Surveillance Of Antimicrobial Resistance And Detection Of Plasmid-Mediated Quinolone Resistance Determinants Among Escherichia Coli Isolates From Animals

Along with the development and clinical abuse of antibiotics and chemical antimicrobial agents resistance of E. coli has become increasingly serious; the majority of antimicrobial drugs are on the verge of being eliminated position. Quinolone resistance in E. coli has been the research focus whether at home or abroad. Plasmid-mediated quinolone resistance (PMQR) which include at least three types (qnr, aac (6’)-Ib-cr, and qepA) of PMQR genes have been known in recent years. Therefore monitoring of drug resistance and the study of PMQR genetic mechanism on the molecular level, not only can guide the rational use of drugs in clinical practice, but also have great significance for the development of new drugs.530E. coli were isolated from samples which collected in different regions and different animals from2006to2011. MICs of E. coli isolates to22antimicrobial agents were determined by using the broth micro dilution method. The assay showed resistance rates have remained at a high level (above55%) in terms of time, especially for quinolones, but not for ceftiofur. amikacin. tetracycline or levofloxacin. The resistant rates of isolates from chicken were higher than that from ducks and swine. The situations of all regions were different, but both showed high level resistance. The multi-drug resistance rate of the isolates was99.8%. and the isolates were mainly resistant to19,20or21antimicrobial agents.Quinolone-resistant E. coli isolates were screened for the presence of PMQR determinants(qnr, aac (6’)-Ib-cr, qepA) by PCR. The assay showed that relevance ratio of qnrA, qnrB, qnrS, qnrD, aac (6’)-Ib-cr and qepA were5.28%(28/530);2.83%(15/530),5.85%(31/530),0.38%(2/580),14.72%(78/530) and6.04%(32/530), the mutation rate of aac (6’)-Ib was100%:however, the qnrC was not detected in any of the isolates. The PCR results of resistance genes were basically in line with the resistance phenotypes. Through the micro-slide agglutination test, it was demonstrated that the103isolates of PMQR gene positive strains distributed in18serogroups and67.62%(71/105) of the isolates belonged to eight O-serogroups:i.e.060, O89, O119, O141, O9. O107; O131and O137,Conjugation experiments were done with azide-resistant E. coli J53as a recipient, with selection for plasmid-mediated antimicrobial resistance. The results showed that the antimicrobial resistance can be conferred by hrizontal spread among different isolates. The transconjugants showed higher MICs than the recipient, especially to quinolones. In conclusion, through the surveillance of antimicrobial resistance to530E. coli from different sources, we found E. coli isolates exhibited very severe resistance to22antimicrobial agents, and widespread multi-drug resistance phenomenon. qnrA、qnrB、 qnrS、qnrD、aac (6’)Ib-cr and qepA has been detected by PCR, and were correlated with the resistance phenotype. The results of conjugation experiments showed the horizontal transmission of these resistance determinants among different bacterial species.