The Prevalence Of Plasmid-mediated Quinolone Resistance Gene In The Community

ObjectivesThis study was designed to investigate the prevalence and molecular characterization of plasmid mediated quinolone resistance(PMQR)genes in commensal Escherichia coli(E.coli).The objectives were to investigate the quinolone resistant mechanism among commensal E.coli isolated from healthy persons in the community.The effective measures to control the dissemination of bacterial resistance may be a possiblility.Methods1.Bacterial Strains.The healthy persons were recruited from those who underwent annual personal physical examination in the Affiliated Union Hospital of Fujuan Medical University during July-October 2013.E.coli isolates were from fecal specimens which were routinely plated on eosin methylene blue plate supplemented with 2μg of levofloxacin per ml.2.Detection of plasmid-mediated quinolone resistance determiants.qnr A,qnr B,qnr S,qnr C,qnr D,aac(6’)-Ib-cr,qep A and oqx AB were detected by PCR3.Antimicrobial susceptibility testing and detection of β lactamase genes.MICs were measured by the agar dilution method for the PMQR positive isolates.β-Lactamase genes were screened by PCR.4.Phylogenetic Characterization.PMQR-positive strains were further characterized by ERIC-PCR.Phylogenetic analysis of PMQR posistive isolates were screened by PCR.Seven housekeeping genes were amplified by PCR and then sequenced.The e BURST were used for phylogenetic analysis.5.Molecular characterization of the qnr S-positive E.coli.MICs were measured by the agar dilution method for the qnr S positive isolates.qnr S-positive strains were further characterized by ERIC-PCR.Phylogenetic analysis of qnr S-posistive isolates were screened by PCR.Seven housekeeping genes were amplified by PCR and then sequenced.The e BURST were used for phylogenetic analysis.Conjugation experiments with azide-resistant E.coli J53 Az R as the recipient.Results1.Strains: 382 nonduplicated fecal E.coli strains were from 429 healthy humans.2.Characterization of PMQR genes.PMQR genes were detected in 120(34.12%)E.coli isolates.qnr genes were detected in 50 E.coli isolates,aac(6’)-Ib-cr were carried by 44 isolates,oqx AB were carried by 43 isolates and qnr B were carried by 3isolates,respectively.3.Antimicrobial susceptibility and characterization of β lactamase genes.The resistance rate to nalidixie acid,ciprofloxacin,levofloxacin resistance rates were100%,78.3% and 66.7%,respectively.To the nine kinds of antibiotics,there were relatively high antibacterial activity as amikacin and imipenem;the sensitive rates were 97.5% and 99.2%,respectively.The amino sugar glycoside of gentamicin resistance rate was 45.8%.The resistance rates to cefotaxime and cefepime were43.3% and 6.7%,respectively.β lactamase genes were detected in 99PMQR-positives E.coli strains.4.Phylogenetic characterization.Phylogentic analysis revealed that 2.5%(3/120)strains were belonged to group B2,14.2%(17/120)strains were belonged to group D,58.3%(70/120)and 25%(30/120)were of group A and group B1,respectively.ERIC-PCR analysis showed great diversity in these isolates.5.Molecular characterization of the qnr S-positive E.coli.Totally,47 strains were comfirmed to be qnr S-positives.The resistance rates to nalidixie acid and tetracycline both were 100%.There were relatively high antibacterial activities as amikacin and imipenem,the sensitive rates both were 100%.9 qnr S-positive E.coli strains were carried other PMQR genes.β lactamase genes were detected in 33 qnr S-positives E.coli strains.The results of phylogentic analysis revealed that 66.0%(31/47)strains were belonged to group A,25.5%(12/47)and 8.5%(4/47)were of group B1 and group D,respectively.ERIC-PCR analysis showed great diversity in these isolates.47 strains of qnr S positive E.coli were analyzed by the method of MLST.ST10 and ST4428 were the main types.Conjugation assays were successful with 11 qnr S-positives E.coli strains.Conclutions: An epidemic of PMQR strains in our city is confirmed.The linkage between PMQR and ESBLs was comfirmed.Escherichia colis which carried plasmid-mediated quinolone resistance derminants were mostly multidrug-resistant isolates,especially to the cephalosporins and quinolones.qnr S was the predominant allele in this study.ST 10 and ST 4428 were the main types.The data of this study revealed a transferability,and non-clonal transmission of qnr S in the community.These results confirm that community isolates can be an important source for spreading antibiotic resistance determinants among Grem negative pathogens.This is the first report from China on detection of PMQR in the community isolates of E.coli.