Mechanism of drug resistance in clonally related clinical isolates of Vibrio fluvialis isolated in Kolkata, India

The molecular mechanisms of drug resistance in 19 strains of Vibrio fluvialis isolated from 1998 to 2002 in Kolkata, India, were investigated. Class 1 integrons were detected in eight strains, and four strains were found to carry SXT integrases. In the presence of carbonyl cyanide m-chlorophenylhydrazone or reserpine, all nalidixic acid- and ciprofloxacin-resistant strains became sensitive, suggesting that drug efflux plays a major role in quinolone resistance in V. fluvialis. It was further seen that strains which had MICs of > 25 mu g/ml for nalidixic acid had a sense mutation (Ser to Ile) at position 83 of the quinolone resistance-determining region of gyrA. All except one of the integron- and SXT integrase-bearing strains belonged to the same ribotype.