Antibacterial resistance pattern among Escherichia coli strains isolated from Mansoura hospitals in Egypt with a special reference to quinolones

Extensive use of fluoroquinolone antibacterial in clinical practice has been associated with increasing frequency of quinolone-resistant Escherichia coli strains. In the current study, a total of 80 E. coli clinical isolates from Mansoura hospitals patients in Egypt were studied for antibacterial susceptibility pattern against 15 different antibacterials. These strains were tested for quinolones resistance by minimum inhibitory concentration (MIC) determination using broth micro-dilution method. The resistance rate of ciprofloxacin and levofloxacin for E. coli isolates was found to be 60%. PCR was performed for detection of plasmid-mediated quinolone resistance genes including qnrA, qnrB and qnrS. 30 and 61.3% of E. coli isolates were positive for qnrA and qnrB, respectively, whereas qnrS was identified in only 15% of isolates. Quinolone resistance-determining region (QRDR) of gyrA and ParC genes was characterized for 17 ciprofloxacin and levofloxacin resistant E. coli isolates (MIC 12.5-200 µg mL-1). Two mutation sites in gyrA were detected in 17 tested E. coli isolates. However, two mutation sites in parC were detected in four E. coli isolates. The amino acid change at Ser-83 and aspartic-87 in GyrA were the most common mutation sites identified in the isolates. These results indicated that multiple mechanisms of quinolone-resistance are commonly found in E. coli isolated from Mansoura hospitals.