Accidental Contamination by Vibrio cholerae biovar eltor Inaba form in the Shorenji River and Distribution of Non-01 Vibrio cholerae in Rivers in Osaka City.

Abstract

After the occurrence of Vibrio cholerae serotype Olin the Shorenji estuary on September 25, 1982, an etiological survey for cholera strain was carried out along the river from September to December 1982. Out of 11 water samples obtained from the Shorenji River, 7 specimens were demonstrated to be contaminated with V. cholerae biovar eltor Inaba. Positive sources supposed to be responsible to the river contamination were examined. However, no isolates was found either from the effluent of Konohana Sewage Disposal Plant or industrial drainages that discharged into the river. Fishes caught in the river or feces of workers engaged in the Flood Control at the river were also negative regarding cholera infection. Therefore, a question where this V. cholerae came from remained unsolved. Amounts of cholera toxin produced by the isolates were from 16 to 256 in reciprocal titer by the reverse passive latex agglutination (RPLA) test. Epidemiological survey on V. cholerae serotype non-01 (NAG) was carried out on various rivers in Osaka City from September 1981 to August 1982. Positive isolation rate of NAG was 61.9% from river water and 26.1% from mud of river. The positive isolation rate of NAG from water was at its peak in summer season (July to September). Regarding specified basin of river, the highest level of NAG comtamination was observed in the basin along the Neyagawa and Kyu-Yodogawa River. As for the mud of river, the basin along the Hirano River was more contaminated by NAG than other basin. In the bacterial population by MPN (most probable number), the largest value, 1400/100ml, was found in the water sample from the Neyagawa River. Positive producers of cholera toxin (above 2 in reciprocal titer by RPLA) were 88.7% among 186 NAG strains.