Quinolone resistance in TB
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ABSTRACT:
PROVIDER: PRJEB81545 | ENA |
REPOSITORIES: ENA
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Project description:TODO
2013-03-26 | E-MTAB-1504 | biostudies-arrayexpress
Project description:Three mechanisms for plasmid-mediated quinolone resistance (PMQR) have been discovered since 1998. Plasmid genes qnrA, qnrB, qnrC, qnrD, qnrS, and qnrVC code for proteins of the pentapeptide repeat family that protects DNA gyrase and topoisomerase IV from quinolone inhibition. The qnr genes appear to have been acquired from chromosomal genes in aquatic bacteria, are usually associated with mobilizing or transposable elements on plasmids, and are often incorporated into sul1-type integrons. The second plasmid-mediated mechanism involves acetylation of quinolones with an appropriate amino nitrogen target by a variant of the common aminoglycoside acetyltransferase AAC(6')-Ib. The third mechanism is enhanced efflux produced by plasmid genes for pumps QepAB and OqxAB. PMQR has been found in clinical and environmental isolates around the world and appears to be spreading. The plasmid-mediated mechanisms provide only low-level resistance that by itself does not exceed the clinical breakpoint for susceptibility but nonetheless facilitates selection of higher-level resistance and makes infection by pathogens containing PMQR harder to treat.
| S-EPMC4288778 | biostudies-other
Project description:Meningococcal quinolone resistance originated from several commensal Neisseria species
| PRJEB35093 | ENA
Project description: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.
| S-EPMC4626314 | biostudies-literature
Project description:Ciprofloxacin was introduced for treatment of patients with cholera in Bangladesh because of resistance to other agents, but its utility has been compromised by the decreasing ciprofloxacin susceptibility of Vibrio cholerae over time. We correlated levels of susceptibility and temporal patterns with the occurrence of mutation in gyrA, which encodes a subunit of DNA gyrase, followed by mutation in parC, which encodes a subunit of DNA topoisomerase IV. We found that ciprofloxacin activity was more recently further compromised in strains containing qnrVC3, which encodes a pentapeptide repeat protein of the Qnr subfamily, members of which protect topoisomerases from quinolone action. We show that qnrVC3 confers transferable low-level quinolone resistance and is present within a member of the SXT integrating conjugative element family found commonly on the chromosomes of multidrug-resistant strains of V. cholerae and on the chromosomes of Escherichia coli transconjugants constructed in the laboratory. Thus, progressive increases in quinolone resistance in V. cholerae are linked to cumulative mutations in quinolone targets and most recently to a qnr gene on a mobile multidrug resistance element, resulting in further challenges for the antimicrobial therapy of cholera.
| S-EPMC2812163 | biostudies-literature
Project description: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.
| S-EPMC3985860 | biostudies-literature
Project description:Quinolone resistance encoded by the qnr gene and mediated by plasmid pMG252 was discovered in a clinical strain of Klebsiella pneumoniae that was isolated in 1994 at the University of Alabama at Birmingham Medical Center. The gene codes for a protein that protects DNA gyrase from quinolone inhibition and that belongs to the pentapeptide repeat family of proteins. The prevalence of the gene has been investigated by using PCR with qnr-specific primers with a sample of more than 350 gram-negative strains that originated in 18 countries and 24 states in the United States and that included many strains with plasmid-mediated AmpC or extended spectrum beta-lactamase enzymes. qnr was found in isolates from the University of Alabama at Birmingham only during 6 months in 1994, despite the persistence of the gene for FOX-5 beta-lactamase, which is linked to qnr on pMG252. Isolates from other locations were negative for qnr. The prevalence of mcbG in the same sample was also examined. mcbG encodes another member of the pentapeptide repeat family and is involved in immunity to microcin B17, which, like quinolones, targets DNA gyrase. A single clinical isolate contained mcbG on a transmissible R plasmid. This plasmid and one carrying the complete microcin B17 operon slightly decreased sparfloxacin susceptibility but had a much less protective effect than pMG252. Plasmid-mediated quinolone resistance was thus rare in the sample examined.
| S-EPMC151764 | biostudies-literature
Project description:Quinolones are potent antibacterial agents that specifically target bacterial DNA gyrase and topoisomerase IV. Widespread use of these agents has contributed to the rise of bacterial quinolone resistance. Previous studies have shown that quinolone resistance arises by mutations in chromosomal genes. Recently, a multiresistance plasmid was discovered that encodes transferable resistance to quinolones. We have cloned the plasmid-quinolone resistance gene, termed qnr, and found it in an integron-like environment upstream from qacE Delta 1 and sulI. The gene product Qnr was a 218-aa protein belonging to the pentapeptide repeat family and shared sequence homology with the immunity protein McbG, which is thought to protect DNA gyrase from the action of microcin B17. Qnr had pentapeptide repeat domains of 11 and 28 tandem copies, separated by a single glycine with a consensus sequence of A/C D/N L/F X X. Because the primary target of quinolones is DNA gyrase in Gram-negative strains, we tested the ability of Qnr to reverse the inhibition of gyrase activity by quinolones. Purified Qnr-His(6) protected Escherichia coli DNA gyrase from inhibition by ciprofloxacin. Gyrase protection was proportional to the concentration of Qnr-His(6) and inversely proportional to the concentration of ciprofloxacin. The protective activity of Qnr-His(6) was lost by boiling the protein and involved neither quinolone inactivation nor independent gyrase activity. Protection of topoisomerase IV, a secondary target of quinolone action in E. coli, was not evident. How Qnr protects DNA gyrase and the prevalence of this resistance mechanism in clinical isolates remains to be determined.
| S-EPMC122823 | biostudies-literature
Project description:Although plasmid-mediated quinolone resistance (PMQR) was thought not to exist before its discovery in 1998, the past decade has seen an explosion of research characterizing this phenomenon. The best-described form of PMQR is determined by the qnr group of genes. These genes, likely originating in aquatic organisms, code for pentapeptide repeat proteins. These proteins reduce susceptibility to quinolones by protecting the complex of DNA and DNA gyrase or topoisomerase IV enzymes from the inhibitory effect of quinolones. Two additional PMQR mechanisms were recently described. aac(6')-Ib-cr encodes a variant aminoglycoside acetyltransferase with two amino acid alterations allowing it to inactivate ciprofloxacin through the acetylation of its piperazinyl substituent. oqxAB and qepA encode efflux pumps that extrude quinolones. All of these genes determine relatively small increases in the MICs of quinolones, but these changes are sufficient to facilitate the selection of mutants with higher levels of resistance. The contribution of these genes to the emergence of quinolone resistance is being actively investigated. Several factors suggest their importance in this process, including their increasing ubiquity, their association with other resistance elements, and their emergence simultaneous with the expansion of clinical quinolone resistance. Of concern, these genes are not yet being taken into account in resistance screening by clinical microbiology laboratories.
| S-EPMC2772364 | biostudies-literature
Project description:We show that quinolone resistance in Helicobacter pylori has reached an alarming level in Germany. Our data suggest that the use of quinolones requires prior antimicrobial susceptibility testing, especially for isolates from patients who have already undergone previous unsuccessful eradication treatments, and also underline the further need for surveillance studies to monitor antibiotic resistance in H. pylori.
| S-EPMC1797685 | biostudies-literature