1992 Volume 66 Issue 6 Pages 761-768
Food poisoning due to “Godofu (Sasayuki tofu)” as a main causative foodstuff which broke out on July 14, 1988. There were 670 out of 918 persons who ingested this food who became ill (incidence 73.0%).
The main symptoms were diarrhea (93.4%), fever (77.5%), abdominal pain (64.5%), and vomiting (19.9%). A high degree of fever and watery diarrhea were characteristic of this poisoning.
The average latent period was 35 hours with a range of one to 156. The O164: H-strains of enteroinvasive Escherichia coli (EIEC) were detected from 22 of the 32 fecal samples collected from the patients, five of ten samples collected from workers engaged in tofu making, and one sample of leftover Godofu.
The virulence of EIEC strains isolated from the patients, workers, and leftover food was confirmed by invasion into HeLa and HEp-2 cells, Sereny test, and ELISA test to detect invasive plasmid-derived protein of the organism (conducted at Tokyo Metropolitan Research Laboratory of Public Health).
These EIEC strains were sensitive (≤ 0.19 to 6.25μg/ml) to GM, ABPC, CBPC, CER, CET, NA, PB, MINO, TC and CP as well as KM and OFLX which were used for treatmnet. However, their susceptibility to FOM varied to some extent (6.25 to 25.0μg/ml) and one strain isolated from a tofu worker was resistant to MINO, TC, FOM and CP (25 to ≥-100μg/ml).
Since investigation revealed that Godofu was left at room temperature about 29°C until ingested, we did a experiment to check the bacterial growth in Godofu under similar conditions at the time of outbreak.
One to ten CFU/ml of EIEC O164: H-strain derived from patients was inoculated into Godofu and left at 29°C. The number of cells was increased to about 102, 105, and 105, and 108 CFU/ml after 6, 12 and 24 hrs of standing, respectively.
Patients probably ingested Godofu contaminated by multified bacteria.
The route of contamination into the causative food could not be elucidated, but contamination of EIEC to the water tank used for harding tofu was suspected.