Abstract
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. Key words: Quinolone resistance, gyrA, parC, qnr gene.
Highlights
Quinolones are powerful broad-spectrum antibacterial agents commonly used in both human and veterinary medicine for the treatment of a wide variety of infections.In the last decade, fluoroquinolones have become first and second-line antibacterials of choice for acute respiretory, enteric and urinary tract infections as well as serious systemic infections such as bacteremia (Jamison, 2006).Their extensive use has been associated with raising level of quinolone resistance in different microorganisms (Robicsek et al, 2006)
Quinolone resistance was always seen in multiple-resistant E. coli, as all quinolone resistant E. coli were resistant to at least one other antimicrobial (Figure 1)
This study suggests that in clinical isolates of E. coli, DNA gyrase is a primary target of quinolones
Summary
Fluoroquinolones have become first and second-line antibacterials of choice for acute respiretory, enteric and urinary tract infections as well as serious systemic infections such as bacteremia (Jamison, 2006). Their extensive use has been associated with raising level of quinolone resistance in different microorganisms (Robicsek et al, 2006). Mutations in QRDRs of gyrA and parC are most commonly documented, resistance is conferred by mutations in parE (Hopkins et al., 2005) These mutations block the action of quinolones resulting in increased level of resistance to fluoroquinolones (Ruiz, 2003).
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