Plasmid profiles and antimicrobial susceptibility patterns of Vibrio cholerae O1 strain isolated during a recent outbreak in Nigeria.

In a study on the outbreak of cholera in Nigeria in 1992, 86 strains of Vibrio cholerae O1 (79 Ogawa serotype and 7 Inaba serotype) were isolated. Antimicrobial susceptibility testing and plasmid profile analysis of the strains were done. Most isolates were highly sensitive to ciprofloxacin, cefotaxime, chloramphenicol, gentamicin, erythromycin, nalidixic acid, and nitrofurantoin, and less sensitive to ampicillin, penicillin, cloxacillin, cotrimoxazole, streptomycin, and tetracycline. The strains showed 13 resistant patterns; the commonest resistant patterns were Apr, Smr, and ApTcr. A total of 41 (47.6%) strains contained one or more plasmid(s) with sizes ranging from 4.5 kilobase to 150 kilobase. Ten isolates were able to transfer resistant plasmids to Escherichia coli K-12 by conjugation. Antibiogram patterns distinguished more isolates than in plasmid profile analysis. Plasmids specifying resistance to ampicillin, tetracycline, and trimethoprim were found. The differing patterns of antibiogram and plasmid profiles indicated that many circulating strains were responsible for the last outbreak in the country.