Genetic, biochemical and molecular characterization of strains of Vibrio cholerae multiresistant to antibiotics.

In order to gain an insight into the distribution of resistance genes in Vibrio cholerae, we studied twenty-nine strains isolated from patients in Africa. Resistance to antibiotics in all strains except one was encoded by self-transferable plasmids belonging to incompatibility group Inc6-C. Tetracycline and chloramphenicol were poorly expressed in the original hosts but were easily detectable in the Escherichia coli transconjugants. Streptomycin resistance was due to synthesis of a 3"- or 6-aminoglycoside phosphotransferase. Based on MIC and hybridization data, high-level resistance to trimethoprim and O/129 was secondary to the presence of a dihydrofolate reductase of a new type, distantly related to type I activity. Our results confirm the presence in V. cholerae of beta-lactamases other than Tem-1.