腸炎ビブリオ食中毒における原因食品からの神奈川現象陽性株回収法の検討 (10-3-100法)

抄録

In laboratory tests of outbreaks of food poisoning, it is important to isolate the same causative microorganisms from stools of patients and the causative food samples. However, in Vibrio parahaemolyticus food poisoning outbreaks, it is difficult to isolate Kanagawa phenomenon-positive (KP+) strains from causative food samples, whereas they are easily isolated from the patients. Therefore, studies were made for a method for effective isolation of KP+strain from the causative seafoód samples. Twelve seafood samples collected from five outbreaks of food poisoning due to V. parahaemolyticus in Hiroshima prefecture were investigated. Each sample was homogenized and inoculated into equal volume of double strength polymyxin broth. After incubation, the polymyxin broth culture was subcultured onto three TCBS agar plates, which were incubated at 35°C for 24 hr. Then, a total of 100 colonies from TCBS agar plates were inoculated onto three modified Wagatsuma agar plates. KP+strains were isolated from all samples by this method. The rate of isolation of KP+strains was 5.96% (75/1, 261) and that from individual sea food sample varied widely from 1.33 to 18.1%. In the experiments using artificially prepared mixtures of KP+and KP- strains, the recovery rate (Y) of the KP+strain from a mixture and the dilution rate (X=log₁₀ (KP-/KP+)) of KP-: KP+was significantly correlated (r=-0.903, p<0.01) and a regression formula of Y=14.393X^-1.536 was obtained. By this formula, the incidence ratio of KP-: KP+strains in the seafood samples investigated was calculated at 1: 1/60. This method is considered to be effective for recovery of KP+strains from seafood samples in food poisoning outbreaks.