Molecular mechanisms of fluoroquinolone resistance in Enterobacteriaceae clinical isolates in Azerbaijan, Iran

Abstract

Fluoroquinolones (FQs) resistance due to their extensive clinical use has been a major problem in clinical settings that lead to limitation of treatment. This study aimed to investigate the resistance genes to FQs in Enterobacteriaceae isolates in Azerbaijan, Iran. A total of 88 Enterobacteriaceae isolated from clinical samples were collected. The presence of mutations in quinolone resistance genes were detected by the PCR and direct sequencing. The expression levels of acrB efflux pump and the ompF porin were evaluated using the Real-Time PCR. Overall, 63 isolates (71.6%) were resistant to FQs. All FQ-resistant Enterobacteriaceae had a mutation in gyrA. We found 100% and 76% mutation at Ser83Leu and Asp87Asn of gyrA, respectively. Mutations of gyrB were including Ser359Ala + Ser367Thr (1.5%) and Ser366Pro + Arg478Trp (1.5%). Also, mutations in Ser80Ile (68%) and Glu84Val (30%) were found in parC gene. The amino-acid substitutions of Ile529Leu, Ser458Ala, and Leu416Phe in parE were detected in 27%, 23.8% and 15.8% of FQ-resistant Enterobacteriaceae, respectively. Forty-eight (92%) of FQ-resistant Enterobacteriaceae were positive for plasmid-mediated quinolone resistance (PMQR) genes. The expression of acrB increased and expression level of ompF decreased by 58.7% and 64.2% FQ-resistant isolates. The high levels of resistance to FQs were observed among Enterobacteriaceae clinical isolates. We found high-level FQ resistance associated with DNA gyrase and topoisomerase IV mutations as a major mechanism, and along with PMQR genes, expression of the acrB efflux pump gene and outer membrane ompF gene in Azerbaijan, Iran.