The frequency of DNA gyrase and topoisomerase IV mutations, and plasmid-mediated quinolone resistance genes among Escherichia coli and Klebsiella pneumoniae isolated from urinary tract infections in Azerbaijan, Iran.

OBJECTIVES: The aims of the study were to assess genetic alterations in gyrA, gyrB, parC and parE genes and the prevalence of plasmid-mediated quinolone resistance (PMQR) among Escherichia coli and Klebsiella pneumoniae isolated from urinary tract infections (UTIs) in Azerbaijan, Iran.

METHODS: A total of 205 clinical isolates of E. coli (n=177) and K. pneumoniae (n=28) were obtained from UTIs. The antimicrobial susceptibility determined by the disk diffusion agar and the agar dilution assays. The presence of PMQR genes was studied by the PCR and sequencing of gyrA, gyrB, parC and parE genes were also done.

RESULTS: The rates of resistance to (fluoroquinolones) FQ in isolates were 77.1%. Mutations of Ser83Leu were observed in tested FQ- resistant isolates. Second common mutation in gyrA was Asp87Val. Mutations in parC were often Ser80Ile and Gln84Val. Ser359Ala, Ser367Thr and Gly385Cys substitution in gyrB were identified in one isolate of E. coli and K. pneumoniae, respectively. ParE had mutations at Ile529Leu, Ser458Ala and Leu416Phe. Overall, PMQR determinants were identified in 90% of E. coli and 100% K. pneumoniae isolates. The prevalence of PMQR genes was as follows: aac (6')-Ib-cr (71.7%), oqxB (51.7%), oqxA (36.7%), qnrB (28.3%), qnrS (21.7%), qnrD (16.7%), qepA (5%), qnrA (1.7%) and qnrC (1.7%).

CONCLUSIONS: The rates of resistance to FQ were high. The mutations of DNA gyrase, topoisomerase IV and the prevalence of PMQR genes in E. coli and K. pneumonia isolates were alarming. Moreover, the combination of these resistance mechanisms plays an important role in high-level resistance to FQ.