Study of plasmid-mediated quinolone resistance gene in Escherichia coli strain isolated from bile

Objective To investigate the drug resistance of Escherichia coli isolated from bile and the distribution of its plasmid-mediated quinolone resistance genes (PMQR) in No. 2 People's Hospital of Kaihua County. Methods A total of 724 strains of E. coli were isolated from clinical specimens from department of gastroenterology in this hospital from January 2011 to June 2013, the identification of the strains were performed with automated microbial analysis instruments VITEK 2 COMPACT. The PMQR genes qnrA, qnrB, qnrS, aac(6')-Ib-cr and qepA were detected by using PCR. Results Among the 724 E. coli strains isolated, 135 were isolated from bile, accounting for 18.65%. All the 135 E. coli strains showed 100% sensitivity to carbapenem, and the resistant rates to ciprofloxacin and levofloxacin were 61.5% (83/135) and 55.6% (75/135) respectively. The PCR results revealed that 121 qnrA gene positive strains, 77 qnrB gene positive strains, 43 qnrS gene positive strains and 34 aac(6')-Ib-cr gene positive strains were detected. No qepA gene positive strains were detected. Among these strains, 45 (33.33%) co-carried qnrA1 and qnrB4 genes, 32 (23.70%) co-carried the qnrA1 and qnrB6 genes, 25 (18.52%) co-carried qnrA1, qnrB4 and qnrS1 genes, 21 (15.56%) co-carried qnrA1, qnrB4, qnrS1 and acc (6')-Ib-cr genes and 12 (100%) co-carried qnrA1, qnrB6, qnrS1, and acc (6')-Ib-cr genes. In addition, the resistant rates to ciprofloxacin and levofloxacin increased with the numbers of PMQR gene types. Conclusion E. coli strains isolated from bile were seriously resistant to fluoroquinolone antibiotics. qnrA1 gene was the major PMQR gene in this study, followed by the qnrB4 and qnrB6. The spread of fluoroquinolone resistant genes poses the challenge to clinical treatment of biliary tract infection in gastroenterology department.