Occurrence of single-point gyrA mutations among ciprofloxacin-susceptible Escherichia coli isolates causing urinary tract infections in Latin America

To detect if isolates susceptible to quinolones already carry mutations in the gyrA and parC genes, we selected 12 ciprofloxacin-susceptible Escherich ia coli strains collected from patients with urinary tract infections in La tin America in 1998, as part of ongoing SENTRY Antimicrobial Surveillance P rogram. The isolates studied exhibited minimal inhibitory concentrations (M ICs) for ciprofloxacin between less than or equal to 0.015 mu g/mL and 0.5 mu g/mL. The molecular characterization of quinolone resistance was determi nated by amplification of the gyrA and parC by PCR followed by sequencing o f the respective amplicons. We observed that E. coli isolates exhibiting MI C, less than or equal to 0.06 mu g/mL for ciprofloxacin did not show mutati ons in either topoisomerase. On the other hand, all isolates with MIC betwe en 0.12 mu g/mL and 0.5 mu g/mL demonstrated single mutation in the gyrA ge ne. The most frequent mutation occurred at position 83, where the amino aci d serine was replaced by leucine. No mutations in the parC gene were observ ed. To preserve the potency and prevent the development of resistance, we s uggest that quinolone usage should be rational, especially in the treatment of urinary tract infections, and in the prophylaxis of immunosupressed pat ient populations. (C) 2000 Elsevier Science Inc. All rights reserved.