High prevalence of fluoroquinolone-resistant Escherichia coli strains isolated from urine clinical samples

Background: Fluoroquinolone resistant Escherichia coli isolates have become an important challenge in healthcare settings in Iran. In this study, we have determined Fluoroquinolone resistant E.coli isolates (from both outpatients and inpatients) and evaluated mutations of gyrA and parC within the quinolone resistance-determining regions (QRDR) of these clinical isolates. Materials and Method : A total of 135 E.coli clinical isolates were recovered from urine of 135 patients (91 outpatients and 44 inpatients) admitted at Alzahra hospital, Iran, between September and February 2013. We assessed antimicrobial susceptibility of all isolates and determined mutations in QRDR of gyrA and parC genes from 13 fluoroquinolone-resistant isolates by DNA sequencing. Results: In this study resistance rate of fluoroquinolones (Ciprofloxacin, Norfloxacin and Ofloxacin) were 45.2%. Two E.coli isolates were shown just a single mutation, but other isolates possessed 2,3,4 and 5 mutations in gyrA and parC genes. Mutations in the QRDR regions of gyrA were at positions Ser83 and Asp87 and parC at positions Ser80, Glu84, Gly78. Conclusions : Ciprofloxacin is the most common antimicrobial agent used for treating urinary tract infections (UTIs) in healthcare settings in Iran. Accumulation of different substitutions in the QRDR regions of gyrA and parC confers high-level resistance of fluoroquinolones in clinical isolates.