Drug susceptibility and beta-lactamase substrate profile of vibrio cholerae non-01

Vibrio cholerae non-01 are organisms that are biochemically indistinguishable from V.cholerae but do not agglutinate in vibrio group 1 antiserum. Some of these strains have been known to produce a cholera-like toxin and cause dehydrating gastroenteritis in humans. Some reports state that more than 20% of V.cholerae isolated from blood are non-01 especially in patients with liver disease. We investigated drug susceptibility and resistance mechanisms to beta-lactam antibiotics in clinical (10 strains) and environmental isolates (80 strains) of V.cholerae non-01. Of the antibiotics tested, ceftizoxime and ofloxacin were extremely active against V.cholerae non-01: both antibiotics inhibited growth of all strains with 0.025 mg/l. None of the 10 strains of the clinical isolates was resistant to other antibiotics tested. On the other hand, 30 strains of the 80 environmental isolates (37.5%) were resistant to ampicillin (ABPC). All these strains showed MICs of ≥12.5 mg/l and all produced beta-lactamase. In a substrate profile study of this enzyme, it was clarified that the beta-lactamase produced by V.cholerae non-01 was basically penicillinase. There is a possibility thit thus resistance to ABPC in environmental isolates of V.cholerae will spread to clinical isolates. We therefore need to be on our guard against the emergence of resistant strains in clinical V.cholerae non-01 infection.