Background: Fluoroquinolone antibiotics are usually used for the treatment of urinary tract infections. The aim of this study was to determine the prevalence and molecular characterization of Plasmid-Mediated Quinolone Resistance (PMQR) genes among ESBL-producing Escherichia coli isolates obtained from tertiary referral hospital in Tehran, Iran.

Methods: A total of 150 uropathogenic E. coli isolates were obtained from Rasool-e- Akram hospital. The bacterial isolates were identified by standard laboratory methods. Then, the susceptibility to quinolone antibiotics was assessed by standard disk diffusion method. The PCR method was used to show presence of qnrA, qnrB, qnrS, aac(6)-Ibcr and qepA genes.

Results: Overall, 79 of the 150 isolates (52.6%) were non-susceptible to quinolone antibiotics. Out of 79 quinolone non-susceptible isolates, 46 (58.2%) isolates harboured PMQR-encoding genes. Further, 36 (24%) had aac(6)-Ib-cr gene and interestingly, amplification assays showed that 33 (41.8%) out of 79 quinolone non-susceptible isolates carried only qnrB gene. Also qnrA, qnrB (30.9%), qepA (7.3%) and qnrS (25.4%) genes showed. ,

Conclusions: This study showed a high prevalence of aac(6)-Ib-cr, qnrB, qnrS and qnrA genes in the uropathogenic E. coli isolates from tertiary referral hospital. Therefore, the application of proper infection control and well-established antibiotic prescription guidelines seems to be highly needed in our medical centers.

Quinolones resistance; Urinary tract infection; aac(6)-Ib-cr, Pyelonephritis; Cystitis