Prevalence of qnr Genes in Extended-Spectrum β-Lactamase Producing Klebsiella pneumoniae Isolated from Clinical Urine Specimens in University Teaching Hospitals, Iran

Background and Aims: Extended-spectrum β-lactamase (ESBL) producing gram negative bacteria are resistant to penicillins, narrow and extended-spectrum cephalosporins, and aztreonam; also they are frequently resistant to trimethoprim-sulfamethoxazole, aminoglycosides, and quinolones. This study aimed to investigate the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants qnrA, qnrB and qnrS in ESBL producing Klebsiella pneumoniae isolates. Materials and Methods: In this descriptive-sectional study, 130 Klebsiella pneumoniae isolates were collected from urine specimens and identified by convectional biochemical tests from December 2013 to August 2014,. Antimicrobial susceptibility testing was performed by disk diffusion method (Kirby-Bauer). The presence of ESBLs was confirmed by combination disk tests. E.test method was used for determination of ceftazidime and ciprofloxacin minimum inhibitory concentration (MIC). qnr genes were investigated by multiplex polymerase chain reaction and after sequencing, indexed in Genbank database. Results: Out of 130 isolates, 46 (35.4%) isolates were identified as ESBL producers, considering all, the highest rate of resistance belonged to amoxicillin, cefotaxime and ceftriaxone (each one 100%) and the lowest rate of resistance was for meropenem and ertapenem (each one 4.3%). 45 (97.8%) isolates were resistant to ceftazidime (MIC ≤ 16) and 24 (52.2%) isolates were resistant to ciprofloxacin (MIC≤4). qnrB and qnrS genes were detected in 21 (45.7%) and 7 (15.2%) isolates, respectively. 7 (15.2%) isolates were positive for both qnrB and qnrS genes. qnrA was not detected. Conclusions: With respect to the high prevalence of qnr genes in ESBL producing Klebsiella pneumoniae isolates, quinolones and beta-lactam agents should be used with caution.