[An ecological study for prediction of Vibrio parahaemolyticus food poisoning in Shizuoka prefecture].

The mean MPN viable cell counts in 15 samples of sea water in which clams were held at the time of the onset of mass outbreaks of food poisoning, the number of food poisoning outbreaks, and prevalence of Kanagawa phenomenon-positive strains, and effectiveness of measures to control food poisoning were investigated over 6 years from 1990 to 1995. The results obtained were as follows: 1. Of 6 materials, including sea water and shellfish, which were examined to determine the best marker material for prediction of Vibrio parahaemolyticus food poisoning, sea water in which clams were held was found to be the most appropriate. 2. Except for the outbreaks in 1994, all Vibrio parahaemolyticus food poisoning occurred after the mean MPN viable cell count in 15 samples of sea water in which clams are kept reached 10(5) cells/100 ml. 3. The number of outbreaks of Vibrio parahaemolyticus food poisoning could be predicted based on the time at which the mean MPN viable cell count reached 10(5) cells/100 ml. 4. In 1995, sea water in which clams were held was cultured and examined for thermostable direct hemolysin gene by PCR method. Thermostable direct hemolysin gene was detected in 3 of 82 samples. Thirty-nine Kanagawa phenomenon-positive strains were isolated from 2 of these 3 samples. 5. Kanagawa phenomenon-positive strains were detected after the mean MPN viable cell count in 15 samples of sea water in which clams were kept reached 10(5) cells/100 ml. 6. Four serotypes of Kanagawa phenomenon-positive strains were detected, and they were involved in 5 (45%) of the 11 cases of Vibrio parahaemolyticus food poisoning that occurred in the same year. These serotypes were observed also in 28 (38%) of the 74 strains isolated from food poisoning patients. 7. No conclusion could be made concerning the effectiveness of measures to control food poisoning.