needed for treatment. Honey may be one such potential therapeutic option. We investigated the susceptibility of hospital acquired pathogens to four honeys from Wisconsin, United States, and then determined if the antibacterial effect of each honey against these pathogens is primarily due to the high sugar content. Methods Thirteen pathogens including: four Clostridium difficile, two Methicillin-resistant Staphylococcus aureus, two Pseudomonas aeruginosa, one Methicillin-Susceptible Staphylococcus aureus, two Vancomycin-resistance Enterococcus, one Enterococcus faecalis and one Klebsiella pneumoniae were exposed to 1-50% (w/v) four Wisconsin honeys and Artificial honey to determine their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using the broth dilution method. Results Buckwheat honey predominantly exhibited a bactericidal mode of action against the tested pathogens, and this varied with each pathogen. C. difficile isolates were more sensitive to the Wisconsin buckwheat honey as compared to the other pathogens. Artificial honey at 50% (w/v) failed to kill any of the pathogens. The high sugar content of Wisconsin buckwheat honey is not the only factor responsible for its bactericidal activity. Conclusion Wisconsin buckwheat honey has the potential to be an important addition to therapeutic armamentarium against resistant pathogens and should be investigated further. PMID:28292167

  14. Pentamidine sensitizes Gram-negative pathogens to antibiotics and overcomes acquired colistin resistance.

    PubMed

    Stokes, Jonathan M; MacNair, Craig R; Ilyas, Bushra; French, Shawn; Côté, Jean-Philippe; Bouwman, Catrien; Farha, Maya A; Sieron, Arthur O; Whitfield, Chris; Coombes, Brian K; Brown, Eric D

    2017-03-06

    The increasing use of polymyxins(1) in addition to the dissemination of plasmid-borne colistin resistance threatens to cause a serious breach in our last line of defence against multidrug-resistant Gram-negative pathogens, and heralds the emergence of truly pan-resistant infections. Colistin resistance often arises through covalent modification of lipid A with cationic residues such as phosphoethanolamine-as is mediated by Mcr-1 (ref. 2)-which reduce the affinity of polymyxins for lipopolysaccharide(3). Thus, new strategies are needed to address the rapidly diminishing number of treatment options for Gram-negative infections(4). The difficulty in eradicating Gram-negative bacteria is largely due to their highly impermeable outer membrane, which serves as a barrier to many otherwise effective antibiotics(5). Here, we describe an unconventional screening platform designed to enrich for non-lethal, outer-membrane-active compounds with potential as adjuvants for conventional antibiotics. This approach identified the antiprotozoal drug pentamidine(6) as an effective perturbant of the Gram-negative outer membrane through its interaction with lipopolysaccharide. Pentamidine displayed synergy with antibiotics typically restricted to Gram-positive bacteria, yielding effective drug combinations with activity against a wide range of Gram-negative pathogens in vitro, and against systemic Acinetobacter baumannii infections in mice. Notably, the adjuvant activity of pentamidine persisted in polymyxin-resistant bacteria in vitro and in vivo. Overall, pentamidine and its structural analogues represent unexploited molecules for the treatment of Gram-negative infections, particularly those having acquired polymyxin resistance determinants.

  15. Bacterial resistance to tetracycline: mechanisms, transfer, and clinical significance.

    PubMed Central

    Speer, B S; Shoemaker, N B; Salyers, A A

    1992-01-01

    Tetracycline has been a widely used antibiotic because of its low toxicity and broad spectrum of activity. However, its clinical usefulness has been declining because of the appearance of an increasing number of tetracycline-resistant isolates of clinically important bacteria. Two types of resistance mechanisms predominate: tetracycline efflux and ribosomal protection. A third mechanism of resistance, tetracycline modification, has been identified, but its clinical relevance is still unclear. For some tetracycline resistance genes, expression is regulated. In efflux genes found in gram-negative enteric bacteria, regulation is via a repressor that interacts with tetracycline. Gram-positive efflux genes appear to be regulated by an attenuation mechanism. Recently it was reported that at least one of the ribosome protection genes is regulated by attenuation. Tetracycline resistance genes are often found on transmissible elements. Efflux resistance genes are generally found on plasmids, whereas genes involved in ribosome protection have been found on both plasmids and self-transmissible chromosomal elements (conjugative transposons). One class of conjugative transposon, originally found in streptococci, can transfer itself from streptococci to a variety of recipients, including other gram-positive bacteria, gram-negative bacteria, and mycoplasmas. Another class of conjugative transposons has been found in the Bacteroides group. An unusual feature of the Bacteroides elements is that their transfer is enhanced by preexposure to tetracycline. Thus, tetracycline has the double effect of selecting for recipients that acquire a resistance gene and stimulating transfer of the gene. PMID:1423217

  16. Antifungal drug resistance among Candida species: mechanisms and clinical impact.

    PubMed

    Sanguinetti, Maurizio; Posteraro, Brunella; Lass-Flörl, Cornelia

    2015-06-01

    The epidemiology of Candida infections has changed in recent years. Although Candida albicans is still the main cause of invasive candidiasis in most clinical settings, a substantial proportion of patients is now infected with non-albicans Candida species. The various Candida species vary in their susceptibility to the most commonly used antifungal agents, and the intrinsic resistance to antifungal therapy seen in some species, along with the development of acquired resistance during treatment in others, is becoming a major problem in the management of Candida infection. A better understanding of the mechanisms and clinical impact of antifungal drug resistance is essential for the efficient treatment of patients with Candida infection and for improving treatment outcomes. Herein, we report resistance to the azoles and echinocandins among Candida species.

  17. Acquired METD1228V Mutation and Resistance to MET Inhibition in Lung Cancer.

    PubMed

    Bahcall, Magda; Sim, Taebo; Paweletz, Cloud P; Patel, Jyoti D; Alden, Ryan S; Kuang, Yanan; Sacher, Adrian G; Kim, Nam Doo; Lydon, Christine A; Awad, Mark M; Jaklitsch, Michael T; Sholl, Lynette M; Jänne, Pasi A; Oxnard, Geoffrey R

    2016-12-01

    Amplified and/or mutated MET can act as both a primary oncogenic driver and as a promoter of tyrosine kinase inhibitor (TKI) resistance in non-small cell lung cancer (NSCLC). However, the landscape of MET-specific targeting agents remains underdeveloped, and understanding of mechanisms of resistance to MET TKIs is limited. Here, we present a case of a patient with lung adenocarcinoma harboring both a mutation in EGFR and an amplification of MET, who after progression on erlotinib responded dramatically to combined MET and EGFR inhibition with savolitinib and osimertinib. When resistance developed to this combination, a new MET kinase domain mutation, D1228V, was detected. Our in vitro findings demonstrate that MET(D1228V) induces resistance to type I MET TKIs through impaired drug binding, while sensitivity to type II MET TKIs is maintained. Based on these findings, the patient was treated with erlotinib combined with cabozantinib, a type II MET inhibitor, and exhibited a response.

  18. Usefulness of plasma HGF level for monitoring acquired resistance to EGFR tyrosine kinase inhibitors in non-small cell lung cancer.

    PubMed

    Umeguchi, Hitomi; Sueoka-Aragane, Naoko; Kobayashi, Naomi; Nakamura, Tomomi; Sato, Akemi; Takeda, Yuji; Hayashi, Shinichiro; Sueoka, Eisaburo; Kimura, Shinya

    2015-01-01

    Monitoring of molecular markers is indispensable for deciding subsequent treatment after acquired resistance to molecular-targeted therapy. According to results using re-biopsy, EGFR T790M mutation and overexpression of hepatocyte growth factor (HGF) are major mechanisms of acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). The aim of the present study was to assess whether quantification of HGF using peripheral blood in addition to detection of T790M with plasma DNA is useful for monitoring as an alternative to invasive re-biopsy. HGF levels in plasma were determined using ELISA and T790M mutation was detected using mutation-biased PCR and quenched probe system (MBP-QP). The median level of HGF in plasma at baseline was 140 pg/ml and was significantly higher in the advanced stage of cancer and in smokers and predicted poor survival as determined using 315 plasma samples from 225 lung cancer patients. T790M was detected with plasma DNA in 9 of 16 patients who acquired resistance to EGFR-TKIs and a greater than 1.5-fold elevation compared with pretreatment HGF levels was observed in 6 patients after acquired resistance. Eleven of 16 patients (69%) showed either HGF elevation or T790M in plasma samples, with both outcomes observed in 25% of patients; this is consistent with results based on re-biopsy reported from other laboratories. Considering these results, assessing HGF and T790M using peripheral blood could be useful for monitoring mechanisms of acquired resistance to EGFR-TKIs.

  19. Mechanisms of resistance to HER2 target therapy.

    PubMed

    Tortora, Giampaolo

    2011-01-01

    In the past years, several agents targeting signaling proteins critical for breast cancer growth and dissemination entered clinical evaluation. They include drugs directed against the HER/ErbB family of receptor tyrosine kinases, especially HER2; several downstream signal transducers; and proteins involved in tumor angiogenesis and dissemination. Unfortunately, resistance to targeted agents is a quite common feature, and understanding of the molecular mechanisms predicting response or failure has become a crucial issue to optimize treatment and select patients who are the best candidates to respond. The neoadjuvant setting offers unique opportunities allowing tumor sampling and search for molecular determinants of response. A variety of tumor and host factors may account for the onset of resistance. Major progress has been made in the understanding of the mechanisms involved in the primary and acquired resistance to targeted agents, especially the anti-HER2 drugs, which play a pivotal role in the weaponry against breast cancer.

  20. IKK phosphorylation of NF-κB at serine 536 contributes to acquired cisplatin resistance in head and neck squamous cell cancer

    PubMed Central

    Li, Zhipeng; Yang, Zejia; Lapidus, Rena G; Liu, Xuefeng; Cullen, Kevin J; Dan, Han C

    2015-01-01

    Current treatment methods for advanced head and neck squamous cell carcinoma (HNSCC) include surgery, radiation therapy and chemotherapy. For recurrent and metastatic HNSCC, cisplatin is the most common treatment option, but most of patients will eventually develop cisplatin resistance. Therefore, it is imperative to define the mechanisms involved in cisplatin resistance and find novel therapeutic strategies to overcome this deadly disease. In order to determine the role of nuclear factor-kappa B (NF-κB) in contributing to acquired cisplatin resistance in HNSCC, the expression and activity of NF-κB and its upstream kinases, IKKα and IKKβ, were evaluated and compared in three pairs of cisplatin sensitive and resistant HNSCC cell lines, including a pair of patient derived HNSCC cell line. The experiments revealed that NF-κB p65 activity was elevated in cisplatin resistant HNSCC cells compared to that in their parent cells. Importantly, the phosphorylation of NF-κB p65 at serine 536 and the phosphorylation of IKKα and IKKβ at their activation loops were dramatically elevated in the resistant cell lines. Furthermore, knockdown of NF-κB or overexpression of p65-S536 alanine (p65-S536A) mutant sensitizes resistant cells to cisplatin. Additionally, the novel IKKβ inhibitor CmpdA has been shown to consistently block the phosphorylation of NF-κB at serine 536 while also dramatically improving the efficacy of cisplatin in inhibition of cell proliferation and induction of apoptosis in the cisplatin resistant cancer cells. These results indicated that IKK/NF-κB plays a pivotal role in controlling acquired cisplatin resistance and that targeting the IKK/NF-κB signaling pathway may provide a possible therapeutic method to overcome the acquired resistance to cisplatin in HNSCC. PMID:26693062

  1. Polo-like kinase 1 inhibition diminishes acquired resistance to epidermal growth factor receptor inhibition in non-small cell lung cancer with T790M mutations

    PubMed Central

    Wang, Liguang; Nilsson, Monique; Goonatilake, Ruchitha; Tong, Pan; Li, Lerong; Giri, Uma; Villalobos, Pamela; Mino, Barbara; Rodriguez-Canales, Jaime; Wistuba, Ignacio; Wang, Jing; Heymach, John V.; Johnson, Faye M.

    2016-01-01

    Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are effective against non-small cell lung cancer (NSCLC) with activating EGFR mutations, but resistance is inevitable. Mechanisms of acquired resistance include T790M mutations and epithelial–mesenchymal transition (EMT). One potential strategy for overcoming this resistance is the inhibition of polo-like kinase 1 (PLK1) based on our previous studies showing that mesenchymal NSCLC cell lines are more sensitive to PLK1 inhibition than epithelial cell lines. To determine the extent to which PLK1 inhibition overcomes EGFR TKI resistance we measured the effects of the PLK1 inhibitor volasertib alone and in combination with the EGFR inhibitor erlotinib in vitro and in vivo in EGFR mutant NSCLC cell lines with acquired resistance to erlotinib. Two erlotinib-resistant cell lines that underwent EMT had higher sensitivity to volasertib, which caused G2/M arrest and apoptosis, than their parental cells. In all NSCLC cell lines with T790M mutations, volasertib markedly reduced erlotinib resistance. All erlotinib-resistant NSCLC cell lines with T790M mutations had higher sensitivity to erlotinib plus volasertib than to erlotinib alone, and the combination treatment caused G2/M arrest and apoptosis. Compared with either agent alone, the combination treatment also caused significantly more DNA damage and greater reductions in tumor size. Our results suggest that PLK1 inhibition is clinically effective against NSCLC that becomes resistant to EGFR inhibition through EMT or the acquisition of a T790M mutation. These results uncover new functions of PLK1 inhibition in the treatment of NSCLC with acquired resistance to EGFR TKIs. PMID:27384992

  2. Is Salicylic Acid a Translocated Signal of Systemic Acquired Resistance in Tobacco?

    PubMed Central

    Shulaev, V.; Leon, J.; Raskin, I.

    1995-01-01

    Salicylic acid (SA) is a likely endogenous signal in the development of systemic acquired resistance (SAR) in some dicotyledonous plants. In tobacco mosaic virus (TMV)-resistant Xanthi-nc tobacco, SA levels increase systemically following the inoculation of a single leaf with TMV. To determine the extent to which systemic increases in SA result from SA export from the inoculated leaf, SA produced in TMV-inoculated or healthy leaves was noninvasively labeled with 18O2. Spatial and temporal distribution of 18O-SA indicated that most of the SA detected in the healthy tissues was synthesized in the inoculated leaf. No significant increase in the activity of benzoic acid 2-hydroxylase, the last enzyme involved in SA biosynthesis, was detected in upper uninoculated leaves, although the basal level of enzyme activity was relatively high. No increases in SA level, pathogenesis-related PR-1 gene expression, or TMV resistance in the upper uninoculated leaf were observed if the TMV-inoculated leaf was detached up to 60 hr after inoculation. Apart from the inoculated tissues, the highest increase in SA was observed in the leaf located directly above the inoculated leaf. The systemic SA increase observed during SAR may be explained by phloem transport of SA from the inoculation sites. PMID:12242358

  3. Characterization of a Pipecolic Acid Biosynthesis Pathway Required for Systemic Acquired Resistance.

    PubMed

    Ding, Pingtao; Rekhter, Dmitrij; Ding, Yuli; Feussner, Kirstin; Busta, Lucas; Haroth, Sven; Xu, Shaohua; Li, Xin; Jetter, Reinhard; Feussner, Ivo; Zhang, Yuelin

    2016-10-01

    Systemic acquired resistance (SAR) is an immune response induced in the distal parts of plants following defense activation in local tissue. Pipecolic acid (Pip) accumulation orchestrates SAR and local resistance responses. Here, we report the identification and characterization of SAR-DEFICIENT4 (SARD4), which encodes a critical enzyme for Pip biosynthesis in Arabidopsis thaliana Loss of function of SARD4 leads to reduced Pip levels and accumulation of a Pip precursor, Δ(1)-piperideine-2-carboxylic acid (P2C). In Escherichia coli, expression of the aminotransferase ALD1 leads to production of P2C and addition of SARD4 results in Pip production, suggesting that a Pip biosynthesis pathway can be reconstituted in bacteria by coexpression of ALD1 and SARD4. In vitro experiments showed that ALD1 can use l-lysine as a substrate to produce P2C and P2C is converted to Pip by SARD4. Analysis of sard4 mutant plants showed that SARD4 is required for SAR as well as enhanced pathogen resistance conditioned by overexpression of the SAR regulator FLAVIN-DEPENDENT MONOOXYGENASE1. Compared with the wild type, pathogen-induced Pip accumulation is only modestly reduced in the local tissue of sard4 mutant plants, but it is below detection in distal leaves, suggesting that Pip is synthesized in systemic tissue by SARD4-mediated reduction of P2C and biosynthesis of Pip in systemic tissue contributes to SAR establishment.

  4. First Resistance Mechanisms Characterization in Glyphosate-Resistant Leptochloa virgata

    PubMed Central

    Alcántara-de la Cruz, Ricardo; Rojano-Delgado, Antonia M.; Giménez, María J.; Cruz-Hipolito, Hugo E.; Domínguez-Valenzuela, José A.; Barro, Francisco; De Prado, Rafael

    2016-01-01

    Leptochloa virgata (L.) P. Beauv. is an annual weed common in citrus groves in the states of Puebla and Veracruz, Mexico limiting their production. Since 2010, several L. virgata populations were identified as being resistant to glyphosate, but studies of their resistance mechanisms developed by this species have been conducted. In this work, three glyphosate-resistant populations (R8, R14, and R15) collected in citrus orchards from Mexico, were used to study their resistance mechanisms comparing them to one susceptible population (S). Dose-response and shikimic acid accumulation assays confirmed the glyphosate resistance of the three resistant populations. Higher doses of up to 720 g ae ha-1 (field dose) were needed to control by 50% plants of resistant populations. The S population absorbed between 7 and 13% more 14C-glyphosate than resistant ones, and translocated up to 32.2% of 14C-glyphosate to the roots at 96 h after treatment (HAT). The R8, R14, and R15 populations translocated only 24.5, 26.5, and 21.9%, respectively. The enzyme activity of 5-enolpyruvyl shikimate-3-phosphate synthase (EPSPS) was not different in the S, R8 and R14 populations. The R15 Population exhibited 165.9 times greater EPSPS activity. Additionally, this population showed a higher EPSPS basal activity and a substitution in the codon 106 from Proline to Serine in the EPSPS protein sequence. EPSPS gene expression in the R15 population was similar to that of S population. In conclusion, the three resistant L. virgata populations show reduced absorption and translocation of 14C-glyphosate. Moreover, a mutation and an enhanced EPSPS basal activity at target-site level confers higher resistance to glyphosate. These results describe for the first time the glyphosate resistance mechanisms developed by resistant L. virgata populations of citrus orchards from Mexico. PMID:27917189

  5. The phenomenon of acquired resistance to metformin in breast cancer cells: The interaction of growth pathways and estrogen receptor signaling.

    PubMed

    Scherbakov, Alexander M; Sorokin, Danila V; Tatarskiy, Victor V; Prokhorov, Nikolay S; Semina, Svetlana E; Berstein, Lev M; Krasil'nikov, Mikhail A

    2016-04-01

    Metformin, a biguanide antidiabetic drug, is used to decrease hyperglycemia in patients with type 2 diabetes. Recently, the epidemiological studies revealed the potential of metformin as an anti-tumor drug for several types of cancer, including breast cancer. Anti-tumor metformin action was found to be mediated, at least in part, via activation of adenosine monophosphate-activated protein kinase (AMPK)-intracellular energy sensor, which inhibits the mammalian target of rapamycin (mTOR) and some other signaling pathways. Nevertheless, some patients can be non-sensitive or resistant to metformin action. Here we analyzed the mechanism of the formation of metformin-resistant phenotype in breast cancer cells and its role in estrogen receptor (ER) regulation. The experiments were performed on the ER-positive MCF-7 breast cancer cells and metformin-resistant MCF-7 subline (MCF-7/M) developed due to long-term metformin treatment. The transcriptional activity of NF-κB and ER was measured by the luciferase reporter gene analysis. The protein expression was determined by immunoblotting (Snail1, (phospho)AMPK, (phospho)IκBα, (phospho)mTOR, cyclin D1, (phospho)Akt and ERα) and immunohistochemical analysis (E-cadherin). We have found that: 1) metformin treatment of MCF-7 cells is accompanied with the stimulation of AMPK and inhibition of growth-related proteins including IκBα, NF-κB, cyclin D1 and ERα; 2) long-term metformin treatment lead to the appearance and progression of cross-resistance to metformin and tamoxifen; the resistant cells are characterized with the unaffected AMPK activity, but the irreversible ER suppression and constitutive activation of Akt/Snail1 signaling; 3) Akt/Snail1 signaling is involved into progression of metformin resistance. The results presented may be considered as the first evidence of the progression of cross-resistance to metformin and tamoxifen in breast cancer cells. Importantly, the acquired resistance to both drugs is based on the

  6. Characterization of Genes Encoding for Acquired Bacitracin Resistance in Clostridium perfringens

    PubMed Central

    Charlebois, Audrey; Jalbert, Louis-Alexandre; Harel, Josée; Masson, Luke; Archambault, Marie

    2012-01-01

    Phenotypic bacitracin resistance has been reported in Clostridium perfringens. However, the genes responsible for the resistance have not yet been characterized. Ninety-nine C. perfringens isolates recovered from broilers and turkeys were tested for phenotypic bacitracin resistance. Bacitracin MIC90 (>256 µg/ml) was identical for both turkey and chicken isolates; whereas MIC50 was higher in turkey isolates (6 µg/ml) than in chicken isolates (3 µg/ml). Twenty-four of the 99 isolates showed high-level bacitracin resistance (MIC breakpoint >256 µg/ml) and the genes encoding for this resistance were characterized in C. perfringens c1261_A strain using primer walking. Sequence analysis and percentages of amino acid identity revealed putative genes encoding for both an ABC transporter and an overproduced undecaprenol kinase in C. perfringens c1261_A strain. These two mechanisms were shown to be both encoded by the putative bcrABD operon under the control of a regulatory gene, bcrR. Efflux pump inhibitor thioridazine was shown to increase significantly the susceptibility of strain c1261_A to bacitracin. Upstream and downstream from the bcr cluster was an IS1216-like element, which may play a role in the dissemination of this resistance determinant. Pulsed-field gel electrophoresis with prior double digestion with I-CeuI/MluI enzymes followed by hybridization analyses revealed that the bacitracin resistance genes bcrABDR were located on the chromosome. Semi-quantitative RT-PCR demonstrated that this gene cluster is expressed under bacitracin stress. Microarray analysis revealed the presence of these genes in all bacitracin resistant strains. This study reports the discovery of genes encoding for a putative ABC transporter and an overproduced undecaprenol kinase associated with high-level bacitracin resistance in C. perfringens isolates from turkeys and broiler chickens. PMID:22970221

  7. CYP3A5 mediates basal and acquired therapy resistance in different subtypes of pancreatic ductal adenocarcinoma

    PubMed Central

    Noll, Elisa M.; Eisen, Christian; Stenzinger, Albrecht; Espinet, Elisa; Muckenhuber, Alexander; Klein, Corinna; Vogel, Vanessa; Klaus, Bernd; Nadler, Wiebke; Rösli, Christoph; Lutz, Christian; Kulke, Michael; Engelhardt, Jan; Zickgraf, Franziska M.; Espinosa, Octavio; Schlesner, Matthias; Jiang, Xiaoqi; Kopp-Schneider, Annette; Neuhaus, Peter; Bahra, Marcus; Sinn, Bruno V.; Eils, Roland; Giese, Nathalia A.; Hackert, Thilo; Strobel, Oliver; Werner, Jens; Büchler, Markus W.; Weichert, Wilko; Trumpp, Andreas; Sprick, Martin R.

    2016-01-01

    Although subtypes of pancreatic ductal adenocarcinoma (PDAC) were described, this malignancy is clinically still treated as a single disease. Here, we present patient-derived models representing the full spectrum of previously identified quasi-mesenchymal (QM-PDA), classical and exocrine-like PDAC subtypes, and identify two markers—HNF1A and KRT81—that enable stratification of tumors into different subtypes by immunohistochemistry. Individuals bearing tumors of these subtypes show significant differences in overall survival and their tumors differ in drug sensitivity, with the exocrine-like subtype being resistant to tyrosine kinase inhibitors and paclitaxel. Cytochrome P450 3A5 (CYP3A5) metabolizes these compounds in tumors of the exocrine-like subtype, and pharmacological or shRNA-mediated CYP3A5 inhibition sensitizes tumor cells to these drugs. Whereas hepatocyte nuclear factor 4 alpha (HNF4A) controls basal expression of CYP3A5, drug-induced CYP3A5 upregulation is mediated by the nuclear receptor NR1I2. CYP3A5 also contributes to acquired drug resistance in QM-PDA and classical PDAC, and is highly expressed in several additional malignancies. These findings designate CYP3A5 as predictor of therapy response and as a tumor cell-autonomous detoxification mechanism that must be overcome to prevent drug resistance. PMID:26855150

  8. Impaired acquired resistance of mice to Klebsiella pneumoniae infection induced by acute NO/sub 2/ exposure

    SciTech Connect

    Bouley, G.; Azoulay-Dupuis, E.; Gaudebout, C.

    1985-12-01

    The natural resistance of nonimmunized C57B1/6 mice to an intraperitoneal Klebsiella pneumoniae challenge was not significantly affected by prior continuous exposure to 20 ppm NO/sub 2/ for 4 days. In contrast, the acquired resistance of mice immunized just before and infected just after NO/sub 2/ exposure was seriously impaired. This could not be explained by the loss of appetite (about 30%) observed in NO/sub 2/ treated mice, for neither the natural nor acquired resistance of control air exposure mice given approximately 70% ad libitum food and water were significantly modified.

  9. Inhibition of ABCB1 Overcomes Cancer Stem Cell-like Properties and Acquired Resistance to MET Inhibitors in Non-Small Cell Lung Cancer.

    PubMed

    Sugano, Teppei; Seike, Masahiro; Noro, Rintaro; Soeno, Chie; Chiba, Mika; Zou, Fenfei; Nakamichi, Shinji; Nishijima, Nobuhiko; Matsumoto, Masaru; Miyanaga, Akihiko; Kubota, Kaoru; Gemma, Akihiko

    2015-11-01

    Patients with non-small cell lung cancer (NSCLC) EGFR mutations have shown a dramatic response to EGFR inhibitors (EGFR-TKI). EGFR T790M mutation and MET amplification have been recognized as major mechanisms of acquired resistance to EGFR-TKI. Therefore, MET inhibitors have recently been used in NSCLC patients in clinical trials. In this study, we tried to identify the mechanism of acquired resistance to MET inhibitors. We analyzed the antitumor effects of two MET inhibitors, PHA-665752 and crizotinib, in 10 NSCLC cell lines. EBC-1 cells with MET amplification were the only cells that were sensitive to both MET inhibitors. We established PHA-665752-resistant EBC-1 cells, namely EBC-1R cells. Activation of KRAS, EGFR, and FGFR2 signaling was observed in EBC-1R cells by FISH and receptor tyrosine kinase phosphorylation antibody arrays. EBC-1R cells also showed overexpression of ATP-binding cassette subfamily B member 1 (ABCB1) as well as phosphorylation of MET. EBC-1R cells grew as cell spheres that exhibited cancer stem cell-like (CSC) properties and epithelial-mesenchymal transition (EMT). The level of miR-138 that targeted ABCB1 was decreased in EBC-1R cells. ABCB1 siRNA and the ABCB1 inhibitor elacridar could reduce sphere numbers and suppress EMT. Elacridar could also reverse resistance to PHA-665752 in EBC-1R cells. Our study demonstrated that ABCB1 overexpression, which was associated with CSC properties and EMT, was involved in the acquired resistance to MET inhibitors. Inhibition of ABCB1 might be a novel therapeutic strategy for NSCLC patients with acquired resistance to MET inhibitors.

  10. Genomic and Molecular Characterization of Miltefosine Resistance in Leishmania infantum Strains with Either Natural or Acquired Resistance through Experimental Selection of Intracellular Amastigotes

    PubMed Central

    Hendrickx, Sarah; Eberhardt, Eline; Garcia-Hernandez, Raquel; Lachaud, Laurence; Cotton, James; Sanders, Mandy; Cuypers, Bart; Imamura, Hideo; Dujardin, Jean-Claude; Delputte, Peter; Cos, Paul; Caljon, Guy; Gamarro, Francisco; Castanys, Santiago

    2016-01-01

    During the last decade miltefosine (MIL) has been used as first-line treatment for visceral leishmaniasis in endemic areas with antimonial resistance, but a decline in clinical effectiveness is now being reported. While only two MIL-resistant Leishmania infantum strains from HIV co-infected patients have been documented, phenotypic MIL-resistance for L. donovani has not yet been identified in the laboratory. Hence, a better understanding of the factors contributing to increased MIL-treatment failure is necessary. Given the paucity of defined MIL-resistant L. donovani clinical isolates, this study used an experimental amastigote-selected MIL-resistant L. infantum isolate (LEM3323). In-depth exploration of the MIL-resistant phenotype was performed by coupling genomic with phenotypic data to gain insight into gene function and the mutant phenotype. A naturally MIL-resistant L. infantum clinical isolate (LEM5159) was included to compare both datasets. Phenotypically, resistance was evaluated by determining intracellular amastigote susceptibility in vitro and actual MIL-uptake. Genomic analysis provided supportive evidence that the resistance selection model on intracellular amastigotes can be a good proxy for the in vivo field situation since both resistant strains showed mutations in the same inward transporter system responsible for the acquired MIL-resistant phenotype. In line with previous literature findings in promastigotes, our data confirm a defective import machinery through inactivation of the LiMT/LiRos3 protein complex as the main mechanism for MIL-resistance also in intracellular amastigotes. Whole genome sequencing analysis of LEM3323 revealed a 2 base pair deletion in the LiMT gene that led to the formation an early stop codon and a truncation of the LiMT protein. Interestingly, LEM5159 revealed mutations in both the LiMT and LiRos3 genes, resulting in an aberrant expression of the LiMT protein. To verify that these mutations were indeed accountable for

  11. Effectiveness of various hospital-based solutions against community- acquired methicillin-resistant Staphylococcus aureus.

    PubMed

    Perona, Paul J; Johnson, Aaron J; Perona, John P; Issa, Kimona; Kapadia, Bhaveen H; Bonutti, Peter M; Mont, Michael A

    2013-01-01

    Periprosthetic infections with methicillin-resistant Staphylococcus aureus (MRSA) can be particularly burdensome and difficult to eradicate. One of the measures that infection control officers have emphasized in our hospitals has been the use of various hand sanitizers throughout the hospital. Our objective was to determine the level of growth inhibition of common hand sanitizers and surgical scrub solutions that are used to prevent the spread of community-acquired strains of MRSA. Various hospital and surgical agents (n = 13) were applied to community-acquired MRSA bacteria that had been cultured on agar plates. These different commercially available solutions were incubated for 48 h, and the plates were assessed to determine the level of growth inhibition (0, 25, 75, or 100%). The negative control was a test in which no agent was added to the MRSA culture, while a positive control tested 100% alcohol. Eight of the solutions tested had 100% growth inhibition, four solutions had partial growth inhibition effects, and one solution did not inhibit MRSA. Of the solutions with alcohol, the 62% solution did not kill MRSA, while the 80% solution only inhibited MRSA. Both the 95 and 100% alcohol solutions had 100% growth inhibition. Of the two surgical scrub solutions, only the one with iodine had 100% growth inhibition, whereas the solution with chloroxylenol (PCMX 3%) had only partial growth inhibition. This study suggests that the solutions with high levels of alcohol, chlorhexidine, or iodine appear to better kill MRSA and might best be used to prevent the spread of community-acquired MRSA in both the hospital and the surgical environment.

  12. Fulminant necrotising fasciitis by community-acquired methicillin-resistant Staphylococcus aureus

    PubMed Central

    Non, Lemuel; Kosmin, Aaron

    2015-01-01

    Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is a rare cause of necrotising fasciitis (NF), and is usually not fulminant as in group A Streptococcus (GAS), the archetypal aetiology. We report an unusually fulminant case of NF by CA-MRSA in an immunocompetent patient. A 52-year-old man presented to the emergency department with 1 week of progressive left thigh pain and swelling. The patient had ecchymoses, bullae and hypoesthesia of the involved skin, and CT scan revealed extensive fascial oedema. He was immediately started on broad spectrum antibiotics. Within 12 h of presentation, he underwent surgical debridement. Despite aggressive supportive care, the patient died less than 24 h after presentation. MRSA, with an antibiogram suggestive of a community-acquired strain, was recovered from intraoperative specimens and admission blood cultures. This case underscores that CA-MRSA, while rarely reported, can cause a fulminant presentation of NF similar to GAS in immunocompetent patients. PMID:25824286

  13. Emergence of antibiotic resistance and prudent use of antibiotic therapy in nosocomially acquired urinary tract infections.

    PubMed

    Wagenlehner, F M E; Naber, K G

    2004-03-01

    Nosocomially acquired urinary tract infections (NAUTI) are common. The reported rates, however, depend very much on the definitions used and the number of investigations requested. In a prospective study on a surgical intensive care unit and adhering closely to the CDC criteria, NAUTI was diagnosed in about 17% of the patients. The urinary catheter associated UTI rate per 1000 catheter days was 14.5 much higher than otherwise reported. Whereas the rates of symptomatic NAUTI and other nosocomially acquired infections were similar, the main difference was found for asymptomatic UTI which depends very much on the effort to search for it systematically. In a prospective study on a urological ward it could be demonstrated that cross-transmission probably plays a much greater role than so far suggested. Continuous surveillance of the bacterial spectrum and resistance is necessary not only on a global but also on a local level. Selection of an appropriate agent for empirical antibacterial therapy can be better tailored if not only the total bacterial spectrum is considered but if all information already available during the identification process is used, such as Gram stain and other simple and rapid tests for stratification of the pathogens. Since in NAUTI usually some kind of biofilm infection is involved, the fluoroquinolones can be considered agents of choice. Only those substances with high antibacterial activity, good bioavailability and those that are mainly excreted by the kidneys should be chosen and they have to be administered at sufficiently high doses.

  14. [MOLECULAR MECHANISMS OF DRUG RESISTANCE NEISSERIA GONORRHOEAE HISTORY AND PROSPECTS].

    PubMed

    Bodoev, I N; Il'ina, E N

    2015-01-01

    Neisseria gonorrhoeae (gonococcus) is a strict human pathogen, which causes gonorrhea--an infectious disease, whose origin dates back to more than two thousand years. Due to the unique plasticity of the genetic material, these bacteria have acquired the capacity to adapt to the host immune system, cause repeated infections, as well as withstand antimicrobials. Since the introduction of antibiotics in 1930s, gonococcus has displayed its propensity to develop resistance to all clinically useful antibiotics. It is important to note that the known resistance determinants of N. gonorrhoeae were acquired through horizontal gene transfer, recombination and spontaneous mutagenesis, and may be located both in the chromosome and on the plasmid. After introduction of a new antimicrobial drug, gonococcus becomes resistant within two decades and replaces sensitive bacterial population. Currently Ceftriaxone is the last remaining antibiotic for first-line treatment of gonorrhea. However, the first gonococcus displaying high-level resistance to Ceftriaxone was isolated in Japan a few years ago. Therefore, in the near future, gonorrhea may become untreatable. In the present review, we discuss the chronology of the anti-gonorrhea drugs (antibiotics) replacement, the evolution of resistance mechanisms emergence and future perspectives of N. gonorrhoeae treatment.

  15. Increased thymidylate synthase in L1210 cells possessing acquired resistance to N10-propargyl-5,8-dideazafolic acid (CB3717): development, characterization, and cross-resistance studies

    SciTech Connect

    Jackman, A.L.; Alison, D.L.; Calvert, A.H.; Harrap, K.R.

    1986-06-01

    The properties are described of a mutant L1210 cell line (L1210:C15) with acquired resistance (greater than 200-fold) to the thymidylate synthase (TS) inhibitor N10-propargyl-5,8-dideazafolic acid. TS was overproduced 45-fold and was accompanied by a small increase in the activity of dihydrofolate reductase (2.6-fold). Both the level of resistance and enzyme activities were maintained in drug-free medium (greater than 300 generations). Failure of N10-propargyl-5,8-dideazafolic acid to suppress the (/sup 3/H)-2'-deoxyuridine incorporation into the acid-precipitable material of the resistant line supported the evidence that TS overproduction was the mechanism of resistance; consequently the L1210:C15 cells were largely cross-resistant to another (but weaker) TS inhibitor, 5,8-dideazafolic acid. Minimal cross-resistance was observed to the dihydrofolate reductase inhibitors methotrexate and 5-methyl-5,8-dideazaaminopterin (5- and 2-fold, respectively). L1210 and L1210:C15 cells were, however, equally sensitive to 5-fluorodeoxyuridine (FdUrd), an unexpected finding since a metabolite, 5-fluorodeoxyuridine monophosphate, is a potent TS inhibitor; however, this cytotoxicity against the L1210:C15 cells was antagonized by coincubation with 5 microM folinic acid although folinic acid potentiated the cytotoxicity of FdUrd to the N10-propargyl-5,8-dideazafolic acid-sensitive L1210 line. Thymidine was much less effective as a FdUrd protecting agent in the L1210:C15 when compared with the L1210 cells; however, a combination of thymidine plus hypoxanthine was without any additional effect (compared with thymidine alone) against the sensitive line but effectively protected L1210:C15 cells.

  16. Resistance mechanisms to arsenicals and antimonials.

    PubMed

    Rosen, B P

    1995-01-01

    Salts and organic derivatives of arsenic and antimony are quite toxic. Living organisms have adapted to this toxicity by the evolution of resistance mechanisms. Both prokaryotic and eukaryotic cells develop resistance when exposed to arsenicals or antimonials. In the case of bacteria resistance is conferred by plasmid-encoded arsenical resistance (ars) operons. The genes and gene products of the ars operon of the clinically-isolated conjugative R-factor R773 have been identified and their mechanism of action elucidated. The operon encodes an ATP-driven pump that extrudes arsenite and antimonite from the cells. The lowering of their intracellular concentration results in resistance. Arsenate resistance results from the action of the plasmid-encoded arsenate reductase that reduces arsenate to arsenite, which is then pumped out of the cell.

  17. Overcoming acquired drug resistance in colorectal cancer cells by targeted delivery of 5-FU with EGF grafted hollow mesoporous silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Lijue; She, Xiaodong; Wang, Tao; He, Li; Shigdar, Sarah; Duan, Wei; Kong, Lingxue

    2015-08-01

    Acquired drug resistance (ADR) can be developed in colorectal cancer cells after 5-fluorouracil (5-FU) treatment and diminish the effectiveness of chemotherapy. In this work, acquired 5-FU resistance in the colorectal cancer cell line SW480 was obtained with the up-regulation of dihydropyrimidine dehydrogenase (DPYD) gene expression which can convert 5-FU to its inactive metabolite. To overcome ADR in colorectal cancer, hollow mesoporous silica nanoparticles (HMSNs) grafted with epidermal growth factor (EGF) were used as nanocarriers to deliver 5-FU to colorectal cancer cells with acquired drug resistance. The effect and mechanism of 5-FU loaded EGF grafted HMSNs (EGF-HMSNs-5-FU) in overcoming acquired drug resistance in SW480/ADR cells were studied. The EGF-HMSNs were demonstrated to be specifically internalized in EGFR overexpressed SW480/ADR cells via a receptor-mediated endocytosis and can escape from endo-lysosomes. The EGF-HMSNs-5-FU exhibited much higher cytotoxicity on SW480/ADR cells than HMSNs-5-FU and free 5-FU while the plain HMSNs did not show significant cytotoxicity. The mechanism of EGF-HMSNs-5-FU in overcoming drug resistance in SW480/ADR cells could be attributed to the specific internalization of EGF-HMSNs-5-FU in EGFR overexpressed cells which can lead to high intracellular drug accumulation and cause cell death through S phase arrest.Acquired drug resistance (ADR) can be developed in colorectal cancer cells after 5-fluorouracil (5-FU) treatment and diminish the effectiveness of chemotherapy. In this work, acquired 5-FU resistance in the colorectal cancer cell line SW480 was obtained with the up-regulation of dihydropyrimidine dehydrogenase (DPYD) gene expression which can convert 5-FU to its inactive metabolite. To overcome ADR in colorectal cancer, hollow mesoporous silica nanoparticles (HMSNs) grafted with epidermal growth factor (EGF) were used as nanocarriers to deliver 5-FU to colorectal cancer cells with acquired drug resistance. The

  18. Disease resistance: Molecular mechanisms and biotechnological applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This special issue “Disease resistance: molecular mechanisms and biotechnological applications” contains 11 review articles and four original research papers. Research in the area of engineering for disease resistance continues to progress although only 10% of the transgenic plants registered for ...

  19. Toxic effects and specific chromium acquired resistance in selected strains of Dyctiosphaerium chlorelloides.

    PubMed

    D'ors, A; Pereira, M; Bartolomé, M C; López-Rodas, V; Costas, E; Sánchez-Fortún, S

    2010-09-01

    Due to its various uses, chromium contamination has become widespread in a diverse array of environments. The present study was carried out to investigate the toxic effect of chromium exposures on sensitive and resistant strains of the green algae Dyctiosphaerium chlorelloides, and to determine the nature and mechanism of chromium-resistant cells that arise. The toxic effect on the photosynthetic performance of chromium exposures in both cell populations, and the sensitive differences due to chromium oxidation state, were estimated, and the results indicate that although the photosynthetic performance in both strains were inhibited, there are not significant differences among IC(50(72)) values obtained in toxicity assays with both chromium oxidation states in wild-type cells, and however these differences are very significant when the assays were performed with Cr(VI) resistant cells. The 72-h 50% inhibitory concentration values obtained with Cr(III) exposures were similar for both strains. Additionally, by means of the SEM/EDX and TEM microscopic techniques, the occurrence of rapid morphological evolution in the microalgal cells and the possible detoxificant mechanisms was observed after exposure of the wild strain to chromium hexavalent. Moreover, the different response in photosynthetic activity observed between sensitive and resistant cells of D. chlorelloides in the presence of Cr(VI) and Cr(III) could be used to obtain a chromium-specific eukaryotic microalgal biosensor.

  20. Caterpillar saliva interferes with induced Arabidopsis thaliana defence responses via the systemic acquired resistance pathway

    PubMed Central

    Weech, Marie-Hélène; Chapleau, Mélanie; Pan, Li; Ide, Christine; Bede, Jacqueline C.

    2008-01-01

    Arabidopsis thaliana (L.) Heynh. genotypes limited in their ability to mount either octadecanoid-dependent induced resistance (IR–) or systemic acquired resistance (SAR–) were used to characterize the roles of these pathways in plant–herbivore interactions. Molecular and biochemical markers of IR were analysed in plants subject to herbivory by caterpillars of the beet armyworm, Spodoptera exigua Hübner, which had either intact or impaired salivary secretions since salivary enzymes, such as glucose oxidase, have been implicated in the ability of caterpillars to circumvent induced plant defences. Transcript expression of genes encoding laccase-like multicopper oxidase [AtLMCO4 (polyphenol oxidase)] and defensin (AtPDF1.2) showed salivary-specific patterns which were disrupted in the SAR– mutant plants. The activity of octadecanoid-associated anti-nutritive proteins, such as LMCO and trypsin inhibitor, showed similar patterns. Gene and protein changes parallel plant hormone levels where elevated jasmonic acid was observed in wild-type plants fed upon by caterpillars with impaired salivary secretions compared with plants subject to herbivory by normal caterpillars. This salivary-specific difference in jasmonic acid levels was alleviated in SAR– mutants. These results support the model that caterpillar saliva interferes with jasmonate-dependent plant defences by activating the SAR pathway. PMID:18487634

  1. Nitric oxide and reactive oxygen species are required for systemic acquired resistance in plants.

    PubMed

    El-Shetehy, Mohamed; Wang, Caixia; Shine, M B; Yu, Keshun; Kachroo, Aardra; Kachroo, Pradeep

    2015-01-01

    Systemic acquired resistance (SAR) is a form of broad-spectrum disease resistance that is induced in response to primary infection and that protects uninfected portions of the plant against secondary infections by related or unrelated pathogens. SAR is associated with an increase in chemical signals that operate in a collective manner to confer protection against secondary infections. These include, the phytohormone salicylic acid (SA), glycerol-3-phosphate (G3P), azelaic acid (AzA) and more recently identified signals nitric oxide (NO) and reactive oxygen species (ROS). NO, ROS, AzA and G3P function in the same branch of the SAR pathway, and in parallel to the SA-regulated branch. NO and ROS function upstream of AzA/G3P and different reactive oxygen species functions in an additive manner to mediate chemical cleavage of the C9 double bond on C18 unsaturated fatty acids to generate AzA. The parallel and additive functioning of various chemical signals provides important new insights in the overlapping pathways leading to SAR.

  2. Diclofop-methyl affects microbial rhizosphere community and induces systemic acquired resistance in rice.

    PubMed

    Chen, Si; Li, Xingxing; Lavoie, Michel; Jin, Yujian; Xu, Jiahui; Fu, Zhengwei; Qian, Haifeng

    2017-01-01

    Diclofop-methyl (DM), a widely used herbicide in food crops, may partly contaminate the soil surface of natural ecosystems in agricultural area and exert toxic effects at low dose to nontarget plants. Even though rhizosphere microorganisms strongly interact with root cells, little is known regarding their potential modulating effect on herbicide toxicity in plants. Here we exposed rice seedlings (Xiushui 63) to 100μg/L DM for 2 to 8days and studied the effects of DM on rice rhizosphere microorganisms, rice systemic acquired resistance (SAR) and rice-microorganisms interactions. The results of metagenomic 16S rDNA Illumina tags show that DM increases bacterial biomass and affects their community structure in the rice rhizosphere. After DM treatment, the relative abundance of the bacterium genera Massilia and Anderseniella increased the most relative to the control. In parallel, malate and oxalate exudation by rice roots increased, potentially acting as a carbon source for several rhizosphere bacteria. Transcriptomic analyses suggest that DM induced SAR in rice seedlings through the salicylic acid (but not the jasmonic acid) signal pathway. This response to DM stress conferred resistance to infection by a pathogenic bacterium, but was not influenced by the presence of bacteria in the rhizosphere since SAR transcripts did not change significantly in xenic and axenic plant roots exposed to DM. The present study provides new insights on the response of rice and its associated microorganisms to DM stress.

  3. Multiplicity of acquired cross-resistance in paclitaxel-resistant cancer cells is associated with feedback control of TUBB3 via FOXO3a-mediated ABCB1 regulation

    PubMed Central

    Aldonza, Mark Borris D.; Hong, Ji-Young; Alinsug, Malona V.; Song, Jayoung; Lee, Sang Kook

    2016-01-01

    Acquired drug resistance is a primary obstacle for effective cancer therapy. The correlation of point mutations in class III β-tubulin (TUBB3) and the prominent overexpression of ATP-binding cassette P-glycoprotein (ABCB1), a multidrug resistance gene, have been protruding mechanisms of resistance to microtubule disruptors such as paclitaxel (PTX) for many cancers. However, the precise underlying mechanism of the rapid onset of cross-resistance to an array of structurally and functionally unrelated drugs in PTX-resistant cancers has been poorly understood. We determined that our established PTX-resistant cancer cells display ABCB1/ABCC1-associated cross-resistance to chemically different drugs such as 5-fluorouracil, docetaxel, and cisplatin. We found that feedback activation of TUBB3 can be triggered through the FOXO3a-dependent regulation of ABCB1, which resulted in the accentuation of induced PTX resistance and encouraged multiplicity in acquired cross-resistance. FOXO3a-directed regulation of P-glycoprotein (P-gp) function suggests that control of ABCB1 involves methylation-dependent activation. Consistently, transcriptional overexpression or downregulation of FOXO3a directs inhibitor-controlled protease-degradation of TUBB3. The functional PI3K/Akt signaling is tightly responsive to FOXO3a activation alongside doxorubicin treatment, which directs FOXO3a arginine hypermethylation. In addition, we found that secretome factors from PTX-resistant cancer cells with acquired cross-resistance support a P-gp-dependent association in multidrug resistance (MDR) development, which assisted the FOXO3a-mediated control of TUBB3 feedback. The direct silencing of TUBB3 reverses induced multiple cross-resistance, reduces drug-resistant tumor mass, and suppresses the impaired microtubule stability status of PTX-resistant cells with transient cross-resistance. These findings highlight the control of the TUBB3 response to ABCB1 genetic suppressors as a mechanism to reverse the

  4. Evaluation of quinolones for use in detection of determinants of acquired quinolone resistance, including the new transmissible resistance mechanisms qnrA, qnrB, qnrS, and aac(6')Ib-cr, in Escherichia coli and Salmonella enterica and determinations of wild-type distributions.

    PubMed

    Cavaco, L M; Aarestrup, F M

    2009-09-01

    Fluoroquinolone resistance in members of the Enterobacteriaceae family is mostly due to mutations in the quinolone resistance-determining regions of the topoisomerase genes. However, transferable genes encoding quinolone resistance have recently been described. The current methods for susceptibility testing are not adapted to the detection of new resistance determinants, which confer low levels of resistance. The aim of this study was to compare the ability of the screening of the different quinolones by disk diffusion assays and MIC determinations to detect fluoroquinolone resistance. Sixty-nine Escherichia coli strains and 62 Salmonella strains, including strains fully susceptible to quinolones, nalidixic acid-resistant strains, strains with resistance to fluoroquinolones (resistant to nalidixic acid), and strains showing low-level resistance to fluoroquinolones conferred by transferable quinolone resistance genes, including qnrA, qnrB, qnrS, and aac(6')Ib-cr, were selected. Disk diffusion assays and MIC determinations by the agar dilution method were performed, according to CLSI standards, with nalidixic acid, flumequine, oxolinic acid, ciprofloxacin, enrofloxacin, marbofloxacin, norfloxacin, ofloxacin, and levofloxacin. The MIC of levofloxacin was determined by an Etest. The results showed a trimodal distribution of the MICs for both E. coli and Salmonella. The MIC distributions for the isolates varied with the compounds tested. Screening for nalidixic acid resistance by MIC testing or disk diffusion assay was not efficient for the detection of some of the isolates carrying qnr and aac(6')Ib-cr. Transferable resistance genes would best be detected by testing for the MIC of ciprofloxacin or norfloxacin, as testing for the MICs of the other compounds would fail to detect isolates carrying aac(6')Ib-cr because the enzyme produced is able to reduce the activities of these two compounds only due to their chemical structures. In conclusion, screening with nalidixic

  5. Evolution of pre-existing versus acquired resistance to platinum drugs and PARP inhibitors in BRCA-associated cancers.

    PubMed

    Yamamoto, Kimiyo N; Hirota, Kouji; Takeda, Shunichi; Haeno, Hiroshi

    2014-01-01

    Platinum drugs and PARP inhibitors ("PARPis") are considered to be effective in BRCA-associated cancers with impaired DNA repair. These agents cause stalled and collapsed replication forks and create double-strand breaks effectively in the absence of repair mechanisms, resulting in arrest of the cell cycle and induction of cell death. However, recent studies have shown failure of these chemotherapeutic agents due to emerging drug resistance. In this study, we developed a stochastic model of BRCA-associated cancer progression in which there are four cancer populations: those with (i) functional BRCA, (ii) dysfunctional BRCA, (iii) functional BRCA and a growth advantage, and (iv) dysfunctional BRCA and a growth advantage. These four cancer populations expand from one cancer cell with normal repair function until the total cell number reaches a detectable amount. We derived formulas for the probability and expected numbers of each population at the time of detection. Furthermore, we extended the model to consider the tumor dynamics during treatment. Results from the model were validated and showed good agreement with clinical and experimental evidence in BRCA-associated cancers. Based on the model, we investigated conditions in which drug resistance during the treatment course originated from either a pre-existing drug-resistant population or a de novo population, due to secondary mutations. Finally, we found that platinum drugs and PARPis were effective if (i) BRCA inactivation is present, (ii) the cancer was diagnosed early, and (iii) tumor growth is rapid. Our results indicate that different types of cancers have a preferential way of acquiring resistance to platinum drugs and PARPis according to their growth and mutational characteristics.

  6. Comparative Proteomics Analysis of Phloem Exudates Collected during the Induction of Systemic Acquired Resistance1[OPEN

    PubMed Central

    Wilson, Daniel C.; Dey, Sanjukta; Hauck, Stefanie M.; Vlot, A. Corina; Cameron, Robin K.

    2016-01-01

    Systemic acquired resistance (SAR) is a plant defense response that provides long-lasting, broad-spectrum pathogen resistance to uninfected systemic leaves following an initial localized infection. In Arabidopsis (Arabidopsis thaliana), local infection with virulent or avirulent strains of Pseudomonas syringae pv tomato generates long-distance SAR signals that travel from locally infected to distant leaves through the phloem to establish SAR. In this study, a proteomics approach was used to identify proteins that accumulate in phloem exudates in response to the induction of SAR. To accomplish this, phloem exudates collected from mock-inoculated or SAR-induced leaves of wild-type Columbia-0 plants were subjected to label-free quantitative liquid chromatography-tandem mass spectrometry proteomics. Comparing mock- and SAR-induced phloem exudate proteomes, 16 proteins were enriched in phloem exudates collected from SAR-induced plants, while 46 proteins were suppressed. SAR-related proteins THIOREDOXIN h3, ACYL-COENZYME A-BINDING PROTEIN6, and PATHOGENESIS-RELATED1 were enriched in phloem exudates of SAR-induced plants, demonstrating the strength of this approach and suggesting a role for these proteins in the phloem during SAR. To identify novel components of SAR, transfer DNA mutants of differentially abundant phloem proteins were assayed for SAR competence. This analysis identified a number of new proteins (m-type thioredoxins, major latex protein-like protein, ULTRAVIOLET-B RESISTANCE8 photoreceptor) that contribute to the SAR response. The Arabidopsis SAR phloem proteome is a valuable resource for understanding SAR long-distance signaling and the dynamic nature of the phloem during plant-pathogen interactions. PMID:27208255

  7. Therapy-induced developmental reprogramming of prostate cancer cells and acquired therapy resistance.

    PubMed

    Nouri, Mannan; Caradec, Josselin; Lubik, Amy Anne; Li, Na; Hollier, Brett G; Takhar, Mandeep; Altimirano-Dimas, Manuel; Chen, Mengqian; Roshan-Moniri, Mani; Butler, Miriam; Lehman, Melanie; Bishop, Jennifer; Truong, Sarah; Huang, Shih-Chieh; Cochrane, Dawn; Cox, Michael; Collins, Colin; Gleave, Martin; Erho, Nicholas; Alshalafa, Mohamed; Davicioni, Elai; Nelson, Colleen; Gregory-Evans, Sheryl; Karnes, R Jeffrey; Jenkins, Robert B; Klein, Eric A; Buttyan, Ralph

    2017-01-27

    Treatment-induced neuroendocrine transdifferentiation (NEtD) complicates therapies for metastatic prostate cancer (PCa). Based on evidence that PCa cells can transdifferentiate to other neuroectodermally-derived cell lineages in vitro, we proposed that NEtD requires first an intermediary reprogramming to metastable cancer stem-like cells (CSCs) of a neural class and we demonstrate that several different AR+/PSA+ PCa cell lines were efficiently reprogrammed to, maintained and propagated as CSCs by growth in androgen-free neural/neural crest (N/NC) stem medium. Such reprogrammed cells lost features of prostate differentiation; gained features of N/NC stem cells and tumor-initiating potential; were resistant to androgen signaling inhibition; and acquired an invasive phenotype in vitro and in vivo. When placed back into serum-containing mediums, reprogrammed cells could be re-differentiated to N-/NC-derived cell lineages or return back to an AR+ prostate-like state. Once returned, the AR+ cells were resistant to androgen signaling inhibition. Acute androgen deprivation or anti-androgen treatment in serum-containing medium led to the transient appearance of a sub-population of cells with similar characteristics. Finally, a 132 gene signature derived from reprogrammed PCa cell lines distinguished tumors from PCa patients with adverse outcomes. This model may explain neural manifestations of PCa associated with lethal disease. The metastable nature of the reprogrammed stem-like PCa cells suggests that cycles of PCa cell reprogramming followed by re-differentiation may support disease progression and therapeutic resistance. The ability of a gene signature from reprogrammed PCa cells to identify tumors from patients with metastasis or PCa-specific mortality implies that developmental reprogramming is linked to aggressive tumor behaviors.

  8. Origin and Evolution of European Community-Acquired Methicillin-Resistant Staphylococcus aureus

    PubMed Central

    Wirth, Thierry; Andersen, Paal S.; Skov, Robert L.; De Grassi, Anna; Simões, Patricia Martins; Tristan, Anne; Petersen, Andreas; Aziz, Maliha; Kiil, Kristoffer; Cirković, Ivana; Udo, Edet E.; del Campo, Rosa; Vuopio-Varkila, Jaana; Ahmad, Norazah; Tokajian, Sima; Peters, Georg; Schaumburg, Frieder; Olsson-Liljequist, Barbro; Givskov, Michael; Driebe, Elizabeth E.; Vigh, Henrik E.; Shittu, Adebayo; Ramdani-Bougessa, Nadjia; Rasigade, Jean-Philippe; Price, Lance B.; Vandenesch, Francois; Larsen, Anders R.; Laurent, Frederic

    2014-01-01

    ABSTRACT Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized in Europe and worldwide in the late 1990s. Within a decade, several genetically and geographically distinct CA-MRSA lineages carrying the small SCCmec type IV and V genetic elements and the Panton-Valentine leukocidin (PVL) emerged around the world. In Europe, the predominant CA-MRSA strain belongs to clonal complex 80 (CC80) and is resistant to kanamycin/amikacin and fusidic acid. CC80 was first reported in 1993 but was relatively rare until the late 1990s. It has since been identified throughout North Africa, the Middle East, and Europe, with recent sporadic reports in sub-Saharan Africa. While strongly associated with skin and soft tissue infections, it is rarely found among asymptomatic carriers. Methicillin-sensitive S. aureus (MSSA) CC80 strains are extremely rare except in sub-Saharan Africa. In the current study, we applied whole-genome sequencing to a global collection of both MSSA and MRSA CC80 isolates. Phylogenetic analyses strongly suggest that the European epidemic CA-MRSA lineage is derived from a PVL-positive MSSA ancestor from sub-Saharan Africa. Moreover, the tree topology suggests a single acquisition of both the SCCmec element and a plasmid encoding the fusidic acid resistance determinant. Four canonical SNPs distinguish the derived CA-MRSA lineage and include a nonsynonymous mutation in accessory gene regulator C (agrC). These changes were associated with a star-like expansion into Europe, the Middle East, and North Africa in the early 1990s, including multiple cases of cross-continent imports likely driven by human migrations. PMID:25161186

  9. Acquired resistance to oxaliplatin is not directly associated with increased resistance to DNA damage in SK-N-ASrOXALI4000, a newly established oxaliplatin-resistant sub-line of the neuroblastoma cell line SK-N-AS

    PubMed Central

    Saintas, Emily; Abrahams, Liam; Ahmad, Gulshan T.; Ajakaiye, Anu-Oluwa M.; AlHumaidi, Abdulaziz S. H. A. M.; Ashmore-Harris, Candice; Clark, Iain; Dura, Usha K.; Fixmer, Carine N.; Ike-Morris, Chinedu; Mato Prado, Mireia; Mccullough, Danielle; Mishra, Shishir; Schöler, Katia M. U.; Timur, Husne; Williamson, Maxwell D. C.; Alatsatianos, Markella; Bahsoun, Basma; Blackburn, Edith; Hogwood, Catherine E.; Lithgow, Pamela E.; Rowe, Michelle; Yiangou, Lyto; Rothweiler, Florian; Cinatl, Jindrich; Zehner, Richard; Baines, Anthony J.; Garrett, Michelle D.; Gourlay, Campbell W.; Griffin, Darren K.; Gullick, William J.; Hargreaves, Emma; Howard, Mark J.; Lloyd, Daniel R.; Rossman, Jeremy S.; Smales, C. Mark; Tsaousis, Anastasios D.; von der Haar, Tobias; Wass, Mark N.

    2017-01-01

    The formation of acquired drug resistance is a major reason for the failure of anti-cancer therapies after initial response. Here, we introduce a novel model of acquired oxaliplatin resistance, a sub-line of the non-MYCN-amplified neuroblastoma cell line SK-N-AS that was adapted to growth in the presence of 4000 ng/mL oxaliplatin (SK-N-ASrOXALI4000). SK-N-ASrOXALI4000 cells displayed enhanced chromosomal aberrations compared to SK-N-AS, as indicated by 24-chromosome fluorescence in situ hybridisation. Moreover, SK-N-ASrOXALI4000 cells were resistant not only to oxaliplatin but also to the two other commonly used anti-cancer platinum agents cisplatin and carboplatin. SK-N-ASrOXALI4000 cells exhibited a stable resistance phenotype that was not affected by culturing the cells for 10 weeks in the absence of oxaliplatin. Interestingly, SK-N-ASrOXALI4000 cells showed no cross resistance to gemcitabine and increased sensitivity to doxorubicin and UVC radiation, alternative treatments that like platinum drugs target DNA integrity. Notably, UVC-induced DNA damage is thought to be predominantly repaired by nucleotide excision repair and nucleotide excision repair has been described as the main oxaliplatin-induced DNA damage repair system. SK-N-ASrOXALI4000 cells were also more sensitive to lysis by influenza A virus, a candidate for oncolytic therapy, than SK-N-AS cells. In conclusion, we introduce a novel oxaliplatin resistance model. The oxaliplatin resistance mechanisms in SK-N-ASrOXALI4000 cells appear to be complex and not to directly depend on enhanced DNA repair capacity. Models of oxaliplatin resistance are of particular relevance since research on platinum drugs has so far predominantly focused on cisplatin and carboplatin. PMID:28192521

  10. Acquired resistance to oxaliplatin is not directly associated with increased resistance to DNA damage in SK-N-ASrOXALI4000, a newly established oxaliplatin-resistant sub-line of the neuroblastoma cell line SK-N-AS.

    PubMed

    Saintas, Emily; Abrahams, Liam; Ahmad, Gulshan T; Ajakaiye, Anu-Oluwa M; AlHumaidi, Abdulaziz S H A M; Ashmore-Harris, Candice; Clark, Iain; Dura, Usha K; Fixmer, Carine N; Ike-Morris, Chinedu; Mato Prado, Mireia; Mccullough, Danielle; Mishra, Shishir; Schöler, Katia M U; Timur, Husne; Williamson, Maxwell D C; Alatsatianos, Markella; Bahsoun, Basma; Blackburn, Edith; Hogwood, Catherine E; Lithgow, Pamela E; Rowe, Michelle; Yiangou, Lyto; Rothweiler, Florian; Cinatl, Jindrich; Zehner, Richard; Baines, Anthony J; Garrett, Michelle D; Gourlay, Campbell W; Griffin, Darren K; Gullick, William J; Hargreaves, Emma; Howard, Mark J; Lloyd, Daniel R; Rossman, Jeremy S; Smales, C Mark; Tsaousis, Anastasios D; von der Haar, Tobias; Wass, Mark N; Michaelis, Martin

    2017-01-01

    The formation of acquired drug resistance is a major reason for the failure of anti-cancer therapies after initial response. Here, we introduce a novel model of acquired oxaliplatin resistance, a sub-line of the non-MYCN-amplified neuroblastoma cell line SK-N-AS that was adapted to growth in the presence of 4000 ng/mL oxaliplatin (SK-N-ASrOXALI4000). SK-N-ASrOXALI4000 cells displayed enhanced chromosomal aberrations compared to SK-N-AS, as indicated by 24-chromosome fluorescence in situ hybridisation. Moreover, SK-N-ASrOXALI4000 cells were resistant not only to oxaliplatin but also to the two other commonly used anti-cancer platinum agents cisplatin and carboplatin. SK-N-ASrOXALI4000 cells exhibited a stable resistance phenotype that was not affected by culturing the cells for 10 weeks in the absence of oxaliplatin. Interestingly, SK-N-ASrOXALI4000 cells showed no cross resistance to gemcitabine and increased sensitivity to doxorubicin and UVC radiation, alternative treatments that like platinum drugs target DNA integrity. Notably, UVC-induced DNA damage is thought to be predominantly repaired by nucleotide excision repair and nucleotide excision repair has been described as the main oxaliplatin-induced DNA damage repair system. SK-N-ASrOXALI4000 cells were also more sensitive to lysis by influenza A virus, a candidate for oncolytic therapy, than SK-N-AS cells. In conclusion, we introduce a novel oxaliplatin resistance model. The oxaliplatin resistance mechanisms in SK-N-ASrOXALI4000 cells appear to be complex and not to directly depend on enhanced DNA repair capacity. Models of oxaliplatin resistance are of particular relevance since research on platinum drugs has so far predominantly focused on cisplatin and carboplatin.

  11. Relationship between the Level of Acquired Resistance to Gentamicin and Synergism with Amoxicillin in Enterococcus faecalis

    PubMed Central

    Aslangul, Elisabeth; Ruimy, Raymond; Chau, Françoise; Garry, Louis; Andremont, Antoine; Fantin, Bruno

    2005-01-01

    In enterococci, intrinsic low-level resistance to gentamicin does not abolish synergism with a cell wall-active antibiotic while high-level resistance due to acquired aminoglycoside-modifying enzymes does. To study the impact of intermediate levels of resistance to gentamicin (64 < MIC < 500 μg/ml), we selected in vitro three consecutive generations of mutants of Enterococcus faecalis JH2-2 with MICs of gentamicin at 128 μg/ml for G1-1477, 256 μg/ml for G2-1573, and 512 μg/ml for G3-1688. E. faecalis 102, which is highly resistant to gentamicin by enzymatic inactivation was used as control. In in vitro killing curves experiments, gentamicin concentrations allowing bactericidal activity and synergism in combination with amoxicillin increased from 4 μg/ml (1/16th the MIC), 16 μg/ml (one-eighth the MIC), 64 μg/ml (one-quarter the MIC), and 256 μg/ml (one-half the MIC) for strains JH2-2, G1-1477, G2-1573 and G3-1688, respectively. As expected, no bactericidal effect of the combination or synergism could be obtained with strain 102. In rabbits with aortic endocarditis caused by strain G1-1477 or G2-1573, combination therapy with amoxicillin and gentamicin was significantly more active than amoxicillin alone (P < 0.05) but not in those infected with the strains G3-1688 and 102. Thus, intermediate levels of resistance to gentamicin was not associated with a loss of a beneficial effect of the gentamicin-amoxicillin combination in vivo even though higher concentrations of gentamicin were necessary to achieve in vitro synergism. Therefore, the use of an MIC of 500 μg/ml as a clinical cutoff limit to predict in vivo benefit of the combination remains a simple and effective tool. PMID:16189091

  12. Mechanisms of antibiotic resistance in enterococci

    PubMed Central

    Miller, William R; Munita, Jose M; Arias, Cesar A

    2015-01-01

    Multidrug-resistant (MDR) enterococci are important nosocomial pathogens and a growing clinical challenge. These organisms have developed resistance to virtually all antimicrobials currently used in clinical practice using a diverse number of genetic strategies. Due to this ability to recruit antibiotic resistance determinants, MDR enterococci display a wide repertoire of antibiotic resistance mechanisms including modification of drug targets, inactivation of therapeutic agents, overexpression of efflux pumps and a sophisticated cell envelope adaptive response that promotes survival in the human host and the nosocomial environment. MDR enterococci are well adapted to survive in the gastrointestinal tract and can become the dominant flora under antibiotic pressure, predisposing the severely ill and immunocompromised patient to invasive infections. A thorough understanding of the mechanisms underlying antibiotic resistance in enterococci is the first step for devising strategies to control the spread of these organisms and potentially establish novel therapeutic approaches. PMID:25199988

  13. Mechanisms of insulin resistance in obesity.

    PubMed

    Ye, Jianping

    2013-03-01

    Obesity increases the risk for type 2 diabetes through induction of insulin resistance. Treatment of type 2 diabetes has been limited by little translational knowledge of insulin resistance although there have been several well-documented hypotheses for insulin resistance. In those hypotheses, inflammation, mitochondrial dysfunction, hyperinsulinemia and lipotoxicity have been the major concepts and have received a lot of attention. Oxidative stress, endoplasmic reticulum (ER) stress, genetic background, aging, fatty liver, hypoxia and lipodystrophy are active subjects in the study of these concepts. However, none of those concepts or views has led to an effective therapy for type 2 diabetes. The reason is that there has been no consensus for a unifying mechanism of insulin resistance. In this review article, literature is critically analyzed and reinterpreted for a new energy-based concept of insulin resistance, in which insulin resistance is a result of energy surplus in cells. The energy surplus signal is mediated by ATP and sensed by adenosine monophosphate-activated protein kinase (AMPK) signaling pathway. Decreasing ATP level by suppression of production or stimulation of utilization is a promising approach in the treatment of insulin resistance. In support, many of existing insulin sensitizing medicines inhibit ATP production in mitochondria. The effective therapies such as weight loss, exercise, and caloric restriction all reduce ATP in insulin sensitive cells. This new concept provides a unifying cellular and molecular mechanism of insulin resistance in obesity, which may apply to insulin resistance in aging and lipodystrophy.

  14. Brush and spray: a high-throughput systemic acquired resistance assay suitable for large-scale genetic screening.

    PubMed

    Jing, Beibei; Xu, Shaohua; Xu, Mo; Li, Yan; Li, Shuxin; Ding, Jinmei; Zhang, Yuelin

    2011-11-01

    Systemic acquired resistance (SAR) is a defense mechanism induced in the distal parts of plants after primary infection. It confers long-lasting protection against a broad spectrum of microbial pathogens. Lack of high-throughput assays has hampered the forward genetic analysis of SAR. Here, we report the development of an easy and efficient assay for SAR and its application in a forward genetic screen for SAR-deficient mutants in Arabidopsis (Arabidopsis thaliana). Using the new assay for SAR, we identified six flavin-dependent monooxygenase1, four AGD2-like defense response protein1, three salicylic acid induction-deficient2, one phytoalexin deficient4, and one avrPphB-susceptible3 alleles as well as a gain-of-function mutant of CALMODULIN-BINDING TRANSCRIPTION ACTIVATOR3 designated camta3-3D. Like transgenic plants overexpressing CAMTA3, camta3-3D mutant plants exhibit compromised SAR and enhanced susceptibility to virulent pathogens, suggesting that CAMTA3 is a critical regulator of both basal resistance and SAR.

  15. Arabidopsis flowering locus D influences systemic-acquired-resistance- induced expression and histone modifications of WRKY genes.

    PubMed

    Singh, Vijayata; Roy, Shweta; Singh, Deepjyoti; Nandi, Ashis Kumar

    2014-03-01

    A plant that is in part infected by a pathogen is more resistant throughout its whole body to subsequent infections--a phenomenon known as systemic acquired resistance (SAR). Mobile signals are synthesized at the site of infection and distributed throughout the plant through vascular tissues. Mechanism of SAR development subsequent to reaching the mobile signal in the distal tissue is largely unknown. Recently we showed that flowering locus D (FLD) gene of Arabidopsis thaliana is required in the distal tissue to activate SAR. FLD codes for a homologue of human-lysine-specific histone demethylase. Here we show that FLD function is required for priming (SAR induced elevated expression during challenge inoculation) of WRKY29 and WRKY6 genes. FLD also differentially influences basal and SAR-induced expression of WRKY38, WRKY65 and WRKY53 genes. In addition, we also show that FLD partly localizes in nucleus and influences histone modifications at the promoters of WRKY29 and WRKY6 genes. The results altogether indicate to the possibility of FLD's involvement in epigenetic regulation of SAR.

  16. Curcumin mediates oxaliplatin-acquired resistance reversion in colorectal cancer cell lines through modulation of CXC-Chemokine/NF-κB signalling pathway

    PubMed Central

    Ruiz de Porras, Vicenç; Bystrup, Sara; Martínez-Cardús, Anna; Pluvinet, Raquel; Sumoy, Lauro; Howells, Lynne; James, Mark I.; Iwuji, Chinenye; Manzano, José Luis; Layos, Laura; Bugés, Cristina; Abad, Albert; Martínez-Balibrea, Eva

    2016-01-01

    Resistance to oxaliplatin (OXA) is a complex process affecting the outcomes of metastatic colorectal cancer (CRC) patients treated with this drug. De-regulation of the NF-κB signalling pathway has been proposed as an important mechanism involved in this phenomenon. Here, we show that NF-κB was hyperactivated in in vitro models of OXA-acquired resistance but was attenuated by the addition of Curcumin, a non-toxic NF-κB inhibitor. The concomitant combination of Curcumin + OXA was more effective and synergistic in cell lines with acquired resistance to OXA, leading to the reversion of their resistant phenotype, through the inhibition of the NF-κB signalling cascade. Transcriptomic profiling revealed the up-regulation of three NF-κB-regulated CXC-chemokines, CXCL8, CXCL1 and CXCL2, in the resistant cells that were more efficiently down-regulated after OXA + Curcumin treatment as compared to the sensitive cells. Moreover, CXCL8 and CXCL1 gene silencing made resistant cells more sensitive to OXA through the inhibition of the Akt/NF-κB pathway. High expression of CXCL1 in FFPE samples from explant cultures of CRC patients-derived liver metastases was associated with response to OXA + Curcumin. In conclusion, we suggest that combination of OXA + Curcumin could be an effective treatment, for which CXCL1 could be used as a predictive marker, in CRC patients. PMID:27091625

  17. Epidemiological mechanisms of genetic resistance to kuru

    PubMed Central

    Atkins, Katherine E.; Townsend, Jeffrey P.; Medlock, Jan; Galvani, Alison P.

    2013-01-01

    Transmissible spongiform encephalopathies (TSEs), such as kuru, are invariably fatal neurodegenerative conditions caused by a malformation of the prion protein. Heterozygosity of codon 129 of the prion protein gene has been associated with increased host resistance to TSEs, although the mechanism by which this resistance is achieved has not been determined. To evaluate the epidemiological mechanism of human resistance to kuru, we developed a model that combines the dynamics of kuru transmission and the population genetics of human resistance. We fitted our model to kuru data from the epidemic that occurred in Papua New Guinea over the last hundred years. To elucidate the epidemiological mechanism of human resistance, we estimated the incubation period and transmission rate of kuru for codon 129 heterozygotes and homozygotes using kuru incidence data and human genotype frequency data from 1957 to 2004. Our results indicate that human resistance arises from a combination of both a longer incubation period and reduced susceptibility to infection. This work provides evidence for balancing selection acting on a human population and the mechanistic basis for the heterozygote resistance to kuru. PMID:23740487

  18. Drug Targets and Mechanisms of Resistance in the Anaerobic Protozoa

    PubMed Central

    Upcroft, Peter; Upcroft, Jacqueline A.

    2001-01-01

    The anaerobic protozoa Giardia duodenalis, Trichomonas vaginalis, and Entamoeba histolytica infect up to a billion people each year. G. duodenalis and E. histolytica are primarily pathogens of the intestinal tract, although E. histolytica can form abscesses and invade other organs, where it can be fatal if left untreated. T. vaginalis infection is a sexually transmitted infection causing vaginitis and acute inflammatory disease of the genital mucosa. T. vaginalis has also been reported in the urinary tract, fallopian tubes, and pelvis and can cause pneumonia, bronchitis, and oral lesions. Respiratory infections can be acquired perinatally. T. vaginalis infections have been associated with preterm delivery, low birth weight, and increased mortality as well as predisposing to human immunodeficiency virus infection, AIDS, and cervical cancer. All three organisms lack mitochondria and are susceptible to the nitroimidazole metronidazole because of similar low-redox-potential anaerobic metabolic pathways. Resistance to metronidazole and other drugs has been observed clinically and in the laboratory. Laboratory studies have identified the enzyme that activates metronidazole, pyruvate:ferredoxin oxidoreductase, to its nitroso form and distinct mechanisms of decreasing drug susceptibility that are induced in each organism. Although the nitroimidazoles have been the drug family of choice for treating the anaerobic protozoa, G. duodenalis is less susceptible to other antiparasitic drugs, such as furazolidone, albendazole, and quinacrine. Resistance has been demonstrated for each agent, and the mechanism of resistance has been investigated. Metronidazole resistance in T. vaginalis is well documented, and the principal mechanisms have been defined. Bypass metabolism, such as alternative oxidoreductases, have been discovered in both organisms. Aerobic versus anaerobic resistance in T. vaginalis is discussed. Mechanisms of metronidazole resistance in E. histolytica have recently

  19. Mechanisms of resistance to paraquat in plants.

    PubMed

    Hawkes, Timothy R

    2014-09-01

    The aim of this brief review is to draw information from studies of the mechanism of evolved resistance in weeds, together with information from laboratory studies of paraquat tolerance in model plants. Plants having mutations that limit paraquat uptake into cytoplasm, that confer various stress tolerances or that have transgenes that co-express two or more of the chloroplast Halliwell-Asada cycle enzymes can all exhibit enhanced tolerance to paraquat. However, none of these mechanisms correspond to the high-level resistances that have evolved naturally in weeds. Most, but not all, of the evidence from studies of paraquat-resistant biotypes of weeds can reasonably be reconciled with the proposal of a single major gene mechanism that sequesters paraquat away from chloroplasts and into the vacuole. However, the molecular details of this putative mechanism remain ill-defined.

  20. Carbapenem-resistant Acinetobacter baumannii acquired before liver transplantation: Impact on recipient outcomes.

    PubMed

    Freire, Maristela Pinheiro; Pierrotti, Ligia Câmera; Oshiro, Isabel Cristina Villela Soares; Bonazzi, Patrícia Rodrigues; Oliveira, Larissa Marques de; Machado, Anna Silva; Van Der Heijden, Inneke Marie; Rossi, Flavia; Costa, Silvia Figueiredo; D'Albuquerque, Luiz Augusto Carneiro; Abdala, Edson

    2016-05-01

    Infection with carbapenem-resistant Acinetobacter baumannii (CRAB) after liver transplantation (LT) is associated with high mortality. This study aimed to identify risk factors for post-LT CRAB infection, as well as to evaluate the impact of pre-LT CRAB acquisition on the incidence of post-LT CRAB infection. This was a prospective cohort study of all patients undergoing LT at our facility between October 2009 and October 2011. Surveillance cultures (SCs) were collected immediately before LT and weekly thereafter, until discharge. We analyzed 196 patients who were submitted to 222 LTs. CRAB was identified in 105 (53.6%); 24 (22.9%) of these patients were found to have acquired CRAB before LT, and 85 (81.0%) tested positive on SCs. Post-LT CRAB infection occurred in 56 (28.6%), the most common site being the surgical wound. Multivariate analysis showed that the risk factors for developing CRAB infection were prolonged cold ischemia, post-LT dialysis, LT due to fulminant hepatitis, and pre-LT CRAB acquisition with pre-LT CRAB acquisition showing a considerable trend toward significance (P = 0.06). Among the recipients with CRAB infection, 60-day mortality was 46.4%, significantly higher than among those without (P < 0.001). Mortality risk factors were post-LT infection with multidrug-resistant bacteria, LT performed because of fulminant hepatitis, retransplantation, prolonged cold ischemia, longer LT surgical time, and pre-LT CRAB acquisition, the last showing a trend toward significance (P = 0.08). In conclusion, pre-LT CRAB acquisition appears to increase the risk of post-LT CRAB infection, which has a negative impact on recipient survival. Liver Transplantation 22 615-626 2016 AASLD.

  1. Genomic analysis of ST88 community-acquired methicillin resistant Staphylococcus aureus in Ghana

    PubMed Central

    Buultjens, Andrew H.; Giulieri, Stefano; Owusu-Mireku, Evelyn; Aboagye, Samuel Y.; Baines, Sarah L.; Gonçalves da Silva, Anders; Howden, Benjamin P.; Pluschke, Gerd; Yeboah-Manu, Dorothy

    2017-01-01

    Background The emergence and evolution of community-acquired methicillin resistant Staphylococcus aureus (CA-MRSA) strains in Africa is poorly understood. However, one particular MRSA lineage called ST88, appears to be rapidly establishing itself as an “African” CA-MRSA clone. In this study, we employed whole genome sequencing to provide more information on the genetic background of ST88 CA-MRSA isolates from Ghana and to describe in detail ST88 CA-MRSA isolates in comparison with other MRSA lineages worldwide. Methods We first established a complete ST88 reference genome (AUS0325) using PacBio SMRT sequencing. We then used comparative genomics to assess relatedness among 17 ST88 CA-MRSA isolates recovered from patients attending Buruli ulcer treatment centres in Ghana, three non-African ST88s and 15 other MRSA lineages. Results We show that Ghanaian ST88 forms a discrete MRSA lineage (harbouring SCCmec-IV [2B]). Gene content analysis identified five distinct genomic regions enriched among ST88 isolates compared with the other S. aureus lineages. The Ghanaian ST88 isolates had only 658 core genome SNPs and there was no correlation between phylogeny and geography, suggesting the recent spread of this clone. The lineage was also resistant to multiple classes of antibiotics including β-lactams, tetracycline and chloramphenicol. Discussion This study reveals that S. aureus ST88-IV is a recently emerging and rapidly spreading CA-MRSA clone in Ghana. The study highlights the capacity of small snapshot genomic studies to provide actionable public health information in resource limited settings. To our knowledge this is the first genomic assessment of the ST88 CA-MRSA clone. PMID:28265515

  2. Nosocomial infection and its molecular mechanisms of antibiotic resistance.

    PubMed

    Xia, Jufeng; Gao, Jianjun; Tang, Wei

    2016-02-01

    Nosocomial infection is a kind of infection, which is spread in various hospital environments, and leads to many serious diseases (e.g. pneumonia, urinary tract infection, gastroenteritis, and puerperal fever), and causes higher mortality than community-acquired infection. Bacteria are predominant among all the nosocomial infection-associated pathogens, thus a large number of antibiotics, such as aminoglycosides, penicillins, cephalosporins, and carbapenems, are adopted in clinical treatment. However, in recent years antibiotic resistance quickly spreads worldwide and causes a critical threat to public health. The predominant bacteria include Methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and Acinetobacter baumannii. In these bacteria, resistance emerged from antibiotic resistant genes and many of those can be exchanged between bacteria. With technical advances, molecular mechanisms of resistance have been gradually unveiled. In this review, recent advances in knowledge about mechanisms by which (i) bacteria hydrolyze antibiotics (e.g. extended spectrum β-lactamases, (ii) AmpC β-lactamases, carbapenemases), (iii) avoid antibiotic targeting (e.g. mutated vanA and mecA genes), (iv) prevent antibiotic permeation (e.g. porin deficiency), or (v) excrete intracellular antibiotics (e.g. active efflux pump) are summarized.

  3. Surveillance of Antibiotic Resistance among Hospital- and Community-Acquired Toxigenic Clostridium difficile Isolates over 5-Year Period in Kuwait

    PubMed Central

    Jamal, Wafaa Y.; Rotimi, Vincent O.

    2016-01-01

    Clostridium difficile infection (CDI) is a leading and an important cause of diarrhea in a healthcare setting especially in industrialized countries. Community-associated CDI appears to add to the burden on healthcare setting problems. The aim of the study was to investigate the antimicrobial resistance of healthcare-associated and community-acquired C. difficile infection over 5 years (2008–2012) in Kuwait. A total of 111 hospital-acquired (HA-CD) and 35 community-acquired Clostridium difficile (CA-CD) clinical isolates from stool of patients with diarrhoea were studied. Antimicrobial susceptibility testing of 15 antimicrobial agents against these pathogens was performed using E test method. There was no evidence of resistance to amoxicillin-clavulanic acid, daptomycin, linezolid, piperacillin-tazobactam, teicoplanin and vancomycin by both HA-CD and CA-CD isolates. Metronidazole had excellent activity against CA-CD but there was a 2.9% resistance rate against HA-CD isolates. Ampicillin, clindamycin, levofloxacin and imipenem resistance rates among the HC-CD vs. CA-CD isolates were 100 vs. 47.4%; 43 vs. 47.4%; 100 vs. 100% and 100 vs. 89%, respectively. An unexpected high rifampicin resistance rate of 15.7% emerged amongst the HA-CD isolates. In conclusion, vancomycin resistance amongst the HA-CD and CA-CD isolates was not encountered in this series but few metronidazole resistant hospital isolates were isolated. High resistance rates of ampicillin, clindamycin, levofloxacin, and imipenem resistance were evident among both CA-CD and HA-CD isolates. Rifampicin resistance is emerging among the HA-CD isolates. PMID:27536994

  4. Antifungal agents: mode of action, mechanisms of resistance, and correlation of these mechanisms with bacterial resistance.

    PubMed

    Ghannoum, M A; Rice, L B

    1999-10-01

    The increased use of antibacterial and antifungal agents in recent years has resulted in the development of resistance to these drugs. The significant clinical implication of resistance has led to heightened interest in the study of antimicrobial resistance from different angles. Areas addressed include mechanisms underlying this resistance, improved methods to detect resistance when it occurs, alternate options for the treatment of infections caused by resistant organisms, and strategies to prevent and control the emergence and spread of resistance. In this review, the mode of action of antifungals and their mechanisms of resistance are discussed. Additionally, an attempt is made to discuss the correlation between fungal and bacterial resistance. Antifungals can be grouped into three classes based on their site of action: azoles, which inhibit the synthesis of ergosterol (the main fungal sterol); polyenes, which interact with fungal membrane sterols physicochemically; and 5-fluorocytosine, which inhibits macromolecular synthesis. Many different types of mechanisms contribute to the development of resistance to antifungals. These mechanisms include alteration in drug target, alteration in sterol biosynthesis, reduction in the intercellular concentration of target enzyme, and overexpression of the antifungal drug target. Although the comparison between the mechanisms of resistance to antifungals and antibacterials is necessarily limited by several factors defined in the review, a correlation between the two exists. For example, modification of enzymes which serve as targets for antimicrobial action and the involvement of membrane pumps in the extrusion of drugs are well characterized in both the eukaryotic and prokaryotic cells.

  5. Mechanisms of doxorubicin resistance in hepatocellular carcinoma

    PubMed Central

    Cox, Josiah; Weinman, Steven

    2015-01-01

    Hepatocellular carcinoma, one of the most common solid tumors worldwide, is poorly responsive to available chemotherapeutic approaches. While systemic chemotherapy is of limited benefit, intra-arterial delivery of doxorubicin to the tumor frequently produces tumor shrinkage. Its utility is limited, in part, by the frequent emergence of doxorubicin resistance. The mechanisms of this resistance include increased expression of multidrug resistance efflux pumps, alterations of the drug target, topoisomerase, and modulation of programmed cell death pathways. Many of these effects result from changes in miRNA expression and are particularly prominent in tumor cells with a stem cell phenotype. This review will summarize the current knowledge on the mechanisms of doxorubicin resistance of hepatocellular carcinoma and the potential for approaches toward therapeutic chemosensitization. PMID:26998221

  6. The Landscape of Pancreatic Cancer Therapeutic Resistance Mechanisms

    PubMed Central

    Chand, Saswati; O'Hayer, Kevin; Blanco, Fernando F.; Winter, Jordan M.; Brody, Jonathan R.

    2016-01-01

    Pancreatic cancer (pancreatic ductal adenocarcinoma, PDA) is infamously moving to the top of the list as one of the most lethal cancers with an overall 5 year survival rate of 7%. Multiple genomic-based and molecular characterization studies of PDA specimens and established animal models have provided the field with multiple targets and a progression model of this disease. Still, to date, the best therapeutic options are surgery and combination cytotoxic therapies. In general, even in the best case scenario (i.e., an early stage diagnosis and a response to a specific therapy), most of these fortunate patients' PDA cells acquire or exert resistance mechanisms and eventually kill the patient. Herein, we touch on a growing field of investigation that focuses on PDA cell therapeutic resistance mechanisms. We examine extrinsic elements (i.e., the tumor microenvironment, hypoxia) to the intrinsic processes within the cell (i.e., post-transcriptional gene regulation and somatic mutations) that are important for therapeutic efficacy and resistance. Even as better targeted and personalized approaches move through the clinical trial pipeline the discussed resistance mechanisms will most likely play a role in the management of this deadly disease. PMID:26929734

  7. Molecular mechanisms of insulin resistance in diabetes.

    PubMed

    Soumaya, Kouidhi

    2012-01-01

    Molecular components of impaired insulin signaling pathway have emerged with growing interest to understand how the environment and genetic susceptibility combine to cause defects in this fundamental pathway that lead to insulin resistance. When insulin resistance is combined with beta-cell defects in glucose-stimulated insulin secretion, impaired glucose tolerance, hyperglycemia, or Type 2 diabetes can result. The most common underlying cause is obesity, although primary insulin resistance in normal-weight individuals is also possible. The adipose tissue releases free fatty acids that contribute to insulin resistance and also acts as a relevant endocrine organ producing mediators (adipokines) that can modulate insulin signalling. This chapter deals with the core elements promoting, insulin resistance, associated with impaired insulin signalling pathway and adipocyte dysfunction. A detailed understanding of these basic pathophysiological mechanisms is critical for the development of novel therapeutic strategies to treat diabetes.

  8. Mechanisms of Resistance and Clinical Relevance of Resistance to β-Lactams, Glycopeptides, and Fluoroquinolones

    PubMed Central

    Rice, Louis B.

    2012-01-01

    The widespread use of antibiotics has resulted in a growing problem of antimicrobial resistance in the community and hospital settings. Antimicrobial classes for which resistance has become a major problem include the β-lactams, the glycopeptides, and the fluoroquinolones. In gram-positive bacteria, β-lactam resistance most commonly results from expression of intrinsic low-affinity penicillin-binding proteins. In gram-negative bacteria, expression of acquired β-lactamases presents a particular challenge owing to some natural spectra that include virtually all β-lactam classes. Glycopeptide resistance has been largely restricted to nosocomial Enterococcus faecium strains, the spread of which is promoted by ineffective infection control mechanisms for fecal organisms and the widespread use of colonization-promoting antimicrobials (especially cephalosporins and antianaerobic antibiotics). Fluoroquinolone resistance in community-associated strains of Escherichia coli, many of which also express β-lactamases that confer cephalosporin resistance, is increasingly prevalent. Economic and regulatory forces have served to discourage large pharmaceutical companies from developing new antibiotics, suggesting that the antibiotics currently on the market may be all that will be available for the coming decade. As such, it is critical that we devise, test, and implement antimicrobial stewardship strategies that are effective at constraining and, ideally, reducing resistance in human pathogenic bacteria. PMID:22305032

  9. The BIM deletion polymorphism: A paradigm of a permissive interaction between germline and acquired TKI resistance factors in chronic myeloid leukemia.

    PubMed

    Ko, Tun Kiat; Chin, Hui San; Chuah, Charles T H; Huang, John W J; Ng, King-Pan; Khaw, Seong Lin; Huang, David C S; Ong, S Tiong

    2016-01-19

    Both germline polymorphisms and tumor-specific genetic alterations can determine the response of a cancer to a given therapy. We previously reported a germline deletion polymorphism in the BIM gene that was sufficient to mediate intrinsic resistance to tyrosine kinase inhibitors (TKI) in chronic myeloid leukemia (CML), as well as other cancers [1]. The deletion polymorphism favored the generation of BIM splice forms lacking the pro-apoptotic BH3 domain, conferring a relative resistance to the TKI imatinib (IM). However, CML patients with the BIM deletion polymorphism developed both partial and complete IM resistance. To understand the mechanisms underlying the latter, we grew CML cells either with or without the BIM deletion polymorphism in increasing IM concentrations. Under these conditions, the BIM deletion polymorphism enhanced the emergence of populations with complete IM resistance, mimicking the situation in patients. Importantly, the combined use of TKIs with the BH3 mimetic ABT-737 overcame the BCR-ABL1-dependent and -independent resistance mechanisms found in these cells. Our results illustrate the interplay between germline and acquired genetic factors in confering TKI resistance, and suggest a therapeutic strategy for patients with complete TKI resistance associated with the BIM deletion polymorphism.

  10. Induction of systemic acquired resistance by Rotylenchulus reniformis and Meloidogyne incognita in cotton following separate and concomitant inoculations.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Systemic acquired resistance (SAR) can be elicited by virulent and avirulent pathogenic strains and SAR against plant-parasitic nematodes has been documented. Our objective was to determine whether co-infection of cotton by Meloidogyne incognita and Rotylenchulus reniformis affects the population le...

  11. Saccharin-induced systemic acquired resistance against rust (Phakopsora pachyrhizi) infection in soybean: Effects on growth and development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We examined the effect of saccharin on the systemic acquired resistance (SAR) response of soybean to the fungus Phakopsora pachyrhizi, the causal agent of soybean rust. Plants were grown hydroponically in half-strength Hoagland’s solution and were challenged with the pathogen 1, 5, 10 and 15 days af...

  12. New Real-Time PCR Assays for Detection of Inducible and Acquired Clarithromycin Resistance in the Mycobacterium abscessus Group

    PubMed Central

    Shallom, Shamira J.; Moura, Natalia S.; Olivier, Kenneth N.; Sampaio, Elizabeth P.; Holland, Steven M.

    2015-01-01

    Members of the Mycobacterium abscessus group (MAG) cause lung, soft tissue, and disseminated infections. The oral macrolides clarithromycin and azithromycin are commonly used for treatment. MAG can display clarithromycin resistance through the inducible erm(41) gene or via acquired mutations in the rrl (23S rRNA) gene. Strains harboring a truncation or a T28C substitution in erm(41) lose the inducible resistance trait. Phenotypic detection of clarithromycin resistance requires extended incubation (14 days), highlighting the need for faster methods to detect resistance. Two real-time PCR-based assays were developed to assess inducible and acquired clarithromycin resistance and tested on a total of 90 clinical and reference strains. A SYBR green assay was designed to distinguish between a full-length and truncated erm(41) gene by temperature shift in melting curve analysis. Single nucleotide polymorphism (SNP) allele discrimination assays were developed to distinguish T or C at position 28 of erm(41) and 23S rRNA rrl gene mutations at position 2058 and/or 2059. Truncated and full-size erm(41) genes were detected in 21/90 and 69/90 strains, respectively, with 64/69 displaying T at nucleotide position 28 and 5/69 containing C at that position. Fifteen isolates showed rrl mutations conferring clarithromycin resistance, including A2058G (11 isolates), A2058C (3 isolates), and A2059G (1 isolate). Targeted sequencing and phenotypic assessment of resistance concurred with molecular assay results. Interestingly, we also noted cooccurring strains harboring an active erm(41), inactive erm(41), and/or acquired mutational resistance, as well as slowly growing MAG strains and also strains displaying an inducible resistance phenotype within 5 days, long before the recommended 14-day extended incubation. PMID:26269619

  13. Hypermorphic mutation of phospholipase C, γ2 acquired in ibrutinib-resistant CLL confers BTK independency upon B-cell receptor activation

    PubMed Central

    Liu, Ta-Ming; Woyach, Jennifer A.; Zhong, Yiming; Lozanski, Arletta; Lozanski, Gerard; Dong, Shuai; Strattan, Ethan; Lehman, Amy; Zhang, Xiaoli; Jones, Jeffrey A.; Flynn, Joseph; Andritsos, Leslie A.; Maddocks, Kami; Jaglowski, Samantha M.; Blum, Kristie A.; Byrd, John C.; Dubovsky, Jason A.

    2015-01-01

    Ibrutinib has significantly improved the outcome of patients with relapsed chronic lymphocytic leukemia (CLL). Recent reports attribute ibrutinib resistance to acquired mutations in Bruton agammaglobulinemia tyrosine kinase (BTK), the target of ibrutinib, as well as the immediate downstream effector phospholipase C, γ2 (PLCG2). Although the C481S mutation found in BTK has been shown to disable ibrutinib’s capacity to irreversibly bind this primary target, the detailed mechanisms of mutations in PLCG2 have yet to be established. Herein, we characterize the enhanced signaling competence, BTK independence, and surface immunoglobulin dependence of the PLCG2 mutation at R665W, which has been documented in ibrutinib-resistant CLL. Our data demonstrate that this missense alteration elicits BTK-independent activation after B-cell receptor engagement, implying the formation of a novel BTK-bypass pathway. Consistent with previous results, PLCG2R665W confers hypermorphic induction of downstream signaling events. Our studies reveal that proximal kinases SYK and LYN are critical for the activation of mutant PLCG2 and that therapeutics targeting SYK and LYN can combat molecular resistance in cell line models and primary CLL cells from ibrutinib-resistant patients. Altogether, our results engender a molecular understanding of the identified aberration at PLCG2 and explore its functional dependency on BTK, SYK, and LYN, suggesting alternative strategies to combat acquired ibrutinib resistance. PMID:25972157

  14. Clinical definition of acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors in non-small-cell lung cancer.

    PubMed

    Jackman, David; Pao, William; Riely, Gregory J; Engelman, Jeffrey A; Kris, Mark G; Jänne, Pasi A; Lynch, Thomas; Johnson, Bruce E; Miller, Vincent A

    2010-01-10

    Ten percent of North American patients with non-small-cell lung cancer have tumors with somatic mutations in the gene for the epidermal growth factor receptor (EGFR). Approximately 70% of patients whose lung cancers harbor somatic mutations in exons encoding the tyrosine kinase domain of EGFR experience significant tumor regressions when treated with the EGFR tyrosine kinase inhibitors (TKIs) gefitinib or erlotinib. However, the overwhelming majority of these patients inevitably acquire resistance to either drug. Currently, the clinical definition of such secondary or acquired resistance is not clear. We propose the following criteria be used to define more precisely acquired resistance to EGFR TKIs. All patients should have the following criteria: previous treatment with a single-agent EGFR TKI (eg, gefitinib or erlotinib); either or both of the following: a tumor that harbors an EGFR mutation known to be associated with drug sensitivity or objective clinical benefit from treatment with an EGFR TKI; systemic progression of disease (Response Evaluation Criteria in Solid Tumors [RECIST] or WHO) while on continuous treatment with gefitinib or erlotinib within the last 30 days; and no intervening systemic therapy between cessation of gefitinib or erlotinib and initiation of new therapy. The relatively simple definition proposed here will lead to a more uniform approach to investigating the problem of acquired resistance to EGFR TKIs in this unique patient population. These guidelines should minimize reporting of false-positive and false-negative activity in these clinical trials and would facilitate the identification of agents that truly overcome acquired resistance to gefitinib and erlotinib.

  15. Mycoplasma bovis: Mechanisms of Resistance and Trends in Antimicrobial Susceptibility

    PubMed Central

    Lysnyansky, Inna; Ayling, Roger D.

    2016-01-01

    Mycoplasma bovis is a cell-wall-less bacterium and belongs to the class Mollicutes. It is the most important etiological agent of bovine mycoplasmoses in North America and Europe, causing respiratory disease, mastitis, otitis media, arthritis, and reproductive disease. Clinical disease associated with M. bovis is often chronic, debilitating, and poorly responsive to antimicrobial therapy, resulting in significant economic loss, the full extent of which is difficult to estimate. Until M. bovis vaccines are universally available, sanitary control measures and antimicrobial treatment are the only approaches that can be used in attempts to control M. bovis infections. However, in vitro studies show that many of the current M. bovis isolates circulating in Europe have high minimum inhibitory concentrations (MIC) for many of the commercially available antimicrobials. In this review we summarize the current MIC trends indicating the development of antimicrobial resistance in M. bovis as well as the known molecular mechanisms by which resistance is acquired. PMID:27199926

  16. Comparative genomics of community-acquired ST59 methicillin-resistant Staphylococcus aureus in Taiwan: novel mobile resistance structures with IS1216V.

    PubMed

    Hung, Wei-Chun; Takano, Tomomi; Higuchi, Wataru; Iwao, Yasuhisa; Khokhlova, Olga; Teng, Lee-Jene; Yamamoto, Tatsuo

    2012-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) with ST59/SCCmecV and Panton-Valentine leukocidin gene is a major community-acquired MRSA (CA-MRSA) lineage in Taiwan and has been multidrug-resistant since its initial isolation. In this study, we studied the acquisition mechanism of multidrug resistance in an ST59 CA-MRSA strain (PM1) by comparative genomics. PM1's non-β-lactam resistance was encoded by two unique genetic traits. One was a 21,832-bp composite mobile element structure (MES(PM1)), which was flanked by direct repeats of enterococcal IS1216V and was inserted into the chromosomal sasK gene; the target sequence (att) was 8 bp long and was duplicated at both ends of MES(PM1). MES(PM1) consisted of two regions: the 5'-end side 12.4-kb region carrying Tn551 (with ermB) and Tn5405-like (with aph[3']-IIIa and aadE), similar to an Enterococcus faecalis plasmid, and the 3'-end side 6,587-bp region (MES(cat)) that carries cat and is flanked by inverted repeats of IS1216V. MES(cat) possessed att duplication at both ends and additional two copies of IS1216V inside. MES(PM1) represents the first enterococcal IS1216V-mediated composite transposon emerged in MRSA. IS1216V-mediated deletion likely occurred in IS1216V-rich MES(PM1), resulting in distinct resistance patterns in PM1-derivative strains. Another structure was a 6,025-bp tet-carrying element (MES(tet)) on a 25,961-bp novel mosaic penicillinase plasmid (pPM1); MES(tet) was flanked by direct repeats of IS431, but with no target sequence repeats. Moreover, the PM1 genome was deficient in a copy of the restriction and modification genes (hsdM and hsdS), which might have contributed to the acquisition of enterococcal multidrug resistance.

  17. Regulatory and Functional Aspects of Indolic Metabolism in Plant Systemic Acquired Resistance.

    PubMed

    Stahl, Elia; Bellwon, Patricia; Huber, Stefan; Schlaeppi, Klaus; Bernsdorff, Friederike; Vallat-Michel, Armelle; Mauch, Felix; Zeier, Jürgen

    2016-05-02

    Tryptophan-derived, indolic metabolites possess diverse functions in Arabidopsis innate immunity to microbial pathogen infection. Here, we investigate the functional role and regulatory characteristics of indolic metabolism in Arabidopsis systemic acquired resistance (SAR) triggered by the bacterial pathogen Pseudomonas syringae. Indolic metabolism is broadly activated in both P. syringae-inoculated and distant, non-inoculated leaves. At inoculation sites, camalexin, indol-3-ylmethylamine (I3A), and indole-3-carboxylic acid (ICA) are the major accumulating compounds. Camalexin accumulation is positively affected by MYB122, and the cytochrome P450 genes CYP81F1 and CYP81F2. Local I3A production, by contrast, occurs via indole glucosinolate breakdown by PEN2- dependent and independent pathways. Moreover, exogenous application of the defense hormone salicylic acid stimulates I3A generation at the expense of its precursor indol-3-ylmethylglucosinolate (I3M), and the SAR regulator pipecolic acid primes plants for enhanced P. syringae-induced activation of distinct branches of indolic metabolism. In uninfected systemic tissue, the metabolic response is more specific and associated with enhanced levels of the indolics I3A, ICA, and indole-3-carbaldehyde (ICC). Systemic indole accumulation fully depends on functional CYP79B2/3, PEN2, and MYB34/51/122, and requires functional SAR signaling. Genetic analyses suggest that systemically elevated indoles are dispensable for SAR and associated systemic increases of salicylic acid. However, soil-grown but not hydroponically -cultivated cyp79b2/3 and pen2 plants, both defective in indolic secondary metabolism, exhibit pre-induced immunity, which abrogates their intrinsic ability to induce SAR.

  18. Proteome studies of bacterial antibiotic resistance mechanisms.

    PubMed

    Vranakis, Iosif; Goniotakis, Ioannis; Psaroulaki, Anna; Sandalakis, Vassilios; Tselentis, Yannis; Gevaert, Kris; Tsiotis, Georgios

    2014-01-31

    Ever since antibiotics were used to help humanity battle infectious diseases, microorganisms straight away fought back. Antibiotic resistance mechanisms indeed provide microbes with possibilities to by-pass and survive the action of antibiotic drugs. Several methods have been employed to identify these microbial resistance mechanisms in an ongoing effort to reduce the steadily increasing number of treatment failures due to multi-drug-resistant microbes. Proteomics has evolved to an important tool for this area of research. Following rapid advances in whole genome sequencing, proteomic technologies have been widely used to investigate microbial gene expression. This review highlights the contribution of proteomics in identifying microbial drug resistance mechanisms. It summarizes different proteomic studies on bacteria resistant to different antibiotic drugs. The review further includes an overview of the methodologies used, as well as lists key proteins identified, thus providing the reader not only a summary of research already done, but also directions for future research. This article is part of a Special Issue entitled: Trends in Microbial Proteomics.

  19. Proteomic analysis of acquired tamoxifen resistance in MCF-7 cells reveals expression signatures associated with enhanced migration

    PubMed Central

    2012-01-01

    Introduction Acquired tamoxifen resistance involves complex signaling events that are not yet fully understood. Successful therapeutic intervention to delay the onset of hormone resistance depends critically on mechanistic elucidation of viable molecular targets associated with hormone resistance. This study was undertaken to investigate the global proteomic alterations in a tamoxifen resistant MCF-7 breast cancer cell line obtained by long term treatment of the wild type MCF-7 cell line with 4-hydroxytamoxifen (4-OH Tam). Methods We cultured MCF-7 cells with 4-OH Tam over a period of 12 months to obtain the resistant cell line. A gel-free, quantitative proteomic method was used to identify and quantify the proteome of the resistant cell line. Nano-flow high-performance liquid chromatography coupled to high resolution Fourier transform mass spectrometry was used to analyze fractionated peptide mixtures that were isobarically labeled from the resistant and control cell lysates. Real time quantitative PCR and Western blots were used to verify selected proteomic changes. Lentiviral vector transduction was used to generate MCF-7 cells stably expressing S100P. Online pathway analysis was performed to assess proteomic signatures in tamoxifen resistance. Survival analysis was done to evaluate clinical relevance of altered proteomic expressions. Results Quantitative proteomic analysis revealed a wide breadth of signaling events during transition to acquired tamoxifen resistance. A total of 629 proteins were found significantly changed with 364 up-regulated and 265 down-regulated. Collectively, these changes demonstrated the suppressed state of estrogen receptor (ER) and ER-regulated genes, activated survival signaling and increased migratory capacity of the resistant cell line. The protein S100P was found to play a critical role in conferring tamoxifen resistance and enhanced cell motility. Conclusions Our data demonstrate that the adaptive changes in the proteome of

  20. Panton-Valentine Leukocidin associated with community acquired methicillin resistant Staphylococcus aureus: a case report and review of interim guidelines.

    PubMed

    Baldwin, L N; Lowe, A D

    2008-07-01

    We report a case of community acquired methicillin resistant Staphylococcus aureus pneumonia. The causative organism was positive for the toxin Panton-Valentine Leukocidin. This resulted in a severe pneumonia requiring a prolonged stay on our intensive care unit. This infection is becoming more common in the United Kingdom. It can cause a far more aggressive illness than the hospital acquired infection with a high mortality if it becomes an invasive infection. The Department of Health has recently produced interim guidelines for its treatment which we have also reviewed.

  1. Pathogenic Rickettsia Species Acquire Vitronectin from Human Serum to Promote Resistance to Complement-mediated Killing

    PubMed Central

    Riley, Sean P.; Patterson, Jennifer L.; Nava, Samantha; Martinez, Juan J.

    2014-01-01

    SUMMARY Bacteria of the genus Rickettsia are transmitted from arthropod vectors and primarily infect cells of the mammalian endothelial system. Throughout this infectious cycle, the bacteria are exposed to the deleterious effects of serum complement. Using Rickettsia conorii, the etiologic agent of Mediterranean spotted fever (MSF), as a model rickettsial species, we have previously demonstrated that this class of pathogen interacts with human factor H to mediate partial survival in human serum. Herein, we demonstrate that R. conorii also interacts with the terminal complement complex inhibitor vitronectin (Vn). We further demonstrate that an evolutionarily conserved rickettsial antigen, Adr1/RC1281, interacts with human vitronectin and is sufficient to mediate resistance to serum killing when expressed at the outer-membrane of serum sensitive E. coli. Adr1 is an integral outer-membrane protein whose structure is predicted to contain eight membrane-embedded β-strands and four “loop” regions that are exposed to extracellular milieu. Site-directed mutagenesis of Adr1 revealed that at least two predicted “loop” regions are required to mediate resistance to complement-mediated killing and vitronectin acquisition. These results demonstrate that rickettsial species have evolved multiple mechanisms to evade complement deposition and that evasion of killing in serum is an evolutionarily conserved virulence attribute for this genus of obligate intracellular pathogens. PMID:24286496

  2. Alectinib: a novel second generation anaplastic lymphoma kinase (ALK) inhibitor for overcoming clinically-acquired resistance

    PubMed Central

    Song, Zilan; Wang, Meining; Zhang, Ao

    2015-01-01

    The development of inhibitors for the tyrosine anaplastic lymphoma kinase (ALK) has advanced rapidly, driven by biology and medicinal chemistry. The first generation ALK inhibitor crizotinib was granted US FDA approval with only four years of preclinical and clinical testing. Although this drug offers significant clinical benefit to the ALK-positive patients, resistance has been developed through a variety of mechanisms. In addition to ceritinib, alectinib is another second-generation ALK inhibitor launched in 2014 in Japan. This drug has a unique chemical structure bearing a 5H-benzo[b]carbazol-11(6H)-one structural scaffold with an IC50 value of 1.9 nmol/L, and is highly potent against ALK bearing the gatekeeper mutation L1196M with an IC50 of 1.56 nmol/L. In the clinic, alectinib is highly efficacious in treatment of ALK-positive non-small cell lung cancer (NSCLC), and retains potency to combat crizotinib-resistant ALK mutations L1196M, F1174L, R1275Q and C1156Y. PMID:26579422

  3. Acquired resistance to innate immune clearance promotes Klebsiella pneumoniae ST258 pulmonary infection

    PubMed Central

    Ahn, Danielle; Peñaloza, Hernán; Wang, Zheng; Wickersham, Matthew; Parker, Dane; Patel, Purvi; Koller, Antonius; Chen, Emily I.; Bueno, Susan M.; Uhlemann, Anne-Catrin; Prince, Alice

    2016-01-01

    Adaptive changes in the genome of a locally predominant clinical isolate of the multidrug-resistant Klebsiella pneumoniae ST258 (KP35) were identified and help to explain the selection of this strain as a successful pulmonary pathogen. The acquisition of 4 new ortholog groups, including an arginine transporter, enabled KP35 to outcompete related ST258 strains lacking these genes. KP35 infection elicited a monocytic response, dominated by Ly6Chi monocytic myeloid-derived suppressor cells that lacked phagocytic capabilities, expressed IL-10, arginase, and antiinflammatory surface markers. In comparison with other K. pneumoniae strains, KP35 induced global changes in the phagocytic response identified with proteomics, including evasion of Ca2+ and calpain activation necessary for phagocytic killing, confirmed in functional studies with neutrophils. This comprehensive analysis of an ST258 K. pneumoniae isolate reveals ongoing genetic adaptation to host microenvironments and innate immune clearance mechanisms that complements its repertoire of antimicrobial resistance genes and facilitates persistence in the lung. PMID:27777978

  4. [Resistance risk, cross-resistance and biochemical resistance mechanism of Laodelphax striatellus to buprofezin].

    PubMed

    Mao, Xu-lian; Liu, Jin; Li, Xu-ke; Chi, Jia-jia; Liu, Yong-jie

    2016-01-01

    In order to investigate the resistance development law and biochemical resistance mechanism of Laodelphax striatellus to buprofezin, spraying rice seedlings was used to continuously screen resistant strains of L. striatellus and dipping rice seedlings was applied to determine the toxicity and cross-resistance of L. striatellus to insecticides. After 32-generation screening with buprofezin, L. striatellus developed 168.49 folds resistance and its reality heritability (h2) was 0.11. If the killing rate was 80%-90%, L. striatellus was expected to develop 10-fold resistance to buprofezin only after 5 to 6 generations breeding. Because the actual reality heritability of field populations was usually lower than that of the resistant strains, the production of field populations increasing with 10-fold resistance would need much longer time. The results of cross-resistance showed that resistant strain had high level cross-resistance with thiamethoxam and imidacloprid, low level cross-resistance with acetamiprid, and no cross-resistance with pymetrozine and chlorpyrifos. The activity of detoxification enzymes of different strains and the syergism of synergist were measured. The results showed that cytochrome P450 monooxygenase played a major role in the resistance of L. striatellus to buprofezin, the esterase played a minor role and the GSH-S-transferase had no effect. Therefore, L. striatellus would have high risk to develop resistance to buprofezin when used in the field and might be delayed by using pymetrozine and chlorpyrifos.

  5. Low Prevalence of Carbapenem-Resistant Bacteria in River Water: Resistance Is Mostly Related to Intrinsic Mechanisms.

    PubMed

    Tacão, Marta; Correia, António; Henriques, Isabel S

    2015-10-01

    Carbapenems are last-resort antibiotics to handle serious infections caused by multiresistant bacteria. The incidence of resistance to these antibiotics has been increasing and new resistance mechanisms have emerged. The dissemination of carbapenem resistance in the environment has been overlooked. The main goal of this research was to assess the prevalence and diversity of carbapenem-resistant bacteria in riverine ecosystems. The presence of frequently reported carbapenemase-encoding genes was inspected. The proportion of imipenem-resistant bacteria was on average 2.24 CFU/ml. Imipenem-resistant strains (n=110) were identified as Pseudomonas spp., Stenotrophomonas maltophilia, Aeromonas spp., Chromobacterium haemolyticum, Shewanella xiamenensis, and members of Enterobacteriaceae. Carbapenem-resistant bacteria were highly resistant to other beta-lactams such as quinolones, aminoglycosides, chloramphenicol, tetracyclines, and sulfamethoxazole/trimethoprim. Carbapenem resistance was mostly associated with intrinsically resistant bacteria. As intrinsic resistance mechanisms, we have identified the blaCphA gene in 77.3% of Aeromonas spp., blaL1 in all S. maltophilia, and blaOXA-48-like in all S. xiamenensis. As acquired resistance mechanisms, we have detected the blaVIM-2 gene in six Pseudomonas spp. (5.45%). Integrons with gene cassettes encoding resistance to aminoglycosides (aacA and aacC genes), trimethoprim (dfrB1b), and carbapenems (blaVIM-2) were found in Pseudomonas spp. Results suggest that carbapenem resistance dissemination in riverine ecosystems is still at an early stage. Nevertheless, monitoring these aquatic compartments for the presence of resistance genes and its host organisms is essential to outline strategies to minimize resistance dissemination.

  6. Acquired resistance to BRAF inhibition induces epithelial-to-mesenchymal transition in BRAF (V600E) mutant thyroid cancer by c-Met-mediated AKT activation

    PubMed Central

    Byeon, Hyung Kwon; Na, Hwi Jung; Yang, Yeon Ju; Ko, Sooah; Yoon, Sun Och; Ku, Minhee; Yang, Jaemoon; Kim, Jae Wook; Ban, Myung Jin; Kim, Ji-Hoon; Kim, Da Hee; Kim, Jung Min; Choi, Eun Chang; Kim, Chang-Hoon; Yoon, Joo-Heon; Koh, Yoon Woo

    2017-01-01

    Previously, the authors have identified that c-Met mediates reactivation of the PI3K/AKT pathway following BRAF inhibitor treatment in BRAF (V600E) mutant anaplastic thyroid cancer, thereby contributing to the acquired drug resistance. Therefore dual inhibition of BRAF and c-Met led to sustained treatment response, thereby maximizing the specific anti-tumor effect of targeted therapy. The present study goes one step further and aims to investigate the effect of acquired resistance of BRAF inhibitor on epithelial-to-mesenchymal transition (EMT) in BRAF mutant thyroid cancer cells and the effect of dual inhibition from combinatorial therapy. Two thyroid cancer cell lines, 8505C and BCPAP were selected and treated with BRAF inhibitor, PLX4032 and its effect on EMT were examined and compared. Further investigation was carried out in orthotopic xenograft mouse models. Unlike BCPAP cells, the BRAF inhibitor resistant 8505C cells showed increased expressions of EMT related markers such as vimentin, β-catenin, and CD44. The combinatorial treatment of PLX4032 and PHA665752, a c-Met inhibitor reversed EMT. Similar results were confirmed in vivo. c-Met-mediated reactivation of the PI3K/AKT pathway contributes to the drug resistance to PLX4032 in BRAF (V600E) mutant anaplastic thyroid cancer cells and further promotes tumor cell migration and invasion by upregulated EMT mechanism. Dual inhibition of BRAF and c-Met leads to reversal of EMT, suggesting a maximal therapeutic response. PMID:27880942

  7. Mechanisms of multidrug resistance in cancer.

    PubMed

    Gillet, Jean-Pierre; Gottesman, Michael M

    2010-01-01

    The development of multidrug resistance (MDR) to chemotherapy remains a major challenge in the treatment of cancer. Resistance exists against every effective anticancer drug and can develop by numerous mechanisms including decreased drug uptake, increased drug efflux, activation of detoxifying systems, activation of DNA repair mechanisms, evasion of drug-induced apoptosis, etc. In the first part of this chapter, we briefly summarize the current knowledge on individual cellular mechanisms responsible for MDR, with a special emphasis on ATP-binding cassette transporters, perhaps the main theme of this textbook. Although extensive work has been done to characterize MDR mechanisms in vitro, the translation of this knowledge to the clinic has not been crowned with success. Therefore, identifying genes and mechanisms critical to the development of MDR in vivo and establishing a reliable method for analyzing clinical samples could help to predict the development of resistance and lead to treatments designed to circumvent it. Our thoughts about translational research needed to achieve significant progress in the understanding of this complex phenomenon are therefore discussed in a third section. The pleotropic response of cancer cells to chemotherapy is summarized in a concluding diagram.

  8. Mechanisms of bacterial resistance to macrolide antibiotics.

    PubMed

    Nakajima, Yoshinori

    1999-06-01

    Macrolides have been used in the treatment of infectious diseases since the late 1950s. Since that time, a finding of antagonistic action between erythromycin and spiramycin in clinical isolates1 led to evidence of the biochemical mechanism and to the current understanding of inducible or constitutive resistance to macrolides mediated by erm genes containing, respectively, the functional regulation mechanism or constitutively mutated regulatory region. These resistant mechanisms to macrolides are recognized in clinically isolated bacteria. (1) A methylase encoded by the erm gene can transform an adenine residue at 2058 (Escherichia coli equivalent) position of 23S rRNA into an 6N, 6N-dimethyladenine. Position 2058 is known to reside either in peptidyltransferase or in the vicinity of the enzyme region of domain V. Dimethylation renders the ribosome resistant to macrolides (MLS). Moreover, another finding adduced as evidence is that a mutation in the domain plays an important role in MLS resistance: one of several mutations (transition and transversion) such as A2058G, A2058C or U, and A2059G, is usually associated with MLS resistance in a few genera of bacteria. (2) M (macrolide antibiotics)- and MS (macrolide and streptogramin type B antibiotics)- or PMS (partial macrolide and streptogramin type B antibiotics)-phenotype resistant bacteria cause decreased accumulation of macrolides, occasionally including streptogramin type B antibiotics. The decreased accumulation, probably via enhanced efflux, is usually inferred from two findings: (i) the extent of the accumulated drug in a resistant cell increases as much as that in a susceptible cell in the presence of an uncoupling agent such as carbonylcyanide-m-chlorophenylhydrazone (CCCP), 2,4-dinitrophenol (DNP), and arsenate; (ii) transporter proteins, in M-type resistants, have mutual similarity to the 12-transmembrane domain present in efflux protein driven by proton-motive force, and in MS- or PMS-type resistants

  9. Glycol porphyrin derivatives and temoporfin elicit resistance to photodynamic therapy by different mechanisms

    PubMed Central

    Kralova, Jarmila; Kolar, Michal; Kahle, Michal; Truksa, Jaroslav; Lettlova, Sandra; Balusikova, Kamila; Bartunek, Petr

    2017-01-01

    The development of drug resistance is a major problem which often occurs during anticancer chemotherapies. Photodynamic therapy (PDT) has been studied as an alternative treatment modality for drug-resistant tumors, however the question of resistance to PDT and potential cross-resistance with chemotherapy has yet to be fully answered. To investigate the mechanism of resistance to PDT, we developed an in vitro experimental model system in a mouse mammary carcinoma cell line 4T1. We used two ethylene glycol derivatives of tetraphenylporphyrin, and tetraphenylchlorin derivative, temoporfin, as photosensitizers (PS). PDT-resistant clones were obtained by exposure to a set concentration of PS followed by irradiation with increasing light doses. PDT resistance to soluble glycol porphyrins was mediated mainly by increased drug efflux through ABCB1 (P-glycoprotein) as we demonstrated by specific ABCB1 knockdown experiments, which in turn rescued the sensitivity of resistant cells to PDT. In contrast, resistance raised to temoporfin, which is generally more lipophilic than glycol porphyrins, elicited mechanism based on sequestration of the drug to lysosomes. The resistance that is acquired from a particular PS could be overcome by using a different PS, which is not susceptible to the same mechanism(s) of resistance. Elucidation of the underlying mechanisms in various types of resistance might facilitate improvements in PDT treatment design. PMID:28295025

  10. Glycol porphyrin derivatives and temoporfin elicit resistance to photodynamic therapy by different mechanisms.

    PubMed

    Kralova, Jarmila; Kolar, Michal; Kahle, Michal; Truksa, Jaroslav; Lettlova, Sandra; Balusikova, Kamila; Bartunek, Petr

    2017-03-15

    The development of drug resistance is a major problem which often occurs during anticancer chemotherapies. Photodynamic therapy (PDT) has been studied as an alternative treatment modality for drug-resistant tumors, however the question of resistance to PDT and potential cross-resistance with chemotherapy has yet to be fully answered. To investigate the mechanism of resistance to PDT, we developed an in vitro experimental model system in a mouse mammary carcinoma cell line 4T1. We used two ethylene glycol derivatives of tetraphenylporphyrin, and tetraphenylchlorin derivative, temoporfin, as photosensitizers (PS). PDT-resistant clones were obtained by exposure to a set concentration of PS followed by irradiation with increasing light doses. PDT resistance to soluble glycol porphyrins was mediated mainly by increased drug efflux through ABCB1 (P-glycoprotein) as we demonstrated by specific ABCB1 knockdown experiments, which in turn rescued the sensitivity of resistant cells to PDT. In contrast, resistance raised to temoporfin, which is generally more lipophilic than glycol porphyrins, elicited mechanism based on sequestration of the drug to lysosomes. The resistance that is acquired from a particular PS could be overcome by using a different PS, which is not susceptible to the same mechanism(s) of resistance. Elucidation of the underlying mechanisms in various types of resistance might facilitate improvements in PDT treatment design.

  11. Mechanism of quinolone action and resistance.

    PubMed

    Aldred, Katie J; Kerns, Robert J; Osheroff, Neil

    2014-03-18

    Quinolones are one of the most commonly prescribed classes of antibacterials in the world and are used to treat a variety of bacterial infections in humans. Because of the wide use (and overuse) of these drugs, the number of quinolone-resistant bacterial strains has been growing steadily since the 1990s. As is the case with other antibacterial agents, the rise in quinolone resistance threatens the clinical utility of this important drug class. Quinolones act by converting their targets, gyrase and topoisomerase IV, into toxic enzymes that fragment the bacterial chromosome. This review describes the development of the quinolones as antibacterials, the structure and function of gyrase and topoisomerase IV, and the mechanistic basis for quinolone action against their enzyme targets. It will then discuss the following three mechanisms that decrease the sensitivity of bacterial cells to quinolones. Target-mediated resistance is the most common and clinically significant form of resistance. It is caused by specific mutations in gyrase and topoisomerase IV that weaken interactions between quinolones and these enzymes. Plasmid-mediated resistance results from extrachromosomal elements that encode proteins that disrupt quinolone-enzyme interactions, alter drug metabolism, or increase quinolone efflux. Chromosome-mediated resistance results from the underexpression of porins or the overexpression of cellular efflux pumps, both of which decrease cellular concentrations of quinolones. Finally, this review will discuss recent advancements in our understanding of how quinolones interact with gyrase and topoisomerase IV and how mutations in these enzymes cause resistance. These last findings suggest approaches to designing new drugs that display improved activity against resistant strains.

  12. Mechanism of Quinolone Action and Resistance

    PubMed Central

    2015-01-01

    Quinolones are one of the most commonly prescribed classes of antibacterials in the world and are used to treat a variety of bacterial infections in humans. Because of the wide use (and overuse) of these drugs, the number of quinolone-resistant bacterial strains has been growing steadily since the 1990s. As is the case with other antibacterial agents, the rise in quinolone resistance threatens the clinical utility of this important drug class. Quinolones act by converting their targets, gyrase and topoisomerase IV, into toxic enzymes that fragment the bacterial chromosome. This review describes the development of the quinolones as antibacterials, the structure and function of gyrase and topoisomerase IV, and the mechanistic basis for quinolone action against their enzyme targets. It will then discuss the following three mechanisms that decrease the sensitivity of bacterial cells to quinolones. Target-mediated resistance is the most common and clinically significant form of resistance. It is caused by specific mutations in gyrase and topoisomerase IV that weaken interactions between quinolones and these enzymes. Plasmid-mediated resistance results from extrachromosomal elements that encode proteins that disrupt quinolone–enzyme interactions, alter drug metabolism, or increase quinolone efflux. Chromosome-mediated resistance results from the underexpression of porins or the overexpression of cellular efflux pumps, both of which decrease cellular concentrations of quinolones. Finally, this review will discuss recent advancements in our understanding of how quinolones interact with gyrase and topoisomerase IV and how mutations in these enzymes cause resistance. These last findings suggest approaches to designing new drugs that display improved activity against resistant strains. PMID:24576155

  13. Herceptin resistance database for understanding mechanism of resistance in breast cancer patients.

    PubMed

    Ahmad, Sahil; Gupta, Sudheer; Kumar, Rahul; Varshney, Grish C; Raghava, Gajendra P S

    2014-03-27

    Monoclonal antibody Trastuzumab/Herceptin is considered as frontline therapy for Her2-positive breast cancer patients. However, it is not effective against several patients due to acquired or de novo resistance. In last one decade, several assays have been performed to understand the mechanism of Herceptin resistance with/without supplementary drugs. This manuscript describes a database HerceptinR, developed for understanding the mechanism of resistance at genetic level. HerceptinR maintains information about 2500 assays performed against various breast cancer cell lines (BCCs), for improving sensitivity of Herceptin with or without supplementary drugs. In order to understand Herceptin resistance at genetic level, we integrated genomic data of BCCs that include expression, mutations and copy number variations in different cell lines. HerceptinR will play a vital role in i) designing biomarkers to identify patients eligible for Herceptin treatment and ii) identification of appropriate supplementary drug for a particular patient. HerceptinR is available at http://crdd.osdd.net/raghava/herceptinr/.

  14. Role of Acinetobacter baumannii UmuD homologs in antibiotic resistance acquired through DNA damage-induced mutagenesis.

    PubMed

    Aranda, Jesús; López, Mario; Leiva, Enoy; Magán, Andrés; Adler, Ben; Bou, Germán; Barbé, Jordi

    2014-01-01

    The role of Acinetobacter baumannii ATCC 17978 UmuDC homologs A1S_0636-A1S_0637, A1S_1174-A1S_1173, and A1S_1389 (UmuDAb) in antibiotic resistance acquired through UV-induced mutagenesis was evaluated. Neither the growth rate nor the UV-related survival of any of the three mutants was significantly different from that of the wild-type parental strain. However, all mutants, and especially the umuDAb mutant, were less able to acquire resistance to rifampin and streptomycin through the activities of their error-prone DNA polymerases. Furthermore, in the A. baumannii mutant defective in the umuDAb gene, the spectrum of mutations included a dramatic reduction in the frequency of transition mutations, the mutagenic signature of the DNA polymerase V encoded by umuDC.

  15. Current role of community-acquired methicillin-resistant Staphylococcus aureus among children with skin and soft tissue infections.

    PubMed

    Teran, Carlos G; Sura, Sunitha; Mohamed, Tarek; Lin, Thant; Meadows, Marsha; Cynthia, Donkor; Wong, Sze H

    2012-01-02

    Community-acquired methicillin-resistant Staphylococcus aureus has become a well-established pathogen with alarming rates during the last decade. The current situation of this bacteria in pediatric infections is very limited and motivated us to conduct this study. This is a retrospective and analytical study including patients less than 18 years of age with the diagnosis of skin or soft tissue infections in 2008 and 2009 meeting the criteria of Community-acquired infection. A prevalence of 41.9% among skin and soft tissue infections was found. Inducible resistance to clindamycin was detected in 1.3% of the strains and the infection shows a seasonal predilection for summer (P=0.003); 57.8% of the cases required hospitalization with a mean stay of 3.3±2.5 days. The susceptibility to clindamycin and co-trimoxazole is 88 and 97% respectively. The resistance to erythromycin has reached 92%. The main diagnoses at presentation was gluteal abscess plus cellulitis (34.2%).The prevalence of CA-MRSA is trending up and seems to become a large burden for the health system in our community. Clindamycin is still an excellent option in the community setting since inducible clindamycin resistance is extremely low in this community. Co-trimoxazole should be kept as a reserved drug to avoid the rapid resurgence resistance in the community.

  16. Molecular mechanisms of resistance to the EGFR monoclonal antibody cetuximab

    PubMed Central

    Brand, Toni M; Iida, Mari

    2011-01-01

    The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase belonging to the HER family of receptor tyrosine kinases. Receptor activation upon ligand binding leads to down stream activation of the PI3K/AKT, RAS/RAF/MEK/ERK and PLCγ/PKC pathways that influence cell proliferation, survival and the metastatic potential of tumor cells. Increased activation by gene amplification, protein overexpression or mutations of the EGFR has been identified as an etiological factor in a number of human epithelial cancers (e.g., NSCLC, CRC, glioblastoma and breast cancer). Therefore, targeting the EGFR has been intensely pursued as a cancer treatment strategy over the last two decades. To date, five EGFR inhibitors, including three small molecule tyrosine kinase inhibitors (TKIs) and two monoclonal antibodies have gained FDA approval for use in oncology. Both approaches to targeting the EGFR have shown clinical promise and the anti-EGFR antibody cetuximab is used to treat HNSCC and CRC. Despite clinical gains arising from use of cetuximab, both intrinsic resistance and the development of acquired resistance are now well recognized. In this review we focus on the biology of the EGFR, the role of EGFR in human cancer, the development of antibody-based anti-EGFR therapies and a summary of their clinical successes. Further, we provide an in depth discussion of described molecular mechanisms of resistance to cetuximab and potential strategies to circumvent this resistance. PMID:21293176

  17. Molecular Mechanisms of Resistance and Toxicity Associated with Platinating Agents

    PubMed Central

    Rabik, Cara A.; Dolan, M. Eileen

    2007-01-01

    Platinating agents, including cisplatin, carboplatin, and oxaliplatin, have been used clinically for nearly thirty years as part of the treatment of many types of cancers, including head and neck, testicular, ovarian, cervical, lung, colorectal and relapsed lymphoma. The cytotoxic lesion of platinating agents is thought to be the platinum intrastrand crosslink that forms on DNA, although treatment activates a number of signal transduction pathways. Treatment with these agents is characterized by resistance, both acquired and intrinsic. This resistance can be caused by a number of cellular adaptations, including reduced uptake, inactivation by glutathione and other anti-oxidants, and increased levels of DNA repair or DNA tolerance. Here we investigate the pathways that treatment with platinating agents activate, the mechanisms of resistance, potential candidate genes involved in the development of resistance, and associated clinical toxicities. Although the purpose of this review is to provide an overview of cisplatin, carboplatin, and oxaliplatin, we have focused primarily on preclinical data that has clinical relevance generated over the past five years. PMID:17084534

  18. Molecular mechanisms of resistance to the EGFR monoclonal antibody cetuximab.

    PubMed

    Brand, Toni M; Iida, Mari; Wheeler, Deric L

    2011-05-01

    The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase belonging to the HER family of receptor tyrosine kinases. Receptor activation upon ligand binding leads to down stream activation of the PI3K/AKT, RAS/RAF/MEK/ERK and PLCγ/PKC pathways that influence cell proliferation, survival and the metastatic potential of tumor cells. Increased activation by gene amplification, protein overexpression or mutations of the EGFR has been identified as an etiological factor in a number of human epithelial cancers (e.g., NSCLC, CRC, glioblastoma and breast cancer). Therefore, targeting the EGFR has been intensely pursued as a cancer treatment strategy over the last two decades. To date, five EGFR inhibitors, including three small molecule tyrosine kinase inhibitors (TKIs) and two monoclonal antibodies have gained FDA approval for use in oncology. Both approaches to targeting the EGFR have shown clinical promise and the anti-EGFR antibody cetuximab is used to treat HNSCC and CRC. Despite clinical gains arising from use of cetuximab, both intrinsic resistance and the development of acquired resistance are now well recognized. In this review we focus on the biology of the EGFR, the role of EGFR in human cancer, the development of antibody-based anti-EGFR therapies and a summary of their clinical successes. Further, we provide an in depth discussion of described molecular mechanisms of resistance to cetuximab and potential strategies to circumvent this resistance.

  19. Antimicrobial Resistance Among Uropathogens That Cause Childhood Community-acquired Urinary Tract Infections in Central Israel.

    PubMed

    Yakubov, Renata; van den Akker, Machiel; Machamad, Kaba; Hochberg, Amit; Nadir, Erez; Klein, Adi

    2017-01-01

    In this retrospective study 829 positive urine cultures were analyzed. Escherichia coli bacterium was the leading uropathogen (86%). Almost 60% were resistant to ampicillin and first generation cephalosporins, and about 30% of them resistant to amoxicillin-clavulanic acid and trimethoprim-sulfamethoxazole. Almost none of them were resistant to second and third generation cephalosporins, aminoglycosides, ciprofloxacin or nitrofurantoin.

  20. Origin and Evolution of Antibiotic Resistance: The Common Mechanisms of Emergence and Spread in Water Bodies

    PubMed Central

    Lupo, Agnese; Coyne, Sébastien; Berendonk, Thomas Ulrich

    2011-01-01

    The environment, and especially freshwater, constitutes a reactor where the evolution and the rise of new resistances occur. In water bodies such as waste water effluents, lakes, and rivers or streams, bacteria from different sources, e.g., urban, industrial, and agricultural waste, probably selected by intensive antibiotic usage, are collected and mixed with environmental species. This may cause two effects on the development of antibiotic resistances: first, the contamination of water by antibiotics or other pollutants lead to the rise of resistances due to selection processes, for instance, of strains over-expressing broad range defensive mechanisms, such as efflux pumps. Second, since environmental species are provided with intrinsic antibiotic resistance mechanisms, the mixture with allochthonous species is likely to cause genetic exchange. In this context, the role of phages and integrons for the spread of resistance mechanisms appears significant. Allochthonous species could acquire new resistances from environmental donors and introduce the newly acquired resistance mechanisms into the clinics. This is illustrated by clinically relevant resistance mechanisms, such as the fluoroquinolones resistance genes qnr. Freshwater appears to play an important role in the emergence and in the spread of antibiotic resistances, highlighting the necessity for strategies of water quality improvement. We assume that further knowledge is needed to better understand the role of the environment as reservoir of antibiotic resistances and to elucidate the link between environmental pollution by anthropogenic pressures and emergence of antibiotic resistances. Only an integrated vision of these two aspects can provide elements to assess the risk of spread of antibiotic resistances via water bodies and suggest, in this context, solutions for this urgent health issue. PMID:22303296

  1. Biology of Acinetobacter baumannii: Pathogenesis, Antibiotic Resistance Mechanisms, and Prospective Treatment Options.

    PubMed

    Lee, Chang-Ro; Lee, Jung Hun; Park, Moonhee; Park, Kwang Seung; Bae, Il Kwon; Kim, Young Bae; Cha, Chang-Jun; Jeong, Byeong Chul; Lee, Sang Hee

    2017-01-01

    Acinetobacter baumannii is undoubtedly one of the most successful pathogens responsible for hospital-acquired nosocomial infections in the modern healthcare system. Due to the prevalence of infections and outbreaks caused by multi-drug resistant A. baumannii, few antibiotics are effective for treating infections caused by this pathogen. To overcome this problem, knowledge of the pathogenesis and antibiotic resistance mechanisms of A. baumannii is important. In this review, we summarize current studies on the virulence factors that contribute to A. baumannii pathogenesis, including porins, capsular polysaccharides, lipopolysaccharides, phospholipases, outer membrane vesicles, metal acquisition systems, and protein secretion systems. Mechanisms of antibiotic resistance of this organism, including acquirement of β-lactamases, up-regulation of multidrug efflux pumps, modification of aminoglycosides, permeability defects, and alteration of target sites, are also discussed. Lastly, novel prospective treatment options for infections caused by multi-drug resistant A. baumannii are summarized.

  2. Biology of Acinetobacter baumannii: Pathogenesis, Antibiotic Resistance Mechanisms, and Prospective Treatment Options

    PubMed Central

    Lee, Chang-Ro; Lee, Jung Hun; Park, Moonhee; Park, Kwang Seung; Bae, Il Kwon; Kim, Young Bae; Cha, Chang-Jun; Jeong, Byeong Chul; Lee, Sang Hee

    2017-01-01

    Acinetobacter baumannii is undoubtedly one of the most successful pathogens responsible for hospital-acquired nosocomial infections in the modern healthcare system. Due to the prevalence of infections and outbreaks caused by multi-drug resistant A. baumannii, few antibiotics are effective for treating infections caused by this pathogen. To overcome this problem, knowledge of the pathogenesis and antibiotic resistance mechanisms of A. baumannii is important. In this review, we summarize current studies on the virulence factors that contribute to A. baumannii pathogenesis, including porins, capsular polysaccharides, lipopolysaccharides, phospholipases, outer membrane vesicles, metal acquisition systems, and protein secretion systems. Mechanisms of antibiotic resistance of this organism, including acquirement of β-lactamases, up-regulation of multidrug efflux pumps, modification of aminoglycosides, permeability defects, and alteration of target sites, are also discussed. Lastly, novel prospective treatment options for infections caused by multi-drug resistant A. baumannii are summarized. PMID:28348979

  3. Systemic acquired resistance in Cavendish banana induced by infection with an incompatible strain of Fusarium oxysporum f. sp. cubense.

    PubMed

    Wu, Yuanli; Yi, Ganjun; Peng, Xinxiang; Huang, Bingzhi; Liu, Ee; Zhang, Jianjun

    2013-07-15

    Fusarium wilt of banana is caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc). The fact that there are no economically viable biological, chemical, or cultural measures of controlling the disease in an infected field leads to search for alternative strategies involving activation of the plant's innate defense system. The mechanisms underlying systemic acquired resistance (SAR) are much less understood in monocots than in dicots. Since systemic protection of plants by attenuated or avirulent pathogens is a typical SAR response, the establishment of a biologically induced SAR model in banana is helpful to investigate the mechanism of SAR to Fusarium wilt. This paper described one such model using incompatible Foc race 1 to induce resistance against Foc tropical race 4 in an in vitro pathosystem. Consistent with the observation that the SAR provided the highest level of protection when the time interval between primary infection and challenge inoculation was 10d, the activities of defense-related enzymes such as phenylalanine ammonia lyase (PAL, EC 4.3.1.5), peroxidase (POD, EC 1.11.1.7), polyphenol oxidase (PPO, EC 1.14.18.1), and superoxide dismutase (SOD, EC 1.15.1.1) in systemic tissues also reached the maximum level and were 2.00-2.43 times higher than that of the corresponding controls on the tenth day. The total salicylic acid (SA) content in roots of banana plantlets increased from about 1 to more than 5 μg g⁻¹ FW after the second leaf being inoculated with Foc race 1. The systemic up-regulation of MaNPR1A and MaNPR1B was followed by the second up-regulation of PR-1 and PR-3. Although SA and jasmonic acid (JA)/ethylene (ET) signaling are mostly antagonistic, systemic expression of PR genes regulated by different signaling pathways were simultaneously up-regulated after primary infection, indicating that both pathways are involved in the activation of the SAR.

  4. Induced systemic resistance (ISR) in plants: mechanism of action.

    PubMed

    Choudhary, Devendra K; Prakash, Anil; Johri, B N

    2007-12-01

    Plants possess a range of active defense apparatuses that can be actively expressed in response to biotic stresses (pathogens and parasites) of various scales (ranging from microscopic viruses to phytophagous insect). The timing of this defense response is critical and reflects on the difference between coping and succumbing to such biotic challenge of necrotizing pathogens/parasites. If defense mechanisms are triggered by a stimulus prior to infection by a plant pathogen, disease can be reduced. Induced resistance is a state of enhanced defensive capacity developed by a plant when appropriately stimulated. Systemic acquired resistance (SAR) and induced systemic resistance (ISR) are two forms of induced resistance wherein plant defenses are preconditioned by prior infection or treatment that results in resistance against subsequent challenge by a pathogen or parasite. Selected strains of plant growth-promoting rhizobacteria (PGPR) suppress diseases by antagonism between the bacteria and soil-borne pathogens as well as by inducing a systemic resistance in plant against both root and foliar pathogens. Rhizobacteria mediated ISR resembles that of pathogen induced SAR in that both types of induced resistance render uninfected plant parts more resistant towards a broad spectrum of plant pathogens. Several rhizobacteria trigger the salicylic acid (SA)-dependent SAR pathway by producing SA at the root surface whereas other rhizobacteria trigger different signaling pathway independent of SA. The existence of SA-independent ISR pathway has been studied in Arabidopsis thaliana, which is dependent on jasmonic acid (JA) and ethylene signaling. Specific Pseudomonas strains induce systemic resistance in viz., carnation, cucumber, radish, tobacco, and Arabidopsis, as evidenced by an enhanced defensive capacity upon challenge inoculation. Combination of ISR and SAR can increase protection against pathogens that are resisted through both pathways besides extended protection to a

  5. Ligand-associated ERBB2/3 activation confers acquired resistance to FGFR inhibition in FGFR3-dependent cancer cells.

    PubMed

    Wang, J; Mikse, O; Liao, R G; Li, Y; Tan, L; Janne, P A; Gray, N S; Wong, K-k; Hammerman, P S

    2015-04-23

    Somatic alterations of fibroblast growth factor receptors (FGFRs) have been described in a wide range of malignancies. A number of anti-FGFR therapies are currently under investigation in clinical trials for subjects with FGFR gene amplifications, mutations and translocations. Here, we develop cell line models of acquired resistance to FGFR inhibition by exposure of cell lines harboring FGFR3 gene amplification and translocation to the selective FGFR inhibitor BGJ398 and multitargeted FGFR inhibitor ponatinib. We show that the acquisition of resistance is rapid, reversible and characterized by an epithelial to mesenchymal transition and a switch from dependency on FGFR3 to ERBB family members. Acquired resistance was associated with demonstrable changes in gene expression including increased production of ERBB2/3 ligands, which were sufficient to drive resistance in the setting of FGFR3 dependency but not dependency on other FGFR family members. These data support the concept that activation of ERBB family members is sufficient to bypass dependency on FGFR3 and suggest that concurrent inhibition of these two pathways may be desirable when targeting FGFR3-dependent cancers.

  6. Apparent Acquired Resistance by a Weevil to Its Parasitoid Is Influenced by Host Plant

    PubMed Central

    Goldson, Stephen L.; Tomasetto, Federico

    2016-01-01

    on parasitism rates under any treatment conditions suggesting that plant architecture may not be contributing to the underlying mechanism resulting in different rates of parasitism. The evolutionary implications of what appears to be plant-mediated resistance of L. bonariensis to parasitism by M. hyperodae are discussed. PMID:27602040

  7. Acquired multi-azole resistance in Candida tropicalis during persistent urinary tract infection in a dog.

    PubMed

    Álvarez-Pérez, Sergio; García, Marta E; Cutuli, María Teresa; Fermín, María Luisa; Daza, María Ángeles; Peláez, Teresa; Blanco, José L

    2016-03-01

    Multi-azole resistance acquisition by Candida tropicalis after prolonged antifungal therapy in a dog with urinary candidiasis is reported. Pre- and post-azole treatment isolates were clonally related and had identical silent mutations in the ERG11 gene, but the latter displayed increased azole minimum inhibitory concentrations. A novel frameshift mutation in ERG3 was found in some isolates recovered after resistance development, so it appears unlikely that this mutation is responsible for multi-azole resistance.

  8. Cancer Cells Acquire Mitotic Drug Resistance Properties Through Beta I-Tubulin Mutations and Alterations in the Expression of Beta-Tubulin Isotypes

    PubMed Central

    Cheung, Chun Hei Antonio; Wu, Su-Ying; Lee, Tian-Ren; Chang, Chi-Yen; Wu, Jian-Sung; Hsieh, Hsing-Pang; Chang, Jang-Yang

    2010-01-01

    Background Anti-mitotic compounds (microtubule de-stabilizers) such as vincristine and vinblastine have been shown clinically successful in treating various cancers. However, development of drug-resistance cells limits their efficacies in clinical situations. Therefore, experiments were performed to determine possible drug resistance mechanisms related to the application of anti-mitotic cancer therapy. Principal Findings A KB-derived microtubule de-stabilizer-resistant KB-L30 cancer cell line was generated for this study. KB-L30 cells showed cross-resistance to various microtubule de-stabilizers including BPR0L075, vincristine and colchicine through multiple-drug resistant (MDR)-independent mechanisms. Surprisingly, KB-L30 cells showed hyper-sensitivity to the microtubule-stabilizer, paclitaxel. Results of the RT-PCR analysis revealed that expression of both class II and III β-tubulin was down-regulated in KB-L30 cells as compared to its parental KB cancer cells. In addition, DNA sequencing analysis revealed six novel mutation sites present in exon four of the βI-tubulin gene. Computational modeling indicated that a direct relationship exists between βI-tubulin mutations and alteration in the microtubule assembly and dynamic instability in KB-L30 cells and this predicted model was supported by an increased microtubule assembly and reduced microtubule dynamic instability in KB-L30 cells, as shown by Western blot analysis. Conclusions and Significance Our study demonstrated that these novel mutations in exon four of the βI-tubulin induced resistance to microtubule de-stabilizers and hyper-sensitivity to microtubule stabilizer through an alteration in the microtubule assembly and dynamics in cancer cells. Importantly, the current study reveals that cancer cells may acquire drug resistance ability to anti-mitotic compounds through multiple changes in the microtubule networks. This study further provided molecular information in drug selection for patients with

  9. [Antibiotic resistance of strains isolated from community acquired urinary tract infections between 2007 and 2011 in Guelma (Algeria)].

    PubMed

    Bentroki, Ahmed Aimen; Gouri, Adel; Yakhlef, Amina; Touaref, Amel; Gueroudj, Abderrahim; Bensouilah, Takieddine

    2012-01-01

    Urinary tract infections are a real public health problem. They are a frequent reason for consultation as they entail a significant and sometimes inappropriate prescription of antibiotics. This is a retrospective study which involved 1,334 patients between October 2007 and February 2011. Enterobacteriaceae accounted for 85% of isolated bacteria, predominantly Escherichia coli (60%). Gram-positive bacteria account for only 11%. The highest rate of acquired resistance of Escherichia coli was observed with ampicillin (70%). This study give an idea on the rates of antibiotic resistance of the main bacteria involved in urinary tract infections and illustrate the importance of the proper use of antibiotics coupled to surveillance in order to control the spread of these resistances.

  10. Community acquired multi drug resistant Staphylococcus aureus in a rural setting of North Western Ethiopia: a tough challenge.

    PubMed

    Tibebu, Martha; Embiyale, Wondimagegn

    2014-07-01

    Commnunity acquired Methicillin Resistant Staphylococcus aureus species are common causes of skin and soft tissue infections. Foot ulcer of former leprosy patients can be invaded by a multi-microbial infection. Cervicitis is usually caused by certain sexually transmitted agents. Here we report a series of cases of methicillin-resistant Staphylococcus aureus, isolated from two patients presenting with foot ulcer and cervicitis respectively, both in an outpatient or community setting (community onset) in rural North Western Ethiopia. The strains were resistant to all commonly available drugs such as trimethoprim-sulfamethoxazole, ciprofloxacin, erythromycin, chloramphenicol and tetracycline but sensitive to clindamycin. This is the first report of CA-MRSA in the study area.

  11. Resistance Emergence Mechanism and Mechanism of Resistance Suppression by Tobramycin for Cefepime for Pseudomonas aeruginosa

    PubMed Central

    Bonomo, Robert A.; Bahniuk, Nadzeya; Bulitta, Juergen B.; VanScoy, Brian; DeFiglio, Holland; Fikes, Steven; Brown, David; Drawz, Sarah M.; Kulawy, Robert; Louie, Arnold

    2012-01-01

    The panoply of resistance mechanisms in Pseudomonas aeruginosa makes resistance suppression difficult. Defining optimal regimens is critical. Cefepime is a cephalosporin whose 3′ side chain provides some stability against AmpC β-lactamases. We examined the activity of cefepime against P. aeruginosa wild-type strain PAO1 and its isogenic AmpC stably derepressed mutant in our hollow-fiber infection model. Dose-ranging studies demonstrated complete failure with resistance emergence (both isolates). Inoculum range studies demonstrated ultimate failure for all inocula. Lower inocula failed last (10 days to 2 weeks). Addition of a β-lactamase inhibitor suppressed resistance even with the stably derepressed isolate. Tobramycin combination studies demonstrated resistance suppression in both the wild-type and the stably derepressed isolates. Quantitating the RNA message by quantitative PCR demonstrated that tobramycin decreased the message relative to that in cefepime-alone experiments. Western blotting with AmpC-specific antibody for P. aeruginosa demonstrated decreased expression. We concluded that suppression of β-lactamase expression by tobramycin (a protein synthesis inhibitor) was at least part of the mechanism behind resistance suppression. Monte Carlo simulation demonstrated that a regimen of 2 g of cefepime every 8 h plus 7 mg/kg of body weight of tobramycin daily would provide robust resistance suppression for Pseudomonas isolates with cefepime MIC values up to 8 mg/liter and tobramycin MIC values up to 1 mg/liter. For P. aeruginosa resistance suppression, combination therapy is critical. PMID:22005996

  12. Multiple transport systems mediate virus-induced acquired resistance to oxidative stress

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this paper, we report the phenomenon of acquired cross-tolerance to oxidative (UV-C and H2O2) stress in Nicotiana benthamiana plants infected with Potato virus X (PVX) and investigate the functional expression of transport systems in mediating this phenomenon. By combining multiple approaches, we...

  13. Efficacy of moxifloxacin for treatment of penicillin-, macrolide- and multidrug-resistant Streptococcus pneumoniae in community-acquired pneumonia.

    PubMed

    Fogarty, C; Torres, A; Choudhri, S; Haverstock, D; Herrington, J; Ambler, J

    2005-11-01

    This pooled analysis of six prospective, multicentre trials aimed to determine the efficacy of moxifloxacin in community-acquired pneumonia (CAP) due to penicillin-, macrolide- and multidrug-resistant Streptococcus pneumoniae (MDRSP). At a central laboratory, isolates were identified and antimicrobial susceptibility determined (microbroth dilution). MDRSP was defined as resistance > or =3 drug classes. Patients received oral or sequential intravenous/oral 400 mg moxifloxacin once daily for 7-14 days. The primary endpoint was clinical success at test-of-cure for efficacy-valid patients with proven pretherapy S. pneumoniae infection. Of 140 S. pneumoniae isolated (112 respiratory, 28 blood), 23 (16.4%) were penicillin resistant, 26 (18.6%) macrolide resistant and 31 (22.1%) MDRSP. The moxifloxacin MIC90 was 0.25 microg/ml. Clinical cure with moxifloxacin was 95.4% (125/131) overall, and 100% (21/21) for penicillin-, 95.7% (22/23) for macrolide- and 96.4% (27/28) for multidrug-resistant strains. Moxifloxacin provided excellent clinical and bacteriological cure rates in CAP due to drug-resistant pneumococci.

  14. The Systemic Acquired Resistance Regulator OsNPR1 Attenuates Growth by Repressing Auxin Signaling through Promoting IAA-Amido Synthase Expression1[OPEN

    PubMed Central

    2016-01-01

    Systemic acquired resistance is a long-lasting and broad-spectrum disease resistance to pathogens. Our previous study demonstrated that overexpression of NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 (OsNPR1), a master gene for systemic acquired resistance in rice (Oryza sativa), greatly enhanced resistance to bacterial blight caused by Xanthomonas oryzae pv oryzae. However, the growth and development of the OsNPR1 overexpression (OsNPR1-OX) plants were restrained, and the mechanism remained elusive. In this study, we dissected the OsNPR1-induced growth inhibition. We found that the OsNPR1-OX lines displayed phenotypes mimicking auxin-defective mutants, with decreases in root system, seed number and weight, internode elongation, and tiller number. Whole-genome expression analysis revealed that genes related to the auxin metabolism and signaling pathway were differentially expressed between the OsNPR1-OX and wild-type plants. Consistently, the indole-3-acetic acid (IAA) content was decreased and the auxin distribution pattern was altered in OsNPR1-OX plants. Importantly, we found that some GH3 family members, in particular OsGH3.8 coding IAA-amido synthetase, were constitutively up-regulated in OsNPR1-OX plants. Decreased OsGH3.8 expression by RNA interference could partially restore IAA level and largely rescue the restrained growth and development phenotypes but did not affect the disease resistance of OsNPR1-OX plants. Taken together, we revealed that OsNPR1 affects rice growth and development by disrupting the auxin pathway at least partially through indirectly up-regulating OsGH3.8 expression. PMID:27378815

  15. Influence of Infection of Cotton by Rotylenchulus Reniformis and Meloidogyne Incognita on the Production of Enzymes Involved in Systemic Acquired Resistance

    PubMed Central

    Aryal, Sudarshan K.; Davis, Richard F.; Stevenson, Katherine L.; Timper, Patricia; Ji, Pingsheng

    2011-01-01

    Systemic acquired resistance (SAR), which results in enhanced defense mechanisms in plants, can be elicited by virulent and avirulent strains of pathogens including nematodes. Recent studies of nematode reproduction strongly suggest that Meloidogyne incognita and Rotylenchulus reniformis induce SAR in cotton, but biochemical evidence of SAR was lacking. Our objective was to determine whether infection of cotton by M. incognita and R. reniformis increases the levels of P-peroxidase, G-peroxidase, and catalase enzymes which are involved in induced resistance. A series of greenhouse trials was conducted; each trial included six replications of four treatments applied to one of three cotton genotypes in a randomized complete block design. The four treatments were cotton plants inoculated with i) R. reniformis, ii) M. incognita, iii) BTH (Actigard), and iv) a nontreated control. Experiments were conducted on cotton genotypes DP 0935 B2RF (susceptible to both nematodes), LONREN-1 (resistant to R. reniformis), and M-120 RNR (resistant to M. incognita), and the level of P-peroxidase, G-peroxidase, and catalase activity was measured before and 2, 4, 6, 10, and 14 d after treatment application. In all cotton genotypes, activities of all three enzymes were higher (P ≤ 0.05) in leaves of plants infected with M. incognita and R. reniformis than in the leaves of control plants, except that M. incognita did not increase catalase activity on LONREN-1. Increased enzyme activity was usually apparent 6 d after treatment. This study documents that infection of cotton by M. incognita or R. reniformis increases the activity of the enzymes involved in systemic acquired resistance; thereby providing biochemical evidence to substantiate previous reports of nematode-induced SAR in cotton. PMID:23431029

  16. Influence of infection of cotton by rotylenchulus reniformis and meloidogyne incognita on the production of enzymes involved in systemic acquired resistance.

    PubMed

    Aryal, Sudarshan K; Davis, Richard F; Stevenson, Katherine L; Timper, Patricia; Ji, Pingsheng

    2011-09-01

    Systemic acquired resistance (SAR), which results in enhanced defense mechanisms in plants, can be elicited by virulent and avirulent strains of pathogens including nematodes. Recent studies of nematode reproduction strongly suggest that Meloidogyne incognita and Rotylenchulus reniformis induce SAR in cotton, but biochemical evidence of SAR was lacking. Our objective was to determine whether infection of cotton by M. incognita and R. reniformis increases the levels of P-peroxidase, G-peroxidase, and catalase enzymes which are involved in induced resistance. A series of greenhouse trials was conducted; each trial included six replications of four treatments applied to one of three cotton genotypes in a randomized complete block design. The four treatments were cotton plants inoculated with i) R. reniformis, ii) M. incognita, iii) BTH (Actigard), and iv) a nontreated control. Experiments were conducted on cotton genotypes DP 0935 B2RF (susceptible to both nematodes), LONREN-1 (resistant to R. reniformis), and M-120 RNR (resistant to M. incognita), and the level of P-peroxidase, G-peroxidase, and catalase activity was measured before and 2, 4, 6, 10, and 14 d after treatment application. In all cotton genotypes, activities of all three enzymes were higher (P ≤ 0.05) in leaves of plants infected with M. incognita and R. reniformis than in the leaves of control plants, except that M. incognita did not increase catalase activity on LONREN-1. Increased enzyme activity was usually apparent 6 d after treatment. This study documents that infection of cotton by M. incognita or R. reniformis increases the activity of the enzymes involved in systemic acquired resistance; thereby providing biochemical evidence to substantiate previous reports of nematode-induced SAR in cotton.

  17. The Systemic Acquired Resistance Regulator OsNPR1 Attenuates Growth by Repressing Auxin Signaling through Promoting IAA-Amido Synthase Expression.

    PubMed

    Li, Xiaozun; Yang, Dong-Lei; Sun, Li; Li, Qun; Mao, Bizeng; He, Zuhua

    2016-09-01

    Systemic acquired resistance is a long-lasting and broad-spectrum disease resistance to pathogens. Our previous study demonstrated that overexpression of NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 (OsNPR1), a master gene for systemic acquired resistance in rice (Oryza sativa), greatly enhanced resistance to bacterial blight caused by Xanthomonas oryzae pv oryzae However, the growth and development of the OsNPR1 overexpression (OsNPR1-OX) plants were restrained, and the mechanism remained elusive. In this study, we dissected the OsNPR1-induced growth inhibition. We found that the OsNPR1-OX lines displayed phenotypes mimicking auxin-defective mutants, with decreases in root system, seed number and weight, internode elongation, and tiller number. Whole-genome expression analysis revealed that genes related to the auxin metabolism and signaling pathway were differentially expressed between the OsNPR1-OX and wild-type plants. Consistently, the indole-3-acetic acid (IAA) content was decreased and the auxin distribution pattern was altered in OsNPR1-OX plants. Importantly, we found that some GH3 family members, in particular OsGH3.8 coding IAA-amido synthetase, were constitutively up-regulated in OsNPR1-OX plants. Decreased OsGH3.8 expression by RNA interference could partially restore IAA level and largely rescue the restrained growth and development phenotypes but did not affect the disease resistance of OsNPR1-OX plants. Taken together, we revealed that OsNPR1 affects rice growth and development by disrupting the auxin pathway at least partially through indirectly up-regulating OsGH3.8 expression.

  18. Trends and predictors of HIV-1 acquired drug resistance in Minas Gerais, Brazil: 2002-2012.

    PubMed

    Duani, Helena; Aleixo, Agdemir Waleria; Tupinambás, Unaí

    Several studies show that the prevalence of multidrug-resistant HIV-1 virus is declining over time. A retrospective cohort study was carried out to evaluate the trends of drug resistance in antiretroviral treatment-exposed individuals in a state of a middle-income country, Minas Gerais, southeast region of Brazil. We analyzed 2115 HIV-1 sequences from 2002 up to 2012, from 52 cities of Minas Gerais. The groups were analyzed according to the definitions: "IAS - 3 class mutations", if ≥1 drug resistance mutation from IAS 2015 list (DRM) was present in each class; "No fully susceptible drugs" as the absence of any fully susceptible drug in Stanford algorithm; and "GSS≥2″, when a maximum calculated GSS (genotypic susceptibility score) was ≥2 or ≥3, counting only drugs available in Brazil and USA at given calendar years. Time trends of resistance were analyzed by Cochran-Armitage test. We observed a decrease in the rate resistance mutations for PI, NRTI, "IAS - 3 class mutations", and "No fully susceptible drugs" over these 11 years, from 69.2% to 20.7%, 92.3% to 90.2%, 46.2% to 22.5%, and 12.8% to 5.7%, respectively (p<0.05). Resistance to NNRTI increased from 74.4% to 81.6%, mainly because of K103N mutation. The GSS score ≥2 increased during the years from 35.9% to 87.3% (p<0.001). We demonstrate that resistance to PI and to the three main classes simultaneously are declining, although the number of patients on of antiretroviral therapy has doubled in the last ten years in Brazil (125,000 in 2002 to 400,000 in 2014). Broader resistance testing and the availability of more therapeutic options might have influenced this decline. The increase in NNRTI resistance can limit this class as first line treatment in Brazil in the future.

  19. Genetic basis for natural and acquired resistance to the diarylquinoline R207910 in mycobacteria.

    PubMed

    Petrella, Stephanie; Cambau, Emmanuelle; Chauffour, Aurelie; Andries, Koen; Jarlier, Vincent; Sougakoff, Wladimir

    2006-08-01

    The atpE gene encoding the subunit c of the ATP synthase of Mycobacterium tuberculosis, the target of the new diarylquinoline drug R207910, has been sequenced from in vitro mutants resistant to the drug. The previously reported mutation A63P and a new mutation, I66M, were found. The genetic diversity of atpE in 13 mycobacterial species was also investigated, revealing that the region involved in resistance to R207910 is conserved, except in Mycobacterium xenopi in which the highly conserved residue Ala63 is replaced by Met, a modification that may be associated with the natural resistance of M. xenopi to R207910.

  20. Genetic Basis for Natural and Acquired Resistance to the Diarylquinoline R207910 in Mycobacteria

    PubMed Central

    Petrella, Stephanie; Cambau, Emmanuelle; Chauffour, Aurelie; Andries, Koen; Jarlier, Vincent; Sougakoff, Wladimir

    2006-01-01

    The atpE gene encoding the subunit c of the ATP synthase of Mycobacterium tuberculosis, the target of the new diarylquinoline drug R207910, has been sequenced from in vitro mutants resistant to the drug. The previously reported mutation A63P and a new mutation, I66M, were found. The genetic diversity of atpE in 13 mycobacterial species was also investigated, revealing that the region involved in resistance to R207910 is conserved, except in Mycobacterium xenopi in which the highly conserved residue Ala63 is replaced by Met, a modification that may be associated with the natural resistance of M. xenopi to R207910. PMID:16870785

  1. Update on the prevention and control of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA).

    PubMed

    Skov, Robert; Christiansen, Keryn; Dancer, Stephanie J; Daum, Robert S; Dryden, Matthew; Huang, Yhu-Chering; Lowy, Franklin D

    2012-03-01

    The rapid dissemination of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) since the early 2000s and the appearance of new successful lineages is a matter of concern. The burden of these infections varies widely between different groups of individuals and in different regions of the world. Estimating the total burden of disease is therefore problematic. Skin and soft-tissue infections, often in otherwise healthy young individuals, are the most common clinical manifestation of these infections. The antibiotic susceptibilities of these strains also vary, although they are often more susceptible to 'traditional' antibiotics than related hospital-acquired strains. Preventing the dissemination of these organisms throughout the general population requires a multifaceted approach, including screening and decolonisation, general hygiene and cleaning measures, antibiotic stewardship programmes and, in the future, vaccination. The current evidence on the prevention and control of CA-MRSA is appraised and summarised in this review.

  2. 'Fetal programming' and 'functional teratogenesis': on epigenetic mechanisms and prevention of perinatally acquired lasting health risks.

    PubMed

    Plagemann, Andreas

    2004-01-01

    Alterations of the intrauterine and early postnatal nutritional, metabolic, and hormonal environment may cause predispositions to the development of disorders and diseases in later life. Mechanisms responsible for this perinatally acquired 'malprogramming' still remain unclear. It has long been known, however, that hormones are environment-dependent organizers of the developing 'neuroendocrine-immune network', which regulates all fundamental processes of life. When present in nonphysiological concentrations during critical ontogenetic periods, hormones can therefore also act as 'endogenous functional teratogens'. Fetal and neonatal hyperinsulinism is a pathognomic feature in the offspring of diabetic mothers. Perinatal hyperinsulinism also occurs due to early postnatal overfeeding. Data obtained by our group indicate that elevated insulin concentrations during critical periods of perinatal life may induce a lasting 'malprogramming' of neuroendocrine systems regulating body weight, food intake, and metabolism. Similar characteristics may occur due to perinatal hyperleptinism, hypercortisolism etc. Since mechanisms of early 'programming' of obesity, diabetes, and the metabolic syndrome X are unclear, a complex 'neuroendocrine malprogramming' of the regulation of body weight and metabolism may provide a general etiopathogenetic concept in this context, exemplarily revealing critical new implications for chances and challenges of perinatal preventive medicine in the future.

  3. Constitutive cyclic GMP accumulation in Arabidopsis thaliana compromises systemic acquired resistance induced by an avirulent pathogen by modulating local signals.

    PubMed

    Hussain, Jamshaid; Chen, Jian; Locato, Vittoria; Sabetta, Wilma; Behera, Smrutisanjita; Cimini, Sara; Griggio, Francesca; Martínez-Jaime, Silvia; Graf, Alexander; Bouneb, Mabrouk; Pachaiappan, Raman; Fincato, Paola; Blanco, Emanuela; Costa, Alex; De Gara, Laura; Bellin, Diana; de Pinto, Maria Concetta; Vandelle, Elodie

    2016-11-04

    The infection of Arabidopsis thaliana plants with avirulent pathogens causes the accumulation of cGMP with a biphasic profile downstream of nitric oxide signalling. However, plant enzymes that modulate cGMP levels have yet to be identified, so we generated transgenic A. thaliana plants expressing the rat soluble guanylate cyclase (GC) to increase genetically the level of cGMP and to study the function of cGMP in plant defence responses. Once confirmed that cGMP levels were higher in the GC transgenic lines than in wild-type controls, the GC transgenic plants were then challenged with bacterial pathogens and their defence responses were characterized. Although local resistance was similar in the GC transgenic and wild-type lines, differences in the redox state suggested potential cross-talk between cGMP and the glutathione redox system. Furthermore, large-scale transcriptomic and proteomic analysis highlighted the significant modulation of both gene expression and protein abundance at the infection site, inhibiting the establishment of systemic acquired resistance. Our data indicate that cGMP plays a key role in local responses controlling the induction of systemic acquired resistance in plants challenged with avirulent pathogens.

  4. Constitutive cyclic GMP accumulation in Arabidopsis thaliana compromises systemic acquired resistance induced by an avirulent pathogen by modulating local signals

    PubMed Central

    Hussain, Jamshaid; Chen, Jian; Locato, Vittoria; Sabetta, Wilma; Behera, Smrutisanjita; Cimini, Sara; Griggio, Francesca; Martínez-Jaime, Silvia; Graf, Alexander; Bouneb, Mabrouk; Pachaiappan, Raman; Fincato, Paola; Blanco, Emanuela; Costa, Alex; De Gara, Laura; Bellin, Diana; de Pinto, Maria Concetta; Vandelle, Elodie

    2016-01-01

    The infection of Arabidopsis thaliana plants with avirulent pathogens causes the accumulation of cGMP with a biphasic profile downstream of nitric oxide signalling. However, plant enzymes that modulate cGMP levels have yet to be identified, so we generated transgenic A. thaliana plants expressing the rat soluble guanylate cyclase (GC) to increase genetically the level of cGMP and to study the function of cGMP in plant defence responses. Once confirmed that cGMP levels were higher in the GC transgenic lines than in wild-type controls, the GC transgenic plants were then challenged with bacterial pathogens and their defence responses were characterized. Although local resistance was similar in the GC transgenic and wild-type lines, differences in the redox state suggested potential cross-talk between cGMP and the glutathione redox system. Furthermore, large-scale transcriptomic and proteomic analysis highlighted the significant modulation of both gene expression and protein abundance at the infection site, inhibiting the establishment of systemic acquired resistance. Our data indicate that cGMP plays a key role in local responses controlling the induction of systemic acquired resistance in plants challenged with avirulent pathogens. PMID:27811978

  5. Interplay between intrinsic and acquired resistance to quinolones in Stenotrophomonas maltophilia.

    PubMed

    García-León, Guillermo; Salgado, Fabiola; Oliveros, Juan Carlos; Sánchez, María Blanca; Martínez, José Luis

    2014-05-01

    To analyse whether the mutation-driven resistance-acquisition potential of a given bacterium might be a function of its intrinsic resistome, quinolones were used as selective agents and Stenotrophomonas maltophilia was chosen as a bacterial model. S. maltophilia has two elements - SmQnr and SmeDEF - that are important in intrinsic resistance to quinolones. Using a battery of mutants in which either or both of these elements had been removed, the apparent mutation frequency for quinolone resistance and the phenotype of the selected mutants were found to be related to the intrinsic resistome and also depended on the concentration of the selector. Most mutants had phenotypes compatible with the overexpression of multidrug efflux pump(s); SmeDEF overexpression was the most common cause of quinolone resistance. Whole genome sequencing showed that mutations of the SmeRv regulator, which result in the overexpression of the efflux pump SmeVWX, are the cause of quinolone resistance in mutants not overexpressing SmeDEF. These results indicate that the development of mutation-driven antibiotic resistance is highly dependent on the intrinsic resistome, which, at least for synthetic antibiotics such as quinolones, did not develop as a response to the presence of antibiotics in the natural ecosystems in which S. maltophilia evolved.

  6. Activating adaptive cellular mechanisms of resistance following sublethal cytotoxic chemotherapy: implications for diagnostic microdosing.

    PubMed

    Wurz, Gregory T; DeGregorio, Michael W

    2015-04-01

    As Phase 0 studies have proven to be reasonably predictive of therapeutic dose pharmacokinetics, the application of microdosing has expanded into metabolism, drug-drug interactions and now diagnostics. One potentially serious issue with this application of microdosing that has not been previously discussed is the possibility of activating cellular mechanisms of drug resistance. Here, we provide an overview of Phase 0 microdosing and drug resistance, with an emphasis on cisplatin resistance, followed by a discussion of the potential for inducing acquired resistance to platinum-based or other types of chemotherapy in cancer patients participating in Phase 0 diagnostic microdosing studies. A number of alternative approaches to diagnostic microdosing, such as the human tumor cloning assay and the use of peripheral blood mononuclear cells as a surrogate for measuring DNA adducts, are discussed that would avoid exposing cancer patients to low doses of first-line chemotherapy and the possible risk of triggering cellular mechanisms of acquired resistance. Until it has been established that diagnostic microdosing in cancer patients poses no risk of acquired drug resistance, such studies should be approached with caution.

  7. Continuous administration of bevacizumab plus capecitabine, even after acquired resistance to bevacizumab, restored anti-angiogenic and antitumor effect in a human colorectal cancer xenograft model

    PubMed Central

    Iwai, Toshiki; Sugimoto, Masamichi; Harada, Suguru; Yorozu, Keigo; Kurasawa, Mitsue; Yamamoto, Kaname

    2016-01-01

    Vascular endothelial growth factor (VEGF)-neutralizing therapy with bevacizumab has become increasingly important for treating colorectal cancer. It was demonstrated that second-line chemotherapy together with bevacizumab after disease progression (PD) on first-line therapy including bevacizumab showed clinical benefits in metastatic colorectal and breast cancers (ML18147 trial, TANIA trial). One of the rationales for these trials was that the refractoriness to first-line therapy is caused by resistance to not so much bevacizumab as to the chemotherapeutic agents. Nevertheless, resistance to bevacizumab cannot be ruled out because VEGF-independent angiogenesis has been reported to be a mechanism of resistance to anti-VEGF therapy. In this study, we used a xenograft model with the human colon cancer HT-29 cells to investigate the mechanisms underlying the effect of continued administration of bevacizumab plus capecitabine even after resistance to bevacizumab was acquired. The combination of capecitabine plus bevacizumab exhibited significantly stronger antitumor and anti-angiogenic activities than did monotherapy with either agent. Capecitabine treatment significantly increased the intratumoral VEGF level compared with the control group; however, the combination with bevacizumab neutralized the VEGF. Among angiogenic factors other than VEGF, intratumoral galectin-3, which reportedly promotes angiogenesis both dependent on, and independently of VEGF, was significantly decreased in the capecitabine group and the combination group compared with the control group. In an in vitro experiment, 5-fluorouracil (5-FU), an active metabolite of capecitabine, inhibited galectin-3 production by HT-29 cells. These results suggested that capecitabine has a dual mode of action: namely, inhibition of tumor cell growth and inhibition of galectin-3 production by tumor cells. Thus, capecitabine and bevacizumab may work in a mutually complementary manner in tumor angiogenesis inhibition

  8. Bacterial Etiology and Antibiotic Resistance Profile of Community-Acquired Urinary Tract Infections in a Cameroonian City

    PubMed Central

    Gonsu, Hortense Kamga; Koulla-Shiro, Sinata

    2016-01-01

    Introduction. Community-acquired urinary tract infections (CAUTIs) are usually treated empirically. Geographical variations in etiologic agents and their antibiotic sensitivity patterns are common. Knowledge of antibiotic resistance trends is important for improving evidence-based recommendations for empirical treatment of UTIs. Our aim was to determine the major bacterial etiologies of CAUTIs and their antibiotic resistance patterns in a cosmopolitan area of Cameroon for comparison with prescription practices of local physicians. Methods. We performed a cross-sectional descriptive study at two main hospitals in Yaoundé, collecting a clean-catch mid-stream urine sample from 92 patients having a clinical diagnosis of UTI. The empirical antibiotherapy was noted, and identification of bacterial species was done on CLED agar; antibiotic susceptibility testing was performed using the Kirby-Bauer disc diffusion method. Results. A total of 55 patients had samples positive for a UTI. Ciprofloxacin and amoxicillin/clavulanic acid were the most empirically prescribed antibiotics (30.9% and 23.6%, resp.); bacterial isolates showed high prevalence of resistance to both compounds. Escherichia coli (50.9%) was the most common pathogen, followed by Klebsiella pneumoniae (16.4%). Prevalence of resistance for ciprofloxacin was higher compared to newer quinolones. Conclusions. E. coli and K. pneumoniae were the predominant bacterial etiologies; the prevalence of resistance to commonly prescribed antibiotics was high. PMID:27667998

  9. Emergence of Multidrug-Resistant Campylobacter Species Isolates with a Horizontally Acquired rRNA Methylase

    PubMed Central

    Wang, Yang; Zhang, Maojun; Deng, Fengru; Shen, Zhangqi; Wu, Congming; Zhang, Jianzhong

    2014-01-01

    Antibiotic-resistant Campylobacter constitutes a serious threat to public health, and resistance to macrolides is of particular concern, as this class of antibiotics is the drug of choice for clinical therapy of campylobacteriosis. Very recently, a horizontally transferrable macrolide resistance mediated by the rRNA methylase gene erm(B) was reported in a Campylobacter coli isolate, but little is known about the dissemination of erm(B) among Campylobacter isolates and the association of erm(B)-carrying isolates with clinical disease. To address this question and facilitate the control of antibiotic-resistant Campylobacter, we determined the distribution of erm(B) in 1,554 C. coli and Campylobacter jejuni isolates derived from food-producing animals and clinically confirmed human diarrheal cases. The results revealed that 58 of the examined isolates harbored erm(B) and exhibited high-level resistance to macrolides, and most were recent isolates, derived in 2011-2012. In addition, the erm(B)-positive isolates were all resistant to fluoroquinolones, another clinically important antibiotic used for treating campylobacteriosis. The erm(B) gene is found to be associated with chromosomal multidrug resistance genomic islands (MDRGIs) of Gram-positive origin or with plasmids of various sizes. All MDRGIs were transferrable to macrolide-susceptible C. jejuni by natural transformation under laboratory conditions. Molecular typing of the erm(B)-carrying isolates by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) identified diverse genotypes and outbreak-associated diarrheal isolates. Molecular typing also suggested zoonotic transmission of erm(B)-positive Campylobacter. These findings reveal an emerging and alarming trend of dissemination of erm(B) and MDRGIs in Campylobacter and underscore the need for heightened efforts to control their further spread. PMID:24982085

  10. Quinolone resistant Aeromonas spp. as carriers and potential tracers of acquired antibiotic resistance in hospital and municipal wastewater.

    PubMed

    Varela, Ana Rita; Nunes, Olga C; Manaia, Célia M

    2016-01-15

    Members of the genus Aeromonas are recognized carriers of antibiotic resistance in aquatic environments. However, their importance on the spread of resistance from hospital effluents to the environment is poorly understood. Quinolone resistant Aeromonas spp. (n = 112) isolated from hospital effluent (HE) and from raw (RWW) and treated wastewater (TWW) of the receiving urban wastewater treatment plant (UWTP) were characterized. Species identification and genetic intraspecies diversity were assessed based on the 16S rRNA, cpn60 and gyrB genes sequence analysis. The antibiotic resistance phenotypes and genotypes (qnrA, qnrB, qnrC, qnrD, qnrS, qnrVC; qepA; oqxAB; aac(6′)-Ib-cr; blaOXA; incU) were analyzed in function of the origin and taxonomic group. Most isolates belonged to the species Aeromonas caviae and Aeromonas hydrophila (50% and 41%, respectively). The quinolone and the beta-lactamase resistance genes aac(6′)-Ib-cr and blaOXA, including gene blaOXA-101, identified for the first time in Aeromonas spp., were detected in 58% and 56% of the isolates, respectively, with identical prevalence in HE and UWTP wastewater. In contrast, the gene qnrS2 was observed mainly in isolates from the UWTP (51%) and rarely in HE isolates (3%), suggesting that its origin is not the clinical setting. Bacterial groups and genes that allow the identification of major routes of antibiotic resistance dissemination are valuable tools to control this problem. In this study, it was concluded that members of the genus Aeromonas harboring the genes aac(6′)-Ib-cr and blaOXA are relevant tracers of antibiotic resistance dissemination in wastewater habitats, while those yielding the gene qnrS2 allow the traceability from non-clinical sources.

  11. Preclinical evidence of multiple mechanisms underlying trastuzumab resistance in gastric cancer

    PubMed Central

    Arienti, Chiara; Zanoni, Michele; Pignatta, Sara; Del Rio, Alberto; Carloni, Silvia; Tebaldi, Michela; Tedaldi, Gianluca; Tesei, Anna

    2016-01-01

    HER2-positive advanced gastric cancer patients frequently develop resistance to trastuzumab through mechanisms still poorly understood. In breast cancer, other members of the HER-family are known to be involved in trastuzumab-resistance, as is overexpression of the scaffold protein IQGAP1. In the present work, we investigated acquired resistance to trastuzumab in gastric cancer experimental models. Trastuzumab-resistant (HR) subclones derived from 3 HER2-overexpressing gastric cancer cells were generated and characterized for alterations in HER2-signaling mechanisms by next-generation sequencing, immunohistochemical, western blot and qRT-PCR techniques, and molecular modeling analysis. All subclones showed a reduced growth rate with respect to parental cell lines but each had a different resistance mechanism. In NCI N87 HR cells, characterized by a marked increase in HER2-signaling pathways with respect to the parental cell line, trastuzumab sensitivity was restored when IQGAP1 expression was silenced. AKG HR subclone showed higher HER3 protein expression than the parental line. High nuclear HER4 levels were observed in KKP HR cells. In conclusion, our study revealed that high IQGAP1 expression leads to resistance to trastuzumab in gastric cancer. Furthermore, 2 new mutations of the HER2 gene that may be involved in acquired resistance were identified in AKG HR and KKP HR subclones. PMID:26919099

  12. The multixenobiotic resistance mechanism in aquatic organisms

    SciTech Connect

    Kurelec, B. )

    1992-01-01

    Many aquatic organisms thrive and reproduce in polluted waters. This fact indicates that they are well equipped with a defense system(s) against several toxic xenobiotics simultaneously because water pollution is typically caused by a mixture of a number of pollutants. We have found that the biochemical mechanism underlying such multixenobiotic' resistance in freshwater and marine mussel, in several marine sponges, and in freshwater fish is similar to the mechanism of multidrug resistance (MDR) found in tumor cells that became refractory to treatment with a variety of chemotherapeutic agents. All these organisms possess a verapamil-sensitive potential to bind 2-acetylaminofluorene and vincristine onto membrane vesicles. They all express mRNA for mdr1 gene, and mdr1 protein product, the glycoprotein P170. Finally, in in vivo experiments, the accumulation of xenobiotics is enhanced in all investigated organisms in the presence of verapamil, the inhibitor of the P170 extrusion pump. The knowledge that the presence of one xenobiotic may block the pumping out, and hence accelerating accumulation, of others, may help us to understand and interpret our present and past data on different environmental parameters obtained using indicator organisms.99 references.

  13. What do we know about the mechanisms of aromatase inhibitor resistance?

    PubMed Central

    Chen, Shiuan; Masri, Selma; Wang, Xin; Phung, Sheryl; Yuan, Yate-Ching; Wu, Xiwei

    2007-01-01

    Clinical trials have demonstrated the importance of aromatase inhibitor (AI) therapy in the effective treatment of hormone-dependent breast cancers. Yet, as with all prolonged drug therapy, resistance to aromatase inhibitors does develop. To date, the precise mechanism responsible for resistance to aromatase inhibitors is not completely understood. In this paper, several mechanisms of de novo/intrinsic resistance and acquired resistance to AIs are discussed. These mechanisms are hypothesized based on important findings from a number of laboratories. To better understand this question, our lab has generated, in vitro, breast cancer cell lines that are resistant to aromatase inhibitors. Resistant cell lines were generated over a prolonged period of time using the MCF-7aro (aromatase overexpressed) breast cancer line. These cell lines are resistant to the aromatase inhibitors letrozole, anastrozole and exemestane and the anti-estrogen tamoxifen, for comparison. Two types of resistant cell lines have been generated, those that grow in the presence of Testosterone (T) which is needed for cell growth, and resistant lines that are cultured in the presence of inhibitor only (no T). In addition to functional characterization of aromatase and ERα in these resistant cell lines, microarray analysis has been employed in order to determine differential gene expression within the aromatase inhibitor resistant cell lines versus tamoxifen, in order to better understand the mechanism responsible for AI resistance on a genome-wide scale. We anticipate that our studies will generate important information on the mechanisms of AI resistance. Such information can be valuable for the development of treatment strategies against AI resistant breast cancers. PMID:17055257

  14. Ductus arteriosus aneurysm with community-acquired methicillin-resistant Staphylococcus aureus infection and spontaneous rupture: a potentially fatal quandary.

    PubMed

    Stewart, Audra; Dyamenahalli, Umesh; Greenberg, S Bruce; Drummond-Webb, Jonathan

    2006-06-01

    We present the case of a 6-month-old previously healthy girl who presented with high fever, labored breathing, and an enlarged cardiac silhouette on her chest radiograph. Comprehensive evaluation discovered a ductus arteriosus aneurysm and pericardial effusion with methicillin-resistant Staphylococcus aureus bacteremia. Despite pericardiocentesis and appropriate intravenous antibiotics, there was rapid enlargement of the aneurysm and accumulation of echogenic material within the ductus arteriosus aneurysm. Infected aneurysm rupture was identified during emergency surgery. This infant also had vocal cord paresis, a likely complication of the surgery. The clinical course, diagnosis, and treatment of this patient are discussed. Infection of a ductus arteriosus or an infected ductal arteriosus aneurysm is a rare and potentially fatal clinical entity. In the era of increasing community-acquired methicillin-resistant S aureus infections, this is a diagnosis that requires a high index of suspicion.

  15. Mechanisms of action of systemic antibiotics used in periodontal treatment and mechanisms of bacterial resistance to these drugs

    PubMed Central

    SOARES, Geisla Mary Silva; FIGUEIREDO, Luciene Cristina; FAVERI, Marcelo; CORTELLI, Sheila Cavalca; DUARTE, Poliana Mendes; FERES, Magda

    2012-01-01

    Antibiotics are important adjuncts in the treatment of infectious diseases, including periodontitis. The most severe criticisms to the indiscriminate use of these drugs are their side effects and, especially, the development of bacterial resistance. The knowledge of the biological mechanisms involved with the antibiotic usage would help the medical and dental communities to overcome these two problems. Therefore, the aim of this manuscript was to review the mechanisms of action of the antibiotics most commonly used in the periodontal treatment (i.e. penicillin, tetracycline, macrolide and metronidazole) and the main mechanisms of bacterial resistance to these drugs. Antimicrobial resistance can be classified into three groups: intrinsic, mutational and acquired. Penicillin, tetracycline and erythromycin are broad-spectrum drugs, effective against gram-positive and gram-negative microorganisms. Bacterial resistance to penicillin may occur due to diminished permeability of the bacterial cell to the antibiotic; alteration of the penicillin-binding proteins, or production of β-lactamases. However, a very small proportion of the subgingival microbiota is resistant to penicillins. Bacteria become resistant to tetracyclines or macrolides by limiting their access to the cell, by altering the ribosome in order to prevent effective binding of the drug, or by producing tetracycline/macrolide-inactivating enzymes. Periodontal pathogens may become resistant to these drugs. Finally, metronidazole can be considered a prodrug in the sense that it requires metabolic activation by strict anaerobe microorganisms. Acquired resistance to this drug has rarely been reported. Due to these low rates of resistance and to its high activity against the gram-negative anaerobic bacterial species, metronidazole is a promising drug for treating periodontal infections. PMID:22858695

  16. Mechanisms of action of systemic antibiotics used in periodontal treatment and mechanisms of bacterial resistance to these drugs.

    PubMed

    Soares, Geisla Mary Silva; Figueiredo, Luciene Cristina; Faveri, Marcelo; Cortelli, Sheila Cavalca; Duarte, Poliana Mendes; Feres, Magda

    2012-01-01

    Antibiotics are important adjuncts in the treatment of infectious diseases, including periodontitis. The most severe criticisms to the indiscriminate use of these drugs are their side effects and, especially, the development of bacterial resistance. The knowledge of the biological mechanisms involved with the antibiotic usage would help the medical and dental communities to overcome these two problems. Therefore, the aim of this manuscript was to review the mechanisms of action of the antibiotics most commonly used in the periodontal treatment (i.e. penicillin, tetracycline, macrolide and metronidazole) and the main mechanisms of bacterial resistance to these drugs. Antimicrobial resistance can be classified into three groups: intrinsic, mutational and acquired. Penicillin, tetracycline and erythromycin are broad-spectrum drugs, effective against gram-positive and gram-negative microorganisms. Bacterial resistance to penicillin may occur due to diminished permeability of the bacterial cell to the antibiotic; alteration of the penicillin-binding proteins, or production of β-lactamases. However, a very small proportion of the subgingival microbiota is resistant to penicillins. Bacteria become resistant to tetracyclines or macrolides by limiting their access to the cell, by altering the ribosome in order to prevent effective binding of the drug, or by producing tetracycline/macrolide-inactivating enzymes. Periodontal pathogens may become resistant to these drugs. Finally, metronidazole can be considered a prodrug in the sense that it requires metabolic activation by strict anaerobe microorganisms. Acquired resistance to this drug has rarely been reported. Due to these low rates of resistance and to its high activity against the gram-negative anaerobic bacterial species, metronidazole is a promising drug for treating periodontal infections.

  17. Etiology and antibiotic resistance patterns of community-acquired urinary tract infections in J N M C Hospital Aligarh, India

    PubMed Central

    Akram, Mohammed; Shahid, Mohammed; Khan, Asad U

    2007-01-01

    Background Urinary tract infections (UTIs) remain the common infections diagnosed in outpatients as well as hospitalized patients. Current knowledge on antimicrobial susceptibility pattern is essential for appropriate therapy. Extended-Spectrum beta-Lactamase (ESBL) producing bacteria may not be detected by routine disk diffusion susceptibility test, leading to inappropriate use of antibiotics and treatment failure. The aim of this study was to determine the distribution and antibiotic susceptibility patterns of bacterial strains isolated from patients with community acquired urinary tract infections (UTIs) at Aligarh hospital in India as well as identification of ESBL producers in the population of different uropathogens. Methods Urinary isolates from symptomatic UTI cases attending to the JN Medical College and hospital at Aligarh were identified by conventional methods. Antimicrobial susceptibility testing was performed by Kirby Bauer's disc diffusion method. Isolates resistant to third generation cephalosporin were tested for ESBL production by double disk synergy test method. Results Of the 920 tested sample 100 samples showed growth of pathogens among which the most prevalent were E. coli (61%) followed by Klebsiella spp (22%). The majority (66.66%) of the isolates were from female while the remaining were from male. Among the gram-negative enteric bacilli high prevalence of resistance was observed against ampicillin and co-trimoxazole. Most of the isolates were resistant to 4 or more number of antibiotics. Forty two percent of isolates were detected to produce ESBL among which 34.42 % were E. coli isolates. Conclusion This study revealed that E. coli was the predominant bacterial pathogen of community acquired UTIs in Aligarh, India. It also demonstrated an increasing resistance to Co-trimoxazole and production of extended spectrum β-lactamase among UTI pathogens in the community. This study is useful for clinician in order to improve the empiric treatment

  18. [Investigation of nasal carriage of community-acquired methicillin resistant Staphylococcus aureus in primary and high school students].

    PubMed

    Ozgüven, Atalay; Tünger, Ozlem; Cetin, Ciğdem Banu; Dinç, Gönül

    2008-10-01

    The aim of this study was to evaluate the carriage rate and risk factors of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) among the students in Manisa, Turkey. A total of 2015 students (1012 from the last phase of high schools and 1003 from the first phase of primary schools) were included in the study. None of the students had nasal MRSA carriage. Methicillin-sensitive S. aureus (MSSA) colonization rate was 14.7% (296/2015). Nasal carriage of MSSA was significantly higher in the primary school students (17.8%) than the high school students (11.6%) (p < 0.001). MSSA carriage was also higher in students of higher socioeconomical status than the students of lower status (p < 0.05). A statistically significant relationship was not determined between the nasal carriage and the risk factors (history of hospitalisation or surgical operation in the previous one year, use of antibiotics or history of skin/soft tissue infection in the last 6 months, presence of children < 15-years-old in the family, presence of healthcare workers in the same house, living in a crowded house). Penicillin and erythromycin resistance was found in 93.6% and 14.2% of MSSA strains, respectively. No resistance was detected against ciprofloxacin, co-trimoxazole, linezolid and vancomycin. There was a statistically significant difference between erythromycin resistance and antibiotic use within the last six months and the number of family members (p < 0.05). In conclusion, current treatment regimens still seem to be affective and safe for the empirical treatment of community-acquired S. aureus infections. Although CA-MRSA infections seem not to be a serious threat in our region yet, it is essential to carry out prevalence studies in the different populations of the community.

  19. Cellular prion protein acquires resistance to proteolytic degradation following copper ion binding.

    PubMed

    Kuczius, Thorsten; Buschmann, Anne; Zhang, Wenlan; Karch, Helge; Becker, Karsten; Peters, Georg; Groschup, Martin H

    2004-08-01

    The conversion of cellular prion protein (PrP(C)) into its pathological isoform (PrP(Sc)) conveys an increase in hydrophobicity and induces a partial resistance to proteinase K (PK). Interestingly, co-incubation with high copper ion concentrations also modifies the solubility of PrP(c) and induces a partial PK resistance which was reminiscent of PrP(Sc). However, concerns were raised whether this effect was not due to a copper-induced inhibition of the PK itself. We have therefore analyzed the kinetics of the formation of PK-resistant PrP(C) and excluded possible interference effects by removing unbound copper ions prior to the addition of PK by methanol precipitation or immobilization of PrP(C) followed by washing steps. We found that preincubation of PrPc with copper ions at concentrations as low as 50 microM indeed rendered these proteins completely PK resistant, while control substrates were proteolyzed. No other divalent cations induced a similar effect. However, in addition to this specific stabilizing effect on PrP(C), higher copper ion concentrations in solution (>200 microM) directly blocked the enzymatic activity of PK, possibly by replacing the Ca2+ ions in the active center of the enzyme. Therefore, as a result of this inhibition the proteolytic degradation of PrP(C) as well as PrP(Sc) molecules was suppressed.

  20. Acquired resistance with epigenetic alterations under long-term anti-angiogenic therapy for hepatocellular carcinoma.

    PubMed

    Ohata, Yoshiteru; Shimada, Shu; Akiyama, Yoshimitsu; Mogushi, Kaoru; Nakao, Keisuke; Matsumura, Satoshi; Aihara, Arihiro; Mitsunori, Yusuke; Ban, Daisuke; Ochiai, Takanori; Kudo, Atsushi; Arii, Shigeki; Tanabe, Minoru; Tanaka, Shinji

    2017-02-28

    Anti-angiogenic therapy is initially effective for several solid tumors including hepatocellular carcinoma (HCC); however, they finally relapse and progress, resulting in poor prognosis. We here established in vivo drug-tolerant subclones of human HCC cells by long-term treatment with vascular endothelial growth factor receptor (VEGFR) inhibitor and serial transplantation in immunocompromised mice (total 12 months), and then compared them with the parental cells in molecular and biological features. Gene expression profiles elucidated a G-actin monomer binding protein thymosin β 4 (Tβ4) as one of the genes enriched in the resistant cancer cells relative to the initially sensitive ones. Highlighting epigenetic alterations involved in drug resistance, we revealed that Tβ4 could be aberrantly expressed following demethylation of DNA and active modification of histone H3 at the promoter region. Ectopic overexpression of Tβ4 in HCC cells could significantly enhance sphere-forming capacities and infiltrating phenotypes in vitro, and promote growth of tumors refractory to the VEGFR mutltikinase inhibitor sorafenib in vivo. Clinically, sorafenib failed to improve the progression-free survival in patients with Tβ4-high HCC, indicating that Tβ4 expression could be available as a surrogate marker of susceptibility to this drug. This study suggests that Tβ4 expression triggered by epigenetic alterations could contribute to the development of resistance to anti-angiogenic therapy by the acquisition of stemness, and that epigenetic control might be one of the key targets to regulate the resistance in HCC.

  1. Acquired resistance of malarial parasites against artemisinin-based drugs: social and economic impacts.

    PubMed

    Porter-Kelley, Johanna M; Cofie, Joann; Jean, Sophonie; Brooks, Mark E; Lassiter, Mia; Mayer, Dc Ghislaine

    2010-01-01

    Malaria, a disease of poverty and high morbidity and mortality in the tropical world, has led to a worldwide search for control measures. To that end, good antimalarial chemotherapies have been difficult to find in the global market and those that seem to be most effective are rapidly becoming ineffective due to the emergence and spread of drug resistance. Artemisinin, a very effective yet expensive antimalarial, has quickly become the recommended drug of choice when all other possibilities fail. However, for all its promise as the next great antimalarial, the outlook is bleak. Resistance is developing to artemisinin while another effective antimalarial is not in sight. Malaria endemic areas which are mostly in developing countries must deal with the multifaceted process of changing and implementing new national malaria treatment guidelines. This requires complex interactions between several sectors of the affected society which in some cases take place within the context of political instability. Moreover, the cost associated with preventing and containing the spread of antimalarial resistance is detrimental to economic progress. This review addresses the impact of artemisinin resistance on the socioeconomic structure of malaria endemic countries.

  2. Low prevalence of fluoroquinolone resistant strains and resistance precursor strains in Streptococcus pneumoniae from patients with community-acquired pneumonia despite high fluoroquinolone usage.

    PubMed

    Pletz, Mathias W; van der Linden, Mark; von Baum, Heike; Duesberg, Christoph B; Klugman, Keith P; Welte, Tobias

    2011-01-01

    We investigated the usage of fluoroquinolones and the prevalence of fluoroquinolone resistant pneumococci and their precursors (first step mutants and efflux expressing isolates) in patients with community-acquired pneumonia, who were enroled into the German CAPNETZ surveillance study from 2002 to 2006 before the introduction of the pneumococcal conjugate vaccine (n=5780). Thirty-eight percent of all outpatients received fluoroquinolones. Moxifloxacin accounted for 70%, levofloxacin for 19% and ciprofloxacin for 9% of all fluoroquinolone prescriptions. One hundred and sixty-three pneumococcal isolates from 556 patients with pneumococcal pneumonia were analyzed for fluoroquinolone resistance, efflux phenotype, prevalence of mutations within the quinolone-resistance determining regions and clonality. None of the isolates exhibited fluoroquinolone resistance, 1.2% of the isolates contained a first step mutation and 6.7% exhibited an efflux phenotype. There was no clonal relationship among these strains at increased risk for fluoroquinolone resistance. The absence of fluoroquinolone resistance in the context of high fluoroquinolone usage might be explained by the high proportion of third-generation fluoroquinolones with enhanced activity against pneumococci.

  3. Antimicrobial Peptide Resistance Mechanisms of Gram-Positive Bacteria.

    PubMed

    Nawrocki, Kathryn L; Crispell, Emily K; McBride, Shonna M

    2014-10-13

    Antimicrobial peptides, or AMPs, play a significant role in many environments as a tool to remove competing organisms. In response, many bacteria have evolved mechanisms to resist these peptides and prevent AMP-mediated killing. The development of AMP resistance mechanisms is driven by direct competition between bacterial species, as well as host and pathogen interactions. Akin to the number of different AMPs found in nature, resistance mechanisms that have evolved are just as varied and may confer broad-range resistance or specific resistance to AMPs. Specific mechanisms of AMP resistance prevent AMP-mediated killing against a single type of AMP, while broad resistance mechanisms often lead to a global change in the bacterial cell surface and protect the bacterium from a large group of AMPs that have similar characteristics. AMP resistance mechanisms can be found in many species of bacteria and can provide a competitive edge against other bacterial species or a host immune response. Gram-positive bacteria are one of the largest AMP producing groups, but characterization of Gram-positive AMP resistance mechanisms lags behind that of Gram-negative species. In this review we present a summary of the AMP resistance mechanisms that have been identified and characterized in Gram-positive bacteria. Understanding the mechanisms of AMP resistance in Gram-positive species can provide guidelines in developing and applying AMPs as therapeutics, and offer insight into the role of resistance in bacterial pathogenesis.

  4. Acquired color vision loss and a possible mechanism of ganglion cell death in glaucoma.

    PubMed Central

    Nork, T M

    2000-01-01

    PURPOSE: First, to study the cellular mechanisms of acquired color vision loss in retinal detachment and diabetic retinopathy. Second, to learn why, in glaucoma, the type of color vision deficit that is observed is more characteristic of a retinal injury than it is of an optic neuropathy. Third, to test a hypothesis of photoreceptor-induced, ganglion cell death in glaucoma. METHODS: Various histologic techniques were employed to distinguish the L/M-cones (long/medium wavelength-sensitive cones, or red/green sensitive cones) from the S-cones (short wavelength-sensitive cones, or blue sensitive cones) in humans and monkeys with retinal detachment, humans with diabetic retinopathy, and both humans and monkeys with glaucoma. To test if the photoreceptors were contributing to ganglion cell death, laser photocoagulation was used in a experimental model of glaucoma to focally eliminate the photoreceptors. As a control, optic nerve transection was done following retinal laser photocoagulation in one animal. RESULTS: Selective and widespread loss of the S-cones was found in retinal detachment as well as diabetic retinopathy. By contrast, in human as well as experimental glaucoma, marked swelling of the L/M-cones was the predominant histopathologic feature. Retinal laser photocoagulation followed by experimental glaucoma resulted in selective protection of ganglion cells overlying the laser spots. This was not seen with retinal laser photocoagulation by optic nerve transection. CONCLUSIONS: In retinal detachment and diabetic retinopathy, acquired tritan-like color vision loss could be caused, or contributed to, by selective loss of the S-cones. Both L- and M-cones are affected in glaucoma, which is also consistent with a tritan-like deficit. Although not a therapeutic option, protection of ganglion cells by retinal laser in experimental glaucoma is consistent with an hypothesis of anterograde, photoreceptor-induced, ganglion cell death. Images FIGURE 1 FIGURE 2 FIGURE 3

  5. Community-acquired bacterial pneumonias in homosexual men: presumptive evidence for a defect in host resistance.

    PubMed

    Murata, G H; Ault, M J; Meyer, R D

    Over a three year period, we encountered seven homosexual men who developed pneumonias due to S. pneumoniae or H. influenzae in the absence of apparent risk factors. When compared to heterosexual controls, the homosexual group had a much higher frequency of bacteremia, complicated primary infections, multilobar involvement, required longer antibiotic therapy, and took longer to defervesce. Three of our seven homosexual patients fulfilled criteria for the acquired immunodeficiency syndrome (AIDS); two of the others had generalized lymphadenopathy and the other two likely AIDS-related abnormalities. Overall they presented with a spectrum of clinical findings. Two of the patients developed other opportunistic infections associated with AIDS. Since recovery from these pyogenic pneumonias requires an appropriate antibody response, our patients may have had a defect in B-cell function. Moreover, these observations suggest that functional B-cell abnormalities may occur in AIDS and syndromes premonitory of AIDS.

  6. The novel ATP-competitive MEK/Aurora kinase inhibitor BI-847325 overcomes acquired BRAF inhibitor resistance through suppression of Mcl-1 and MEK expression

    PubMed Central

    Phadke, Manali S.; Sini, Patrizia; Smalley, Keiran S. M.

    2015-01-01

    Resistance to BRAF inhibitors is a major clinical problem. Here we evaluate BI-847325, an ATP-competitive inhibitor of MEK and Aurora kinases, in treatment-naïve and drug-resistant BRAF-mutant melanoma models. BI-847325 potently inhibited growth and survival of melanoma cell lines that were both BRAF inhibitor naïve and resistant in 2D culture, 3D cell culture conditions and in colony formation assays. Western blot studies showed BI-847325 to reduce expression of phospho-ERK and phospho-histone 3 in multiple models of vemurafenib resistance. Mechanistically, BI-847325 decreased the expression of MEK and Mcl-1 while increasing the expression of the pro-apoptotic protein BIM. Strong suppression of MEK expression was observed after 48 h of treatment, with no recovery following >72 h of washout. siRNA mediated knockdown of Mcl-1 enhanced the effects of BI-847325, whereas Mcl-1 overexpression reversed this in both 2D cell culture and 3D spheroid melanoma models. In vivo, once weekly BI-847325 (70 mg/kg) led to durable regression of BRAF-inhibitor naive xenografts with no regrowth seen (>65 days of treatment). In contrast, treatment with the vemurafenib analog PLX4720 was associated with tumor relapse at >30 days. BI-847325 also suppressed the long-term growth of xenografts with acquired PLX4720 resistance. Analysis of tumor samples revealed BI-847325 to induce apoptosis associated with suppression of phospho-ERK, total MEK, phospho-Histone3 and Mcl-1 expression. Our studies indicate that BI-847325 is effective in overcoming BRAF inhibitor resistance and has long-term inhibitory effects upon BRAF-mutant melanoma in vivo, through a mechanism associated with the decreased expression of both MEK and Mcl-1. PMID:25873592

  7. Contrasting Roles of the Apoplastic Aspartyl Protease APOPLASTIC, ENHANCED DISEASE SUSCEPTIBILITY1-DEPENDENT1 and LEGUME LECTIN-LIKE PROTEIN1 in Arabidopsis Systemic Acquired Resistance.

    PubMed

    Breitenbach, Heiko H; Wenig, Marion; Wittek, Finni; Jordá, Lucia; Maldonado-Alconada, Ana M; Sarioglu, Hakan; Colby, Thomas; Knappe, Claudia; Bichlmeier, Marlies; Pabst, Elisabeth; Mackey, David; Parker, Jane E; Vlot, A Corina

    2014-06-01

    Systemic acquired resistance (SAR) is an inducible immune response that depends on ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1). Here, we show that Arabidopsis (Arabidopsis thaliana) EDS1 is required for both SAR signal generation in primary infected leaves and SAR signal perception in systemic uninfected tissues. In contrast to SAR signal generation, local resistance remains intact in eds1 mutant plants in response to Pseudomonas syringae delivering the effector protein AvrRpm1. We utilized the SAR-specific phenotype of the eds1 mutant to identify new SAR regulatory proteins in plants conditionally expressing AvrRpm1. Comparative proteomic analysis of apoplast-enriched extracts from AvrRpm1-expressing wild-type and eds1 mutant plants led to the identification of 12 APOPLASTIC, EDS1-DEPENDENT (AED) proteins. The genes encoding AED1, a predicted aspartyl protease, and another AED, LEGUME LECTIN-LIKE PROTEIN1 (LLP1), were induced locally and systemically during SAR signaling and locally by salicylic acid (SA) or its functional analog, benzo 1,2,3-thiadiazole-7-carbothioic acid S-methyl ester. Because conditional overaccumulation of AED1-hemagglutinin inhibited SA-induced resistance and SAR but not local resistance, the data suggest that AED1 is part of a homeostatic feedback mechanism regulating systemic immunity. In llp1 mutant plants, SAR was compromised, whereas the local resistance that is normally associated with EDS1 and SA as well as responses to exogenous SA appeared largely unaffected. Together, these data indicate that LLP1 promotes systemic rather than local immunity, possibly in parallel with SA. Our analysis reveals new positive and negative components of SAR and reinforces the notion that SAR represents a distinct phase of plant immunity beyond local resistance.

  8. Bile resistance mechanisms in Lactobacillus and Bifidobacterium

    PubMed Central

    Ruiz, Lorena; Margolles, Abelardo; Sánchez, Borja

    2013-01-01

    Probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host. Most of the probiotic bacteria currently available in the market belong to the genera Lactobacillus and Bifidobacterium, and specific health-promoting activities, such as treatment of diarrhea or amelioration of gastrointestinal discomfort, have been attributed to them. In order to be able to survive the gastrointestinal transit and transiently colonize our gut, these bacteria must be able to counteract the deleterious action of bile salts, which are the main components of bile. Bile salts are detergent-like biological substances synthesized in the liver from cholesterol. Host enzymes conjugate the newly synthesized free bile acids in the liver with the amino acids glycine or taurine, generating conjugated bile salts. These compounds are stored in the gall bladder and they are released into the duodenum during digestion to perform their physiological function, which is the solubilization of fat coming from diet. These bile salts possess strong antimicrobial activity, since they are able to disorganize the structure of the cell membrane, as well as trigger DNA damage. This means that bacteria inhabiting our intestinal tract must have intrinsic resistance mechanisms to cope with bile salts. To do that, Lactobacillus and Bifidobacterium display a variety of proteins devoted to the efflux of bile salts or protons, to modify sugar metabolism or to prevent protein misfolding. In this manuscript, we review and discuss specific bile resistance mechanisms, as well as the processes responsible for the adaptation of bifidobacteria and lactobacilli to bile. PMID:24399996

  9. Mechanisms of resistance to third-generation EGFR tyrosine kinase inhibitors.

    PubMed

    Wang, Shuhang; Song, Yongping; Yan, Feifei; Liu, Delong

    2016-12-01

    The tyrosine kinase inhibitors (TKI) of the epidermal growth factor receptor (EGFR) are becoming the first line of therapy for advanced non-small cell lung cancer (NSCLC). Acquired mutations in EGFR account for one of the major mechanisms of resistance to the TKIs. Three generations of EGFR TKIs have been used in clinical applications. AZD9291 (osimertinib; Tagrisso) is the first and only FDA approved third-generation EGFR TKI for T790M-positive advanced NSCLC patients. However, resistance to AZD9291 arises after 9-13 months of therapy. The mechanisms of resistance to third-generation inhibitors reported to date include the EGFR C797S mutation, EGFR L718Q mutation, and amplifications of HER-2, MET, or ERBB2. To overcome the acquired resistance to AZD9291, EAI045 was discovered and recently reported to be an allosteric EGFR inhibitor that overcomes T790M- and C797S-mediated resistance. This review summarizes recent investigations on the mechanisms of resistance to the EGFR TKIs, as well as the latest development of EAI045 as a fourth-generation EGFR inhibitor.

  10. Role of major histocompatibility complex class II in resistance of mice to naturally acquired infection with Syphacia obvelata

    NASA Technical Reports Server (NTRS)

    Stewart, Patricia W.; Chapes, Stephen K.

    2003-01-01

    Genetics plays a substantial role in host resistance in many host-parasite interactions. We examined the prevalence of naturally acquired infection with Syphacia obvelata in a number of mouse strains housed in a non-barrier facility. These mice, which included cross-bred and congenic, inbred strains on various genetic backgrounds, differ in the loci for the immune function genes--major histocompatibility complex class II (MHCII), toll-like receptor 4 (Tlr4), and solute carrier family 11, member 1 (Slc11a1)--which allowed comparisons of the impact of these genes on resistance to pinworm infection. Male and female mice of various ages were sampled over an 18-month period; infection was determined by use of the cellophane tape test. Results indicated that mice that were MHCII+/+ had a significantly lower prevalence of infection than did mice that were MHCII-/-. Differences were not seen between male and female mice. Although MHCII+/+ mice had an age-associated decrease in infection prevalence, such decrease was not seen in MHCII-/- mice. In contrast, infection prevalence in mice with the normal Tlr4 gene (Tlr4(LPS-n/LPS-n)) gene did not differ significantly compared with that in mice that were homozygous for either the point mutation (Tlr4(LPS-d/LPS-d)) or deletion (Tlr4(LPS-del/LPS-del)) of that gene. Likewise, the presence (Sle11a1r/r) or absence (Slc11a1s/s) of functional alleles for Slc11a1 had no effect on the prevalence of infection with S. obvelata. In conclusion, presence of MHCII, but not Tlr4 or Slc11a1 significantly influences prevalence of naturally acquired infection with S. obvelata. These data justify further comprehensive analyses of the immune components that are involved in pinworm resistance.

  11. Mouse Oocytes Acquire Mechanisms that Permit Independent Cell Volume Regulation at the End of Oogenesis.

    PubMed

    Richard, Samantha; Tartia, Alina P; Boison, Detlev; Baltz, Jay M

    2016-09-02

    Mouse embryos employ a unique mechanism of cell volume regulation in which glycine is imported via the GLYT1 transporter to regulate intracellular osmotic pressure. Independent cell volume regulation normally becomes active in the oocyte after ovulation is triggered. This involves two steps: the first is the release of the strong adhesion between the oocyte and zona pellucida (ZP) while the second is the activation of GLYT1. In fully-grown oocytes, release of adhesion and GLYT1 activation also occur spontaneously in oocytes removed from the follicle. It is unknown, however, whether the capacity to release oocyte-ZP adhesion or activate GLYT1 first arises in the oocyte after ovulation is triggered or instead growing oocytes already possess these capabilities but they are suppressed in the follicle. Here, we assessed when during oogenesis oocyte-ZP adhesion can be released and when GLYT1 can be activated, with adhesion assessed by an osmotic assay and GLYT1 activity determined by [(3) H]-glycine uptake. Oocyte-ZP adhesion could not be released by growing oocytes until they were nearly fully grown. Similarly, the amount of GLYT1 activity that can be elicited in oocytes increased sharply at the end of oogenesis. The SLC6A9 protein that is responsible for GLYT1 activity and Slc6a9 transcripts are present in growing oocytes and increased over the course of oogenesis. Furthermore, SLC6A9 becomes localized to the oocyte plasma membrane as the oocyte grows. Thus, oocytes acquire the ability to regulate their cell volume by releasing adhesion to the ZP and activating GLYT1 as they approach the end of oogenesis. This article is protected by copyright. All rights reserved.

  12. Azithromycin Dose To Maximize Efficacy and Suppress Acquired Drug Resistance in Pulmonary Mycobacterium avium Disease

    PubMed Central

    Deshpande, Devyani; Pasipanodya, Jotam G.

    2016-01-01

    Mycobacterium avium complex is now the leading mycobacterial cause of chronic pneumonia in the United States. Macrolides and ethambutol form the backbone of the regimen used in the treatment of pulmonary disease. However, therapy outcomes remain poor, with microbial cure rates of 4% in cavitary disease. The treatment dose of azithromycin has mostly been borrowed from that used to treat other bacterial pneumonias; there are no formal dose-response studies in pulmonary M. avium disease and the optimal dose is unclear. We utilized population pharmacokinetics and pharmacokinetics/pharmacodynamics-derived azithromycin exposures associated with optimal microbial kill or resistance suppression to perform 10,000 patient Monte Carlo simulations of dose effect studies for daily azithromycin doses of 0.5 to 10 g. The currently recommended dose of 500 mg per day achieved the target exposures in 0% of patients. Exposures associated with optimal kill and resistance suppression were achieved in 87 and 54% of patients, respectively, only by the very high dose of 8 g per day. The azithromycin susceptibility breakpoint above which patients failed therapy on the very high doses of 8 g per day was an MIC of 16 mg/liter, suggesting a critical concentration of 32 mg/liter, which is 8-fold lower than the currently used susceptibility breakpoint of 256 mg/liter. If the standard dose of 500 mg a day were used, then the critical concentration would fall to 2 mg/liter, 128-fold lower than 256 mg/liter. The misclassification of resistant isolates as susceptible could explain the high failure rates of current doses. PMID:26810646

  13. Effectiveness of Antipseudomonal Antibiotics and Mechanisms of Multidrug Resistance in Pseudomonas aeruginosa.

    PubMed

    El ZOWALATYl, Mohamed E; Gyetvaii, Bpla

    2016-01-01

    Pseudomonas aeruginosa is a leading human pathogen that causes serious infections at various tissues and organs leading to life threatening health problems and possible deadly outcomes. Resistance patterns vary widely whether it is from hospitals or community acquired infections. Reporting resistance profiles to a certain antibiotics provide valuable information in a given setting, but may be extrapolated outside the sampling location. In the present study, P. aeruginosa isolates were screened to determine their susceptibilities against anti-pseudomonal antimicrobial agents and possible existing mechanisms of resistance were determined. Eighty-six isolates of P. aeruginosa were recovered. Isolates representing different resistance profiles were screened for the existence of three different resistance mechanisms including drug inactivation due to metallo-β-lactamases, drug impermeability by outer membrane proteins and drug efflux. All tested isolates showed uniform susceptibility (100%, n = 86/86) to piperacillin, meropenem, amikacin, and polymyxin B. A single isolate was found to be imipenem resistant (99%, n = 85/86). The possible mechanisms of resistance of P. aeruginosa to imipenem involve active drug efflux pumps, outer membrane impermeability as well as drug inactivating enzymes. These findings demonstrate the fundamental importance of the in vitro susceptibility testing of antibiotics prior to antipseudomonal therapy and highlight the need for a continuous antimicrobial resistance surveillance programs to monitor the changing resistance patterns so that clinicians and health care officials are updated as to the most effective therapeutic agents to combat the serious outcomes of P. aeruginosa infections.

  14. [Acquired partial lipodystrophy. Insulin resistance, hepatic lipase activity and small and dense LDL particles].

    PubMed

    Paglione, A M; Ferrari, N; Berg, G; Frechtel, G; Taverna, M; Fasulo, V; Lopez, G I; Gomez, R M; Bruno, O; Ruiz, M; Wikinski, R L

    2001-01-01

    Partial lipodystrophy (PLD) is an infrequent condition characterized by symmetric loss of subcutaneous adipose tissue in the upper or lower part of the body, although occasionally it affects only the extremities. In all cases it appears along with acantosis nigricans (AN), insulin resistance and impairment in the metabolism of lipids and carbohydrates. The case depicted pertains to a 49 year old female with no family history involving loss of adipose tissue in face and upper body. No fat in lower part of body was observed. The patient showed facial thinning at age 8, AN at 11 and gestational diabetes during her fourth pregnancy at 33. At present, the patient presents severe hyperglycemia and hyperinsulinemia with a marked insulin resistance. Type IV hyperlipoproteinemia (OMS), declined C-HDL and Apo A1 and low C-LDL but with a high proportion of small and dense LDL particles were present. Non esterified fatty acids were high. Lipoprotein lipase and hepatic lipase activities are in the lower limit and increased respectively. Fraction C3 of the complement was diminished. No mutations were observed either in codons 170, 809 and 972 of the IRS-1 receptor or in codon 276 of the adrenergic beta 2 gene.

  15. Plasmodesmata-located protein overexpression negatively impacts the manifestation of systemic acquired resistance and the long-distance movement of Defective in Induced Resistance1 in Arabidopsis.

    PubMed

    Carella, P; Isaacs, M; Cameron, R K

    2015-03-01

    Systemic acquired resistance (SAR) is a plant defence response that provides immunity to distant uninfected leaves after an initial localised infection. The lipid transfer protein (LTP) Defective in Induced Resistance1 (DIR1) is an essential component of SAR that moves from induced to distant leaves following a SAR-inducing local infection. To understand how DIR1 is transported to distant leaves during SAR, we analysed DIR1 movement in transgenic Arabidopsis lines with reduced cell-to-cell movement caused by the overexpression of Plasmodesmata-Located Proteins PDLP1 and PDLP5. These PDLP-overexpressing lines were defective for SAR, and DIR1 antibody signals were not observed in phloem sap-enriched petiole exudates collected from distant leaves. Our data support the idea that cell-to-cell movement of DIR1 through plasmodesmata is important during long-distance SAR signalling in Arabidopsis.

  16. High rate of mutation K103N causing resistance to nevirapine in Indian children with acquired immunodeficiency syndrome.

    PubMed

    Sehgal, S; Pasricha, N; Singh, S

    2008-01-01

    In north India the number of paediatric cases with acquired immunodeficiency syndrome (AIDS) is on the rise. Most drug combinations used for treatment of AIDS incorporate nevirapine, resistance to which develops very fast if given singly or because of unplanned interruptions. This paper investigates presence of mutations at codon 103 and codon 215 of the HIV pol gene causing resistance to nevirapine and zidovudine (AZT) respectively in 25 children with AIDS. Mutations T215Y and K103N were detected by a nested cum amplification refractory mutation system polymerase chain reaction (ARMS PCR) and the results were confirmed by direct sequencing in five randomly selected cases. Nineteen patients had received nevirapine containing regimen and six were drug naive. Mutation K103N was observed in 56% (14/25) of the children while mutation T215Y was found in none. Two of the six drug naïve children also showed K103N mutation. Thus, Indian children drug naïve or treated with nevirapine containing regimens show a high rate of mutation conferring resistance to nevirapine which calls for a judicious use of nevirapine both in antenatal and postnatal setting.

  17. Benzoylsalicylic acid isolated from seed coats of Givotia rottleriformis induces systemic acquired resistance in tobacco and Arabidopsis.

    PubMed

    Kamatham, Samuel; Neela, Kishore Babu; Pasupulati, Anil Kumar; Pallu, Reddanna; Singh, Surya Satyanarayana; Gudipalli, Padmaja

    2016-06-01

    Systemic acquired resistance (SAR), a whole plant defense response to a broad spectrum of pathogens, is characterized by a coordinated expression of a large number of defense genes. Plants synthesize a variety of secondary metabolites to protect themselves from the invading microbial pathogens. Several studies have shown that salicylic acid (SA) is a key endogenous component of local and systemic disease resistance in plants. Although SA is a critical signal for SAR, accumulation of endogenous SA levels alone is insufficient to establish SAR. Here, we have identified a new acyl derivative of SA, the benzoylsalicylic acid (BzSA) also known as 2-(benzoyloxy) benzoic acid from the seed coats of Givotia rottleriformis and investigated its role in inducing SAR in tobacco and Arabidopsis. Interestingly, exogenous BzSA treatment induced the expression of NPR1 (Non-expressor of pathogenesis-related gene-1) and pathogenesis related (PR) genes. BzSA enhanced the expression of hypersensitivity related (HSR), mitogen activated protein kinase (MAPK) and WRKY genes in tobacco. Moreover, Arabidopsis NahG plants that were treated with BzSA showed enhanced resistance to tobacco mosaic virus (TMV) as evidenced by reduced leaf necrosis and TMV-coat protein levels in systemic leaves. We, therefore, conclude that BzSA, hitherto unknown natural plant product, is a new SAR inducer in plants.

  18. Quinolone resistance in bacteria: emphasis on plasmid-mediated mechanisms.

    PubMed

    Li, Xian-Zhi

    2005-06-01

    Bacterial resistance to quinolones/fluoroquinolones has emerged rapidly and such resistance has traditionally been attributed to the chromosomally mediated mechanisms that alter the quinolone targets (i.e. DNA gyrase and topoisomerase IV) and/or overproduce multidrug resistance efflux pumps. However, the discovery of the plasmid-borne quinolone resistance determinant, named qnr, has substantially broadened our horizon on the molecular mechanisms of quinolone resistance. Several recent reports of Qnr or its homologues encoded by transferable plasmids in Gram-negative bacteria isolated worldwide highlight the significance of the emerging plasmid-mediated mechanism(s). This also alerts us to the potential rapid dissemination of quinolone resistance determinants. Qnr belongs to the pentapeptide repeat family and protects DNA gyrase from the action of quinolone agents including the newer fluoroquinolones. This protection interplays with chromosomal mechanisms to raise significantly the resistance levels. The qnr-bearing strains generate quinolone-resistant mutants at a much higher frequency than those qnr-free strains. Furthermore, the qnr-plasmids are integron-associated and carry multiple resistance determinants providing resistance to several classes of antimicrobials including beta-lactams and aminoglycosides. The high quinolone resistance rates in Escherichia coli are used to address issues of quinolone resistance, and possible strategies for minimising quinolone resistance are discussed.

  19. Microstructure and mechanics of human resistance arteries

    PubMed Central

    Adio, A. O.; Pitt, A.; Hayman, L.; Thorn, C. E.; Shore, A. C.; Whatmore, J. L.; Winlove, C. P.

    2016-01-01

    Vascular diseases such as diabetes and hypertension cause changes to the vasculature that can lead to vessel stiffening and the loss of vasoactivity. The microstructural bases of these changes are not presently fully understood. We present a new methodology for stain-free visualization, at a microscopic scale, of the morphology of the main passive components of the walls of unfixed resistance arteries and their response to changes in transmural pressure. Human resistance arteries were dissected from subcutaneous fat biopsies, mounted on a perfusion myograph, and imaged at varying transmural pressures using a multimodal nonlinear microscope. High-resolution three-dimensional images of elastic fibers, collagen, and cell nuclei were constructed. The honeycomb structure of the elastic fibers comprising the internal elastic layer became visible at a transmural pressure of 30 mmHg. The adventitia, comprising wavy collagen fibers punctuated by straight elastic fibers, thinned under pressure as the collagen network straightened and pulled taut. Quantitative measurements of fiber orientation were made as a function of pressure. A multilayer analytical model was used to calculate the stiffness and stress in each layer. The adventitia was calculated to be up to 10 times as stiff as the media and experienced up to 8 times the stress, depending on lumen diameter. This work reveals that pressure-induced reorganization of fibrous proteins gives rise to very high local strain fields and highlights the unique mechanical roles of both fibrous networks. It thereby provides a basis for understanding the micromechanical significance of structural changes that occur with age and disease. PMID:27663767

  20. Evolutionary malignant resistance of cells to damaging factors as common biological defence mechanism in neoplastic development. Review of conception.

    PubMed

    Monceviciute-Eringiene, E

    2000-09-01

    Cells have some inborn resistance to harmful factors, which could be called physiological or natural resistance. The mechanisms of multixenobiotic resistance (MXR) and multidrug resistance (MDR) have common features in the formation of acquired resistance in microorganisms, carcinogenesis, tumour metastases and chemotherapy or irradiation. ATP-dependent membrane P-glycoprotein, as an MDR efflux pump, glutathione S-transferases and other products of evolutionary resistance-related genes arised for exportation and detoxification of cytotoxic xenobiotics and drugs are transmitted from bacteria to man. On the one hand, this evolutionary MXR as a common biological defence mechanism is a "driving" power to conserve homeostasis of cells, tissues and organs. On the other hand, mutation, selection and simplification of properties are the causes of functional and morphological changes in tumour cells which regress to a more primitive mode of existence (atavism) for adaptation to survival. In the present work are presented data on the forms of E. coli resistant to antibiotics and of sarcoma 45 resistant to alkylic preparations. They may be helpful in revealing the causes of resistance and acquired accelerated growth of cells. The development of tumours as fibromas 14-15 years following injection of a vital dye trypan blue into human skin supports our conception that neoplastic growth is a particular case of the evolutionary resistance of cells adapted to the damaging factors. So, tumour cells adopting the enhancement mechanisms of general biological persistent resistance, i. e. undergoing repeated cycles of malignancy enhancement, adapt themselves to survive under the changed unfavourable conditions.

  1. Clinical and molecular epidemiology of community-acquired, healthcare-associated and nosocomial methicillin-resistant Staphylococus aureus in Spain.

    PubMed

    Rodríguez-Baño, J; Angeles Domínguez, M; Blas Millán, A; Borraz, C; Pau González, M; Almirante, B; Cercenado, E; Padilla, B; Pujol, M

    2009-12-01

    A prospective cohort study including all new cases of methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection in 64 Spanish hospitals during June 2003 was performed to investigate the epidemiology of MRSA in Spain. Only patients who yielded clinical MRSA-positive samples were included. Epidemiological and clinical data for a total of 370 cases were collected. Genotyping was performed using pulsed-field gel electrophoresis and multilocus sequence typing. Panton-Valentine leukocidin genes and the staphylococcal chromosomal cassette mec (SCCmec) were identified in representative isolates. MRSA was considered to be nosocomially acquired in 202 cases (55%), healthcare-associated (HCA) in 139 cases (38%), community-acquired (CA) in three cases, and of uncertain mode of acquisition in 26 (7%) cases. The pooled population-based rate was 2.31 cases/100,000 population/month, and the pooled nosocomial rate was 0.21 cases/1000 hospital stays (20.2% of S. aureus). Peripheral vascular disease, respiratory tract infections, catheter infections, bloodstream infections and crude mortality were more frequent among HCA cases, whereas neoplasia and urinary tract infections were more frequent among nosocomially acquired cases. Two clones related to the paediatric clone ST5-IV accounted for 71% of the isolates; EMRSA-16 has emerged in two different geographical areas. Only one isolate belonged to the formerly predominant Iberian clone. The three CA isolates were related to the USA300 clone. SCCmec type IV was the most frequent type in nosocomial and HCA isolates. The epidemiology of MRSA has changed in Spain; outpatients with previous healthcare contact represent a very important reservoir of MRSA, and community isolates are emerging.

  2. Comparative 2D-DIGE proteomic analysis of ovarian carcinoma cells: toward a reorientation of biosynthesis pathways associated with acquired platinum resistance.

    PubMed

    Lincet, Hubert; Guével, Blandine; Pineau, Charles; Allouche, Stéphane; Lemoisson, Edwige; Poulain, Laurent; Gauduchon, Pascal

    2012-02-02

    Ovarian cancer is the fifth most frequent cause of cancer death in women. Emergence of chemoresistance in the course of treatments with platinum drugs is in part responsible for therapeutic failures. In order to improve the understanding of the complex mechanisms involved in acquired platinum chemoresistance, we decided to compare the basal protein expression profile of the platinum-sensitive cell line OAW42 and that of its resistant counterpart OAW42-R by a proteomic approach. Reversed-phase HPLC pre-fractionated extracts from both cell lines were subjected to 2D-DIGE coupled to mass spectrometry (MS). Forty eight differentially expressed proteins were identified, 39 being up-regulated and 19 down-regulated in OAW42-R versus OAW42 cells. From the current knowledge on biological activities of most differentially expressed proteins, it can be inferred that the acquisition of resistance was associated with a global reorganization of biochemical pathways favoring the production of precursors for biosynthesis, and with the mobilization of macromolecule quality control mechanisms, preserving RNA and protein integrity under damage-inducing conditions.

  3. Staphylococcal enterotoxin B toxic shock syndrome induced by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA).

    PubMed

    Kashiwada, Takeru; Kikuchi, Ken; Abe, Shinji; Kato, Hidehito; Hayashi, Hiroki; Morimoto, Taisuke; Kamio, Koichiro; Usuki, Jiro; Takeda, Shinhiro; Tanaka, Keiji; Imanishi, Ken'ichi; Yagi, Junji; Azuma, Arata; Gemma, Akihiko

    2012-01-01

    We herein report a case of toxic shock syndrome (TSS) associated with the 2009 pandemic H1N1 (pH1N1) influenza virus and a community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection in a 16-year-old Vietnamese girl. Staphylococcal enterotoxin B (SEB) was detected in the patient's serum, and the level of anti-SEB antibodies was found to be elevated. A flow cytometric analysis showed evidence of activated SEB-reactive Vβ3+ and Vβ12+ T cells. These data suggest that the CA-MRSA-induced activation of SEB-reactive T cells may cause TSS in patients with pH1N1 virus infection. Moreover, this is the first report describing immunological confirmation of SEB contributing directly to TSS in a patient fulfilling the diagnostic criteria of TSS.

  4. Integrating Enzymatic Self-Assembly and Mitochondria Targeting for Selectively Killing Cancer Cells without Acquired Drug Resistance.

    PubMed

    Wang, Huaimin; Feng, Zhaoqianqi; Wang, Youzhi; Zhou, Rong; Yang, Zhimou; Xu, Bing

    2016-12-14

    Targeting organelles by modulating the redox potential of mitochondria is a promising approach to kill cancer cells that minimizes acquired drug resistance. However, it lacks selectivity because mitochondria perform essential functions for (almost) all cells. We show that enzyme-instructed self-assembly (EISA), a bioinspired molecular process, selectively generates the assemblies of redox modulators (e.g., triphenyl phosphinium (TPP)) in the pericellular space of cancer cells for uptake, which allows selectively targeting the mitochondria of cancer cells. The attachment of TPP to a pair of enantiomeric, phosphorylated tetrapeptides produces the precursors (L-1P or D-1P) that form oligomers. Upon dephosphorylation catalyzed by ectophosphatases (e.g., alkaline phosphatase (ALP)) overexpressed on cancer cells (e.g., Saos2), the oligomers self-assemble to form nanoscale assemblies only on the surface of the cancer cells. The cancer cells thus uptake these assemblies of TPP via endocytosis, mainly via a caveolae/raft-dependent pathway. Inside the cells, the assemblies of TPP-peptide conjugates escape from the lysosome, induce dysfunction of mitochondria to release cytochrome c, and result in cell death, while the controls (i.e., omitting TPP motif, inhibiting ALP, or removing phosphate trigger) hardly kill the Saos2 cells. Most importantly, the repeated stimulation of the cancers by the precursors, unexpectedly, sensitizes the cancer cells to the precursors. As the first example of the integration of subcellular targeting with cell targeting, this study validates the spatial control of the assemblies of nonspecific cytotoxic agents by EISA as a promising molecular process for selectively killing cancer cells without inducing acquired drug resistance.

  5. Fibroblasts that resist cigarette smoke-induced senescence acquire profibrotic phenotypes.

    PubMed

    Kanaji, Nobuhiro; Basma, Hesham; Nelson, Amy; Farid, Maha; Sato, Tadashi; Nakanishi, Masanori; Wang, Xingqi; Michalski, Joel; Li, YingJi; Gunji, Yoko; Feghali-Bostwick, Carol; Liu, Xiangde; Rennard, Stephen I

    2014-09-01

    This study assessed the effect of extended exposure to cigarette smoke extract (CSE) on tissue repair functions in lung fibroblasts. Human fetal (HFL-1) and adult lung fibroblasts were exposed to CSE for 14 days. Senescence-associated β-galactosidase (SA β-gal) expression, cell proliferation, and tissue repair functions including chemotaxis and gel contraction were assessed. HFL-1 proliferation was inhibited by CSE and nearly half of the CSE-exposed cells were SA β-gal positive after 14 days exposure, whereas 33% of adult lung fibroblasts were SA β-gal positive in response to 10% CSE exposure. The SA β-gal-positive cells did not proliferate as indicated by bromodeoxyuridine incorporation. In contrast, cells negative for SA β-gal after CSE exposure proliferated faster than cells never exposed to CSE. These nonsenescent cells migrated more and contracted collagen gels more than control cells. CSE exposure stimulated TGF-β1 production, and both inhibition of TGF-β receptor kinase and TGF-β1 siRNA blocked CSE modulation of fibroblast function. Extended exposure to CSE might induce two different fibroblast phenotypes, a senescent and a profibrotic phenotype. The fibroblasts that resist CSE-induced cellular senescence may contribute to the pathogenesis of idiopathic pulmonary fibrosis and could contribute to fibrotic lesions in chronic obstructive pulmonary disease acting through a TGF-β1-mediated pathway. In contrast, the senescent cells may contribute to the pathogenesis of emphysema.

  6. Capsule Switching and Antimicrobial Resistance Acquired during Repeated Streptococcus pneumoniae Pneumonia Episodes.

    PubMed

    Chang, Bin; Nariai, Akiyoshi; Sekizuka, Tsuyoshi; Akeda, Yukihiro; Kuroda, Makoto; Oishi, Kazunori; Ohnishi, Makoto

    2015-10-01

    Streptococcus pneumoniae colonizes the nasopharyngeal mucus in healthy people and causes otitis media, pneumonia, bacteremia, and meningitis. In this study, we analyzed an S. pneumoniae strain that caused 7 repeated pneumonia episodes in an 80-month-old patient with cerebral palsy during a period of 25 months. A total of 10 S. pneumoniae strains were obtained from sputum samples, and serotype 6B was isolated from samples from the first 5 episodes, whereas serotype 6A was isolated from samples from the last 2. Whole-genome sequencing showed clonality of the 10 isolates with 10 single nucleotide polymorphisms (SNPs) in the genomes. Among these SNPs, one single point mutation in the wciP gene was presumed to relate to the serotype switching from 6B to 6A, and the other mutations in parC and gyrA were related to fluoroquinolone resistance. These results suggested that an S. pneumoniae strain, which asymptomatically colonized the patient's nasopharynx or was horizontally transmitted from an asymptomatic carrier, caused the repeated pneumonia events. Phenotypic variations in the capsule type and antimicrobial susceptibility occurred during the carrier state. Hyporesponsiveness to serotypes 6B and 6A of S. pneumoniae was found even after vaccination with the 7-valent pneumococcal conjugate vaccine and the 23-valent pneumococcal polysaccharide vaccine. After an additional vaccination with the 13-valent pneumococcal conjugate vaccine, opsonic activities for both serotypes 6A and 6B significantly increased and are expected to prevent relapse by the same strain.

  7. Lupinus albus plants acquire mercury tolerance when inoculated with an Hg-resistant Bradyrhizobium strain.

    PubMed

    Quiñones, Miguel A; Ruiz-Díez, Beatriz; Fajardo, Susana; López-Berdonces, Miguel A; Higueras, Pablo L; Fernández-Pascual, Mercedes

    2013-12-01

    One strain of Bradyrhizobium canariense (L-7AH) was selected for its metal-resistance and ability to nodulate white lupin (Lupinus albus L.) plants, from a collection of rhizobial strains previously created from soils of the Almadén mining district (Spain) with varying levels of Hg contamination. Plants were inoculated with either strain L-7AH (Hg-tolerant) or L-3 (Hg-sensitive, used as control), and watered with nutrient solutions supplemented with various concentrations (0-200 μM) of HgCl2 in a growth chamber. L. albus inoculated with L-7AH were able to nodulate even at the highest concentration of Hg while those inoculated with L-3 had virtually no nodules at Hg concentrations above 25 μM. Plants inoculated with L-7AH, but not those with the control strain, were able to accumulate large amounts of Hg in their roots and nodules. Nodulation with L-7AH allowed plants to maintain constant levels of both chlorophylls and carotenoids in their leaves and a high photosynthetic efficiency, whereas in those inoculated with L-3 both pigment content and photosynthetic efficiency decreased significantly as Hg concentration increased. Nitrogenase activity of plants nodulated with L-7AH remained fairly constant at all concentrations of Hg used. Results suggest that this symbiotic pair may be used for rhizoremediation of Hg-contaminated soils.

  8. High prevalence of hospital-acquired infections caused by gram-negative carbapenem resistant strains in Vietnamese pediatric ICUs

    PubMed Central

    Le, Ngai Kien; HF, Wertheim; Vu, Phu Dinh; Khu, Dung Thi Khanh; Le, Hai Thanh; Hoang, Bich Thi Ngoc; Vo, Vu Thanh; Lam, Yen Minh; Vu, Dung Tien Viet; Nguyen, Thu Hoai; Thai, Tung Quang; Nilsson, Lennart E.; Rydell, Ulf; Nguyen, Kinh Van; Nadjm, Behzad; Clarkson, Louise; Hanberger, Håkan; Larsson, Mattias

    2016-01-01

    Abstract There is scarce information regarding hospital-acquired infections (HAIs) among children in resource-constrained settings. This study aims to measure prevalence of HAIs in Vietnamese pediatric hospitals. Monthly point prevalence surveys (PPSs) in 6 pediatric intensive care units (ICUs) in 3 referral hospitals during 1 year. A total of 1363 cases (1143 children) were surveyed, 59.9% male, average age 11 months. Admission sources were: other hospital 49.3%, current hospital 36.5%, and community 15.3%. Reasons for admission were: infectious disease (66%), noninfectious (20.8%), and surgery/trauma (11.3%). Intubation rate was 47.8%, central venous catheter 29.4%, peripheral venous catheter 86.2%, urinary catheter 14.6%, and hemodialysis/filtration 1.7%. HAI was diagnosed in 33.1% of the cases: pneumonia (52.2%), septicemia (26.4%), surgical site infection (2%), and necrotizing enterocolitis (2%). Significant risk factors for HAI included age under 7 months, intubation and infection at admission. Microbiological findings were reported in 212 cases (43%) with 276 isolates: 50 Klebsiella pneumoniae, 46 Pseudomonas aeruginosa, and 39 Acinetobacter baumannii, with carbapenem resistance detected in 55%, 71%, and 65%, respectively. Staphylococcus aureus was cultured in 18 cases, with 81% methicillin-resistant Staphylococcus aureus. Most children (87.6%) received antibiotics, with an average of 1.6 antibiotics per case. Colistin was administered to 96 patients, 93% with HAI and 49% with culture confirmed carbapenem resistance. The high prevalence of HAI with carbapenem resistant gram-negative strains and common treatment with broad-spectrum antibiotics and colistin suggests that interventions are needed to prevent HAI and to optimize antibiotic use. PMID:27399106

  9. Osteopontin is involved in the development of acquired chemo-resistance of cisplatin in small cell lung cancer.

    PubMed

    Gu, Tao; Ohashi, Rina; Cui, Ri; Tajima, Ken; Yoshioka, Masakata; Iwakami, Shinichiro; Sasaki, Shinichi; Shinohara, Atsuko; Matsukawa, Takehisa; Kobayashi, Jun; Inaba, Yutaka; Takahashi, Kazuhisa

    2009-11-01

    Osteopontin (OPN) is a multi-functional cytokine involved in cell survival, migration and adhesion which is associated with tumorigenesis, progression and metastasis. However, the role of OPN in chemo-sensitivity of human lung cancer has not yet been elucidated. The purpose of this study is to investigate the role of OPN in chemo-sensitivity of lung cancer cells. We developed a stable OPN transfectant (SBC-3/OPN) and a control transfectant (SBC-3/NEO) from human small cell lung cancer cell line, SBC-3. SBC-3/OPN cells were more resistant to cisplatin than SBC-3/NEO cells. Multi-drug resistance-associated protein (MRP) does not appear to be involved in the development of acquired chemo-resistance, since MRP inhibitor did not alter chemo-sensitivity. After exposure to cisplatin, the apoptotic SBC-3/OPN cells were reduced in number compared to SBC-3/NEO cells. Treatment with cisplatin revealed that the expression of anti-apoptotic protein, bcl-2, was down-regulated in SBC-3/NEO cells, while that of SBC-3/OPN cells was not altered. In contrast, pro-apoptotic protein, bax, was not altered in both SBC-3/OPN and SBC-3/NEO cells, thus bcl-2/bax ratio was decreased in SBC-3/NEO but not altered in SBC-3/OPN cells. Activation of caspase-3 and caspase-9 was increased in SBC-3/NEO cells, but not in SBC-3/OPN cells. Our results suggest that OPN enhances chemo-resistance of cisplatin in SBC-3 cells by suppressing bcl-2 protein down-regulation, thereby blocking the caspase-9- and caspase-3-dependent cell apoptosis.

  10. Evaluation of acquired acid resistance of enamel surrounding orthodontic brackets irradiated by laser and fluoride application.

    PubMed

    Fekrazad, Reza; Ebrahimpour, Leila

    2014-11-01

    Demineralization of enamel around orthodontic brackets is a clinical problem which can lead to some esthetic concerns like white spot lesions. The aim of this in vitro study was to evaluate the effect of the Er, Cr:YSGG laser and fluoride application on the acid resistance of enamel adjacent to orthodontic brackets. A total of 60 healthy, permanent, human premolars were selected and bonded with brackets, then they were randomly assigned to four groups (n = 15): topical APF gel (1.23% F, pH 3.5, for 4 min); Er,Cr:YSGG laser (P:0.25 W, E:12.5 mJ, RR:20 Hz, PD:140 μs, 11% air, without water, for 10 s); fluoride + laser group (F + L), and control group (C). All specimens were demineralized for 10 days in a 0.2 M acetate buffer solution, and the calcium content were subsequently determined with atomic absorption spectrometry. There were significant differences between the calcium content of F + L and F group in comparison to control group. The least concentration of calcium was seen in F + L group, and the most value was observed in C group. Combination of Er, Cr:YSGG laser with fluoride and fluoride alone decreased enamel solubility significantly more than laser alone. In addition, combination of laser and fluoride leads to less consumption of fluoride amount. And patients can use it at the beginning of treatment instead of daily use of fluoride. So we suggest using it in preventing enamel demineralization around orthodontic brackets.

  11. Acute haematogenous community-acquired methicillin-resistant Staphylococcus aureus osteomyelitis in an adult: Case report and review of literature

    PubMed Central

    2012-01-01

    Background Methicillin-resistant Staphylococcus aureus (MRSA) has of late emerged as a cause of community-acquired infections among immunocompetent adults without risk factors. Skin and soft tissue infections represent the majority of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clinical presentations, whilst invasive and life-threatening illness like necrotizing pneumonia, necrotizing fasciitis, pyomyositis, osteomyelitis and sepsis syndrome are less common. Although more widely described in the pediatric age group, the occurrence of CA-MRSA osteomyelitis in adults is an uncommonly reported entity. Case presentation We describe an invasive CA-MRSA infection in a 28 year-old previously healthy male, manifesting with bacteraemia, osteomyelitis of femur, pyomyositis and septic arthritis of the knee. Initially a preliminary diagnosis of osteosarcoma was suggested by imaging studies and patient underwent a bone biopsy. MRSA was subsequently isolated from blood cultures taken on day of admission, bone, tissue and pus cultures. Incision and drainage of abscess was performed and patient was treated with vancomycin, with fusidic acid added later. It took 6 months for the inflammatory markers to normalize, warranting 6-months of anti-MRSA therapy. Patient was a fervent deer hunter and we speculate that he acquired this infection from extensive direct contact with deer. Molecular characterization of this isolate showed that it belonged to multilocus sequence type (MLST) ST30 and exhibited the staphylococcal chromosome cassette mec (SCCmec) type IV, staphylococcus protein A (spa) type t019, accessory gene regulator (agr) type III and dru type dt10m. This strain harbored Panton-Valentine leukocidin (pvl) genes together with 3 other virulent genes; sei (enterotoxin), hlg (hemolysin) and fnbA (fibronectin binding protein). Conclusion This case study alerts physicians that beyond the most commonly encountered skin and soft tissue infections, pvl

  12. MET amplification and epithelial-to-mesenchymal transition exist as parallel resistance mechanisms in erlotinib-resistant, EGFR-mutated, NSCLC HCC827 cells.

    PubMed

    Jakobsen, K R; Demuth, C; Madsen, A T; Hussmann, D; Vad-Nielsen, J; Nielsen, A L; Sorensen, B S

    2017-04-03

    Although many epidermal growth factor receptor (EGFR)-mutated lung cancer patients initially benefit from the EGFR-inhibitor erlotinib, all acquire resistance. So far, several mechanisms implicated in resistance have been identified, but the existence of multiple resistance mechanisms in parallel have only been sparsely investigated. In this study, we investigated parallel resistance mechanisms acquired by HCC827, an EGFR-mutated adenocarcinoma cell line dependent on EGFR activity and sensitive to erlotinib. The cell line was treated with erlotinib by stepwise escalation of the drug-concentration and erlotinib-resistant (HCC827ER) cells created. HCC827ER cells depicted a mixed epithelial and mesenchymal phenotype. To clarify potential parallel resistance mechanisms, 14 resistant subclones were established by limited dilution. Interestingly, all HCC827ER subclones harbored either a MET-amplification (6/14) or underwent EMT (8/14), mechanisms both found in previous studies, but not in co-occurrence. Both subclone-types were resistant to erlotinib, but only MET-subclones responded to the MET-inhibitors crizotinib and capmatinib. EMT-subclones on the other hand had markedly increased FGFR1 expression and responded to the FGFR-inhibitor AZD4547, whereas MET-subclones did not. Monitoring gene expression through the development of HCC827ER revealed upregulation of FGFR1 expression as an early response to erlotinib. In addition, FGFR1 expression increased upon short-term erlotinib treatment (48 h) identifying a physiological role immediately after erlotinib exposure. The high FGFR1 expression seen in EMT-subclones was stable even after five passages without erlotinib. Here we show, that parallel resistance mechanisms appear during erlotinib-resistance development in EGFR-mutated NSCLC cells and highlight a role for FGFR1 expression changes as an early response to erlotinib as well as a bypass-signaling mechanism.

  13. Mechanisms of Drug Resistance in Plasmodium falciparum

    DTIC Science & Technology

    1992-09-11

    parasites. With the collaboration of Dr. Esther Orozco, we cloned two mdr-like genes from Entamoeba histolytica and demonstrated an association of...Orozco (1990). " Entamoeba histolytica : "Physiology of multidrug resistance." Exp Parasitol. 71:169-175. Buschman, E., and P. Gros. (1991). "Functional...Ayala, E. Orozco, and D. Wirth. (1990). "Emetine-resistant mutants of Entamoeba histolytica overexpress mRNAs for multidrug resistance." Mol Biochem

  14. CXCR4-targeted lipid-coated PLGA nanoparticles deliver sorafenib and overcome acquired drug resistance in liver cancer.

    PubMed

    Gao, Dong-Yu; Lin, Ts-Ting; Sung, Yun-Chieh; Liu, Ya Chi; Chiang, Wen-Hsuan; Chang, Chih-Chun; Liu, Jia-Yu; Chen, Yunching

    2015-10-01

    Sorafenib, a multikinase inhibitor, has been used as an anti-angiogenic agent against highly vascular hepatocellular carcinoma (HCC) - yet associated with only moderate therapeutic effect and the high incidence of HCC recurrence. We have shown intratumoral hypoxia induced by sorafenib activated C-X-C receptor type 4 (CXCR4)/stromal-derived factor 1α (SDF1α) axis, resulting in polarization toward a tumor-promoting microenvironment and resistance to anti-angiogenic therapy in HCC. Herein, we formulated sorafenib in CXCR4-targeted lipid-coated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) modified with a CXCR4 antagonist, AMD3100 to systemically deliver sorafenib into HCC and sensitize HCC to sorafenib treatment. We demonstrated that CXCR4-targeted NPs efficiently delivered sorafenib into HCCs and human umbilical vein endothelial cells (HUVECs) to achieve cytotoxicity and anti-angiogenic effect in vitro and in vivo. Despite the increased expression of SDF1α upon the persistent hypoxia induced by sorafenib-loaded CXCR4-targeted NPs, AMD3100 attached to the NPs can block CXCR4/SDF1α, leading to the reduced infiltration of tumor-associated macrophages, enhanced anti-angiogenic effect, a delay in tumor progression and increased overall survival in the orthotopic HCC model compared with other control groups. In conclusion, our results highlight the clinical potential of CXCR4-targeted NPs for delivering sorafenib and overcoming acquired drug resistance in liver cancer.

  15. Hospital Acquired Pneumonia Due to Achromobacter spp. in a Geriatric Ward in China: Clinical Characteristic, Genome Variability, Biofilm Production, Antibiotic Resistance and Integron in Isolated Strains

    PubMed Central

    Liu, Chao; Pan, Fei; Guo, Jun; Yan, Weifeng; Jin, Yi; Liu, Changting; Qin, Long; Fang, Xiangqun

    2016-01-01

    Background: Hospital-acquired pneumonia (HAP) due to Achromobacter has become a substantial concern in recent years. However, HAP due to Achromobacter in the elderly is rare. Methods: A retrospective analysis was performed on 15 elderly patients with HAP due to Achromobacter spp., in which the sequence types (STs), integrons, biofilm production and antibiotic resistance of the Achromobacter spp. were examined. Results: The mean age of the 15 elderly patients was 88.8 ± 5.4 years. All patients had at least three underlying diseases and catheters. Clinical outcomes improved in 10 of the 15 patients after antibiotic and/or mechanical ventilation treatment, but three patients had chronic infections lasting more than 1 year. The mortality rate was 33.3% (5/15). All strains were resistant to aminoglycosides, aztreonam, nitrofurantoin, and third- and fourth-generation cephalosporins (except ceftazidime and cefoperazone). Six new STs were detected. The most frequent ST was ST306. ST5 was identified in two separate buildings of the hospital. ST313 showed higher MIC in cephalosporins, quinolones and carbapenems, which should be more closely considered in clinical practice. All strains produced biofilm and had integron I and blaOXA-114-like. The main type was blaOXA-114q. The variable region of integron I was different among strains, and the resistance gene of the aminoglycosides was most commonly inserted in integron I. Additionally, blaPSE-1 was first reported in this isolate. Conclusion: Achromobacter spp. infection often occurs in severely ill elders with underlying diseases. The variable region of integrons differs, suggesting that Achromobacter spp. is a reservoir of various resistance genes. PMID:27242678

  16. Arabidopsis ENHANCED DISEASE SUSCEPTIBILITY1 promotes systemic acquired resistance via azelaic acid and its precursor 9-oxo nonanoic acid.

    PubMed

    Wittek, Finni; Hoffmann, Thomas; Kanawati, Basem; Bichlmeier, Marlies; Knappe, Claudia; Wenig, Marion; Schmitt-Kopplin, Philippe; Parker, Jane E; Schwab, Wilfried; Vlot, A Corina

    2014-11-01

    Systemic acquired resistance (SAR) is a form of inducible disease resistance that depends on salicylic acid and its upstream regulator ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1). Although local Arabidopsis thaliana defence responses activated by the Pseudomonas syringae effector protein AvrRpm1 are intact in eds1 mutant plants, SAR signal generation is abolished. Here, the SAR-specific phenotype of the eds1 mutant is utilized to identify metabolites that contribute to SAR. To this end, SAR bioassay-assisted fractionation of extracts from the wild type compared with eds1 mutant plants that conditionally express AvrRpm1 was performed. Using high-performance liquid chromatography followed by mass spectrometry, systemic immunity was associated with the accumulation of 60 metabolites, including the putative SAR signal azelaic acid (AzA) and its precursors 9-hydroperoxy octadecadienoic acid (9-HPOD) and 9-oxo nonanoic acid (ONA). Exogenous ONA induced SAR in systemic untreated leaves when applied at a 4-fold lower concentration than AzA. The data suggest that in planta oxidation of ONA to AzA might be partially responsible for this response and provide further evidence that AzA mobilizes Arabidopsis immunity in a concentration-dependent manner. The AzA fragmentation product pimelic acid did not induce SAR. The results link the C9 lipid peroxidation products ONA and AzA with systemic rather than local resistance and suggest that EDS1 directly or indirectly promotes the accumulation of ONA, AzA, or one or more of their common precursors possibly by activating one or more pathways that either result in the release of these compounds from galactolipids or promote lipid peroxidation.

  17. Induction of Systemic Acquired Resistance by Rotylenchulus reniformis and Meloidogyne incognita in Cotton Following Separate and Concomitant Inoculations.

    PubMed

    Aryal, Sudarshan K; Davis, Richard F; Stevenson, Katherine L; Timper, Patricia; Ji, Pingsheng

    2011-09-01

    Systemic acquired resistance (SAR) can be elicited by virulent and avirulent pathogenic strains and SAR against plant-parasitic nematodes has been documented. Our objective was to determine whether co-infection of cotton by Meloidogyne incognita and Rotylenchulus reniformis affects the population level of either nematode compared to infection by each species individually. Split-root trials were conducted in which plants were inoculated with i) R. reniformis only, ii) M. incognita only, iii) both R. reniformis and M. incognita, or iv) no nematodes. Half of the root system was inoculated with R. reniformis or M. incognita on day 0 and the other half with M. incognita or R. reniformis on day 0 or day 14 depending on the experiment. Experiments were conducted on cotton cultivar DP 0935 B2RF (susceptible to both nematodes), LONREN-1 (germplasm line resistant to R. reniformis), and M-120 RNR (germplasm line resistant to M. incognita), and tests were terminated 8 wk after the last inoculation. Both soil (vermiform) and roots (egg) extracted from each half of the root system to determine the total nematode population levels, and root galling was rated on a 0 to 10 scale. Mixed models analysis and comparison of least squares means indicated no differences in root galling (except on LONREN-1) or population levels when the two nematode species were introduced on the same day. When M. incognita was introduced 14 d after R. reniformis, reduction in galling (36% on DP 0935 and 33% on LONREN-1) and M. incognita population levels (35% on DP 0935 and 45% on LONREN-1) were significant (P ≤ 0.05). When R. reniformis was inoculated 14 d after M. incognita, reduction in R. reniformis population levels (18% on DP 0935 and 26% on M-120) were significant. This study documents for the first time that infection of cotton by a nematode can elicit SAR to another nematode species.

  18. Mechanisms of Antimicrobial Peptide Resistance in Gram-Negative Bacteria

    PubMed Central

    Band, Victor I.; Weiss, David S.

    2014-01-01

    Cationic antimicrobial peptides (CAMPs) are important innate immune defenses that inhibit colonization by pathogens and contribute to clearance of infections. Gram-negative bacterial pathogens are a major target, yet many of them have evolved mechanisms to resist these antimicrobials. These resistance mechanisms can be critical contributors to bacterial virulence and are often crucial for survival within the host. Here, we summarize methods used by Gram-negative bacteria to resist CAMPs. Understanding these mechanisms may lead to new therapeutic strategies against pathogens with extensive CAMP resistance. PMID:25927010

  19. Mechanisms of Antimicrobial Peptide Resistance in Gram-Negative Bacteria.

    PubMed

    Band, Victor I; Weiss, David S

    2015-03-01

    Cationic antimicrobial peptides (CAMPs) are important innate immune defenses that inhibit colonization by pathogens and contribute to clearance of infections. Gram-negative bacterial pathogens are a major target, yet many of them have evolved mechanisms to resist these antimicrobials. These resistance mechanisms can be critical contributors to bacterial virulence and are often crucial for survival within the host. Here, we summarize methods used by Gram-negative bacteria to resist CAMPs. Understanding these mechanisms may lead to new therapeutic strategies against pathogens with extensive CAMP resistance.

  20. Trends in occurrence of antimicrobial resistance in Campylobacter jejuni isolates from broiler chickens, broiler chicken meat, and human domestically acquired cases and travel associated cases in Denmark.

    PubMed

    Skjøt-Rasmussen, Line; Ethelberg, Steen; Emborg, Hanne-Dorthe; Agersø, Yvonne; Larsen, Lars S; Nordentoft, Steen; Olsen, Stefan S; Ejlertsen, Tove; Holt, Hanne; Nielsen, Eva Møller; Hammerum, Anette M

    2009-05-31

    Campylobacter jejuni is a frequent cause of bacterial gastroenteritis. Often it causes self-limiting disease but severe or prolonged cases may require antimicrobial treatment. The agricultural use of antimicrobial agents selects for resistance among C. jejuni which is transmitted to humans via food. In Denmark, the use of fluoroquinolones in animal husbandry has been restricted since 2003. The purpose of the present study was to look at trends in occurrence of resistance among C. jejuni from broiler chickens, broiler chicken meat and human domestically acquired or travel associated cases. From 1997 through 2007, C. jejuni isolates were obtained from The Danish Integrated Antimicrobial Resistance Monitoring and Research Programme (DANMAP) and susceptibility tested for ciprofloxacin, erythromycin, nalidixic acid, and tetracycline. Erythromycin resistance was at a low level in all the reservoirs during the study period. Resistance to ciprofloxacin, nalidixic acid and tetracycline was significantly higher in C. jejuni from imported broiler chicken meat compared to Danish broiler chicken meat. In domestically acquired human C. jejuni isolates, resistance to ciprofloxacin and nalidixic acid was for most years significantly higher compared to the level found in isolates from Danish broiler chicken meat, whereas the resistance level was similar to the level found in isolates from imported broiler chicken meat. Imported broiler chicken meat may therefore contribute to the high level of ciprofloxacin and nalidixic acid resistance in C. jejuni isolates from domestically acquired human infections. In 2006 and 2007, the occurrence of resistance to ciprofloxacin, nalidixic acid and tetracycline was significantly higher in travel associated C. jejuni isolates compared to isolates acquired domestically. Even though the use of fluoroquinolones is restricted for animal use in Denmark, Danes are still often infected by fluoroquinolone resistant C. jejuni from imported chicken meat or

  1. Kinome-wide RNA interference screen reveals a role for PDK1 in acquired resistance to CDK4/6 inhibition in ER-positive breast cancer.

    PubMed

    Jansen, Valerie M; Bhola, Neil E; Bauer, Joshua A; Formisano, Luigi; Lee, Kyung-Min; Hutchinson, Katherine E; Witkiewicz, Agnieszka K; Moore, Preston D; Estrada, Monica Valeria; Sanchez, Violeta; Ericsson, Paula G; Sanders, Melinda; Pohlmann, Paula R; Pishvaian, Michael J; Riddle, David A; Wei, Wenyi; Dugger, Teresa C; Knudsen, Erik; Arteaga, Carlos L

    2017-03-01

    To discover mechanisms of resistance to CDK4/6 inhibitors, we used a kinome-wide siRNA screen to identify kinases that, when downregulated, promote sensitivity to ribociclib. We identified 3-phosphoinositide dependent protein kinase 1 (PDK1) as the top siRNA that sensitized ER+ MCF-7 cells to ribociclib. Pharmacological inhibition of PDK1 with GSK2334470 in combination with ribociclib or palbociclib, synergistically inhibited proliferation and increased apoptosis in a panel of ER+ breast cancer cell lines. Ribociclib-resistant MCF-7, T47D and HCC1428 cells, selected after chronic drug exposure, displayed increased levels of PDK1, P-RSK2, P-AKT and P-S6 compared to parental drug-sensitive cells. Cell cycle analysis revealed that CDK4/6 inhibition failed to induce G1 arrest, a reduction in S phase, and senescence in ribociclib-resistant cells, suggesting an upregulation of S-phase cyclins/CDKs. The resistant cells exhibited significantly higher levels of P-CDK2, cyclin A, cyclin D1, cyclin E and S477/T479 P-AKT, a CDK2-dependent phosphorylation site within AKT required for full kinase activity and limited to the S-phase of the cell cycle. Treatment with GSK2334470 or the CDK2 inhibitor dinaciclib re-sensitized ribociclib-resistant cells to CDK4/6 inhibitors; however, ribociclib/GSK2334470 inhibited the ribociclib-resistant cells more potently than ribociclib/dinaciclib. Ribociclib/GSK2334470 but not ribociclib/dinaciclib completely abrogated P-Rb, P-S6, P-RSK2, P-CDK2, cyclin A, cyclin D1 and cyclin E expression. Further, ribociclib in combination with GSK2334470 or the PI3Kα inhibitor alpelisib induced regression of MCF-7 xenografts. Finally, primary ER+ tumors displayed increased PDK1, P-S6 and cyclin D1 levels after short treatment with palbociclib. These data support a role for PI3K/PDK1 in mediating acquired resistance to CDK4/6 inhibitors.

  2. Mechanisms underlying acquired von Willebrand syndrome associated with an IgM paraprotein.

    PubMed

    Mayerhofer, M; Haushofer, A; Kyrle, P A; Chott, A; Müllner, C; Quehenberger, P; Worel, N; Traby, L; Eichinger, S

    2009-09-01

    Acquired von Willebrand (vW) syndrome is a rare bleeding disorder which is frequently associated with immunological, malignant or cardiovascular disorders. The underlying pathomechanisms, particularly in patients with IgM monoclonal gammopathies, often remain unknown. We report a patient with indolent small B-cell lymphoma (immunocytoma) and plasmacytic differentiation with an IgM kappa paraprotein who was admitted with retroperitoneal haematoma. Medical history and coagulation testing were consistent with acquired vW syndrome. vW immunohistochemistry showed normal cytoplasmic labelling of endothelial cells and megakaryocytes, whereas the lymphomatous infiltrate was negative. Acquired vW syndrome due to adsorption of vW factor on malignant cells was thus excluded. In the multimeric analysis, all multimers were present similar to that in type 1 vW syndrome, but the triplet structures were blurred. The bands on serum immunofixation electrophoresis were also atypically broadened, which suggested complex formation between the IgM and vW factor. Immunoprecipitation studies showed that the 176-kDa proteolytic fragment of vW factor co-precipitated with the IgM paraprotein in the patient but not in the controls, suggesting a specific interaction between vW factor and the paraprotein in the patient. The patient required surgery and was successfully managed by chemotherapy consisting of rituximab and fludarabin as well as plasma exchange.

  3. Significant Differences in the Development of Acquired Resistance to the MDM2 Inhibitor SAR405838 between In Vitro and In Vivo Drug Treatment

    PubMed Central

    Hoffman-Luca, C. Gianna; Yang, Chao-Yie; Lu, Jianfeng; Ziazadeh, Daniel; McEachern, Donna; Debussche, Laurent; Wang, Shaomeng

    2015-01-01

    SAR405838 is a potent and specific MDM2 inhibitor currently being evaluated in Phase I clinical trials for the treatment of human cancer. Using the SJSA-1 osteosarcoma cell line which harbors an amplified MDM2 gene and wild-type p53, we have investigated the acquired resistance mechanisms both in vitro and in vivo to SAR405838. Treatment of SJSA-1 cells with SAR405838 in vitro leads to dose-dependent cell growth inhibition, cell cycle arrest and robust apoptosis. However, prolonged treatment of SJSA-1 cells in vitro with SAR405838 results in profound acquired resistance to the drug. Analysis of in vitro-derived resistant cell lines showed that p53 is mutated in the DNA binding domain and can no longer be activated by SAR405838. Treatment of the parental SJSA-1 xenograft tumors with SAR405838 in mice yields rapid tumor regression but the tumors eventually regrow. Culturing the regrown tumors established a number of sublines, which showed only modest (3–5 times) loss of sensitivity to SAR405838 in vitro. Sequencing of the p53 showed that it retains its wild-type status in these in vivo sublines, with the exception of one subline, which harbors a single heterozygous C176F p53 mutation. Using xenograft models of two in vivo derived sublines, which has either wild-type p53 or p53 containing a single heterozygous C176F mutation, we showed that while SAR405838 effectively achieves partial tumor regression in these models, it no longer induces complete tumor regression and tumors resume growth once the treatment is stopped. Harvesting and culturing tumors obtained from a prolonged treatment with SAR405838 in mice established additional in vivo sublines, which all contain a single heterozygous C176F mutation with no additional p53 mutation detected. Interestingly, SAR405838 can still effectively activate p53 in all sublines containing a single heterozygous C176F mutation, with a moderately reduced potency as compared to that in the parental cell line. Consistently, SAR

  4. Targeting glucosylceramide synthase induction of cell surface globotriaosylceramide (Gb3) in acquired cisplatin-resistance of lung cancer and malignant pleural mesothelioma cells

    SciTech Connect

    Tyler, Andreas; Johansson, Anders; Karlsson, Terese; Gudey, Shyam Kumar; Brännström, Thomas; Grankvist, Kjell; Behnam-Motlagh, Parviz

    2015-08-01

    Background: Acquired resistance to cisplatin treatment is a caveat when treating patients with non-small cell lung cancer (NSCLC) and malignant pleural mesothelioma (MPM). Ceramide increases in response to chemotherapy, leading to proliferation arrest and apoptosis. However, a tumour stress activation of glucosylceramide synthase (GCS) follows to eliminate ceramide by formation of glycosphingolipids (GSLs) such as globotriaosylceramide (Gb3), the functional receptor of verotoxin-1. Ceramide elimination enhances cell proliferation and apoptosis blockade, thus stimulating tumor progression. GSLs transactivate multidrug resistance 1/P-glycoprotein (MDR1) and multidrug resistance-associated protein 1 (MRP1) expression which further prevents ceramide accumulation and stimulates drug efflux. We investigated the expression of Gb3, MDR1 and MRP1 in NSCLC and MPM cells with acquired cisplatin resistance, and if GCS activity or MDR1 pump inhibitors would reduce their expression and reverse cisplatin-resistance. Methods: Cell surface expression of Gb3, MDR1 and MRP1 and intracellular expression of MDR1 and MRP1 was analyzed by flow cytometry and confocal microscopy on P31 MPM and H1299 NSCLC cells and subline cells with acquired cisplatin resistance. The effect of GCS inhibitor PPMP and MDR1 pump inhibitor cyclosporin A for 72 h on expression and cisplatin cytotoxicity was tested. Results: The cisplatin-resistant cells expressed increased cell surface Gb3. Cell surface Gb3 expression of resistant cells was annihilated by PPMP whereas cyclosporin A decreased Gb3 and MDR1 expression in H1299 cells. No decrease of MDR1 by PPMP was noted in using flow cytometry, whereas a decrease of MDR1 in H1299 and H1299res was indicated with confocal microscopy. No certain co-localization of Gb3 and MDR1 was noted. PPMP, but not cyclosporin A, potentiated cisplatin cytotoxicity in all cells. Conclusions: Cell surface Gb3 expression is a likely tumour biomarker for acquired cisplatin

  5. What have the mechanisms of resistance to glyphosate taught us?

    PubMed

    Shaner, Dale L; Lindenmeyer, Richard Bradley; Ostlie, Michael H

    2012-01-01

    The intensive use of glyphosate alone to manage weeds has selected populations that are glyphosate resistant. The three mechanisms of glyphosate resistance that have been elucidated are (1) target-site mutations, (2) gene amplification and (3) altered translocation due to sequestration. What have we learned from the selection of these mechanisms, and how can we apply those lessons to future herbicide-resistant crops and new mechanisms of action? First, the diversity of glyphosate resistance mechanisms has helped further our understanding of the mechanism of action of glyphosate and advanced our knowledge of plant physiology. Second, the relatively rapid evolution of glyphosate-resistant weed populations provides further evidence that no herbicide is invulnerable to resistance. Third, as new herbicide-resistant crops are developed and new mechanisms of action are discovered, the weed science community needs to ensure that we apply the lessons we have learned on resistance management from the experience with glyphosate. Every new weed management system must be evaluated during development for its potential to select for resistance, and stewardship programs should be in place when the new program is introduced.

  6. Community-acquired necrotizing pneumonia caused by methicillin-resistant Staphylococcus aureus ST30-SCCmecIVc-spat019-PVL positive in San Antonio de Areco, Argentina.

    PubMed

    Fernandez, Silvina; Murzicato, Sofía; Sandoval, Orlando; Fernández-Canigia, Liliana; Mollerach, Marta

    2015-01-01

    Community-acquired methicillin-resistant Staphylococcus aureus is the first cause of skin and soft tissue infections, but can also produce severe diseases such as bacteremia, osteomyelitis and necrotizing pneumonia. Some S. aureus lineages have been described in cases of necrotizing pneumonia worldwide, usually in young, previously healthy patients. In this work, we describe a fatal case of necrotizing pneumonia due to community-acquired methicillin-resistant S. aureus clone ST30-SCCmecIVc-spat019-PVL positive in an immunocompetent adult patient.

  7. Acquired hyperpigmentations*

    PubMed Central

    Cestari, Tania Ferreira; Dantas, Lia Pinheiro; Boza, Juliana Catucci

    2014-01-01

    Cutaneous hyperpigmentations are frequent complaints, motivating around 8.5% of all dermatological consultations in our country. They can be congenital, with different patterns of inheritance, or acquired in consequence of skin problems, systemic diseases or secondary to environmental factors. The vast majority of them are linked to alterations on the pigment melanin, induced by different mechanisms. This review will focus on the major acquired hyperpigmentations associated with increased melanin, reviewing their mechanisms of action and possible preventive measures. Particularly prominent aspects of diagnosis and therapy will be emphasized, with focus on melasma, post-inflammatory hyperpigmentation, periorbital pigmentation, dermatosis papulosa nigra, phytophotodermatoses, flagellate dermatosis, erythema dyschromicum perstans, cervical poikiloderma (Poikiloderma of Civatte), acanthosis nigricans, cutaneous amyloidosis and reticulated confluent dermatitis PMID:24626644

  8. Mechanisms of Resistance in Microbial Spores

    DTIC Science & Technology

    1990-12-20

    heat shock affects permeability and resistance of Bacillus stearotbermo2hilus spores; low heat resistance of )2. SQhaericus spores correlated with...DNA content in~· megaterium spores; compact structure of cortical peptidoglycans from bacterial spores. The titles of four published re-.view...among 8 Bacillus species spanning a 3,000-fold range in SHR, which was altered by acid demineralization and specific remineralization and also by

  9. Microtubule inhibitors: Differentiating tubulin-inhibiting agents based on mechanisms of action, clinical activity, and resistance.

    PubMed

    Perez, Edith A

    2009-08-01

    Microtubules are important cellular targets for anticancer therapy because of their key role in mitosis. Microtubule inhibitors (MTI) such as taxanes, vinca alkaloids, and epothilones stabilize or destabilize microtubules, thereby suppressing microtubule dynamics required for proper mitotic function, effectively blocking cell cycle progression and resulting in apoptosis. In spite of their antitumor activity, innate or acquired drug resistance to MTIs such as the taxanes is common, limiting their overall clinical efficacy. Further insight into the mechanisms of action of microtubule-targeting drugs has lead to the discovery of novel agents that may provide higher efficacy with limited toxicity and help overcome resistance to conventional MTIs. This review will focus on the different mechanisms of action of MTIs, potential factors related to resistance and tolerability, and will discuss the recent approval as well as the development of new antineoplastic agents.

  10. Emerging Mechanisms of Resistance to Androgen Receptor Inhibitors in Prostate Cancer

    PubMed Central

    Arora, Vivek K.

    2016-01-01

    Preface Over the past ten years, preclinical studies implicating sustained androgen receptor (AR) signaling as the primary driver of castration resistant prostate cancer (CRPC) led to the development of novel agents targeting the AR pathway that are now in widespread clinical use. These drugs prolong survival of patients with late stage prostate cancer but are not curative. In this review, we highlight emerging mechanisms of acquired resistance to these contemporary therapies, which fall into the three broad categories of restored AR signaling, AR bypass signaling and complete AR independence. This diverse spectrum of resistance mechanisms presents new challenges for long term disease control, which may be addressable through early use of combination therapies guided by recent insights from genomic landscape studies of CRPC. PMID:26563462

  11. Tracking Cefoperazone/Sulbactam Resistance Development In vivo in A. baumannii Isolated from a Patient with Hospital-Acquired Pneumonia by Whole-Genome Sequencing

    PubMed Central

    Liu, Xiaofen; Zheng, Huajun; Zhang, Weipeng; Shen, Zhen; Zhao, Miao; Chen, Yuancheng; Sun, Li; Shi, Jun; Zhang, Jing

    2016-01-01

    Cefoperazone/sulbactam has been shown to be efficacious for the treatment of infections caused by Acinetobacter baumannii; however, the mechanism underlying resistance to this synergistic combination is not well understood. In the present study, two A. baumannii isolates, AB1845 and AB2092, were isolated from a patient with hospital-acquired pneumonia before and after 20 days of cefoperazone/sulbactam therapy (2:1, 3 g every 8 h with a 1-h infusion). The minimum inhibitory concentration (MIC) of cefoperazone/sulbactam for AB1845 and AB2092 was 16/8 and 128/64 mg/L, respectively. Blood samples were collected on day 4 of the treatment to determine the concentration of cefoperazone and sulbactam. The pharmacokinetic/pharmacodynamic (PK/PD) indices (%T>MIC) were calculated to evaluate the dosage regimen and resistance development. The results showed that %T>MIC of cefoperazone and sulbactam was 100% and 34.5% for AB1845, and 0% and 0% for AB2092, respectively. Although there was no available PK/PD target for sulbactam, it was proposed that sulbactam should be administered at higher doses or for prolonged infusion times to achieve better efficacy. To investigate the mechanism of A. baumannii resistance to the cefoperazone/sulbactam combination in vivo, whole-genome sequencing of these two isolates was further performed. The sequencing results showed that 97.6% of the genome sequences were identical and 33 non-synonymous mutations were detected between AB1845 and AB2092. The only difference of these two isolates was showed in sequencing coverage comparison. There was a 6-kb amplified DNA fragment which was three times higher in AB2092, compared with AB1845. The amplified DNA fragment containing the blaOXA-23 gene on transposon Tn2009. Further quantitative real-time PCR results demonstrated that gene expression at the mRNA level of blaOXA-23 was >5 times higher in AB2092 than in AB1845. These results suggested that the blaOXA-23 gene had higher expression level in AB2092

  12. Mechanisms of β-lactam killing and resistance in the context of Mycobacterium tuberculosis.

    PubMed

    Wivagg, Carl N; Bhattacharyya, Roby P; Hung, Deborah T

    2014-09-01

    β-Lactams are one of the most useful classes of antibiotics against many common bacterial pathogens. One exception is Mycobacterium tuberculosis. However, with increasing incidence of multidrug-resistant tuberculosis and a need for new agents to treat it, the use of β-lactams, specifically the combination of carbapenem and clavulanate, is now being revisited. With this attention, comes the need to better understand both the mechanisms of action of β-lactams against M. tuberculosis as well as possible mechanisms of resistance, within the context of what is known about the β-lactam action in other bacteria. M. tuberculosis has two major mechanisms of intrinsic resistance: a highly active β-lactamase and a poorly permeable outer membrane. Within the cell wall, β-lactams bind several enzymes with differing peptidoglycan-synthetic and -lytic functions. The inhibition of these enzymes may lead to cell death through several mechanisms, involving disruption of the balance of synthetic and lethal activities. Currently, all known means of resistance to the β-lactams rely on diminishing the proportion of peptidoglycan-synthetic proteins bound and inhibited by β-lactams, through either exclusion or destruction of the antibiotic, or through replacement or supplementation of target enzymes. In this review, we discuss possible mechanisms for β-lactam activity in M. tuberculosis and the means by which it may acquire resistance, within the context of what is known in other bacterial species.

  13. Understanding the mechanisms and drivers of antimicrobial resistance.

    PubMed

    Holmes, Alison H; Moore, Luke S P; Sundsfjord, Arnfinn; Steinbakk, Martin; Regmi, Sadie; Karkey, Abhilasha; Guerin, Philippe J; Piddock, Laura J V

    2016-01-09

    To combat the threat to human health and biosecurity from antimicrobial resistance, an understanding of its mechanisms and drivers is needed. Emergence of antimicrobial resistance in microorganisms is a natural phenomenon, yet antimicrobial resistance selection has been driven by antimicrobial exposure in health care, agriculture, and the environment. Onward transmission is affected by standards of infection control, sanitation, access to clean water, access to assured quality antimicrobials and diagnostics, travel, and migration. Strategies to reduce antimicrobial resistance by removing antimicrobial selective pressure alone rely upon resistance imparting a fitness cost, an effect not always apparent. Minimising resistance should therefore be considered comprehensively, by resistance mechanism, microorganism, antimicrobial drug, host, and context; parallel to new drug discovery, broad ranging, multidisciplinary research is needed across these five levels, interlinked across the health-care, agriculture, and environment sectors. Intelligent, integrated approaches, mindful of potential unintended results, are needed to ensure sustained, worldwide access to effective antimicrobials.

  14. Atypical Cell Populations Associated with Acquired Resistance to Cytostatics and Cancer Stem Cell Features: The Role of Mitochondria in Nuclear Encapsulation

    PubMed Central

    Gustmann, Sebastian; Jastrow, Holger; Acikelli, Ali Haydar; Dammann, Philip; Klein, Jacqueline; Dembinski, Ulrike; Bardenheuer, Walter; Malak, Sascha; Araúzo-Bravo, Marcos J.; Schultheis, Beate; Aldinger, Constanze; Strumberg, Dirk

    2014-01-01

    Until recently, acquired resistance to cytostatics had mostly been attributed to biochemical mechanisms such as decreased intake and/or increased efflux of therapeutics, enhanced DNA repair, and altered activity or deregulation of target proteins. Although these mechanisms have been widely investigated, little is known about membrane barriers responsible for the chemical imperviousness of cell compartments and cellular segregation in cytostatic-treated tumors. In highly heterogeneous cross-resistant and radiorefractory cell populations selected by exposure to anticancer agents, we found a number of atypical recurrent cell types in (1) tumor cell cultures of different embryonic origins, (2) mouse xenografts, and (3) paraffin sections from patient tumors. Alongside morphologic peculiarities, these populations presented cancer stem cell markers, aberrant signaling pathways, and a set of deregulated miRNAs known to confer both stem-cell phenotypes and highly aggressive tumor behavior. The first type, named spiral cells, is marked by a spiral arrangement of nuclei. The second type, monastery cells, is characterized by prominent walls inside which daughter cells can be seen maturing amid a rich mitochondrial environment. The third type, called pregnant cells, is a giant cell with a syncytium-like morphology, a main nucleus, and many endoreplicative functional progeny cells. A rare fourth cell type identified in leukemia was christened shepherd cells, as it was always associated with clusters of smaller cells. Furthermore, a portion of resistant tumor cells displayed nuclear encapsulation via mitochondrial aggregation in the nuclear perimeter in response to cytostatic insults, probably conferring imperviousness to drugs and long periods of dormancy until nuclear eclosion takes place. This phenomenon was correlated with an increase in both intracellular and intercellular mitochondrial traffic as well as with the uptake of free extracellular mitochondria. All these cellular

  15. Atypical cell populations associated with acquired resistance to cytostatics and cancer stem cell features: the role of mitochondria in nuclear encapsulation.

    PubMed

    Díaz-Carballo, David; Gustmann, Sebastian; Jastrow, Holger; Acikelli, Ali Haydar; Dammann, Philip; Klein, Jacqueline; Dembinski, Ulrike; Bardenheuer, Walter; Malak, Sascha; Araúzo-Bravo, Marcos J; Schultheis, Beate; Aldinger, Constanze; Strumberg, Dirk

    2014-11-01

    Until recently, acquired resistance to cytostatics had mostly been attributed to biochemical mechanisms such as decreased intake and/or increased efflux of therapeutics, enhanced DNA repair, and altered activity or deregulation of target proteins. Although these mechanisms have been widely investigated, little is known about membrane barriers responsible for the chemical imperviousness of cell compartments and cellular segregation in cytostatic-treated tumors. In highly heterogeneous cross-resistant and radiorefractory cell populations selected by exposure to anticancer agents, we found a number of atypical recurrent cell types in (1) tumor cell cultures of different embryonic origins, (2) mouse xenografts, and (3) paraffin sections from patient tumors. Alongside morphologic peculiarities, these populations presented cancer stem cell markers, aberrant signaling pathways, and a set of deregulated miRNAs known to confer both stem-cell phenotypes and highly aggressive tumor behavior. The first type, named spiral cells, is marked by a spiral arrangement of nuclei. The second type, monastery cells, is characterized by prominent walls inside which daughter cells can be seen maturing amid a rich mitochondrial environment. The third type, called pregnant cells, is a giant cell with a syncytium-like morphology, a main nucleus, and many endoreplicative functional progeny cells. A rare fourth cell type identified in leukemia was christened shepherd cells, as it was always associated with clusters of smaller cells. Furthermore, a portion of resistant tumor cells displayed nuclear encapsulation via mitochondrial aggregation in the nuclear perimeter in response to cytostatic insults, probably conferring imperviousness to drugs and long periods of dormancy until nuclear eclosion takes place. This phenomenon was correlated with an increase in both intracellular and intercellular mitochondrial traffic as well as with the uptake of free extracellular mitochondria. All these cellular

  16. A platinum-based hybrid drug design approach to circumvent acquired resistance to molecular targeted tyrosine kinase inhibitors

    NASA Astrophysics Data System (ADS)

    Wei, Yuming; Poon, Daniel C.; Fei, Rong; Lam, Amy S. M.; Au-Yeung, Steve C. F.; To, Kenneth K. W.

    2016-05-01

    Three molecular targeted tyrosine kinase inhibitors (TKI) were conjugated to classical platinum-based drugs with an aim to circumvent TKI resistance, predominately mediated by the emergence of secondary mutations on oncogenic kinases. The hybrids were found to maintain specificity towards the same oncogenic kinases as the original TKI. Importantly, they are remarkably less affected by TKI resistance, presumably due to their unique structure and the observed dual mechanism of anticancer activity (kinase inhibition and DNA damage). The study is also the first to report the application of a hybrid drug approach to switch TKIs from being efflux transporter substrates into non-substrates. TKIs cannot penetrate into the brain for treating metastases because of efflux transporters at the blood brain barrier. The hybrids were found to escape drug efflux and they accumulate more than the original TKI in the brain in BALB/c mice. Further development of the hybrid compounds is warranted.

  17. A platinum-based hybrid drug design approach to circumvent acquired resistance to molecular targeted tyrosine kinase inhibitors

    PubMed Central

    Wei, Yuming; Poon, Daniel C.; Fei, Rong; Lam, Amy S. M.; Au-Yeung, Steve C. F.; To, Kenneth K. W.

    2016-01-01

    Three molecular targeted tyrosine kinase inhibitors (TKI) were conjugated to classical platinum-based drugs with an aim to circumvent TKI resistance, predominately mediated by the emergence of secondary mutations on oncogenic kinases. The hybrids were found to maintain specificity towards the same oncogenic kinases as the original TKI. Importantly, they are remarkably less affected by TKI resistance, presumably due to their unique structure and the observed dual mechanism of anticancer activity (kinase inhibition and DNA damage). The study is also the first to report the application of a hybrid drug approach to switch TKIs from being efflux transporter substrates into non-substrates. TKIs cannot penetrate into the brain for treating metastases because of efflux transporters at the blood brain barrier. The hybrids were found to escape drug efflux and they accumulate more than the original TKI in the brain in BALB/c mice. Further development of the hybrid compounds is warranted. PMID:27150583

  18. Successful Use of Cyclophosphamide as an Add-On Therapy for Multiple Myeloma Patients with Acquired Resistance to Bortezomib or Lenalidomide

    PubMed Central

    Ito, Shigeki; Oyake, Tatsuo; Murai, Kazunori; Ishida, Yoji

    2013-01-01

    Novel agents such as thalidomide, lenalidomide, and bortezomib have been shown to possess potent activity against multiple myeloma. However, the treatment strategy for patients who acquired resistance to these agents has not been established. In addition to switching drug classes, intensified treatment strategy, including increase in the dosage of current agents and addition of other agents, may be considered for these patients. We here describe 2 myeloma patients with acquired resistance to bortezomib or lenalidomide, in whom add-on therapy with low-dose cyclophosphamide was effective and tolerable. These cases suggest that add-on therapy with cyclophosphamide is one of the treatment options to overcome resistance to novel agents in patients with multiple myeloma. A larger prospective study is needed to clarify the efficacy and safety of this strategy for novel agent-resistant multiple myeloma. PMID:23607005

  19. Cationic Antimicrobial Peptide Resistance Mechanisms of Streptococcal Pathogens

    PubMed Central

    LaRock, Christopher N.; Nizet, Victor

    2015-01-01

    Cationic antimicrobial peptides (CAMPs) are critical front line contributors to host defense against invasive bacterial infection. These immune factors have direct killing activity toward microbes, but many pathogens are able to resist their effects. Group A Streptococcus, group B Streptococcus and Streptococcus pneumoniae are among the most common pathogens of humans and display a variety of phenotypic adaptations to resist CAMPs. Common themes of CAMP resistance mechanisms among the pathogenic streptococci are repulsion, sequestration, export, and destruction. Each pathogen has a different array of CAMP-resistant mechanisms, with invasive disease potential reflecting the utilization of several mechanisms that may act in synergy. Here we discuss recent progress in identifying the sources of CAMP resistance in the medically important Streptococcus genus. Further study of these mechanisms can contribute to our understanding of streptococcal pathogenesis, and may provide new therapeutic targets for therapy and disease prevention. PMID:25701232

  20. Acquired Color Vision Defects and Hexane Exposure: A Study of San Francisco Bay Area Automotive Mechanics.

    PubMed

    Beckman, Stella; Eisen, Ellen A; Bates, Michael N; Liu, Sa; Haegerstrom-Portnoy, Gunilla; Hammond, S Katharine

    2016-06-01

    Occupational exposure to solvents, including n-hexane, has been associated with acquired color vision defects. Blue-yellow defects are most common and may be due to neurotoxicity or retinal damage. Acetone may potentiate the neurotoxicity of n-hexane. We present results on nonhexane solvent and hexane exposure and color vision from a cross-sectional study of 835 automotive repair workers in the San Francisco Bay Area, California (2007-2013). Cumulative exposure was estimated from self-reported work history, and color vision was assessed using the Lanthony desaturated D-15 panel test. Log-binomial regression was used to estimate prevalence ratios for color vision defects. Acquired color vision defects were present in 29% of participants, of which 70% were blue-yellow. Elevated prevalence ratios were found for nonhexane solvent exposure, with a maximum of 1.31 (95% confidence interval (CI): 0.86, 2.00) for blue-yellow. Among participants aged ≤50 years, the prevalence ratio for blue-yellow defects was 2.17 (95% CI: 1.03, 4.56) in the highest quartile of nonhexane solvent exposure and 1.62 (95% CI: 0.97, 2.72) in the highest category of exposure to hexane with acetone coexposure. Cumulative exposures to hexane and nonhexane solvents in the highest exposure categories were associated with elevated prevalence ratios for color vision defects in younger participants.

  1. Healthcare-associated, community-acquired and hospital-acquired bacteraemic urinary tract infections in hospitalized patients: a prospective multicentre cohort study in the era of antimicrobial resistance.

    PubMed

    Horcajada, J P; Shaw, E; Padilla, B; Pintado, V; Calbo, E; Benito, N; Gamallo, R; Gozalo, M; Rodríguez-Baño, J

    2013-10-01

    The clinical and microbiological characteristics of community-onset healthcare-associated (HCA) bacteraemia of urinary source are not well defined. We conducted a prospective cohort study at eight tertiary-care hospitals in Spain, from October 2010 to June 2011. All consecutive adult patients hospitalized with bacteraemic urinary tract infection (BUTI) were included. HCA-BUTI episodes were compared with community-acquired (CA) and hospital-acquired (HA) BUTI. A logistic regression analysis was performed to identify 30-day mortality risk factors. We included 667 episodes of BUTI (246 HCA, 279 CA and 142 HA). Differences between HCA-BUTI and CA-BUTI were female gender (40% vs 69%, p <0.001), McCabe score II-III (48% vs 14%, p <0.001), Pitt score ≥2 (40% vs 31%, p 0.03), isolation of extended spectrum β-lactamase-producing Enterobacteriaciae (13% vs 5%, p <0.001), median hospital stay (9 vs 7 days, p 0.03), inappropriate empirical antimicrobial therapy (21% vs 13%, p 0.02) and mortality (11.4% vs 3.9%, p 0.001). Pseudomonas aeruginosa was more frequently isolated in HA-BUTI (16%) than in HCA-BUTI (4%, p <0.001). Independent factors for mortality were age (OR 1.04; 95% CI 1.01-1.07), McCabe score II-III (OR 3.2; 95% CI 1.8-5.5), Pitt score ≥2 (OR 3.2 (1.8-5.5) and HA-BUTI OR 3.4 (1.2-9.0)). Patients with HCA-BUTI are a specific group with significant clinical and microbiological differences from patients with CA-BUTI, and some similarities with patients with HA-BUTI. Mortality was associated with patient condition, the severity of infection and hospital acquisition.

  2. Effects of Inducers of Systemic Acquired Resistance on Reproduction of Meloidogyne javanica and Rotylenchulus reniformis in Pineapple

    PubMed Central

    Chinnasri, B.; Sipes, B.S.; Schmitt, D.P.

    2006-01-01

    The potency of the inducers of systemic acquired resistance (SAR), acibenzolar-s-methyl, DL-α-amino-n-butyric acid (AABA), DL-β-amino-n-butyric acid (BABA), γ-amino-n-butyric acid (GABA), p-aminobenzoic acid (PABA), riboflavin, and salicylic acid (SA), in reducing reproduction of Meloidogyne javanica and Rotylenchulus reniformis in pineapple was investigated. All inducers were applied as foliar sprays to 1-mon-old pineapple plants (20 ml/plant) grown in 22-cm-diam. pots in the greenhouse. Two days after application, 10,000 eggs of M. javanica or R. reniformis were inoculated onto the plants. Six months after inoculation, nematode reproduction was measured. Acibenzolar decreased R. reniformis egg production by 58% compared to the nontreated control (P ≤ 0.05). Acibenzolar, BABA, and riboflavin reduced M. javanica egg production by 60% to 64% compared to the nontreated control (P ≤ 0.05). The point in the pineapple SAR pathway that each compound activates may explain the differing results between M. javanica and its giant cells and R. reniformis and its syncytia. Foliar application of acibenzolar at 100 and 200 mg/liter decreased by 30% and 60%, respectively, the number of M. javanica eggs as compared to the nontreated control. Fresh shoot weight of pineapple treated with 50, 100, 200, and 400 mg/liter acibenzolar was reduced by 1.2%, 3.3%, 9.9%, and 33% compared to the nontreated pineapple, respectively (P ≤ 0.05). Foliar application of acibenzolar may activate intrinsic resistance of pineapple to M. javanica and R. reniformis and may have a role in the sustainable management of nematodes in pineapple. PMID:19259535

  3. Risk factors for infection with multidrug-resistant bacteria in non-ventilated patients with hospital-acquired pneumonia*,**

    PubMed Central

    Seligman, Renato; Ramos-Lima, Luis Francisco; Oliveira, Vivian do Amaral; Sanvicente, Carina; Sartori, Juliana; Pacheco, Elyara Fiorin

    2013-01-01

    OBJECTIVE: To identify risk factors for the development of hospital-acquired pneumonia (HAP) caused by multidrug-resistant (MDR) bacteria in non-ventilated patients. METHODS: This was a retrospective observational cohort study conducted over a three-year period at a tertiary-care teaching hospital. We included only non-ventilated patients diagnosed with HAP and presenting with positive bacterial cultures. Categorical variables were compared with chi-square test. Logistic regression analysis was used to determine risk factors for HAP caused by MDR bacteria. RESULTS: Of the 140 patients diagnosed with HAP, 59 (42.1%) were infected with MDR strains. Among the patients infected with methicillin-resistant Staphylococcus aureus and those infected with methicillin-susceptible S. aureus, mortality was 45.9% and 50.0%, respectively (p = 0.763). Among the patients infected with MDR and those infected with non-MDR gram-negative bacilli, mortality was 45.8% and 38.3%, respectively (p = 0.527). Univariate analysis identified the following risk factors for infection with MDR bacteria: COPD; congestive heart failure; chronic renal failure; dialysis; urinary catheterization; extrapulmonary infection; and use of antimicrobial therapy within the last 10 days before the diagnosis of HAP. Multivariate analysis showed that the use of antibiotics within the last 10 days before the diagnosis of HAP was the only independent predictor of infection with MDR bacteria (OR = 3.45; 95% CI: 1.56-7.61; p = 0.002). CONCLUSIONS: In this single-center study, the use of broad-spectrum antibiotics within the last 10 days before the diagnosis of HAP was the only independent predictor of infection with MDR bacteria in non-ventilated patients with HAP. PMID:23857697

  4. Demography and Intercontinental Spread of the USA300 Community-Acquired Methicillin-Resistant Staphylococcus aureus Lineage

    PubMed Central

    Glaser, Philippe; Martins-Simões, Patrícia; Villain, Adrien; Barbier, Maxime; Tristan, Anne; Bouchier, Christiane; Ma, Laurence; Bes, Michele; Laurent, Frederic; Guillemot, Didier; Wirth, Thierry

    2016-01-01

    ABSTRACT Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized worldwide during the 1990s; in less than a decade, several genetically distinct CA-MRSA lineages carrying Panton-Valentine leukocidin genes have emerged on every continent. Most notably, in the United States, the sequence type 18-IV (ST8-IV) clone known as USA300 has become highly prevalent, outcompeting methicillin-susceptible S. aureus (MSSA) and other MRSA strains in both community and hospital settings. CA-MRSA bacteria are much less prevalent in Europe, where the European ST80-IV European CA-MRSA clone, USA300 CA-MRSA strains, and other lineages, such as ST22-IV, coexist. The question that arises is whether the USA300 CA-MRSA present in Europe (i) was imported once or on very few occasions, followed by a broad geographic spread, anticipating an increased prevalence in the future, or (ii) derived from multiple importations with limited spreading success. In the present study, we applied whole-genome sequencing to a collection of French USA300 CA-MRSA strains responsible for sporadic cases and micro-outbreaks over the past decade and United States ST8 MSSA and MRSA isolates. Genome-wide phylogenetic analysis demonstrated that the population structure of the French isolates is the product of multiple introductions dating back to the onset of the USA300 CA-MRSA clone in North America. Coalescent-based demography of the USA300 lineage shows that a strong expansion occurred during the 1990s concomitant with the acquisition of the arginine catabolic mobile element and antibiotic resistance, followed by a sharp decline initiated around 2008, reminiscent of the rise-and-fall pattern previously observed in the ST80 lineage. A future expansion of the USA300 lineage in Europe is therefore very unlikely. PMID:26884428

  5. Molecular mechanisms of methicillin resistance in Staphylococcus aureus.

    PubMed

    Domínguez, M A; Liñares, J; Martín, R

    1997-09-01

    Methicillin-resistant Staphylococcus aureus (MRSA) strains are among the most common nosocomial pathogens. The most significant mechanism of resistance to methicillin in this-species is the acquisition of a genetic determinant (mecA gene). However, resistance seems to have a more complex molecular basis, since additional chromosomal material is involved in such resistance. Besides, overproduction of penicillinase and/or alterations in the PBPs can contribute to the formation of resistance phenotypes. Genetic and environmental factors leading to MRSA are reviewed.

  6. Role of Chemotherapy and Mechanisms of Resistance to Chemotherapy in Metastatic Castration-Resistant Prostate Cancer

    PubMed Central

    Lohiya, Vipin; Aragon-Ching, Jeanny B.; Sonpavde, Guru

    2016-01-01

    Chemotherapy using the taxanes, docetaxel and cabazitaxel, remains an important therapeutic option in metastatic castration-resistant prostate cancer (CRPC). However, despite the survival benefits afforded by these agents, the survival increments are modest and resistance occurs universally. Efforts to overcome resistance to docetaxel by combining with biologic agents have heretofore been unsuccessful. Indeed, resistance to these taxanes is also associated with cross-resistance to the antiandrogen drugs, abiraterone and enzalutamide. Here, we discuss the various mechanisms of resistance to chemotherapy in metastatic CRPC and the potential role of emerging regimens and agents in varying clinical phases of development. PMID:27773999

  7. Targeting the miR-200c/LIN28B axis in acquired EGFR-TKI resistance non-small cell lung cancer cells harboring EMT features

    PubMed Central

    Sato, Hiroki; Shien, Kazuhiko; Tomida, Shuta; Okayasu, Kazuhiro; Suzawa, Ken; Hashida, Shinsuke; Torigoe, Hidejiro; Watanabe, Mototsugu; Yamamoto, Hiromasa; Soh, Junichi; Asano, Hiroaki; Tsukuda, Kazunori; Miyoshi, Shinichiro; Toyooka, Shinichi

    2017-01-01

    MicroRNA (miR)-200 family members (miR-200s) are frequently silenced in advanced cancer and have been implicated in the process of epithelial-to-mesenchymal transition (EMT). We previously reported that miR-200s were silenced through promoter methylation in acquired EGFR-tyrosine kinase inhibitor (TKI) resistant non-small cell lung cancer (NSCLC) cells harboring EMT features. In this study, we examined the functional role of miR-200s in NSCLC cells and investigated a novel approach to overcoming acquired EGFR-TKI resistance. In the analysis of NSCLC cell lines, each of the miR-200s expression-silenced cell lines showed promoter methylation. Significant correlations between miR-200c silencing and several oncogenic pathway alterations, including EMT-changes and LIN28B overexpression, were observed in the database analysis. In addition, EGFR-wild type cell lines had lower miR-200s expression levels than EGFR-mutant cell lines. The introduction of miR-200c using pre-miR-200c caused LIN28B suppression in cells with acquired EGFR-TKI resistance that harbored EMT features. Interestingly, both the introduction of miR-200c and the knockdown of LIN28B produced an antitumor effect in acquired EGFR-TKI resistance cells, whereas these manipulations were not effective in parental cells. The miR-200c/LIN28B axis plays an important role in cells with acquired resistance to EGFR-TKI that harbor EMT features and might be a useful therapeutic target for overcoming resistance. PMID:28084458

  8. Pipecolic Acid Orchestrates Plant Systemic Acquired Resistance and Defense Priming via Salicylic Acid-Dependent and -Independent Pathways

    PubMed Central

    Bernsdorff, Friederike; Döring, Anne-Christin; Gruner, Katrin; Schuck, Stefan; Bräutigam, Andrea; Zeier, Jürgen

    2016-01-01

    We investigated the relationships of the two immune-regulatory plant metabolites, salicylic acid (SA) and pipecolic acid (Pip), in the establishment of plant systemic acquired resistance (SAR), SAR-associated defense priming, and basal immunity. Using SA-deficient sid2, Pip-deficient ald1, and sid2 ald1 plants deficient in both SA and Pip, we show that SA and Pip act both independently from each other and synergistically in Arabidopsis thaliana basal immunity to Pseudomonas syringae. Transcriptome analyses reveal that SAR establishment in Arabidopsis is characterized by a strong transcriptional response systemically induced in the foliage that prepares plants for future pathogen attack by preactivating multiple stages of defense signaling and that SA accumulation upon SAR activation leads to the downregulation of photosynthesis and attenuated jasmonate responses systemically within the plant. Whereas systemic Pip elevations are indispensable for SAR and necessary for virtually the whole transcriptional SAR response, a moderate but significant SA-independent component of SAR activation and SAR gene expression is revealed. During SAR, Pip orchestrates SA-dependent and SA-independent priming of pathogen responses in a FLAVIN-DEPENDENT-MONOOXYGENASE1 (FMO1)-dependent manner. We conclude that a Pip/FMO1 signaling module acts as an indispensable switch for the activation of SAR and associated defense priming events and that SA amplifies Pip-triggered responses to different degrees in the distal tissue of SAR-activated plants. PMID:26672068

  9. Mechanism of Escherichia coli Resistance to Pyrrhocoricin

    PubMed Central

    Narayanan, Shalini; Modak, Joyanta K.; Ryan, Catherine S.; Garcia-Bustos, Jose; Davies, John K.

    2014-01-01

    Due to their lack of toxicity to mammalian cells and good serum stability, proline-rich antimicrobial peptides (PR-AMPs) have been proposed as promising candidates for the treatment of infections caused by antimicrobial-resistant bacterial pathogens. It has been hypothesized that these peptides act on multiple targets within bacterial cells, and therefore the likelihood of the emergence of resistance was considered to be low. Here, we show that spontaneous Escherichia coli mutants resistant to pyrrhocoricin arise at a frequency of approximately 6 × 10−7. Multiple independently derived mutants all contained a deletion in a nonessential gene that encodes the putative peptide uptake permease SbmA. Sensitivity could be restored to the mutants by complementation with an intact copy of the sbmA gene. These findings question the viability of the development of insect PR-AMPs as antimicrobials. PMID:24590485

  10. TrxR1 inhibition overcomes both hypoxia-induced and acquired bortezomib resistance in multiple myeloma through NF-кβ inhibition.

    PubMed

    Raninga, Prahlad V; Di Trapani, Giovanna; Vuckovic, Slavica; Tonissen, Kathryn F

    2016-01-01

    Multiple myeloma (MM) is a B-cell malignancy characterized by an accumulation of abnormal clonal plasma cells in the bone marrow. Introduction of the proteasome-inhibitor bortezomib has improved MM prognosis and survival; however hypoxia-induced or acquired bortezomib resistance remains a clinical problem. This study highlighted the role of thioredoxin reductase 1 (TrxR1) in the hypoxia-induced and acquired bortezomib resistance in MM. Higher TrxR1 gene expression correlated with high-risk disease, adverse overall survival, and poor prognosis in myeloma patients. We demonstrated that hypoxia induced bortezomib resistance in myeloma cells and increased TrxR1 protein levels. Inhibition of TrxR1 using auranofin overcame hypoxia-induced bortezomib resistance and restored the sensitivity of hypoxic-myeloma cells to bortezomib. Hypoxia increased NF-кβ subunit p65 nuclear protein levels and TrxR1 inhibition decreased hypoxia-induced NF-кβ p65 protein levels in the nucleus and reduced the expression of NF-кβ-regulated genes. In addition, higher TrxR1 protein levels were observed in bortezomib-resistant myeloma cells compared to the naïve cells, and its inhibition using either auranofin or TrxR1-specific siRNAs reversed bortezomib resistance. TrxR1 inhibition reduced p65 mRNA and protein expression in bortezomib-resistant myeloma cells, and also decreased the expression of NF-кβ-regulated anti-apoptotic and proliferative genes. Thus, TrxR1 inhibition overcomes both hypoxia-induced and acquired bortezomib resistance by inhibiting the NF-кβ signaling pathway. Our findings demonstrate that elevated TrxR1 levels correlate with the acquisition of bortezomib resistance in MM. We propose considering TrxR1-inhibiting drugs, such as auranofin, either for single agent or combination therapy to circumvent bortezomib-resistance and improve survival outcomes of MM patients.

  11. Mechanisms of Pyrazinamide Action and Resistance

    PubMed Central

    Zhang, Ying; Shi, Wanliang; Zhang, Wenhong; Mitchison, Denis

    2014-01-01

    PZA is a unique anti-tuberculosis drug that plays a key role in shortening the TB therapy. PZA kills non-replicating persisters that other TB drugs fail to kill, and thus making it an essential drug for inclusion in any drug combinations for treating drug susceptible and drug-resistant TB such as MDR-TB. PZA acts differently from common antibiotics by inhibiting multiple targets such as energy production, trans-translation and perhaps pantothenate /coenzyme A required for persister survival. Resistance to PZA is mostly caused by mutations in the pncA gene encoding pyrazinamidase involved in conversion of the prodrug PZA to the active form POA. Mutations in the drug target RpsA are also found in some PZA-resistant strains. The recent finding that panD mutations are found in some PZA-resistant strains without pncA or rpsA mutations may suggest a third PZA resistance gene and a potential new target of PZA. Current phenotype based PZA susceptibility testing is not reliable due to false resistance, and sequencing of the pncA gene represents a more rapid, cost-effective and more reliable molecular test for PZA susceptibility testing and should be used for guiding improved treatment of MDR/XDR-TB. Finally, the story of PZA has important implications for not only TB therapy but also chemotherapy in general. PZA serves as a model prototype persister drug and hopefully a ‘tipping point’ that inspires new efforts at developing a new type of antibiotics or drugs that target non-replicating persisters for improved treatment of not only TB but also other persistent bacterial infections. PMID:25530919

  12. Understanding the mechanisms of aromatase inhibitor resistance

    PubMed Central

    2012-01-01

    Aromatase inhibitors (AIs) have a central role in the treatment of breast cancer; however, resistance is a major obstacle to optimal management. Evidence from endocrine, molecular and pathological measurements in clinical material taken before and after therapy with AIs and data from clinical trials in which AIs have been given as treatment either alone or in combination with other targeted agents suggest diverse causes for resistance. These include inherent tumour insensitivity to oestrogen, ineffective inhibition of aromatase, sources of oestrogenic hormones independent of aromatase, activation of signalling by non-endocrine pathways, enhanced cell survival and selection of hormone-insensitive cellular clones during treatment. PMID:22277572

  13. Drug resistance mechanisms and novel drug targets for tuberculosis therapy.

    PubMed

    Islam, Md Mahmudul; Hameed, H M Adnan; Mugweru, Julius; Chhotaray, Chiranjibi; Wang, Changwei; Tan, Yaoju; Liu, Jianxiong; Li, Xinjie; Tan, Shouyong; Ojima, Iwao; Yew, Wing Wai; Nuermberger, Eric; Lamichhane, Gyanu; Zhang, Tianyu

    2017-01-20

    Drug-resistant tuberculosis (TB) poses a significant challenge to the successful treatment and control of TB worldwide. Resistance to anti-TB drugs has existed since the beginning of the chemotherapy era. New insights into the resistant mechanisms of anti-TB drugs have been provided. Better understanding of drug resistance mechanisms helps in the development of new tools for the rapid diagnosis of drug-resistant TB. There is also a pressing need in the development of new drugs with novel targets to improve the current treatment of TB and to prevent the emergence of drug resistance in Mycobacterium tuberculosis. This review summarizes the anti-TB drug resistance mechanisms, furnishes some possible novel drug targets in the development of new agents for TB therapy and discusses the usefulness using known targets to develop new anti-TB drugs. Whole genome sequencing is currently an advanced technology to uncover drug resistance mechanisms in M. tuberculosis. However, further research is required to unravel the significance of some newly discovered gene mutations in their contribution to drug resistance.

  14. Components of respiratory resistance monitored in mechanically ventilated patients.

    PubMed

    Babik, B; Peták, F; Asztalos, T; Deák, Z I; Bogáts, G; Hantos, Z

    2002-12-01

    The interrupter technique is commonly adopted to monitor respiratory resistance (Rrs,int) during mechanical ventilation; however, Rrs,int is often interpreted as an index of airway resistance (Raw). This study compared the values of Rrs,int provided by a Siemens 940 Lung Mechanics Monitor with total respiratory impedance (Zrs) parameters in 39 patients with normal spirometric parameters, who were undergoing elective coronary bypass surgery. Zrs was determined at the airway opening with pseudorandom oscillations of 0.2-6 Hz at end inspiration. Raw and tissue resistance (Rti) were derived from the Zrs data by model fitting; Rti and total resistance (Rrs,osc=Raw+Rti) were calculated at the actual respirator frequencies. Lower airway resistance (Rawl) was estimated by measuring tracheal pressure. Although good agreement was obtained between Rrs,osc and Rrs,int, with a ratio of 1.07+/-0.19 (mean+/-SD), they correlated poorly (r2=0.36). Rti and the equipment component of Raw accounted for most of Rrs,osc (39.8+/-11.9 and 43.0+/-6.9%, respectively), whereas only a small portion belonged to Rawl (17.2+/-6.3%). It is concluded that respiratory resistance may become very insensitive to changes in lower airway resistance and therefore, inappropriate for following alterations in airway tone during mechanical ventilation, especially in patients with relatively normal respiratory mechanics, where the tissue and equipment resistances represent the vast majority of the total resistance.

  15. Microbial resistance to disinfectants: mechanisms and significance

    SciTech Connect

    Hoff, J.C.; Akin, E.W.

    1986-11-01

    Drinking water disinfection provides the final barrier to transmission of a wide variety of potentially waterborne infectious agents including pathogenic bacteria, viruses, and protozoa. These agents differ greatly in their innate resistance to inactivation by disinfectants, ranging from extremely sensitive bacteria to highly resistant protozoan cysts. The close similarity between microorganism inactivation rates and the kinetics of chemical reactions has long been recognized. Ideally, under carefully controlled conditions, microorganism inactivation rates simulate first-order chemical reaction rates, making it possible to predict the effectiveness of disinfection under specific conditions. In practice, changes in relative resistance and deviations from first-order kinetics are caused by a number of factors, including microbial growth conditions, aggregation, and association with particulate materials. The net effect of all these factors is a reduction in the effectiveness and predictability of disinfection processes. To ensure effective pathogen control, disinfectant concentrations and contact times greater than experimentally determined values may be required. Of the factors causing enhanced disinfection resistance, protection by association with particulate matter is the most significant. Therefore, removal of particulate matter is an important step in increasing the effectiveness of disinfection processes.

  16. Mechanical resistance of silver halide infrared fibers

    NASA Astrophysics Data System (ADS)

    Barkay, Nitzan; Katzir, Abraham

    1992-01-01

    Flexibility resistance of silver-halide infrared fibers was investigated in the plastic bending regime, which is especially useful for internal medical applications. The CO2 laser transmission of the fibers was measured in several positions while being bent. The fibers have been found to operate even after large plastic deformations, and values for various fibers and bending conditions are reported.

  17. Fluoroquinolone resistance mechanisms in an Escherichia coli isolate, HUE1, without quinolone resistance-determining region mutations

    PubMed Central

    Sato, Toyotaka; Yokota, Shin-ichi; Uchida, Ikuo; Okubo, Torahiko; Usui, Masaru; Kusumoto, Masahiro; Akiba, Masato; Fujii, Nobuhiro; Tamura, Yutaka

    2013-01-01

    Fluoroquinolone resistance can cause major clinical problems. Here, we investigated fluoroquinolone resistance mechanisms in a clinical Escherichia coli isolate, HUE1, which had no mutations quinolone resistance-determining regions (QRDRs) of DNA gyrase and topoisomerase IV. HUE1 demonstrated MICs that exceeded the breakpoints for ciprofloxacin, levofloxacin, and norfloxacin. HUE1 harbored oqxAB and qnrS1 on distinct plasmids. In addition, it exhibited lower intracellular ciprofloxacin concentrations and higher mRNA expression levels of efflux pumps and their global activators than did reference strains. The genes encoding AcrR (local AcrAB repressor) and MarR (MarA repressor) were disrupted by insertion of the transposon IS3-IS629 and a frameshift mutation, respectively. A series of mutants derived from HUE1 were obtained by plasmid curing and gene knockout using homologous recombination. Compared to the MICs of the parent strain HUE1, the fluoroquinolone MICs of these mutants indicated that qnrS1, oqxAB, acrAB, acrF, acrD, mdtK, mdfA, and tolC contributed to the reduced susceptibility to fluoroquinolone in HUE1. Therefore, fluoroquinolone resistance in HUE1 is caused by concomitant acquisition of QnrS1 and OqxAB and overexpression of AcrAB–TolC and other chromosome-encoded efflux pumps. Thus, we have demonstrated that QRDR mutations are not absolutely necessary for acquiring fluoroquinolone resistance in E. coli. PMID:23745120

  18. HLA class I downregulation is associated with enhanced NK-cell killing of melanoma cells with acquired drug resistance to BRAF inhibitors.

    PubMed

    Sottile, Rosa; Pangigadde, Pradeepa N; Tan, Thomas; Anichini, Andrea; Sabbatino, Francesco; Trecroci, Francesca; Favoino, Elvira; Orgiano, Laura; Roberts, James; Ferrone, Soldano; Kärre, Klas; Colucci, Francesco; Carbone, Ennio

    2016-02-01

    The frequent development of drug resistance to targeted therapies in cancer patients has stimulated interest in strategies counteracting resistance. Combining immunotherapies with targeted therapies is one such strategy. In this context, we asked whether human NK cells can target melanoma cells that have acquired resistance to selective inhibitors targeting activating mutants of the B-Raf kinase (BRAF inhibitors, BRAFi). We generated drug-resistant cell variants in vitro from human BRAF-mutant melanoma cell lines MEL-HO, COLO-38, SK-MEL-37, 1520 and from primary melanoma cells freshly isolated from two patients. All drug-resistant cell variants remained susceptible to lysis by IL-2-activated NK cells; and two BRAFi-resistant lines (BRAFi-R) became significantly more susceptible to NK-cell lysis than their parental lines. This was associated with significant HLA class I antigen downregulation and PD-L1 upregulation on the drug-resistant lines. Although blocking HLA class I enhanced the extent of lysis of both BRAFi-R and parental cells to NK-cell-mediated lysis, antibody-mediated inhibition of PD1-PD-L1 interactions had no detectable effect. HLA class I antigen expression on BRAFi-R melanoma variants thus appears to play a major role in their susceptibility to NK-cell cytotoxicity. These findings suggest that NK-cell-based immunotherapy may be a viable approach to treat melanoma patients with acquired resistance to BRAF inhibitors.

  19. HLA class I downregulation is associated with enhanced NK‐cell killing of melanoma cells with acquired drug resistance to BRAF inhibitors

    PubMed Central

    Sottile, Rosa; Pangigadde, Pradeepa N.; Tan, Thomas; Anichini, Andrea; Sabbatino, Francesco; Trecroci, Francesca; Favoino, Elvira; Orgiano, Laura; Roberts, James; Ferrone, Soldano; Kärre, Klas; Colucci, Francesco

    2015-01-01

    The frequent development of drug resistance to targeted therapies in cancer patients has stimulated interest in strategies counteracting resistance. Combining immunotherapies with targeted therapies is one such strategy. In this context, we asked whether human NK cells can target melanoma cells that have acquired resistance to selective inhibitors targeting activating mutants of the B‐Raf kinase (BRAF inhibitors, BRAFi). We generated drug‐resistant cell variants in vitro from human BRAF‐mutant melanoma cell lines MEL‐HO, COLO‐38, SK‐MEL‐37, 1520 and from primary melanoma cells freshly isolated from two patients. All drug‐resistant cell variants remained susceptible to lysis by IL‐2‐activated NK cells; and two BRAFi‐resistant lines (BRAFi‐R) became significantly more susceptible to NK‐cell lysis than their parental lines. This was associated with significant HLA class I antigen downregulation and PD‐L1 upregulation on the drug‐resistant lines. Although blocking HLA class I enhanced the extent of lysis of both BRAFi‐R and parental cells to NK‐cell‐mediated lysis, antibody‐mediated inhibition of PD1–PD‐L1 interactions had no detectable effect. HLA class I antigen expression on BRAFi‐R melanoma variants thus appears to play a major role in their susceptibility to NK‐cell cytotoxicity. These findings suggest that NK‐cell‐based immunotherapy may be a viable approach to treat melanoma patients with acquired resistance to BRAF inhibitors. PMID:26564811

  20. Loss of AXIN1 drives acquired resistance to WNT pathway blockade in colorectal cancer cells carrying RSPO3 fusions.

    PubMed

    Picco, Gabriele; Petti, Consalvo; Centonze, Alessia; Torchiaro, Erica; Crisafulli, Giovanni; Novara, Luca; Acquaviva, Andrea; Bardelli, Alberto; Medico, Enzo

    2017-03-01

    In colorectal cancer (CRC), WNT pathway activation by genetic rearrangements of RSPO3 is emerging as a promising target. However, its low prevalence severely limits availability of preclinical models for in-depth characterization. Using a pipeline designed to suppress stroma-derived signal, we find that RSPO3 "outlier" expression in CRC samples highlights translocation and fusion transcript expression. Outlier search in 151 CRC cell lines identified VACO6 and SNU1411 cells as carriers of, respectively, a canonical PTPRK(e1)-RSPO3(e2) fusion and a novel PTPRK(e13)-RSPO3(e2) fusion. Both lines displayed marked in vitro and in vivo sensitivity to WNT blockade by the porcupine inhibitor LGK974, associated with transcriptional and morphological evidence of WNT pathway suppression. Long-term treatment of VACO6 cells with LGK974 led to the emergence of a resistant population carrying two frameshift deletions of the WNT pathway inhibitor AXIN1, with consequent protein loss. Suppression of AXIN1 in parental VACO6 cells by RNA interference conferred marked resistance to LGK974. These results provide the first mechanism of secondary resistance to WNT pathway inhibition.

  1. Mechanisms of Evolution in High-Consequence Drug Resistance Plasmids

    PubMed Central

    He, Susu; Chandler, Michael; Varani, Alessandro M.; Hickman, Alison B.; Dekker, John P.

    2016-01-01

    ABSTRACT The dissemination of resistance among bacteria has been facilitated by the fact that resistance genes are usually located on a diverse and evolving set of transmissible plasmids. However, the mechanisms generating diversity and enabling adaptation within highly successful resistance plasmids have remained obscure, despite their profound clinical significance. To understand these mechanisms, we have performed a detailed analysis of the mobilome (the entire mobile genetic element content) of a set of previously sequenced carbapenemase-producing Enterobacteriaceae (CPE) from the National Institutes of Health Clinical Center. This analysis revealed that plasmid reorganizations occurring in the natural context of colonization of human hosts were overwhelmingly driven by genetic rearrangements carried out by replicative transposons working in concert with the process of homologous recombination. A more complete understanding of the molecular mechanisms and evolutionary forces driving rearrangements in resistance plasmids may lead to fundamentally new strategies to address the problem of antibiotic resistance. PMID:27923922

  2. Mechanism of Insect Resistance to the Microbial Insecticide Bacillus thuringiensis

    NASA Astrophysics Data System (ADS)

    van Rie, J.; McGaughey, W. H.; Johnson, D. E.; Barnett, B. D.; van Mellaert, H.

    1990-01-01

    Receptor binding studies show that resistance of a laboratory-selected Plodia interpunctella strain to a Bacillus thuringiensis insecticidal crystal protein (ICP) is correlated with a 50-fold reduction in affinity of the membrane receptor for this protein. The strain is sensitive to a second type of ICP that apparently recognizes a different receptor. Understanding the mechanism of resistance will provide strategies to prevent or delay resistance and hence prolong the usefulness of B. thuringiensis ICPs as environmentally safe insecticides.

  3. Evolution of herbicide resistance mechanisms in grass weeds.

    PubMed

    Matzrafi, Maor; Gadri, Yaron; Frenkel, Eyal; Rubin, Baruch; Peleg, Zvi

    2014-12-01

    Herbicide resistant weeds are becoming increasingly common, threatening global food security. Here, we present BrIFAR: a new model system for the functional study of mechanisms of herbicide resistance in grass weeds. We have developed a large collection of Brachypodium accessions, the BrI collection, representing a wide range of habitats. Wide screening of the responses of the accessions to four major herbicide groups (PSII, ACCase, ALS/AHAS and EPSPS inhibitors) identified 28 herbicide-resistance candidate accessions. Target-site resistance to PSII inhibitors was found in accessions collected from habitats with a known history of herbicide applications. An amino acid substitution in the psbA gene (serine264 to glycine) conferred resistance and also significantly affected the flowering and shoot dry weight of the resistant accession, as compared to the sensitive accession. Non-target site resistance to ACCase inhibitors was found in accessions collected from habitats with a history of herbicide application and from a nature reserve. In-vitro enzyme activity tests and responses following pre-treatment with malathion (a cytochrome-P450 inhibitor) indicated sensitivity at the enzyme level, and give strong support to diclofop-methyl and pinoxaden enhanced detoxification as NTS resistance mechanism. BrIFAR can promote better understanding of the evolution of mechanisms of herbicide resistance and aid the implementation of integrative management approaches for sustainable agriculture.

  4. Herbicide resistance in weeds: Survey, characterization, and mechanisms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The goal of this paper is to present a systematic diagnostic approach towards the characterization of herbicide resistance in a given weed population with regards to profile (single, multiple, cross resistance), magnitude (fold level), mechanism, and related bio-physiological aspects. Diagnosing her...

  5. What have the mechanisms of resistance to glyphosate taught us?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The intensive use of glyphosate alone to manage weeds has selected populations that are glyphosate resistant. The three mechanisms of glyphosate resistance that have been elucidated are 1) target site mutations; 2) gene amplification; and 3) altered translocation due to sequestration. What have we...

  6. c-Met Overexpression Contributes to the Acquired Apoptotic Resistance of Nonadherent Ovarian Cancer Cells through a Cross Talk Mediated by Phosphatidylinositol 3-Kinase and Extracellular Signal-Regulated Kinase 1/212

    PubMed Central

    Tang, Maggie K S; Zhou, Hong Y; Yam, Judy W P; Wong, Alice S T

    2010-01-01

    Ovarian cancer is the most lethal gynecologic cancer mainly because of widespread peritoneal dissemination and malignant ascites. Key to this is the capacity of tumor cells to escape suspension-induced apoptosis (anoikis), which also underlies their resistance to chemotherapy. Here, we used a nonadherent cell culture model to investigate the molecular mechanisms of apoptotic resistance of ovarian cancer cells that may mimic the chemoresistance found in solid tumors. We found that ovarian cancer cells acquired a remarkable resistance to anoikis and apoptosis induced by exposure to clinically relevant doses of two front-line chemotherapeutic drugs cisplatin and paclitaxel when grown in three-dimensional than monolayer cultures. Inhibition of the hepatocyte growth factor (HGF) receptor c-Met, which is frequently overexpressed in ovarian cancer, by a specific inhibitor or small interfering RNA blocked the acquired anoikis resistance and restored chemosensitivity in three-dimensional not in two-dimensional cultures. These effects were found to be dependent on both phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) 1/2 signaling pathways. Inhibitors of PI3K/Akt abrogated ERK1/2 activation and its associated anoikis resistance in response to HGF, suggesting a signaling relay between these two pathways. Furthermore, we identified a central role of Ras as a mechanism of this cross talk. Interestingly, Ras did not lie upstream of PI3K/Akt, whereas PI3K/Akt signaling to ERK1/2 involved Ras. These findings shed new light on the apoptotic resistance mechanism of nonadherent ovarian cancer ascites cells and may have important clinical implications. PMID:20126471

  7. Mechanisms of Resistance in Microbial Spores.

    DTIC Science & Technology

    1986-11-14

    characterization of forespores isolated from Bacillus meqaterium ATCC 19213. J. Bacteriol. 153:436-442. Isolated stage III forespores of Bacillus megaterium ...other factors is complex. At Michigan State University, four morphotypes of B. megaterium spores, obtained by progressive divestment of the integument...permeating medium. Thereby, the PWC was determined with 28 types among 7 Bacillus species spanning a 3,OCO-fold range in heat resistance, which was

  8. Mechanisms of Drug Resistance in Plasmodium Falciparum

    DTIC Science & Technology

    1994-06-14

    major threat to world health. Efforts to control the disease have focused on chemotherapy, mosquito control and most recently vaccine development. These...resistant mosquitoes and upheavals in spraying programs and the complicated problems of vaccine development and testing. The world is facing an...development of vaccines for several important bacterial pathogens. The malaria parasite presents a unique challenge for transfection in that it is

  9. Camptothecin resistance in cancer: insights into the molecular mechanisms of a DNA-damaging drug.

    PubMed

    Beretta, G L; Gatti, L; Perego, P; Zaffaroni, N

    2013-01-01

    Poisoning of DNA topoisomerase I is the mechanism by which camptothecins interfere with tumor growth. Although the clinical use of camptothecins has had a significant impact on cancer therapy, de novo or acquired clinical resistance to these drugs is common. Clinical resistance to camptothecins is still a poorly understood phenomenon, likely involving pharmacological and tumor-related factors. Experimental models including yeast and mammalian cell cultures suggest three general mechanisms of camptothecin resistance: i) reduced cellular accumulation of drugs, ii) alteration in the structure/expression of topoisomerase I, and iii) alterations in the cellular response to camptothecin-DNA-ternary complex formation. Some lines of evidence have also suggested links between cellular camptothecin resistance, the existence of a subset of tumor-initiating cells and miRNA deregulation. In this regard, a better definition of the molecular events clarifying the regulation of tumorigenesis and gene expression might contribute to gain insight into the molecular mechanisms on the basis of camptothecin resistance of tumors and to identify new molecular tools for targeting cancer cells. The relevance of these mechanisms to clinical drug resistance has not yet been completely defined, but their evaluation in clinical specimens should help to define personalized treatments including camptothecins as single agents or in combination with other cytotoxic and target-specific anticancer agents. The present review focuses on the cellular/ molecular aspects involved in resistance of tumor cells to camptothecins, including the potential role of cancer stem cells and deregulated miRNAs, and on the approaches proposed for overcoming resistance.

  10. Pathways and mechanisms of venetoclax resistance.

    PubMed

    Bose, Prithviraj; Gandhi, Varsha; Konopleva, Marina

    2017-01-31

    The approval of venetoclax, a 'BH3-mimetic' antagonist of the BCL-2 anti-apoptotic protein, for chronic lymphocytic leukemia represents a major milestone in translational apoptosis research. Venetoclax has already received 'breakthrough' designation for acute myeloid leukemia, and is being studied in many other tumor types. However, resistance to BCL-2 inhibitor monotherapy may rapidly ensue. Several studies have shown that the other two major anti-apoptotic BCL-2 family proteins, BCL-XL and MCL-1, are the main determinants of resistance to venetoclax. This opens up possibilities for rationally combining venetoclax with other targeted agents to circumvent resistance. Here, we summarize the most promising combinations, and highlight those already in clinical trials. There is also increasing recognition that different tumors display different degrees of addiction to individual BCL-2 family proteins, and of the need to refine current 'BH3 profiling' techniques. Finally, the successful clinical development of potent and selective antagonists of BCL-XL and MCL-1 is eagerly awaited.

  11. Chemotherapy Resistance Mechanisms in Advanced Skin Cancer

    PubMed Central

    Kalal, Bhuvanesh Sukhlal; Upadhya, Dinesh; Pai, Vinitha Ramanath

    2017-01-01

    Melanoma is a most dangerous and deadly type of skin cancer, and considered intrinsically resistant to both radiotherapy and chemotherapy. It has become a major public health concern as the incidence of melanoma has been rising steadily over recent decades with a 5-year survival remaining less than 5%. Detection of the disease in early stage may be curable, but late stage metastatic disease that has spread to other organs has an extremely poor prognosis with a median survival of less than 10 months. Since metastatic melanoma is unresponsive to therapy that is currently available, research is now focused on different treatment strategies such as combinations of surgery, chemotherapy and radiotherapy. The molecular basis of resistance to chemotherapy seen in melanoma is multifactorial; defective drug transport system, altered apoptotic pathway, deregulation of apoptosis and/or changes in enzymatic systems that mediate cellular metabolic machinery. Understanding of alterations in molecular processes involved in drug resistance may help in developing new therapeutic approaches to treatment of malignant melanoma. PMID:28382191

  12. Molecular mechanism of fluoroquinolones resistance in Mycoplasma hominis clinical isolates.

    PubMed

    Meng, Dong-Ya; Sun, Chang-Jian; Yu, Jing-Bo; Ma, Jun; Xue, Wen-Cheng

    2014-01-01

    To evaluate the molecular mechanism of fluoroquinolones resistance in Mycoplasma hominis (MH) clinical strains isolated from urogenital specimens. 15 MH clinical isolates with different phenotypes of resistance to fluoroquinolones antibiotics were screened for mutations in the quinolone resistance-determining regions (QRDRs) of DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE) in comparison with the reference strain PG21, which is susceptible to fluoroquinolones antibiotics. 15 MH isolates with three kinds of quinolone resistance phenotypes were obtained. Thirteen out of these quinolone-resistant isolates were found to carry nucleotide substitutions in either gyrA or parC. There were no alterations in gyrB and no mutations were found in the isolates with a phenotype of resistance to Ofloxacin (OFX), intermediate resistant to Levofloxacin (LVX) and Sparfloxacin (SFX), and those susceptible to all three tested antibiotics. The molecular mechanism of fluoroquinolone resistance in clinical isolates of MH was reported in this study. The single amino acid mutation in ParC of MH may relate to the resistance to OFX and LVX and the high-level resistance to fluoroquinolones for MH is likely associated with mutations in both DNA gyrase and the ParC subunit of topoisomerase IV.

  13. Resistance mechanisms against arthropod herbivores in cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton plants from the genus Gossypium are grown on more than 30 million hectares worldwide and are a major source of fiber. The plants possess a wide-range of indirect and direct-defense mechanisms against arthropod pests. Direct defense mechanisms include morphological traits such as trichomes and...

  14. The battle against multi-resistant strains: Renaissance of antimicrobial essential oils as a promising force to fight hospital-acquired infections.

    PubMed

    Warnke, Patrick H; Becker, Stephan T; Podschun, Rainer; Sivananthan, Sureshan; Springer, Ingo N; Russo, Paul A J; Wiltfang, Joerg; Fickenscher, Helmut; Sherry, Eugene

    2009-10-01

    Hospital-acquired infections and antibiotic-resistant bacteria continue to be major health concerns worldwide. Particularly problematic is methicillin-resistant Staphylococcus aureus (MRSA) and its ability to cause severe soft tissue, bone or implant infections. First used by the Australian Aborigines, Tea tree oil and Eucalyptus oil (and several other essential oils) have each demonstrated promising efficacy against several bacteria and have been used clinically against multi-resistant strains. Several common and hospital-acquired bacterial and yeast isolates (6 Staphylococcus strains including MRSA, 4 Streptococcus strains and 3 Candida strains including Candida krusei) were tested for their susceptibility for Eucalyptus, Tea tree, Thyme white, Lavender, Lemon, Lemongrass, Cinnamon, Grapefruit, Clove Bud, Sandalwood, Peppermint, Kunzea and Sage oil with the agar diffusion test. Olive oil, Paraffin oil, Ethanol (70%), Povidone iodine, Chlorhexidine and hydrogen peroxide (H(2)O(2)) served as controls. Large prevailing effective zones of inhibition were observed for Thyme white, Lemon, Lemongrass and Cinnamon oil. The other oils also showed considerable efficacy. Remarkably, almost all tested oils demonstrated efficacy against hospital-acquired isolates and reference strains, whereas Olive and Paraffin oil from the control group produced no inhibition. As proven in vitro, essential oils represent a cheap and effective antiseptic topical treatment option even for antibiotic-resistant strains as MRSA and antimycotic-resistant Candida species.

  15. Characterizing Mechanisms of Resistance to Androgen Deprivation in Prostate Cancer

    DTIC Science & Technology

    2015-11-01

    AWARD NUMBER: W81XWH-13-1-0161 TITLE: Characterizing Mechanisms of Resistance to Androgen Deprivation in Prostate Cancer PRINCIPAL...INVESTIGATOR: Ginevra Botta CONTRACTING ORGANIZATION: DANA-FARBER CANCER INSTITUTE BOSTON MA 02215 REPORT DATE: November 2015 TYPE OF REPORT: Final...Characterizing mechanisms of Resistance to Androgen Deprivation in Prostate Cancer 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-13-1-0161 5c. PROGRAM

  16. Transformation of sweet orange [Citrus sinensis (L.) Osbeck] with pthA-nls for acquiring resistance to citrus canker disease.

    PubMed

    Yang, Li; Hu, Chunhua; Li, Na; Zhang, Jiayin; Yan, Jiawen; Deng, Ziniu

    2011-01-01

    The COOH terminal of pthA encoding three nuclear localizing signals (NLS) was amplified by polymerase chain reaction (PCR) from the plasmid of Xanthomonas axonopodis pv. citri, the pathogen of citrus canker disease. Then the sense and antisense strands of the nls were cloned into pBI121 vector. pthA-nls driven by the CaMV35 s promoter was transferred into sweet orange via Agrobacterium -mediated transformation. Successful integration was confirmed by PCR and Southern blotting, and 12 sense-nls (nls (+)) and 9 antisense-nls (nls (-)) transgenic clones were obtained. The expression of nls fragment was analyzed by RT-PCR, Real time q-PCR and Western blotting, in which the specific NLS protein was detected only in nls (+) transgenic clones. In an in vitro assay, when pin-puncture inoculation was performed with 2.5 × 10(7) cfu/ml of bacterial solution, the nls (+) transgenic clones showed no typical lesion development, while typical symptoms were observed in the wild types and the nls (-) transgenic clones. In vivo assay results indicated that the nls (+) transgenic clones showed less disease incidence, in comparison with the wild types and the nls (-) transgenic clones, when pin-puncture inoculation was performed with 10(4)-10(5) cfu/ml. The minimum disease incidence was 23.3% for 'Sucarri' sweet orange and 33.3% for 'Bingtang' sweet orange. When 10(4)-10(7) cfu/ml of pathogen was spray inoculated, the nls (+) transgenic clones did not show any symptom, and even the concentration raised to 10(9) cfu/ml, the disease incidence was 20-80%, while the wild types and the nls (-) transgenic clones had 100% disease development with whatever concentration of inoculum. Two transgenic clones were confirmed to be resistant to citrus canker disease in the repeated inoculation. The results suggested that the transformation of nls sense strands may offer an effective way to acquire resistance to citrus canker disease.

  17. Molecular mechanism of ATP-dependent solute transport by multidrug resistance-associated protein 1.

    PubMed

    Chang, Xiu-bao

    2010-01-01

    Millions of new cancer patients are diagnosed each year and over half of these patients die from this devastating disease. Thus, cancer causes a major public health problem worldwide. Chemotherapy remains the principal mode to treat many metastatic cancers. However, occurrence of cellular multidrug resistance (MDR) prevents efficient killing of cancer cells, leading to chemotherapeutic treatment failure. Over-expression of ATP-binding cassette transporters, such as P-glycoprotein, breast cancer resistance protein and/or multidrug resistance-associated protein 1 (MRP1), confers an acquired MDR due to their capabilities of transporting a broad range of chemically diverse anticancer drugs across the cell membrane barrier. In this review, the molecular mechanism of ATP-dependent solute transport by MRP1 will be addressed.

  18. Molecular mechanisms of polymyxin resistance: knowns and unknowns.

    PubMed

    Baron, Sophie; Hadjadj, Linda; Rolain, Jean-Marc; Olaitan, Abiola Olumuyiwa

    2016-12-01

    Colistin, also referred to as polymyxin E, is an effective antibiotic against most multidrug-resistant Gram-negative bacteria and is currently used as a last-line drug for treating severe bacterial infections. Colistin resistance has increased gradually for the last few years, and knowledge of its multifaceted mechanisms is expanding. This includes the newly discovered plasmid-mediated colistin resistance gene mcr-1, which has been detected in over 20 countries within 3 months of its first report. We previously reported all of the known mechanisms of polymyxin resistance in our first review in 2014, but an update seems necessary in 2016, considering the significant recent discoveries that have been made in this domain. This review provides an update about what is already known, what is new, and some unresolved questions with respect to colistin resistance.

  19. Targeting bacterial topoisomerases: how to counter mechanisms of resistance.

    PubMed

    Tse-Dinh, Yuk-Ching

    2016-06-01

    DNA gyrase and topoisomerase IV are type IIA bacterial topoisomerases that are targeted by highly effective antibiotics. However, resistance via multiple mechanisms arises to limit the efficacies of these drugs. Continued research on type IIA bacterial topoisomerases has provided novel approaches to counter the most common resistance mechanism for utilization of these proven targets in antibacterial therapy. Bacterial topoisomerase I is being explored as an alternative target that is not expected to show cross-resistance. Dual targeting or combination therapy could be strategies for circumventing the development of resistance to topoisomerase-targeting antibiotics. Bacterial topoisomerases are high-value bactericidal targets that could continue to be exploited for antibacterial therapy, if new tactics to counter resistance can be adopted.

  20. Trends towards lower antimicrobial susceptibility and characterization of acquired resistance among clinical isolates of Brachyspira hyodysenteriae in Spain.

    PubMed

    Hidalgo, Álvaro; Carvajal, Ana; Vester, Birte; Pringle, Märit; Naharro, Germán; Rubio, Pedro

    2011-07-01

    The antimicrobial susceptibility of clinical isolates of Brachyspira hyodysenteriae in Spain was monitored, and the underlying molecular mechanisms of resistance were investigated. MICs of tylosin, tiamulin, valnemulin, lincomycin, and tylvalosin were determined for 87 B. hyodysenteriae isolates recovered from 2008 to 2009 by broth dilution. Domain V of the 23S rRNA gene and the ribosomal protein L3 gene were sequenced in 20 isolates for which the tiamulin MIC was ≥ 4 μg/ml, presenting decreased susceptibility, and in 18 tiamulin-susceptible isolates (MIC ≤ 0.125 μg/ml), and all isolates were typed by multiple-locus variable-number tandem repeats analysis. A comparison with antimicrobial susceptibility data from 2000 to 2007 showed an increase in pleuromutilin resistance over time, doubling the number of isolates with decreased susceptibility to tiamulin. No alteration in susceptibility was detected for lincomycin, and the MIC of tylosin remained high (MIC(50) > 128 μg/ml). The decreased susceptibility to tylosin and lincomycin can be explained by mutations at position A2058 of the 23S rRNA gene (Escherichia coli numbering). A2058T was the predominant mutation, but A2058G also was found together with a change of the neighboring base pair at positions 2057 to 2611. The role of additional point mutations in the vicinity of the peptidyl transferase center and mutations in the L3 at amino acids 148 and 149 and their possible involvement in antimicrobial susceptibility are considered. An association between G2032A and high levels of tiamulin and lincomycin MICs was found, suggesting an increasing importance of this mutation in antimicrobial resistance of clinical isolates of B. hyodysenteriae.

  1. Liquid biopsy monitoring uncovers acquired RAS-mediated resistance to cetuximab in a substantial proportion of patients with head and neck squamous cell carcinoma

    PubMed Central

    Schieferdecker, Aneta; Busch, Chia-Jung; Laban, Simon; Grob, Tobias; Kriegs, Malte; Knecht, Rainald; Bokemeyer, Carsten; Binder, Mascha

    2016-01-01

    Resistance to epidermal growth factor receptor (EGFR)-targeted therapy is insufficiently understood in head and neck squamous cell carcinoma (HNSCC), entailing the lack of predictive biomarkers. Here, we studied resistance-mediating EGFR ectodomain and activating RAS mutations by next-generation sequencing (NGS) of cell lines and tumor tissue of cetuximab-naïve patients (46 cases, 12 cell lines), as well as liquid biopsies taken during and after cetuximab/platinum/5-fluorouracil treatment (20 cases). Tumors of cetuximab-naïve patients were unmutated, except for HRAS mutations in 4.3% of patients. Liquid biopsies revealed acquired KRAS, NRAS or HRAS mutations in more than one third of patients after cetuximab exposure. 46% of patients with on-treatment disease progression showed acquired RAS mutations, while no RAS mutations were found in the non-progressive subset of patients, indicating that acquisition of RAS mutant clones correlated significantly with clinical resistance (Chi square p=0.032). The emergence of mutations preceded clinical progression in half of the patients, with a maximum time from mutation detection to clinical progression of 16 weeks. RAS mutations account for acquired resistance to EGFR-targeting in a substantial proportion of HNSCC patients, even though these tumors are rarely mutated at baseline. Liquid biopsies may be used for mutational monitoring to guide treatment decisions. PMID:27119512

  2. XPO1 inhibitor combination therapy with bortezomib or carfilzomib induces nuclear localization of IκBα and overcomes acquired proteasome inhibitor resistance in human multiple myeloma.

    PubMed

    Turner, Joel G; Kashyap, Trinayan; Dawson, Jana L; Gomez, Juan; Bauer, Alexis A; Grant, Steven; Dai, Yun; Shain, Kenneth H; Meads, Mark; Landesman, Yosef; Sullivan, Daniel M

    2016-11-29

    Acquired proteasome-inhibitor (PI) resistance is a major obstacle in the treatment of multiple myeloma (MM). We investigated whether the clinical XPO1-inhibitor selinexor, when combined with bortezomib or carfilzomib, could overcome acquired resistance in MM. PI-resistant myeloma cell lines both in vitro and in vivo and refractory myeloma patient biopsies were treated with selinexor/bortezomib or carfilzomib and assayed for apoptosis. Mechanistic studies included NFκB pathway protein expression assays, immunofluorescence microscopy, ImageStream flow-cytometry, and proximity-ligation assays. IκBα knockdown and NFκB activity were measured in selinexor/bortezomib-treated MM cells. We found that selinexor restored sensitivity of PI-resistant MM to bortezomib and carfilzomib. Selinexor/bortezomib treatment inhibited PI-resistant MM tumor growth and increased survival in mice. Myeloma cells from PI-refractory MM patients were sensitized by selinexor to bortezomib and carfilzomib without affecting non-myeloma cells. Immunofluorescence microscopy, Western blot, and ImageStream analyses of MM cells showed increases in total and nuclear IκBα by selinexor/bortezomib. Proximity ligation found increased IκBα-NFκB complexes in treated MM cells. IκBα knockdown abrogated selinexor/bortezomib-induced cytotoxicity in MM cells. Selinexor/bortezomib treatment decreased NFκB transcriptional activity. Selinexor, when used with bortezomib or carfilzomib, has the potential to overcome PI drug resistance in MM. Sensitization may be due to inactivation of the NFκB pathway by IκBα.

  3. Investigating Genomic Mechanisms of Treatment Resistance in Castration Resistant Prostate Cancer

    DTIC Science & Technology

    2015-05-01

    Prostate Cancer PRINCIPAL INVESTIGATOR: Terence W. Friedlander, MD CONTRACTING ORGANIZATION: University of California, San Francisco San...5a. CONTRACT NUMBER W81XWH-12-1-0160 Castration Resistant Prostate Cancer 5b. GRANT NUMBER PC110126 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...mechanisms of resistance to androgen biosynthesis inhibitors in men with castration resistant prostate cancer , and to investigate clinical methods of

  4. Emerging and existing mechanisms co-operate in generating diverse β-lactam resistance phenotypes in geographically dispersed and genetically disparate Pseudomonas aeruginosa strains.

    PubMed

    Martinez, Elena; Pérez, Javier Escobar; Márquez, Carolina; Vilacoba, Elisabet; Centrón, Daniela; Leal, Aura L; Saavedra, Carlos; Saavedra, Sandra Y; Tovar, Catalina; Vanegas, Natasha; Stokes, H W

    2013-09-01

    β-Lactam resistance in Pseudomonas aeruginosa clinical isolates is driven by a number of mechanisms. Whilst several are understood, how they act co-operatively in pathogenic strains is less clear. In some isolates, resistance profiles cannot always be explained by identifying the common resistance-determining pathways, suggesting that other mechanisms may be important. Pathogenic P. aeruginosa isolates from four countries were characterised by PCR. Quantitative expression analysis was also assessed for the activity of several pathways that influence antibiotic resistance, and culture experiments were conducted to test how random transposition of the insertion sequence IS26 during growth may influence resistance to some antibiotics. In most strains, antibiotic resistance was being driven by changes in multiple pathways and by the presence or absence of genes acquired by lateral gene transfer. Multiple mechanisms of resistance were prevalent in strains from all of the countries examined, although regional differences in the type of interacting mechanisms were apparent. Changes in chromosomal pathways included overexpression of AmpC and two efflux pumps. Also, gain or loss of IS26 at some chromosomal locations, most notably oprD, could influence resistance to carbapenems. IS26-related resistance was found in strains from Argentina and geographically linked Uruguay, but not in strains from either Colombia or Australia. Pseudomonas aeruginosa pathogenic strains are evolving to become multidrug-resistant in more complex ways. This is being influenced by single strains acquiring changes in numerous known pathways as well as by newly emerging resistance mechanisms in this species.

  5. [Molecular characterization of resistance mechanisms: methicillin resistance Staphylococcus aureus, extended spectrum β-lactamases and carbapenemases].

    PubMed

    Oteo, Jesús; Belén Aracil, María

    2015-07-01

    Multi-drug resistance in bacterial pathogens increases morbidity and mortality in infected patients and it is a threat to public health concern by their high capacity to spread. For both reasons, the rapid detection of multi-drug resistant bacteria is critical. Standard microbiological procedures require 48-72 h to provide the antimicrobial susceptibility results, thus there is emerging interest in the development of rapid detection techniques. In recent years, the use of selective and differential culture-based methods has widely spread. However, the capacity for detecting antibiotic resistance genes and their low turnaround times has made molecular methods a reference for diagnosis of multidrug resistance. This review focusses on the molecular methods for detecting some mechanisms of antibiotic resistance with a high clinical and epidemiological impact: a) Enzymatic resistance to broad spectrum β-lactam antibiotics in Enterobacteriaceae, mainly extended spectrum β-lactamases (ESBL) and carbapenemases; and b) methicillin resistance in Staphylococcus aureus.

  6. Pseudomonas aeruginosa: arsenal of resistance mechanisms, decades of changing resistance profiles, and future antimicrobial therapies.

    PubMed

    El Zowalaty, Mohamed E; Al Thani, Asmaa A; Webster, Thomas J; El Zowalaty, Ahmed E; Schweizer, Herbert P; Nasrallah, Gheyath K; Marei, Hany E; Ashour, Hossam M

    2015-01-01

    Antimicrobial resistance is one of the most serious public health issues facing humans since the discovery of antimicrobial agents. The frequent, prolonged, and uncontrolled use of antimicrobial agents are major factors in the emergence of antimicrobial-resistant bacterial strains, including multidrug-resistant variants. Pseudomonas aeruginosa is a leading cause of nosocomial infections. The abundant data on the increased resistance to antipseudomonal agents support the need for global action. There is a paucity of new classes of antibiotics active against P. aeruginosa. Here, we discuss recent antibacterial resistance profiles and mechanisms of resistance by P. aeruginosa. We also review future potential methods for controlling antibiotic-resistant bacteria, such as phage therapy, nanotechnology and antipseudomonal vaccines.

  7. Molecular mechanism of brain impairment caused by drinking-acquired fluorosis and selenium intervention.

    PubMed

    Zheng, Xiangren; Sun, Yan; Ke, Lulu; Ouyang, Wei; Zhang, Zigui

    2016-04-01

    This study investigated the molecular mechanism of brain impairment induced by drinking fluoridated water and selenium intervention. Results showed that the learning and memory of rats in NaF group significantly decreased. Moreover, the number of apoptotic cells, the expression levels of Cytc mRNA and protein, and the expression levels of Caspase-9 and Caspase-3 mRNA significantly increased; by contrast, Caspase-9 and Caspase-3 protein levels significantly decreased. Compared with the NaF group, the mRNA levels of Cytc and Caspase-9, as well as the protein levels of Cytc in NaF+Se group, significantly decreased. Conversely, the protein levels of Caspase-3 and Caspase-9, as well as the mRNA levels of Caspase-3, significantly increased. Thus, the mitochondrial CytC-Caspase-9-Caspase-3 apoptosis pathway in the hippocampus was one of the mechanisms leading to fluorosis-induced brain damage. Furthermore, the Cytc signaling molecules were possibly the key target molecules in fluorosis-induced apoptosis, and selenium could alleviate fluorosis-induced brain injury.

  8. Fungal Resistance to Plant Antibiotics as a Mechanism of Pathogenesis

    PubMed Central

    Morrissey, John P.; Osbourn, Anne E.

    1999-01-01

    Many plants produce low-molecular-weight compounds which inhibit the growth of phytopathogenic fungi in vitro. These compounds may be preformed inhibitors that are present constitutively in healthy plants (also known as phytoanticipins), or they may be synthesized in response to pathogen attack (phytoalexins). Successful pathogens must be able to circumvent or overcome these antifungal defenses, and this review focuses on the significance of fungal resistance to plant antibiotics as a mechanism of pathogenesis. There is increasing evidence that resistance of fungal pathogens to plant antibiotics can be important for pathogenicity, at least for some fungus-plant interactions. This evidence has emerged largely from studies of fungal degradative enzymes and also from experiments in which plants with altered levels of antifungal secondary metabolites were generated. Whereas the emphasis to date has been on degradative mechanisms of resistance of phytopathogenic fungi to antifungal secondary metabolites, in the future we are likely to see a rapid expansion in our knowledge of alternative mechanisms of resistance. These may include membrane efflux systems of the kind associated with multidrug resistance and innate resistance due to insensitivity of the target site. The manipulation of plant biosynthetic pathways to give altered antibiotic profiles will also be valuable in telling us more about the significance of antifungal secondary metabolites for plant defense and clearly has great potential for enhancing disease resistance for commercial purposes. PMID:10477313

  9. Resistance Mechanisms of Anopheles stephensi (Diptera: Culicidae) to Temephos

    PubMed Central

    Soltani, Aboozar; Vatandoost, Hassan; Oshaghi, Mohammad Ali; Ravasan, Naseh Maleki; Enayati, Ahmad Ali; Asgarian, Fatemeh

    2015-01-01

    Background: Anopheles stephensi is a sub-tropical species and has been considered as one of the most important vector of human malaria throughout the Middle East and South Asian region including the malarious areas of southern Iran. Current reports confirmed An. stephensi resistance to temephos in Oman and India. However, there is no comprehensive research on mechanisms of temephos resistance in An. stephensi in the literature. This study was designed in order to clarify the enzymatic and molecular mechanisms of temephos resistance in this species. Methods: Profile activities of α- and ß-esterases, mixed function oxidase (MFO), glutathione-S-transferase (GST), insensitive acetylcholinesterase, and para-nitrophenyl acetate (PNPA)-esterase enzymes were tested for An. stephensi strain with resistance ratio of 15.82 to temephos in comparison with susceptible strain. Results: Results showed that the mean activity of α-EST, GST and AChE enzymes were classified as altered indicating metabolic mechanisms have considerable role in resistance of An. stephensi to temephos. Molecular study using PCR-RFLP method to trace the G119S mutation in ACE-1 gene showed lack of the mutation responsible for organophosphate insecticide resistance in the temephos-selected strain of An. stephensi. Conclusion: This study showed that the altered enzymes but not targets site insensitivity of ACE-1 are responsible for temephos resistance in An. stephensi in south of Iran. PMID:26114145

  10. Label-free SRM-based relative quantification of antibiotic resistance mechanisms in Pseudomonas aeruginosa clinical isolates.

    PubMed

    Charretier, Yannick; Köhler, Thilo; Cecchini, Tiphaine; Bardet, Chloé; Cherkaoui, Abdessalam; Llanes, Catherine; Bogaerts, Pierre; Chatellier, Sonia; Charrier, Jean-Philippe; Schrenzel, Jacques

    2015-01-01

    Both acquired and intrinsic mechanisms play a crucial role in Pseudomonas aeruginosa antibiotic resistance. Many clinically relevant resistance mechanisms result from changes in gene expression, namely multidrug efflux pump overproduction, AmpC β-lactamase induction or derepression, and inactivation or repression of the carbapenem-specific porin OprD. Changes in gene expression are usually assessed using reverse-transcription quantitative real-time PCR (RT-qPCR) assays. Here, we evaluated label-free Selected Reaction Monitoring (SRM)-based mass spectrometry to directly quantify proteins involved in antibiotic resistance. We evaluated the label-free SRM using a defined set of P. aeruginosa isolates with known resistance mechanisms and compared it with RT-qPCR. Referring to efflux systems, we found a more robust relative quantification of antibiotic resistance mechanisms by SRM than RT-qPCR. The SRM-based approach was applied to a set of clinical P. aeruginosa isolates to detect antibiotic resistance proteins. This multiplexed SRM-based approach is a rapid and reliable method for the simultaneous detection and quantification of resistance mechanisms and we demonstrate its relevance for antibiotic resistance prediction.

  11. Label-free SRM-based relative quantification of antibiotic resistance mechanisms in Pseudomonas aeruginosa clinical isolates

    PubMed Central

    Charretier, Yannick; Köhler, Thilo; Cecchini, Tiphaine; Bardet, Chloé; Cherkaoui, Abdessalam; Llanes, Catherine; Bogaerts, Pierre; Chatellier, Sonia; Charrier, Jean-Philippe; Schrenzel, Jacques

    2015-01-01

    Both acquired and intrinsic mechanisms play a crucial role in Pseudomonas aeruginosa antibiotic resistance. Many clinically relevant resistance mechanisms result from changes in gene expression, namely multidrug efflux pump overproduction, AmpC β-lactamase induction or derepression, and inactivation or repression of the carbapenem-specific porin OprD. Changes in gene expression are usually assessed using reverse-transcription quantitative real-time PCR (RT-qPCR) assays. Here, we evaluated label-free Selected Reaction Monitoring (SRM)-based mass spectrometry to directly quantify proteins involved in antibiotic resistance. We evaluated the label-free SRM using a defined set of P. aeruginosa isolates with known resistance mechanisms and compared it with RT-qPCR. Referring to efflux systems, we found a more robust relative quantification of antibiotic resistance mechanisms by SRM than RT-qPCR. The SRM-based approach was applied to a set of clinical P. aeruginosa isolates to detect antibiotic resistance proteins. This multiplexed SRM-based approach is a rapid and reliable method for the simultaneous detection and quantification of resistance mechanisms and we demonstrate its relevance for antibiotic resistance prediction. PMID:25713571

  12. Insecticide resistance in vector Chagas disease: evolution, mechanisms and management.

    PubMed

    Mougabure-Cueto, Gastón; Picollo, María Inés

    2015-09-01

    Chagas disease is a chronic parasitic infection restricted to America. The disease is caused by the protozoa Trypanosoma cruzi, which is transmitted to human through the feces of infected triatomine insects. Because no treatment is available for the chronic forms of the disease, vector chemical control represents the best way to reduce the incidence of the disease. Chemical control has been based principally on spraying dwellings with insecticide formulations and led to the reduction of triatomine distribution and consequent interruption of disease transmission in several areas from endemic region. However, in the last decade it has been repeatedly reported the presence triatomnes, mainly Triatoma infestans, after spraying with pyrethroid insecticides, which was associated to evolution to insecticide resistance. In this paper the evolution of insecticide resistance in triatomines is reviewed. The insecticide resistance was detected in 1970s in Rhodnius prolixus and 1990s in R. prolixus and T. infestans, but not until the 2000s resistance to pyrthroids in T. infestans associated to control failures was described in Argentina and Bolivia. The main resistance mechanisms (i.e. enhanced metabolism, altered site of action and reduced penetration) were described in the T. infestans resistant to pyrethrods. Different resistant profiles were demonstrated suggesting independent origin of the different resistant foci of Argentina and Bolivia. The deltamethrin resistance in T. infestans was showed to be controlled by semi-dominant, autosomally inherited factors. Reproductive and developmental costs were also demonstrated for the resistant T. infestans. A discussion about resistance and tolerance concepts and the persistence of T. infestans in Gran Chaco region are presented. In addition, theoretical concepts related to toxicological, evolutionary and ecological aspects of insecticide resistance are discussed in order to understand the particular scenario of pyrethroid

  13. Mechanisms of hormonal therapy resistance in breast cancer.

    PubMed

    Hayashi, Shin-ichi; Kimura, Mariko

    2015-04-01

    Whilst estrogen receptor (ER)-positive breast cancers are preferentially treated with hormone therapy, approximately one-third of them relapse. The mechanisms of refractoriness have been investigated by numerous studies but have not been fully clarified. Hormonal therapy resistance, particularly aromatase inhibitor (AI) resistance, may be related to the acquisition of alternative intracellular ER signaling. We have been investing the mechanisms using cancer specimens and cell lines by monitoring the transcription activity of ERs. AI refractory specimens showed diverse ER activity in the adenovirus estrogen receptor element-green fluorescent protein (ERE-GFP) assay and varied sensitivity to anti-estrogens, indicating the existence of multiple resistant mechanisms. We established six different types of cell lines mimicking AI resistance from ERE-GFP-introduced ER-positive cell lines. They revealed that multiple and alternative ER activating pathways were involved in the resistance, such as phosphorylation-dependent or androgen metabolite-dependent mechanisms. The response to fulvestrant and mammalian target of rapamycin inhibitor also varied among individual resistant cell lines. These results indicate that further subclassification of ER-positive breast cancer is extremely important to decide the therapeutic management of not only hormonal therapy but also new molecular target therapy.

  14. Different mechanisms of resistance modulate sulfite tolerance in wine yeasts.

    PubMed

    Nadai, Chiara; Treu, Laura; Campanaro, Stefano; Giacomini, Alessio; Corich, Viviana

    2016-01-01

    From a technological point of view, yeast resistance to sulfite is of great interest and represents an important technological character for winemaking. Several mechanisms are involved, and strain-dependent strategies to obtain SO2 resistance can deeply influence wine quality, although this choice is less relevant in determining the technological performance of the strain during fermentation. In this study, to better understand the strain-specific mechanisms of resistance, 11 Saccharomyces cerevisiae strains, whose genomes have been previously sequenced, were selected. Their attitude towards sulfites, in terms of resistance and production, was evaluated, and RNA-sequencing of four selected strains was performed during fermentation process in synthetic grape must in the presence of SO2. Results demonstrated that at molecular level, the physical effect of SO2 triggered multiple stress responses in the cell and high tolerance to general enological stressing condition increased SO2 resistance. Adaptation mechanism due to high basal gene expression level rather than specific gene induction in the presence of sulfite seemed to be responsible in modulating strain resistance. This mechanism involved higher basal gene expression level of specific cell wall proteins, enzymes for lipid biosynthesis, and enzymes directly involved in SO2 assimilation pathway and efflux.

  15. The Role of PIK3CA Mutations among Lung Adenocarcinoma Patients with Primary and Acquired Resistance to EGFR Tyrosine Kinase Inhibition

    PubMed Central

    Wu, Shang-Gin; Chang, Yih-Leong; Yu, Chong-Jen; Yang, Pan-Chyr; Shih, Jin-Yuan

    2016-01-01

    To understand the impact of PIK3CA mutations on clinical characteristics and treatment response to epidermal growth factor tyrosine kinase inhibitors (EGFR TKIs) of lung adenocarcinoma, we examined PIK3CA and EGFR mutations in lung adenocarcinoma patients, and analyzed their clinical outcomes. Surgically excised tumor, bronchoscopy biopsy/brushing specimens and pleural effusions were prospectively collected from 1029 patients. PIK3CA and EGFR mutations were analyzed by RT-PCR and direct sequencing. In EGFR TKI-nave specimens, PIK3CA mutation rate was 1.8% (14/760). Twelve patients had coexisting PIK3CA and EGFR mutations. Among the 344 EGFR TKI-treated EGFR mutant patients, there was no significant difference in treatment response (p = 0.476) and progression-free survival (p = 0.401) of EGFR TKI between PIK3CA mutation-positive and negative patients. The PIK3CA mutation rate in lung adenocarcinoma with acquired resistance to EGFR TKI is not higher than that in EGFR TKI-naïve tissue specimens (2.9% (6/207) vs. 1.8%; p = 0.344). Of the 74 patients with paired specimens (TKI-naïve and acquired resistance to TKIs) only one patient (1.4%) developed acquired PIK3CA (E545K) mutation, and he also had acquired EGFR (T790M) mutation. In conclusion, PIK3CA mutation may not be associated with primary resistance to EGFR TKI among lung adenocarcinoma patients. Acquired PIK3CA mutation related to EGFR TKI treatment is rare. PMID:27734950

  16. Non-mechanical sub-pixel image shifter for acquiring super-resolution digital images.

    PubMed

    Lan, Hsiao-Chin; Wu, Mount-Learn; Yeatman, Eric M

    2009-12-07

    A sub-pixel image shifter is presented, for use in enhancing the spatial resolution of digital image sensors by combining multiple displaced sub-images using a super-resolution (SR) algorithm. The device uses the walk-off phenomenon in birefringent crystals to separate images with opposite polarizations by a sub-pixel displacement. A liquid crystal (LC) waveplate plus a polarizer can then select the specific image to be exposed, with fast, non-mechanical control. This cascaded device, comprising two sapphire crystals, two LCs, and a single polarizer, is capable of 2-dimensional image shift with displacements of 0.5 pixels. The experimental results show that the image registration stability can be precisely controlled within 0.05 pixels and the contrast transfer function ratio of the SR image is enhanced by up to 1.36 times compared to the original captured image. Moreover, based on the fast transition time of LCs, the displaced sub-images can be recorded in video form with a frame rate of 40 fps.

  17. The mechanism of resistance to sulfa drugs in Plasmodium falciparum.

    PubMed

    Triglia, Tony; Cowman, Alan F.

    1999-02-01

    The sulfonamide and sulfone (sulfa) group of antimalarials has been used extensively throughout malaria endemic regions of the world to control this important infectious disease of humans. Sulfadoxine is the most extensively used drug of this group of drugs and is usually combined with pyrimethamine (Fansidar), particularly for the control of Plasmodium falciparum, the causative agent of the most lethal form of malaria. Resistance to the sulfadoxine/pyrimethamine combination is widespread. Analysis using molecular, genetic and biochemical approaches has shown that the mechanism of resistance to sulfadoxine involves mutation of dihydropteroate synthase, the enzyme target of this group of drugs. Understanding the mechanism of resistance of P. falciparum to sulfa drugs has allowed detailed analysis of the epidemiology of the spread of drug resistance alleles in the field(1)and, in the future, opens the way to the development of novel antimalarials to this target enzyme. Copyright 1999 Harcourt Publishers Ltd.

  18. New insights in leptin resistance mechanisms in mice.

    PubMed

    Balland, Eglantine; Cowley, Michael A

    2015-10-01

    Leptin resistance is one of the main challenges of obesity. To date, two levels of resistance have been identified, first a decreased rate of leptin uptake into the brain and secondly a diminished central response to leptin. New findings have identified the mechanisms of leptin transport and demonstrated that it can be rescued in obesity, but it did not overcome the problem of central resistance. Alteration in the actions of leptin following diet-induced obesity (DIO) appears to be a multifactorial condition. Several phosphatases are inhibiting leptin signaling pathways in a pathological way. Besides, hypothalamic inflammation alters the neuronal circuits that control metabolism. Recent studies describing both mechanisms (inhibition of leptin signaling and inflammation), have provided key insights to potential new targets for treatment. However, recent data showing that DIO mice may conserve a cellular and physiological response to endogenous leptin, highlights the need to redefine the concept of "leptin resistance".

  19. [Correlations between the level of bacterial resistance and the rate of clinical efficiency in the therapy of community-acquired respiratory tract infections].

    PubMed

    Slănină, Ana-Maria; Filip, Olguţa; Felea, Doina; Cosmescu, Adriana; Petroaie, Antoneta; Barbacariu, Liliana; Novac, Otilia; Manole, Mihaela; Silvia, Mătăsaru

    2009-01-01

    The aim of the study is to evaluate the efficiency of the first-line antibiotic treatment of the community-acquired respiratory tract infections in a population of young adults from an urban setting and to establish the pattern of antibiotic resistance of the germs involved. The bacteria most frequently identified have been: S. pneumoniae, H. influenzae, M. catarrhalis, atypical agents also being suspected. Antibiotic treatment has been chosen accordingly to the recent guidelines, total clinical remission rate being of 91.08%, despite the increasing resistance for the commonly used antibiotics; a close monitoring of the phenomenon is mandatory.

  20. Lack of dissemination of acquired resistance to β-lactams in small wild mammals around an isolated village in the Amazonian forest.

    PubMed

    Grall, Nathalie; Barraud, Olivier; Wieder, Ingrid; Hua, Anna; Perrier, Marion; Babosan, Ana; Gaschet, Margaux; Clermont, Olivier; Denamur, Erick; Catzeflis, François; Decré, Dominique; Ploy, Marie-Cécile; Andremont, Antoine

    2015-10-01

    In this study, we quantitatively evaluated the spread of resistance to β-lactams and of integrons in small rodents and marsupials living at various distances from a point of antibiotic's use. Rectal swabs from 114 animals were collected in Trois-Sauts, an isolated village in French Guiana, and along a 3 km transect heading through the non-anthropized primary forest. Prevalence of ticarcillin-resistant enterobacteria was 36% (41/114). Klebsiella spp., naturally resistant to ticarcillin, were found in 31.1% (23/73) of animals from the village and in an equal ratio of 31.7% (13/41) of animals trapped along the transect. By contrast Escherichia coli with acquired resistance to ticarcillin were found in 13.7% (10/73) of animals from the village and in only 2.4% (1/41) of those from the transect (600 m from the village). There was a huge diversity of E. coli and Klebsiella pneumoniae strains with very unique and infrequent sequence types. The overall prevalence of class 1 integrons carriage was 19.3% (22/114) homogenously distributed between animals from the village and the transect, which suggests a co-selection by a non-antibiotic environmental factor. Our results indicate that the anthropogenic acquired antibiotic resistance did not disseminate in the wild far from the point of selective pressure.

  1. New approaches for understanding mechanisms of drug resistance in schistosomes

    PubMed Central

    GREENBERG, ROBERT M.

    2013-01-01

    SUMMARY Schistosomes are parasitic flatworms that cause schistosomiasis, a neglected tropical disease that affects hundreds of millions worldwide. Treatment and control of schistosomiasis relies almost entirely on the single drug praziquantel (PZQ), making the prospect of emerging drug resistance particularly worrisome. This review will survey reports of PZQ (and other drug) resistance in schistosomes and other platyhelminths, and explore mechanisms by which drug resistance might develop. Newer genomic and post-genomic strategies that offer the promise of better understanding of how drug resistance might arise in these organisms will be discussed. These approaches could also lead to insights into the mode of action of these drugs and potentially provide markers for monitoring the emergence of resistance. PMID:23552512

  2. Non-Invasive Methods to Monitor Mechanisms of Resistance to Tyrosine Kinase Inhibitors in Non-Small-Cell Lung Cancer: Where Do We Stand?

    PubMed Central

    Ulivi, Paola

    2016-01-01

    The induction of resistance mechanisms represents an important problem for the targeted therapy of patients with non-small-cell lung cancer (NSCLC). The best-known resistance mechanism induced during treatment with epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) is EGFR T790M mutation for which specific drugs are have been developed. However, other molecular alterations have also been reported as induced resistance mechanisms to EGFR-TKIs. Similarly, there is growing evidence of acquired resistance mechanisms to anaplastic lymphoma kinase (ALK)-TKI treatment. A better understanding of these acquired resistance mechanisms is essential in clinical practice as patients could be treated with specific drugs that are active against the induced alterations. The use of free circulating tumor nucleic acids or circulating tumor cells (CTCs) enables resistance mechanisms to be characterized in a non-invasive manner and reduces the need for tumor re-biopsy. This review discusses the main resistance mechanisms to TKIs and provides a comprehensive overview of innovative strategies to evaluate known resistance mechanisms in free circulating nucleic acids or CTCs and potential future orientations for these non-invasive approaches. PMID:27455248

  3. Non-Invasive Methods to Monitor Mechanisms of Resistance to Tyrosine Kinase Inhibitors in Non-Small-Cell Lung Cancer: Where Do We Stand?

    PubMed

    Ulivi, Paola

    2016-07-22

    The induction of resistance mechanisms represents an important problem for the targeted therapy of patients with non-small-cell lung cancer (NSCLC). The best-known resistance mechanism induced during treatment with epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) is EGFR T790M mutation for which specific drugs are have been developed. However, other molecular alterations have also been reported as induced resistance mechanisms to EGFR-TKIs. Similarly, there is growing evidence of acquired resistance mechanisms to anaplastic lymphoma kinase (ALK)-TKI treatment. A better understanding of these acquired resistance mechanisms is essential in clinical practice as patients could be treated with specific drugs that are active against the induced alterations. The use of free circulating tumor nucleic acids or circulating tumor cells (CTCs) enables resistance mechanisms to be characterized in a non-invasive manner and reduces the need for tumor re-biopsy. This review discusses the main resistance mechanisms to TKIs and provides a comprehensive overview of innovative strategies to evaluate known resistance mechanisms in free circulating nucleic acids or CTCs and potential future orientations for these non-invasive approaches.

  4. Community-acquired meticillin-resistant Staphylococcus aureus strain USA300 resists staphylococcal protein A modulation by antibiotics and antimicrobial peptides.

    PubMed

    Cardot Martin, E; Michel, A; Raynal, B; Badiou, C; Laurent, F; Vandenesch, F; Etienne, J; Lina, G; Dumitrescu, O

    2015-01-01

    Community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) causes severe diseases through virulence factors such as staphylococcal protein A (SpA), which favours immune evasion. We have previously shown that antimicrobial peptides (AMPs) and antibiotics decrease SpA expression in CA-MRSA strains. Here we examined the effects of antibiotics and AMPs, alone and in combination, on SpA expression in various CA-MRSA strains. Six S. aureus isolates corresponding to the major worldwide CA-MRSA clones (ST8-USA300, ST80 and ST30) were selected. Strains were cultured to exponential growth phase and were subsequently incubated with antibiotics (tigecycline, linezolid, clindamycin and vancomycin) at 0.25× MIC or with AMPs [human neutrophil peptide (HNP)-1-3] at the LD50, alone and in combination. After 6h, cultures were assessed for spa mRNA by RT-PCR, whilst SpA protein was measured by specific ELISA after 18h. When used alone, antibiotics (clindamycin, linezolid and tigecycline) or HNPs significantly reduced both SpA production and mRNA levels in ST30 and ST80 strains. When used in combination, HNPs and clindamycin, linezolid or tigecycline synergistically reduced SpA production (6-100-fold) and spa mRNA levels (4-20-fold) in ST80 and ST30 strains. In contrast, for USA300 strains, among all antibiotics, clindamycin alone reduced SpA production (3.5-fold), whereas with combined treatments including HNPs, only a slight reduction in SpA production (1.7-2.2-fold) was observed. In conclusion, antibiotics and AMPs do not modulate SpA expression in USA300, unlike in other CA-MRSA clones. This observation suggests that the virulence and successful spread of USA300 strains is associated with a specific regulatory network.

  5. Spontaneous bacteriocin resistance in Listeria monocytogenes as a susceptibility screen for identifying different mechanisms of resistance and modes of action by bacteriocins of lactic acid bacteria.

    PubMed

    Macwana, Sunita; Muriana, Peter M

    2012-01-01

    A practical system was devised for grouping bacteriocins of lactic acid bacteria (LAB) based on mode of action as determined by changes in inhibitory activity to spontaneously-acquired bacteriocin resistance (Bac(R)). Wild type Listeria monocytogenes 39-2 was sensitive to five bacteriocins produced by 3 genera of LAB: pediocin PA-1 and pediocin Bac3 (Pediococcus), lacticin FS97 and lacticin FS56 (Lactococcus), and curvaticin FS47 (Lactobacillus). A spontaneous Bac(R) derivative of L. monocytogenes 39-2 obtained by selective recovery against lacticin FS56 provided complete resistance to the bacteriocin made by Lactococcus lactis FS56. The lacticin FS56-resistant strain of L. monocyotgenes 39-2 was also cross-resistant to curvaticin FS47 and pediocin PA-1, but not to lacticin FS97 or pediocin Bac3. The same pattern of cross-resistance was also observed with Bac(R) isolates obtained with L. monocytogenes Scott A-2. A spontaneous mutation that renders a strain cross-resistant to different bacteriocins indicates that they share a common mechanism of resistance due to similar modes of action of the bacteriocins. Spontaneous resistance was acquired to other bacteriocins (in aggregate) by following the same procedure against which the Bac(R) strain was still sensitive. In subsequent challenge assays, mixtures of bacteriocins of different modes of action provided greater inhibition than mixtures of bacteriocins of the same mode of action (as determined by our screening method). This study identifies a methodical approach to classify bacteriocins into functional groups based on mechanism of resistance (i.e., mode of action) that could be used for identifying the best mixture of bacteriocins for use as biopreservatives.

  6. Interaction of gatifloxacin with efflux transporters: a possible mechanism for drug resistance

    PubMed Central

    Kwatra, Deep; Vadlapatla, Ramya Krishna; Vadlapudi, Aswani Dutt; Pal, Dhananjay; Mitra, Ashim K.

    2010-01-01

    The purpose of the study is to screen the interactions of fourth generation fluoroquinolone-gatifloxacin with efflux pumps i.e. P-gp, MRP2 and BCRP. Mechanism of gatifloxacin interaction with efflux transporters may explain its acquired resistance. Such clarification may lead to the development of strategies to overcome efflux and enhance its bioavailability at target site. This process will aid in the reduction of dose volume, further eliminating the chances of systemic toxicity from topical gatifloxacin eye drops. MDCK cell lines transfected with the targeted efflux transporters were used for this study. [14C] Erythromycin was selected as a model substrate for P-gp and MRP2 whereas Hoechst 33342 was employed as a substrate for BCRP. Uptake and transport studies of these substrates were performed in the presence of gatifloxacin to delineate its interaction with efflux transporters. Further the efflux ratio in the presence of gatifloxacin was calculated from bidirectional transport studies. The concentration of [14C] erythromycin and Hoechst 33342 were measured using scintillation counter and fluorescence plate reader respectively. A concentration dependent inhibition effect in the presence of gatifloxacin was revealed on [14C] erythromycin uptake. The efflux ratio (BL-AP/AP-BL) of substrates was found to approach unity at higher gatifloxacin concentrations. Increased concentration of gatifloxacin did not elevate uptake of Hoechst 33342. All these studies were validated with known inhibitors as positive control. Uptake and transport studies support the hypothesis that gatifloxacin is a substrate for P-gp, MRP2 but not for BCRP. Possible interactions of gatifloxacin with P-gp and MRP2 may be a possible mechanism for acquired resistance of gatifloxacin. This information can be further extended to design prodrugs or formulations in order to prevent development of acquired resistance and improve therapeutic efficacy with its reduction in side effects. PMID:20573570

  7. Mechanisms of resistance to bacteriocins targeting the mannose phosphotransferase system.

    PubMed

    Kjos, Morten; Nes, Ingolf F; Diep, Dzung B

    2011-05-01

    The membrane proteins IIC and IID of the mannose phosphotransferase system (Man-PTS) together form a membrane-located complex that serves as a receptor for several different bacteriocins, including the pediocin-like class IIa bacteriocins and the class IIc bacteriocin lactococcin A. Bacterial strains sensitive to class IIa bacteriocins readily give rise to resistant mutants upon bacteriocin exposure. In the present study, we have therefore investigated lactococcin A-resistant mutants of Lactococcus lactis as well as natural food isolates of Listeria monocytogenes with different susceptibilities to class IIa bacteriocins. We found two major mechanisms of resistance. The first involves downregulation of Man-PTS gene expression, which takes place both in spontaneous resistant mutants and in natural resistant isolates. The second involves normal expression of the Man-PTS system, but the underlying mechanism of resistance for these cells is unknown. In some cases, the resistant phenotype was linked to a shift in the metabolism; i.e., reduced growth on glucose due to reduction in Man-PTS expression was accompanied by enhanced growth on another sugar, such as galactose. The implications of these findings in terms of metabolic heterogeneity are discussed.

  8. Drug resistance. Population transcriptomics of human malaria parasites reveals the mechanism of artemisinin resistance.

    PubMed

    Mok, Sachel; Ashley, Elizabeth A; Ferreira, Pedro E; Zhu, Lei; Lin, Zhaoting; Yeo, Tomas; Chotivanich, Kesinee; Imwong, Mallika; Pukrittayakamee, Sasithon; Dhorda, Mehul; Nguon, Chea; Lim, Pharath; Amaratunga, Chanaki; Suon, Seila; Hien, Tran Tinh; Htut, Ye; Faiz, M Abul; Onyamboko, Marie A; Mayxay, Mayfong; Newton, Paul N; Tripura, Rupam; Woodrow, Charles J; Miotto, Olivo; Kwiatkowski, Dominic P; Nosten, François; Day, Nicholas P J; Preiser, Peter R; White, Nicholas J; Dondorp, Arjen M; Fairhurst, Rick M; Bozdech, Zbynek

    2015-01-23

    Artemisinin resistance in Plasmodium falciparum threatens global efforts to control and eliminate malaria. Polymorphisms in the kelch domain-carrying protein K13 are associated with artemisinin resistance, but the underlying molecular mechanisms are unknown. We analyzed the in vivo transcriptomes of 1043 P. falciparum isolates from patients with acute malaria and found that artemisinin resistance is associated with increased expression of unfolded protein response (UPR) pathways involving the major PROSC and TRiC chaperone complexes. Artemisinin-resistant parasites also exhibit decelerated progression through the first part of the asexual intraerythrocytic development cycle. These findings suggest that artemisinin-resistant parasites remain in a state of decelerated development at the young ring stage, whereas their up-regulated UPR pathways mitigate protein damage caused by artemisinin. The expression profiles of UPR-related genes also associate with the geographical origin of parasite isolates, further suggesting their role in emerging artemisinin resistance in the Greater Mekong Subregion.

  9. Lead resistant bacteria: lead resistance mechanisms, their applications in lead bioremediation and biomonitoring.

    PubMed

    Naik, Milind Mohan; Dubey, Santosh Kumar

    2013-12-01

    Lead (Pb) is non-bioessential, persistent and hazardous heavy metal pollutant of environmental concern. Bioremediation has become a potential alternative to the existing technologies for the removal and/or recovery of toxic lead from waste waters before releasing it into natural water bodies for environmental safety. To our best knowledge, this is a first review presenting different mechanisms employed by lead resistant bacteria to resist high levels of lead and their applications in cost effective and eco-friendly ways of lead bioremediation and biomonitoring. Various lead resistant mechanisms employed by lead resistant bacteria includes efflux mechanism, extracellular sequestration, biosorption, precipitation, alteration in cell morphology, enhanced siderophore production and intracellular lead bioaccumulation.

  10. Resistant mechanisms and molecular epidemiology of imipenem-resistant Acinetobacter baumannii

    PubMed Central

    Xiao, Shu-Zhen; Chu, Hai-Qing; Han, Li-Zhong; Zhang, Zhe-Min; Li, Bing; Zhao, Lan; Xu, Liyun

    2016-01-01

    The aim of the study was to investigate the resistant mechanisms and homology of imipenem-resistant Acinetobacter baumannii (A. baumannii). A total of 46 non-duplicate imipenem-resistant A. baumannii clinical isolates were collected from three tertiary hospitals between July, 2011 and June, 2012. The minimal inhibitory concentrations (MICs) of antimicrobial agents were determined using the agar dilution method. Phenylalanine-arginine β-naphthylamide was used to detect the presence of the efflux pump-mediated resistant mechanism. Polymerase chain reaction was employed to amplify genes associated with drug resistance, including β-lactamase genes, efflux pump genes and outer membrane protein gene CarO. A few amplicons were randomly selected and sequenced. Multilocus sequence analysis (MLST) was employed in typing A. baumanni. A. baumannii was resistant to imipenem, simultaneously showing resistance to several other antimicrobials. In addition, 13 A. baumannii were found to mediate drug resistance through operation of the efflux pump. Of the various drug resistance genes tested, blaOXA-51 was present in 46 isolates, blaOXA-23 gene was present in 44 isolates and blaNDM gene was found in only one strain. Other drug resistant-associated genes, including blaKPC, blaIMP, blaOXA-24, blaOXA-58, blaSHV, blaGIM and blaVIM were not detected. Mutation of adeS and outer membrane protein gene CarO were found in a few of the imipenem-resistant isolates. The MLST analysis revealed that all 46 clinical isolates were clustered into 11 genotypes and the most frequent genotype was ST208. In conclusion, β-lactamase genes, genes involved in efflux pump and mutation of outer membrane protein encoding gene may be important in mediating imipenem resistance in A. baumannii. Of the 11 different genotypes, ST11 was shared by the majority of A. baumannii, which may be due to horizontal transfer of patients from hospitals. PMID:27485638

  11. Pathophysiological mechanisms of death resistance in colorectal carcinoma

    PubMed Central

    Huang, Ching-Ying; Yu, Linda Chia-Hui

    2015-01-01

    Colon cancers develop adaptive mechanisms to survive under extreme conditions and display hallmarks of unlimited proliferation and resistance to cell death. The deregulation of cell death is a key factor that contributes to chemoresistance in tumors. In a physiological context, balance between cell proliferation and death, and protection against cell damage are fundamental processes for maintaining gut epithelial homeostasis. The mechanisms underlying anti-death cytoprotection and tumor resistance often bear common pathways, and although distinguishing them would be a challenge, it would also provide an opportunity to develop advanced anti-cancer therapeutics. This review will outline cell death pathways (i.e., apoptosis, necrosis, and necroptosis), and discuss cytoprotective strategies in normal intestinal epithelium and death resistance mechanisms of colon tumor. In colorectal cancers, the intracellular mechanisms of death resistance include the direct alteration of apoptotic and necroptotic machinery and the upstream events modulating death effectors such as tumor suppressor gene inactivation and pro-survival signaling pathways. The autocrine, paracrine and exogenous factors within a tumor microenvironment can also instigate resistance against apoptotic and necroptotic cell death in colon cancers through changes in receptor signaling or transporter uptake. The roles of cyclooxygenase-2/prostaglandin E2, growth factors, glucose, and bacterial lipopolysaccharides in colorectal cancer will be highlighted. Targeting anti-death pathways in the colon cancer tissue might be a promising approach outside of anti-proliferation and anti-angiogenesis strategies for developing novel drugs to treat refractory tumors. PMID:26557002

  12. Mechanisms of resistance to malathion in the medfly Ceratitis capitata.

    PubMed

    Magaña, Cristina; Hernández-Crespo, Pedro; Brun-Barale, Alexandra; Couso-Ferrer, Francisco; Bride, Jean-Marc; Castañera, Pedro; Feyereisen, René; Ortego, Félix

    2008-08-01

    Target site insensitivity and metabolic resistance mediated by esterases have been previously suggested to be involved in resistance to malathion in a field-derived strain (W) of Ceratitis capitata. In the present study, we have obtained the coding sequence for acetylcholinesterase (AChE) gene (Ccace) of C. capitata. An allele of Ccace carrying only a point mutation Gly328Ala (Torpedo numbering) adjacent to the glutamate of the catalytic triad was found in individuals of the W strain. Adult flies homozygotes for this mutant allele showed reduced AChE activity and less sensitivity to inhibition by malaoxon, showing that target site insensitivity is one of the factors of malathion resistance. In addition, all individuals from the resistant W strain showed reduced aliesterase activity, which has been associated with specific malathion resistance in higher Diptera. However, the alphaE7 gene (CcalphaE7), sequenced in susceptible and resistant individuals, did not carry any of the mutations associated with organophosphorus insecticide resistance in other Diptera. Another esterase mechanism, perhaps a carboxylesterase selective for malathion, in addition to mutant AChE, thus contributes to malathion resistance in C. capitata.

  13. Acquired resistance to rechallenge injury in rats recovered from subclinical renal damage with uranyl acetate-Importance of proliferative activity of tubular cells

    SciTech Connect

    Sun, Yuan; Fujigaki, Yoshihide; Sakakima, Masanori; Hishida, Akira

    2010-02-15

    Animals recovered from acute renal failure are resistant to subsequent insult. We investigated whether rats recovered from mild proximal tubule (PT) injury without renal dysfunction (subclinical renal damage) acquire the same resistance. Rats 14 days after recovering from subclinical renal damage, which was induced by 0.2 mg/kg of uranyl acetate (UA) (sub-toxic dose), were rechallenged with 4 mg/kg of UA (nephrotoxic dose). Fate of PT cells and renal function were examined in response to nephrotoxic dose of UA. All divided cells after sub-toxic dose of UA insult were labeled with bromodeoxyuridine (BrdU) for 14 days then the number of PT cells with or without BrdU-labeling was counted following nephrotoxic dose of UA insult. Rats recovered from subclinical renal damage gained resistance to nephrotoxic dose of UA with reduced renal dysfunction, less severity of peak damage (necrotic and TUNEL+ apoptotic cells) and accelerated PT cell proliferation, but with earlier peak of PT damage. The decrease in number of PT cells in the early phase of rechallenge injury with nephrotoxic UA was more in rats pretreated with sub-toxic dose of UA than vehicle pretreated rats. The exaggerated loss of PT cells was mainly caused by the exaggerated loss of BrdU+ divided cells. In contrast, accelerated cell proliferation in rats recovered from sub-toxic dose of UA was observed mainly in BrdU- non-divided cells. The findings suggest that rats recovered from subclinical renal damage showed partial acquired resistance to nephrotoxic insult. Accelerated recovery with increased proliferative activity of non-divided PT cells after subclinical renal damage may mainly contribute to acquired resistance.

  14. Macrolide resistance mechanisms in Enterobacteriaceae: Focus on azithromycin.

    PubMed

    Gomes, Cláudia; Martínez-Puchol, Sandra; Palma, Noemí; Horna, Gertrudis; Ruiz-Roldán, Lidia; Pons, Maria J; Ruiz, Joaquim

    2017-02-01

    From its introduction in 1952 onwards, the clinical use of macrolides has been steadily increasing, both in human and veterinary medicine. Although initially designed to the treatment of Gram-positive microorganisms, this antimicrobial family has also been used to treat specific Gram-negative bacteria. Some of them, as azithromycin, are considered in the armamentarium against Enterobacteriaceae infections. However, the facility that this bacterial genus has to gain or develop mechanisms of antibiotic resistance may compromise the future usefulness of these antibiotics to fight against Enterobacteriaceae infections. The present review is focused on the mechanisms of macrolide resistance, currently described in Enterobacteriaceae.

  15. Fluoroquinolone-Resistant Sequence Type 131 Subgroups O25b and O16 Among Extraintestinal Escherichia coli Isolates from Community-Acquired Urinary Tract Infections.

    PubMed

    Hefzy, Enas Mamdouh; Hassuna, Noha Anwar

    2017-03-01

    The multidrug-resistant sequence type 131 (ST131) Escherichia coli is a spreading epidemiological burden particularly among isolates resistant to fluoroquinolones. We aimed to evaluate the commonality of ST131-O25b and ST131-O16 among fluoroquinolone-resistant E. coli isolates causing community-acquired urinary tract infections (UTIs) at Fayoum University Hospital, in Egypt. Ninety-two fluoroquinolone-resistant E. coli isolates were subjected to multiplex PCR for detection of ST131 of either O25b or O16 subgroups. Positive isolates were then assessed for antimicrobial susceptibility and virulence genotyping. Out of 92 fluoroquinolone-resistant E. coli isolates, 56 (60.9%) isolates were O25b/O16 subgroups of ST131, including 44 (78.6%) ST131-O25b and 12 (21.4%) ST131-O16 subgroups. All the O25b/O16 ST131 isolates were sensitive to meropenem, where ST131-O25b isolates were significantly more resistant to extended spectrum cephalosporins compared to S131-O16 strains. All the O25b/O16 ST131 isolates harbored three or more of the virulence factors associated with extraintestinal pathogenic E. coli status. ST131-O16 showed a significantly higher virulence score than ST131-O25b isolates. Our results bring to highlight the emergence of O25b/O16 ST131 isolates between community acquired UTIs among Egyptian patients. This is the first report for the presence of O16 isolates in Egypt, showing a lower predominance than the O25b subgroup. The high prevalence of O25b/O16 ST131 isolates requires strict stewardship on antimicrobial use, notably fluoroquinolones, to control the endemicity of such emerging multidrug-resistant clone in the community.

  16. Mechanisms of biotic resistance across complex life cycles.

    PubMed

    Rius, Marc; Potter, Elaine E; Aguirre, J David; Stachowicz, John J

    2014-01-01

    Biotic resistance is the ability of communities to inhibit the establishment, spread or impact of novel species. However, the interactions that underlie biotic resistance depend heavily on the contexts in which species interact. Consequently, studies of biotic resistance that consider single processes, patches, species or life-history stages may provide an incomplete picture of the capacity for communities to resist invasion. Many organisms have multiphasic life cycles, where individuals can occupy distinct niches at different stages of the life history. Generally, studies of biotic resistance focus on interactions within a single life-history stage, and interactions at other life-history stages are overlooked. Here, we demonstrate that different mechanisms of biotic resistance occur across the life history and together limit the invasion success of an introduced marine invertebrate (Ciona intestinalis) in Northern California. We tested the role of interactions (competition and predation) with the resident community in limiting the abundance of Ciona through experiments conducted on fertilization, larval survival, settlement, early postsettlement survival, and the survival of juveniles and adults. Under some circumstances, Ciona became abundant in mid-successional stages and showed more rapid growth rates than a morphologically similar native species, Ascidia ceratodes. However, predators reduced Ciona abundance much more than that of Ascidia at several life stages. Furthermore, Ciona appeared to be a weaker competitor at the adult stage. Early life-history interactions with other sessile species at the fertilization, larval and recruit stages had modest to no effects on Ciona abundance. The presence of biotic resistance mechanisms acting at multiple life stages, and potentially under different conditions, suggests that different components of biotic resistance interact to enhance the resident community's resistance to invasion.

  17. Potential of L-Buthionine Sulfoximine to Enhance the Apoptotic Action of Estradiol to Reverse Acquired Antihormonal Resistance in Metastatic Breast Cancer

    PubMed Central

    Lewis-Wambi, Joan S; Swaby, Ramona; Kim, Helen; Jordan, V. Craig

    2010-01-01

    L-buthionine sulfoximine (BSO) is a potent inhibitor of glutathione biosynthesis and studies have shown that it is capable of enhancing the apoptotic effects of several chemotherapeutic agents. Previous studies have shown that long term antihormonal therapy leads to acquired drug resistance and that estrogen, which is normally a survival signal, is a potent apoptotic agent in these resistant cells. Interestingly, we have developed an antihormone resistant breast cancer cell line, MCF-7:2A, which is resistant to estrogen-induced apoptosis but has elevated levels of glutathione. In the present study, we examined whether BSO is capable of sensitizing antihormone resistant MCF-7:2A cells to estrogen-induced apoptosis. Our results showed that treatment of MCF-7:2A cells with 1 nM E2 plus 100 μM BSO combination for 1 week reduced the growth of these cells by almost 80-90% whereas the individual treatments had no significant effect on growth. TUNEL and DAPI staining showed that the inhibitory effect of the combination treatment was due to apoptosis. Our data indicates that glutathione participates in retarding apoptosis in antihormone-resistant human breast cancer cells and that depletion of this molecule by BSO may be critical in predisposing resistant cells to estrogen-induced apoptosis. PMID:19167492

  18. Mechanism of resistance of evolved glyphosate-resistant Palmer amaranth (Amaranthus palmeri).

    PubMed

    Gaines, Todd A; Shaner, Dale L; Ward, Sarah M; Leach, Jan E; Preston, Christopher; Westra, Philip

    2011-06-08

    Evolved glyphosate resistance in weedy species represents a challenge for the continued success and utility of glyphosate-resistant crops. Glyphosate functions by inhibiting the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). The resistance mechanism was determined in a population of glyphosate-resistant Palmer amaranth from Georgia (U.S.). Within this population, glyphosate resistance correlates with increases in (a) genomic copy number of EPSPS, (b) expression of the EPSPS transcript, (c) EPSPS protein level, and (d) EPSPS enzymatic activity. Dose response results from the resistant and an F(2) population suggest that between 30 and 50 EPSPS genomic copies are necessary to survive glyphosate rates between 0.5 and 1.0 kg ha(-1). These results further confirm the role of EPSPS gene amplification in conferring glyphosate resistance in this population of Palmer amaranth. Questions remain related to how the EPSPS amplification initially occurred and the occurrence of this mechanism in other Palmer amaranth populations and other glyphosate-resistant species.

  19. miRNAs and ovarian cancer: a miRiad of mechanisms to induce cisplatin drug resistance.

    PubMed

    Samuel, Priya; Pink, Ryan Charles; Brooks, Susan Ann; Carter, David RaulFrancisco

    2016-01-01

    Ovarian cancer is the most aggressive gynecological cancer. One reason for the low 5-year survival rate of under 40% is that ovarian tumors usually acquire resistance to the platinum-based compounds used to treat them. Resistance to one such compound, cisplatin, can arise via numerous mechanisms that can be categorized as pre-, post-, on- or off-target. Pre-target mechanisms prevent accumulation of cisplatin in the cell, on-target mechanisms allow DNA damage to be repaired more efficiently, post-target mechanisms prevent the damage from inducing apoptosis and off-target mechanisms increase resistance via unrelated compensatory mechanisms. miRNAs are short non-coding RNAs that influence cellular function by repressing gene expression. Here we describe how miRNAs can induce cisplatin resistance in ovarian cancer cells via pre-, post-, on- and off-target mechanisms. A better understanding of how miRNAs feed into the mechanisms of drug resistance will inform the rational design of combination therapies for ovarian cancer.

  20. Resistance Mechanisms for the Bruton’s Tyrosine Kinase Inhibitor Ibrutinib

    PubMed Central

    Woyach, Jennifer A.; Furman, Richard R.; Liu, Ta-Ming; Ozer, Hatice Gulcin; Zapatka, Marc; Ruppert, Amy S.; Xue, Ling; Li, Daniel Hsieh-Hsin; Steggerda, Susanne M.; Versele, Matthias; Dave, Sandeep S.; Zhang, Jenny; Yilmaz, Ayse Selen; Jaglowski, Samantha M.; Blum, Kristie A.; Lozanski, Arletta; Lozanski, Gerard; James, Danelle F.; Barrientos, Jacqueline C.; Lichter, Peter; Stilgenbauer, Stephan; Buggy, Joseph J.; Chang, Betty Y.; Johnson, Amy J.; Byrd, John C.

    2014-01-01

    BACKGROUND Ibrutinib is an irreversible inhibitor of Bruton’s tyrosine kinase (BTK) and is effective in chronic lymphocytic leukemia (CLL). Resistance to irreversible kinase inhibitors and resistance associated with BTK inhibition have not been characterized. Although only a small proportion of patients have had a relapse during ibrutinib therapy, an understanding of resistance mechanisms is important. We evaluated patients with relapsed disease to identify mutations that may mediate ibrutinib resistance. METHODS We performed whole-exome sequencing at baseline and the time of relapse on samples from six patients with acquired resistance to ibrutinib therapy. We then performed functional analysis of identified mutations. In addition, we performed Ion Torrent sequencing for identified resistance mutations on samples from nine patients with prolonged lymphocytosis. RESULTS We identified a cysteine-to-serine mutation in BTK at the binding site of ibrutinib in five patients and identified three distinct mutations in PLCγ2 in two patients. Functional analysis showed that the C481S mutation of BTK results in a protein that is only reversibly inhibited by ibrutinib. The R665W and L845F mutations in PLCγ2 are both potentially gain-of-function mutations that lead to autonomous B-cell–receptor activity. These mutations were not found in any of the patients with prolonged lymphocytosis who were taking ibrutinib. CONCLUSIONS Resistance to the irreversible BTK inhibitor ibrutinib often involves mutation of a cysteine residue where ibrutinib binding occurs. This finding, combined with two additional mutations in PLCγ2 that are immediately downstream of BTK, underscores the importance of the B-cell–receptor pathway in the mechanism of action of ibrutinib in CLL. (Funded by the National Cancer Institute and others.) PMID:24869598

  1. Cross-resistance of bisultap resistant strain of Nilaparvata lugens and its biochemical mechanism.

    PubMed

    Ling, Shanfeng; Zhang, Runjie

    2011-02-01

    The resistant (R) strain of the planthopper Nilaparvata lugens (Stål) selected for bisultap resistance displayed 7.7-fold resistance to bisultap and also had cross-resistance to nereistoxin (monosultap, thiocyclam, and cartap), chlorpyrifos, dimethoate, and malathion but no cross-resistance to buprofezin, imidacloprid, and fipronil. To find out the biochemical mechanism of resistance to bisultap, biochemical assay was done. The results showed that cytochrome P450 monooxygenases (P450) activity in R strain was 2.71-fold that in susceptible strain (S strain), in which the changed activity for general esterase (EST) was 1.91 and for glutathione S-transferases only 1.32. Piperonyl butoxide (PBO) could significantly inhibit P450 activity (percentage of inhibition [PI]: 37.31%) in the R strain, with ESTs PI = 16.04% by triphenyl phosphate (TPP). The results also demonstrated that diethyl maleate had no synergism with bisultap. However, PBO displayed significant synergism in three different strains, and the synergism increased with resistance (S strain 1.42, Lab strain, 2.24 and R strain, 3.23). TPP also showed synergism for three strains, especially in R strain (synergistic ratio = 2.47). An in vitro biochemical study and in vivo synergistic study indicated that P450 might be play important role in the biochemical mechanism of bisultap resistance and that esterase might be the important factor of bisultap resistance. Acetylcholinesterase (AChE) insensitivity play important role in bisultap resistance. We suggest that buprofezin, imidacloprid, and fipronil could be used in resistance management programs for N. lugens via alternation and rotation with bisultap.

  2. Effect of mechanical surface and heat treatments on erosion resistance

    NASA Technical Reports Server (NTRS)

    Salik, J.; Buckley, D. H.

    1980-01-01

    The effects of mechanical surface treatments as well as heat treatments on the erosion resistance of 6061 aluminum alloy and 1045 steel were studied. Mechanical surface treatments were found to have little or no effect on the erosion resistance. This is due to the formation by particle impact of a work hardened surface layer regardless of the initial surface condition. The erosion resistance of Al single crystals is found to be independent of orientation. This is due to destruction of the surface microstructure and formation of a polycrystalline surface layer by the impact of erodant particles as observed by X-ray diffraction. While upon solution treatment of annealed 6061 aluminum the increase in hardness is accompanied by an increase in erosion resistance, precipitation treatment which causes a further increase in hardness results in slightly lower erosion resistance. Using two types of erodant particles, glass beads and crushed glass, the erosion rate is found to be strongly dependent on erodant particle shape, being an order of magnitude higher for erosion with crushed glass as compared to glass beads. While for erosion with glass beads heat treatment of 1045 steel had a profound effect on its erosion resistance, little or no such effect was observed for erosion with crushed glass.

  3. Resistive switching characteristics and mechanisms in silicon oxide memory devices

    NASA Astrophysics Data System (ADS)

    Chang, Yao-Feng; Fowler, Burt; Chen, Ying-Chen; Zhou, Fei; Wu, Xiaohan; Chen, Yen-Ting; Wang, Yanzhen; Xue, Fei; Lee, Jack C.

    2016-05-01

    Intrinsic unipolar SiOx-based resistance random access memories (ReRAM) characterization, switching mechanisms, and applications have been investigated. Device structures, material compositions, and electrical characteristics are identified that enable ReRAM cells with high ON/OFF ratio, low static power consumption, low switching power, and high readout-margin using complementary metal-oxide semiconductor transistor (CMOS)-compatible SiOx-based materials. These ideas are combined with the use of horizontal and vertical device structure designs, composition optimization, electrical control, and external factors to help understand resistive switching (RS) mechanisms. Measured temperature effects, pulse response, and carrier transport behaviors lead to compact models of RS mechanisms and energy band diagrams in order to aid the development of computer-aided design for ultralarge-v scale integration. This chapter presents a comprehensive investigation of SiOx-based RS characteristics and mechanisms for the post-CMOS device era.

  4. Daunorubicin-Loaded DNA Origami Nanostructures Circumvent Drug-Resistance Mechanisms in a Leukemia Model.

    PubMed

    Halley, Patrick D; Lucas, Christopher R; McWilliams, Emily M; Webber, Matthew J; Patton, Randy A; Kural, Comert; Lucas, David M; Byrd, John C; Castro, Carlos E

    2016-01-20

    Many cancers show primary or acquired drug resistance due to the overexpression of efflux pumps. A novel mechanism to circumvent this is to integrate drugs, such as anthracycline antibiotics, with nanoparticle delivery vehicles that can bypass intrinsic tumor drug-resistance mechanisms. DNA nanoparticles serve as an efficient binding platform for intercalating drugs (e.g., anthracyclines doxorubicin and daunorubicin, which are widely used to treat acute leukemias) and enable precise structure design and chemical modifications, for example, for incorporating targeting capabilities. Here, DNA nanostructures are utilized to circumvent daunorubicin drug resistance at clinically relevant doses in a leukemia cell line model. The fabrication of a rod-like DNA origami drug carrier is reported that can be controllably loaded with daunorubicin. It is further directly verified that nanostructure-mediated daunorubicin delivery leads to increased drug entry and retention in cells relative to free daunorubicin at equal concentrations, which yields significantly enhanced drug efficacy. Our results indicate that DNA origami nanostructures can circumvent efflux-pump-mediated drug resistance in leukemia cells at clinically relevant drug concentrations and provide a robust DNA nanostructure design that could be implemented in a wide range of cellular applications due to its remarkably fast self-assembly (≈5 min) and excellent stability in cell culture conditions.

  5. Mechanism and Fitness Costs of PR-39 Resistance in Salmonella enterica Serovar Typhimurium LT2 ▿

    PubMed Central

    Pränting, Maria; Negrea, Aurel; Rhen, Mikael; Andersson, Dan I.

    2008-01-01

    PR-39 is a porcine antimicrobial peptide that kills bacteria with a mechanism that does not involve cell lysis. Here, we demonstrate that Salmonella enterica serovar Typhimurium can rapidly acquire mutations that reduce susceptibility to PR-39. Resistant mutants appeared at a rate of 0.4 × 10−6 per cell per generation. These mutants were about four times more resistant than the wild type and showed a greatly reduced rate of killing. Genetic analysis revealed mutations in the putative transport protein SbmA as being responsible for the observed resistance. These sbmA mutants were as fit as the wild-type parental strain as measured by growth rates in culture medium and mice and by long-term survival in stationary phase. These results suggest that resistance to certain antimicrobial peptides can rapidly develop without an obvious fitness cost for the bacteria and that resistance development could become a threat to the efficacy of antimicrobial peptides if used in a clinical setting. PMID:18519732

  6. Esterase mutation is a mechanism of resistance to antimalarial compounds

    PubMed Central

    Istvan, Eva S.; Mallari, Jeremy P.; Corey, Victoria C.; Dharia, Neekesh V.; Marshall, Garland R.; Winzeler, Elizabeth A.; Goldberg, Daniel E.

    2017-01-01

    Pepstatin is a potent peptidyl inhibitor of various malarial aspartic proteases, and also has parasiticidal activity. Activity of pepstatin against cultured Plasmodium falciparum is highly variable depending on the commercial source. Here we identify a minor contaminant (pepstatin butyl ester) as the active anti-parasitic principle. We synthesize a series of derivatives and characterize an analogue (pepstatin hexyl ester) with low nanomolar activity. By selecting resistant parasite mutants, we find that a parasite esterase, PfPARE (P. falciparum Prodrug Activation and Resistance Esterase) is required for activation of esterified pepstatin. Parasites with esterase mutations are resistant to pepstatin esters and to an open source antimalarial compound, MMV011438. Recombinant PfPARE hydrolyses pepstatin esters and de-esterifies MMV011438. We conclude that (1) pepstatin is a potent but poorly bioavailable antimalarial; (2) PfPARE is a functional esterase that is capable of activating prodrugs; (3) Mutations in PfPARE constitute a mechanism of antimalarial resistance. PMID:28106035

  7. New findings on primary and acquired resistance to anti-EGFR therapy in metastatic colorectal cancer: do all roads lead to RAS?

    PubMed

    Bronte, Giuseppe; Silvestris, Nicola; Castiglia, Marta; Galvano, Antonio; Passiglia, Francesco; Sortino, Giovanni; Cicero, Giuseppe; Rolfo, Christian; Peeters, Marc; Bazan, Viviana; Fanale, Daniele; Giordano, Antonio; Russo, Antonio

    2015-09-22

    Anti-epidermal growth factor receptor therapy with the monoclonal antibodies cetuximab and panitumumab is the main targeted treatment to combine with standard chemotherapy for metastatic colorectal cancer. Many clinical studies have shown the benefit of the addition of these agents for patients without mutations in the EGFR pathway. Many biomarkers, including KRAS and NRAS mutations, BRAF mutations, PIK3CA mutations, PTEN loss, AREG and EREG expression, and HER-2 amplification have already been identified to select responders to anti-EGFR agents. Among these alterations KRAS and NRAS mutations are currently recognized as the best predictive factors for primary resistance. Liquid biopsy, which helps to isolate circulating tumor DNA, is an innovative method to study both primary and acquired resistance to anti-EGFR monoclonal antibodies. However, high-sensitivity techniques should be used to enable the identification of a wide set of gene mutations related to resistance.

  8. New findings on primary and acquired resistance to anti-EGFR therapy in metastatic colorectal cancer: do all roads lead to RAS?

    PubMed Central

    Castiglia, Marta; Galvano, Antonio; Passiglia, Francesco; Sortino, Giovanni; Cicero, Giuseppe; Rolfo, Christian; Peeters, Marc; Bazan, Viviana; Fanale, Daniele; Giordano, Antonio; Russo, Antonio

    2015-01-01

    Anti-epidermal growth factor receptor therapy with the monoclonal antibodies cetuximab and panitumumab is the main targeted treatment to combine with standard chemotherapy for metastatic colorectal cancer. Many clinical studies have shown the benefit of the addition of these agents for patients without mutations in the EGFR pathway. Many biomarkers, including KRAS and NRAS mutations, BRAF mutations, PIK3CA mutations, PTEN loss, AREG and EREG expression, and HER-2 amplification have already been identified to select responders to anti-EGFR agents. Among these alterations KRAS and NRAS mutations are currently recognized as the best predictive factors for primary resistance. Liquid biopsy, which helps to isolate circulating tumor DNA, is an innovative method to study both primary and acquired resistance to anti-EGFR monoclonal antibodies. However, high-sensitivity techniques should be used to enable the identification of a wide set of gene mutations related to resistance. PMID:26318427

  9. Mechanisms of resistance to EGFR tyrosine kinase inhibitors

    PubMed Central

    Huang, Lihua; Fu, Liwu

    2015-01-01

    Since the discovery that non-small cell lung cancer (NSCLC) is driven by epidermal growth factor receptor (EGFR) mutations, the EGFR tyrosine kinase inhibitors (EGFR-TKIs, e.g., gefitinib and elrotinib) have been effectively used for clinical treatment. However, patients eventually develop drug resistance. Resistance to EGFR-TKIs is inevitable due to various mechanisms, such as the secondary mutation (T790M), activation of alternative pathways (c-Met, HGF, AXL), aberrance of the downstream pathways (K-RAS mutations, loss of PTEN), impairment of the EGFR-TKIs-mediated apoptosis pathway (BCL2-like 11/BIM deletion polymorphism), histologic transformation, ATP binding cassette (ABC) transporter effusion, etc. Here we review and summarize the known resistant mechanisms to EGFR-TKIs and provide potential targets for development of new therapeutic strategies. PMID:26579470

  10. Mechanisms of Drug Resistance in Relapse and Refractory Multiple Myeloma

    PubMed Central

    Yang, Wen-Chi; Lin, Sheng-Fung

    2015-01-01

    Multiple myeloma (MM) is a hematological malignancy that remains incurable because most patients eventually relapse or become refractory to current treatments. Although the treatments have improved, the major problem in MM is resistance to therapy. Clonal evolution of MM cells and bone marrow microenvironment changes contribute to drug resistance. Some mechanisms affect both MM cells and microenvironment, including the up- and downregulation of microRNAs and programmed death factor 1 (PD-1)/PD-L1 interaction. Here, we review the pathogenesis of MM cells and bone marrow microenvironment and highlight possible drug resistance mechanisms. We also review a potential molecular targeting treatment and immunotherapy for patients with refractory or relapse MM. PMID:26649299

  11. Prevalence and characterisation of quinolone resistance mechanisms in Salmonella spp.

    PubMed

    Wasyl, Dariusz; Hoszowski, Andrzej; Zając, Magdalena

    2014-07-16

    The study was focused on characterisation of quinolone resistance mechanisms in Salmonella isolated from animals, food, and feed between 2008 and 2011. Testing of Minimal Inhibitory Concentrations revealed 6.4% of 2680 isolates conferring ciprofloxacin resistance. Simultaneously 37.7% and 40.8% were accounted for, respectively, nalidixic acid and ciprofloxacin Non Wild-Type populations. Amplification and sequencing of quinolone resistance determining region of topoisomerases genes in 44 isolates identified multiple amino-acid substitutions in gyrA at positions Ser83 (N=22; → Leu, → Phe, → Tyr), Asp87 (N=22; → Asn, → Gly, → Tyr) and parC (Thr57Ser, N=23; Ala141Ser, N=1). No relevant mutations were identified in gyrB and parE. Twelve patterns combining one or two substitutions were related to neither serovar nor ciprofloxacin MIC. In 92 isolates suspected for plasmid mediated quinolone resistance two qnr alleles were found: qnrS1 (or qnrS3; N=50) and qnrB19 (or qnrB10; N=24). Additionally, two isolates with chromosomally encoded mechanisms carried qnrS1 and qnrS2. All tested isolates were negative for qnrA, qnrC, qnrD, qepA, aac(6')-Ib-cr. Both chromosomal and plasmid mediated quinolone resistance determinants were found in several Salmonella serovars and Pulsed Field Gel Electrophoresis was used to assess phylogenetic similarity of selected isolates (N=82). Salmonella Newport was found to accumulate quinolone resistance determinants and the serovar was spreading clonally with either variable gyrA mutations, qnrS1/S3, or qnrB10/B19. Alternatively, various determinants are dispersed among related S. Enteritidis isolates. Antimicrobial selection pressure, multiple resistance determinants and scenarios for their acquisition and spread make extremely difficult to combat quinolone resistance.

  12. PI3Kδ inhibitor idelalisib in combination with BTK inhibitor ONO/GS-4059 in diffuse large B cell lymphoma with acquired resistance to PI3Kδ and BTK inhibitors

    PubMed Central

    Sorensen, Rick A.; Cui, Zhi-Hua; Keegan, Kathleen S.; Brockett, Robert; Chen, Guang; Quéva, Christophe; Li, Li; Tannheimer, Stacey L.

    2017-01-01

    Activated B-cell-like diffuse large B-cell lymphoma relies on B-cell receptor signaling to drive proliferation and survival. Downstream of the B-cell receptor, the key signaling kinases Bruton’s tyrosine kinase and phosphoinositide 3-kinase δ offer opportunities for therapeutic intervention by agents such as ibrutinib, ONO/GS-4059, and idelalisib. Combination therapy with such targeted agents could provide enhanced efficacy due to complimentary mechanisms of action. In this study, we describe both the additive interaction of and resistance mechanisms to idelalisib and ONO/GS-4059 in a model of activated B-cell-like diffuse large B-cell lymphoma. Significant tumor regression was observed with a combination of PI3Kδ and Bruton’s tyrosine kinase inhibitors in the mouse TMD8 xenograft. Acquired resistance to idelalisib in the TMD8 cell line occurred by loss of phosphatase and tensin homolog and phosphoinositide 3-kinase pathway upregulation, but not by mutation of PIK3CD. Sensitivity to idelalisib could be restored by combining idelalisib and ONO/GS-4059. Further evaluation of targeted inhibitors revealed that the combination of idelalisib and the phosphoinositide-dependent kinase-1 inhibitor GSK2334470 or the AKT inhibitor MK-2206 could partially overcome resistance. Characterization of acquired Bruton’s tyrosine kinase inhibitor resistance revealed a novel tumor necrosis factor alpha induced protein 3 mutation (TNFAIP3 Q143*), which led to a loss of A20 protein, and increased p-IκBα. The combination of idelalisib and ONO/GS-4059 partially restored sensitivity in this resistant line. Additionally, a mutation in Bruton’s tyrosine kinase at C481F was identified as a mechanism of resistance. The combination activity observed with idelalisib and ONO/GS-4059, taken together with the ability to overcome resistance, could lead to a new therapeutic option in activated B-cell-like diffuse large B-cell lymphoma. A clinical trial is currently underway to evaluate the

  13. XPO1 inhibitor combination therapy with bortezomib or carfilzomib induces nuclear localization of IκBα and overcomes acquired proteasome inhibitor resistance in human multiple myeloma

    PubMed Central

    Turner, Joel G.; Kashyap, Trinayan; Dawson, Jana L.; Gomez, Juan; Bauer, Alexis A.; Grant, Steven; Dai, Yun; Shain, Kenneth H.; Meads, Mark; Landesman, Yosef; Sullivan, Daniel M.

    2016-01-01

    Acquired proteasome-inhibitor (PI) resistance is a major obstacle in the treatment of multiple myeloma (MM). We investigated whether the clinical XPO1-inhibitor selinexor, when combined with bortezomib or carfilzomib, could overcome acquired resistance in MM. PI-resistant myeloma cell lines both in vitro and in vivo and refractory myeloma patient biopsies were treated with selinexor/bortezomib or carfilzomib and assayed for apoptosis. Mechanistic studies included NFκB pathway protein expression assays, immunofluorescence microscopy, ImageStream flow-cytometry, and proximity-ligation assays. IκBα knockdown and NFκB activity were measured in selinexor/bortezomib-treated MM cells. We found that selinexor restored sensitivity of PI-resistant MM to bortezomib and carfilzomib. Selinexor/bortezomib treatment inhibited PI-resistant MM tumor growth and increased survival in mice. Myeloma cells from PI-refractory MM patients were sensitized by selinexor to bortezomib and carfilzomib without affecting non-myeloma cells. Immunofluorescence microscopy, Western blot, and ImageStream analyses of MM cells showed increases in total and nuclear IκBα by selinexor/bortezomib. Proximity ligation found increased IκBα-NFκB complexes in treated MM cells. IκBα knockdown abrogated selinexor/bortezomib-induced cytotoxicity in MM cells. Selinexor/bortezomib treatment decreased NFκB transcriptional activity. Selinexor, when used with bortezomib or carfilzomib, has the potential to overcome PI drug resistance in MM. Sensitization may be due to inactivation of the NFκB pathway by IκBα. PMID:27806331

  14. Gallic acid inhibition of Src-Stat3 signaling overcomes acquired resistance to EGF receptor tyrosine kinase inhibitors in advanced non-small cell lung cancer

    PubMed Central

    Phan, Ai N.H.; Hua, Tuyen N.M.; Kim, Min-Kyu; Vo, Vu T.A.; Choi, Jong-Whan; Kim, Hyun-Won; Rho, Jin Kyung; Kim, Ki Woo; Jeong, Yangsik

    2016-01-01

    Tyrosine kinase inhibitors (TKIs) targeting epidermal growth factor receptor (EGFR) have clinically benefited to lung cancer patients harboring a subset of activating EGFR mutations. However, even with the remarkable therapeutic response at the initial TKI treatment, most lung cancer patients eventually have relapsed aggressive tumors due to acquired resistance to the TKIs. Here, we report that 3, 4, 5-trihydroxybenzoic acid or gallic acid (GA), a natural polyphenolic compound, shows anti-tumorigenic effects in TKI-resistant non-small cell lung cancer (NSCLC). Using both in vitro growth assay and in vivo xenograft animal model, we demonstrated tumor suppressive effect of GA was more selective for the TKI-resistant cancer compared to the TKI-sensitive one. Mechanistically, GA treatment inhibited Src-Stat3-mediated signaling and decreased the expression of Stat3-regulated tumor promoting genes, subsequently inducing apoptosis and cell cycle arrest in the TKI-resistant lung cancer but not in the TKI-sensitive one. Consistent with the in vitro results, in vivo xenograft experiments showed the TKI-resistant tumor-selective growth inhibition and suppression of Src-Stat3-dependent signaling in the GA-treated tumors isolated from the xenograft model. This finding identified an importance of Src-Stat3 signaling cascade in GA-mediated tumor-suppression activity and, more importantly, provides a novel therapeutic insight of GA for advanced TKI-resistant lung cancer. PMID:27419630

  15. Loss of TRIM33 causes resistance to BET bromodomain inhibitors through MYC- and TGF-β–dependent mechanisms

    PubMed Central

    Shi, Xiarong; Mihaylova, Valia T.; Kuruvilla, Leena; Chen, Fang; Viviano, Stephen; Baldassarre, Massimiliano; Sperandio, David; Martinez, Ruben; Yue, Peng; Bates, Jamie G.; Breckenridge, David G.; Schlessinger, Joseph; Turk, Benjamin E.; Calderwood, David A.

    2016-01-01

    Bromodomain and extraterminal domain protein inhibitors (BETi) hold great promise as a novel class of cancer therapeutics. Because acquired resistance typically limits durable responses to targeted therapies, it is important to understand mechanisms by which tumor cells adapt to BETi. Here, through pooled shRNA screening of colorectal cancer cells, we identified tripartite motif-containing protein 33 (TRIM33) as a factor promoting sensitivity to BETi. We demonstrate that loss of TRIM33 reprograms cancer cells to a more resistant state through at least two mechanisms. TRIM33 silencing attenuates down-regulation of MYC in response to BETi. Moreover, loss of TRIM33 enhances TGF-β receptor expression and signaling, and blocking TGF-β receptor activity potentiates the antiproliferative effect of BETi. These results describe a mechanism for BETi resistance and suggest that combining inhibition of TGF-β signaling with BET bromodomain inhibition may offer new therapeutic benefits. PMID:27432991

  16. Mechanisms and consequences of bacterial resistance to antimicrobial peptides.

    PubMed

    Andersson, D I; Hughes, D; Kubicek-Sutherland, J Z

    2016-05-01

    Cationic antimicrobial peptides (AMPs) are an intrinsic part of the human innate immune system. Over 100 different human AMPs are known to exhibit broad-spectrum antibacterial activity. Because of the increased frequency of resistance to conventional