Plasmid-mediated quinolone resistance determinants among Gram-negative bacteraemia isolates: a hidden threat (original) (raw)
Related papers
Memórias do Instituto Oswaldo Cruz, 2013
OBJECTIVES: To analyze the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants in ciprofloxacin-nonsusceptible Escherichia coli and Klebsiella pneumoniae isolated from patients at a tertiary care hospital in Korea. METHODS: A total of 102 nonduplicate isolates of ciprofloxacinintermediate or ciprofloxacin-resistant E coli (n=80) and K pneumoniae (n=22) from blood cultures were obtained. The qnr (qnrA, qnrB, qnrS), aac(6')-Ib-cr, qepA and oqxAB genes were detected using polymerase chain reaction (PCR) and confirmed using direct sequencing. To determine whether the PMQR-positive plasmid was horizontally transferable, conjugation experiments were performed. RESULTS: Of the 102 isolates, 81 (79.4%) had one or more PMQR genes; these consisted of 59 (73.8%) E coli and 22 (100%) K pneumoniae isolates. The qnr genes were present in 15 isolates (14.7%): qnrB4 was detected in 10.8% and qnrS1 was detected in 3.9%. The aac(6')-Ib-cr, qepA and oqxAB genes were detected in 77.5%, 3.9% and 10.8%, respectively. In conjugation experiments, PMQR genes were successfully transferred from seven (8.6%) isolates. The range of minimum inhibitory concentrations of ciprofloxacin for these seven transconjugants increased to 0.5 mg/L to 1 mg/L, which was 16-to 33-fold that of the recipient E coli J53 bacteria. CONCLUSIONS: PMQR genes were highly prevalent among ciprofloxacin-nonsusceptible E coli and K pneumoniae from blood cultures in the authors' hospital. Therefore, it is necessary to monitor for the spread of PMQR genes of clinical isolates and to ensure careful antibiotic use in a hospital setting.
Medical Laboratory Journal, 2017
Background and Objective: Klebsiella pneumoniae is one of the most common causes of bacterial infections. Presence of plasmid-mediated quinolone resistance genes causes low level of resistance in K. pneumoniae. This study investigated the prevalence of resistance to quinolones and fluoroquinolones, and the frequency of qnrA, qnrB and qnrS genes among K. pneumoniae strains. Methods: The study was performed on 100 K. pneumoniae strains isolated from hospitals in city of Borujerd (Iran) during April to September 2014. Susceptibility of the isolates to nalidixic acid, ciprofloxacin, norfloxacin and ofloxacin was evaluated. Minimum inhibitory concentration (MIC) of ciprofloxacin was determined using ciprofloxacin Etest strips. Polymerase chain reaction was performed to detect qnrA, qnrB and qnrS genes in quinolone-resistant isolates using specific primers. Results: The results showed that 38% of the isolates were resistance to both nalidixic acid and ciprofloxacin. The prevalence of ofloxacin-and norfloxacin-resistant isolates was determined to be 18% and 15%, respectively. The MIC values for ciprofloxacin were ranging from 0.064 to ≥256 μg/ml. In addition, four ciprofloxacin-resistant isolates (10%) had MIC of ≥256 μg/ml. The qnrA gene was not detected in any of the quinolone-resistant isolates. Moreover, 23.6% (n=9) and 5.2% (n=2) of the quinolones-resistant isolates contained the qnrB and qnrS genes, respectively. Conclusion: Although 38 isolates were ciprofloxacin-resistant, the qnrB, qnrS genes were detected in a small number of isolates. This indicates the involvement of factors other than the qnr genes in resistance of these isolates to quinolones.
International Journal of Clinical & Medical Microbiology, 2017
Quinolone resistance limits the therapeutic potential for the Extended-Spectrum β-lactamase (ESBL) producing Enterobacteriaceae. The aim of this study was to investigate the most common mechanisms of quinolones resistance in ESBL-producing Enterobacteriaceae using both phenotypic and genotypic methods. Out of 1766 clinical isolates collected between October 2012 and September 2013, 219 Enterobacteriaceae clinical isolates were ESBL producers, nalidixic acid and ciprofloxacin resistant were identified by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF/MS) and the Minimal Inhibitory Concentration (MIC) values of ciprofloxacin and nalidixic acid wasdetected before and after addition of phenylalanine-arginine β-naphthylamide (PaβN) efflux pump inhibitor. Thirty three isolates were selected for screening of the plasmid-mediated fluoroquinolone resistance (PMQR) genes; (qnr, aac(6')-Ib-cr and qepA) and the efflux pump genes (oqxAB genes) by multiplex PCR. Whereas GyrA and ParC genes mutations were detected by PCR-RFLP assay. The PaβN changed the MIC values of 28 isolates. The GyrA gene mutation was detected in 24/33 (72.7%), while the par C gene mutation was detected in 3/33 (9.1%). Qnr-genes were detected in 13/33 (39.4%), aac(6')-Ib gene was detected in 24/33 (72.7%). qepA gene was detected in only one Klebsiella pneumoniae isolate. Finally the oqxA gene was detected in 16/33 (48.5%) of the studied isolates. The present study indicated that the PaβN was an effective phenotypic screening method for quinolones resistance efflux pump; moreover PCR-RFLP offered simple and rapid method for detection of ciprofloxacin-resistance that could be useful for clinical diagnosis and epidemiological studies
Background: Plasmid mediated quinolone resistance is an additional burden consequent to extended spectrum beta lactamase production identified in Enterobactericeae isolates worldwide. The present study aimed at detection of qnrA mediated resistance in quinolone resistant E.coli and Klebsiella pneumoniae isolated in our University Teaching hospital in Northwest Iran. Materials and Methods: A total of 63 E.coli and 71 K.pneumoniae isolates found resistant to ciprofloxacin or nalidixic acid on disk agar diffusion were collected between May and December 2013 for the presence of qnrA gene by polymerase chain reaction and their association with ESBL was confirmed on disk diffusion confirmatory test as per clinical and laboratory standards institute (CLSI) guidelines. Presence of resistance to 3 more than three antibiotics was considered as multidrug resistance (MDR). Minimum inhibitory concentration (MICs) of ciprofloxacin and nalidixic acid for the qnrA positive isolates were determined according to CLSI. Results: Of 71 E.coli isolates, 39(54.9%) and 29(40.8%) were resistant to nalidixic acid and ciprofloxacin respectively. qnrA gene was detected in 3 (4.2%) ciprofloxacin resistant isolates. Among 63 K.pneumoniae isolates, resistance to ciprofloxacin and nalidixic acid was found in 35(55.5%) and 15(23.8%) isolates. qnrA gene was detected in 2(3.2%) ciprofloxacin resistant isolates. The ciprofloxacin MIC for all of qnrA positive E.coli and K.pneumoniae isolates was high (≥32 μg/mL). Surprisingly, no nalidixic acid resistant isolate was positive for qnrA. Additionally, all qnrA positive isolates were found ESBL producers and 80% were MDR. Discussions: Our results showed emergence of qnrA mediated resistance, however, this resistance was lower compared to other published studies from Iran. ESBL and MDR accompanying quinolone resistance in E.coli and K. pneumoniae isolates suggests revising the choice of antibiotic therapy.. qnrA implicated quinolone resistance in Escherichia coli and Klebsiella pneumoniae clinical isolates from a University Teaching Hospital. Life Sci J 2014;11(12s):1032-1035]. (ISSN:1097-8135). http://www.lifesciencesite.com. 223
Resistance to Quinolones in Gram-Negative Microorganisms: Mechanisms and Prevention
European Urology
Bacterial resistance to quinolones is essentially the result of mutations on several genes involved in the synthesis of DNA-gyrase or in proteins of the cellular envelope. A single mutational event may lead to complete resistance to older quinolones, but clinical resistance to newer quinolones such as norfloxacin requires two or more mutations. Prevention of resistance to norfloxacin requires prevention of the strains carrying 'first mutations' (by a controlled use of older quinolones) and the early detection of such strains. If microbiologie and pharmacologic data are taken into account at the same time, the incidence of norfloxacin-resistant strains in urinary tract infections will remain insignificant. coli Kl 2. In these experiments the strain is heavily inoc ulated on culture media containing different quinolone concentrations, and the survivors (presumptively mu tants) are studied and further characterized. The opera tive designation of mutants is arbitrarily chosen by each author. Thus, mutants selected on norfloxacin have been designated as nfx or nor, those selected on ciprofloxacin as cfx, and those selected on nalidixic acid as nal. These designations do not imply any relationship with the accepted designations of the bacterial genes [1], For instance, the nalA mutation has been localized inside the gene gyrA-as have nfxZ, norA and cfxA-and must be considered as gyrA mutations. Whether they are the same or different mutations inside the gene will be ascer tained by precise genetic studies and, finally, by DNA sequencing. Although mutations on the same gene tend to produce similar or identical phenotypes, this is not always the case. The modified regions of the gene may have differ ent functional consequences in the resulting polypeptide, leading, for instance, to different levels of quinolone resistance. In order to prevent confusion about the dif ferent published designations of the mutants resistant to quinolones, table 1 summarizes the different mutations in relation to the presumed bacterial gene involved.
Interaction of plasmid and host quinolone resistance
Journal of Antimicrobial Chemotherapy, 2003
Sir, Resistance to quinolones in Gram-negative bacteria is usually caused by chromosomal mutations that alter the target enzymes DNA gyrase and topoisomerase IV or activate the efflux systems that pump the drugs out of the cytoplasm. Loss of porin channels for drug entry may also contribute to resistance, but is less important. Plasmid-mediated quinolone resistance, long thought not to exist, has recently been discovered. 1 Conjugative plasmid pMG252, found in a clinical isolate of Klebsiella pneumoniae, mediates a four-to 16-fold increase in resistance to fluoroquinolones and nalidixic acid, thus facilitating ciprofloxacin MICs as high as 32 mg/L in a K. pneumoniae strain already partially quinolone resistant. In wild-type K. pneumoniae or Escherichia coli strains pMG252 still augmented resistance but only to ciprofloxacin MICs of 0.125-0.25 mg/L, well below the clinical breakpoint for loss of susceptibility. However, from such an E. coli strain carrying pMG252, mutants could be selected with successively higher levels of resistance up to a ciprofloxacin MIC of 4 mg/L. 1 The plasmid locus responsible for quinolone resistance is termed qnr. The gene has been cloned and sequenced. It encodes a 218-amino-acid protein that belongs to the pentapeptide repeat family of proteins. 2 Purified Qnr has been shown to block inhibition of E. coli DNA gyrase by ciprofloxacin in a cell-free system. 2 The objective of the present study was to evaluate the interaction of resistance determined by plasmid pMG252 with defined chromosomal mechanisms of quinolone resistance to gain an insight into how higher levels of resistance could develop.
Molecular basis of quinolone resistance in Enterobacterial isolates
Journal of Microbiology and Infectious Diseases, 2016
Objective: Fluoroquinolones are the commonly prescribed antimicrobial for Gram-negative and Gram-positive microorganisms. The resistance against these antibiotics is of importance in therapy. The current study aimed at determination of aac(6')-Ib-cr gene within the Enterobacterial isolates and their transmission dynamics. Materials and Methods: Ninety-seven isolates of Enterobacteriaceae collected during May 2013 to October 2013 were screened by the antimicrobial susceptibility test. The plasmids from these isolates were analysed by specific Polymerase chain Reaction (PCR) for qnrA, qnrB, qnrD, qnrC, and aac(6')-1b-cr and the horizontal dissemination of these plasmid mediated quinolone determinants and aac(6')-1b-cr genes were determined by transformation. Results: Our analysis showed that 94 out of 97 phenotypically screened positive isolates, 85.57% (n = 83), 84.53% (n=82) were resistant to norfloxacin, ciprofloxacin respectively. Coexisting qnrD genes was identified in 11isolates carrying aac(6')-Ib-cr gene. The PMQR and aac(6')-Ib-cr was demonstrated by transforming the plasmid carrying qnrD and aac(6')-Ib-cr gene into E. coli strain DH5ɑ. PCR assay confirmed that aac(6')-Ib-cr was present in all the transformants. Conclusion: Our report shows the presence of heterogenous resistance mechanism can lead to worrisome condition at the nosocomial level and community acquired infection. So aac(6')-Ib-cr containing strains should be promptly detected and referred to clinicians so that the treatment with non-hydrophilic FQs, such as levofloxacin and ofloxacin, or other classes of antibiotics to prevent high level resistance onset and spread.
2018
Plasmid mediated quinolone resistance (PMQR) determinants have arisen as a significant concern in recent years. The aim of this study was screening of resistant-clinical isolates to fluoroquinolone antibiotics and detection of qnr and aac(6′)-Ib-cr genes. For this purpose we collected 100 fluoroquinolone-resistant Enterobacteriaceae which were from 3 hospitals in Hamadan, west provinces of Iran, between October 2012 and June 2013. The all samples were identified by biochemical tests and confirmed by PCR method. Antimicrobial susceptibility to 14 antimicrobial agents including levofloxacin and ciprofloxacin were determined by disk diffusion methods and ciprofloxacin MIC was obtained by broth microdilution method as Clinical Laboratory Standards Institute (CLSI) recommendations. The isolates were screened for the presence of qnrA, qnrB, qnrS and aac(6′)-Ib-cr genes using PCR assay. Among the screened isolates, 64 strains (64%) of Escherichia coli, 23 strains (23%) of Klebsiella pneumo...
Journal of Clinical Microbiology, 2009
We have studied by PCR and DNA sequencing the presence of the qnrA, qnrB, qnrS, aac(6)-Ib-cr, qepA, intI1, and ISCR1 genes in 200 clinical isolates of Enterobacter cloacae (n ؍ 153) and E. aerogenes (n ؍ 47) consecutively collected between January 2004 and October 2005 in two hospitals located in Santander (northern Spain) and Seville (southern Spain). Mutations in the quinolone resistance-determining region of gyrA and parC also were investigated in organisms containing plasmid-mediated quinolone resistance genes. The isolates had different resistant phenotypes, including AmpC hyperproduction, extended-spectrum -lactamase production, resistance or decreased susceptibility to quinolones, and/or resistance to aminoglycosides. Among the 116 E. cloacae isolates from Santander, qnrS1, qnrB5, qnrB2, and aac(6)-Ib-cr were detected in 22 (19%), 1 (0.9%), 1 (0.9%), and 3 (2.6%) isolates, respectively. Twenty-one, 17, and 2 qnrS1-positive isolates also contained bla LAP-1 , intI1, and ISCR1, respectively. A qnrB7-like gene was detected in one E. aerogenes isolate from Santander. No plasmid-mediated quinolone resistance gene was detected in the isolates from Seville. The qnrS1-containing isolates corresponded to four pulsed-field gel electrophoresis patterns and showed various levels of resistance to quinolones. Six isolates were susceptible to nalidixic acid and presented reduced susceptibility to ciprofloxacin. The qnrS1 gene was contained in a conjugative plasmid of ca. 110 kb, and when the plasmid was transferred to recipient strains that did not have a specific mechanism of quinolone resistance, the ciprofloxacin MICs ranged from 0.047 to 0.125 g/ml.