[Studies of Vibrio cholerae O140 (serogroup Hakata) isolated from river water]

Strains of Vibrio cholerae O140, which were isolated from river (Hikichi River) water in Kanagawa, Japan, were studied for their biochemical characteristics and toxin genes, and analyzed by an amplified polymorphic DNA method in comparison with both clinical and environmental isolates of V. cholerae O140. Biochemical characteristics of 4 river isolates studied were found to be unanimous by conventional tests and a commercially available identification kit (Api 50 CH). The strains were also found to react positively with both cholera Inaba factor (C) and V. cholerae O140 specific factor (F). A total of 34 V. cholerae O140 strains including the 4 stains, a reference strains (487-95), 25 strains isolated from samples of river or sea water in Japan, 4 strains isolated from a patient and imported foods, was investigated by the PCR method for presence of ctx, zot, hlyA, and NAG-ST genes. It was found that all strains carried the hlyA gene but none of them carried either ctx, zot, or NAG-ST genes. V. cholerae O140 shared a common antigenic structure with pathogenic V. cholerae strains but its pathogenicity seems to be comparable to that of V. cholerae non-O1 non-O139. Subsequent RAPD analysis indicated that the strains can be divided into 9 groups. Four strains from the Hikichi River showed the same RAPD pattern. The results suggest that the analysis can be a useful epidemiological tool for V. cholerae O140, and that V. cholerae O140 persists in the Hikichi River throughout years.