Ac. Gales et al., Occurrence of single-point gyrA mutations among ciprofloxacin-susceptible Escherichia coli isolates causing urinary tract infections in Latin America, DIAG MICR I, 36(1), 2000, pp. 61-64
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.