An outbreak of food poisoning caused by Salmonella sp. (1) Champaign occurred in children joined for a Bon festival party in Hiroshima Prefecture in August 1988. It involved 330 patients among 550 children who had eaten roast cuttlefish “yaki-ika”. This is the first report on food poisoning caused by Salmonella sp. (1) Champaign. The mean incubation time was 34.5 hr and the major clinical symptoms were diarrhea (91.8%), abdominal pain (78.8%), fever (44.2%) and headache (39.1%). The incriminated “yaki-ika” was cooked after thawing the frozen cuttlefish at ambient temperature for 27-30 hr, during which period contamination and proliferation of the causative organism may have occurred. S. Champaign increased in number to 6-7 log10/ml at 20°C for 27 hr in the extract of cuttlefish. The maximum temperature of the body cavity of the cuttlefish reached 78°C during boiling for 5 min, but the retention time at 60°C or above in the cavity was 8.5 min. Linear reduction of S. Champaign under boilng was calculated at log10Y (cells) =-0.68T (min) +7.33 and the D90 value 1.47 min.
The distribution of Morganella morganii in fish and fish products on the market was investigated. Sliced raw fish both wrapped and unwrapped were frequently contaminated with Morganella morganii. We then investigated the effect of the temperature on the formation of histamine in raw fish and fish products inoculated or not inoculated with Morganella morganii, paying special attention to the effect of cold storage. During the storage at 5°C or 7.5°C, histamine was hardly produced in sliced raw tuna not inoculated with Morgalla morganii and the sliced raw yellowtail inoculated with Morganella morganii, but during the storage at 10°C, much histamine was produced in both fish. When 10 g of jack mackerel (for frying) inoculated with 1 ml of a suspension of Morganella morganii at 2 × 106/ml was inoculated for 6 hr at 30°C, the formation of histamine comtinued even during the storage at 5°C. In jack mackerel (for frying) inoculated with Morganella morganii, the amount of histamine formed depended on the viable count of Morganella morganii. During the storage at 5°C, the growth of Morganella morganii was suppressed but when the viable count reached around 108/g, histamine was produced. The effects of the concentration of sodium chloride on histamine formation was investigated. Histamine was hardly produced in the meat with 7.5% or 25% sodium chloride but was produced much in the meat with 2% and 5% sodium chloride.
SDS-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell preparations of Campylobacter jejuni was performed to find whether the profiles obtained by silver staining could be used for bacterial epidemiological analysis of outbreaks of enteritis cases due to C. jejuni. The electrophoretic profiles of C. jejuni isolated from sporadic cases could be differentiated from one another by analyzing both major and minor bands, especially the molecular weight ranging close to 43, 000 daltons, not stained by silver staining, was most valuable. Two C. jejuni isolates from a particular domestic case showed identical profiles. In six cases of nine outbreaks examined, SDS-PAGE profiles correlated well with other epidemiological markers such as serotyping and antibiotic resistance. In two cases, the isolates showed two different profiles and serogroups, but only one antibiotic resistance pattern. In one case, the isolates showed three different profiles, but two different serogroups and two different antibiotic patterns. These results suggest that the SDS-PAGE profile serves as a useful epidemiological marker for studying outbreaks of C. jejuni enteritis and might subdivide C. jejuni strains belonging to the same serogroup into several groups.
The membrane filter technique with AC agar medium (designated as the AC·MF technique) for enumeration of enterococci in frozen foods was examined for the applicability for food examination. Ten grams of a frozen food was homogenized in 90 ml of 0.1 % peptone medium by the stomacher using stomafilter and 10 ml of the homogenate was filtered through a membrane filter. The membrane filter was put on an AC agar plate, which was incubated at 37°C for 18 hr followed by further incubation at 45°C for 24 hr. All the colonies grown on the membrane filters were identified as enterococci, and the count of enterococci obtained by the AC·MF technique was in good agreement with that by the AC·MPN technique. The AC·MF technique seems usefull for accurate and rapid enumeration of enterococci in frozen food, if the homogenate is so prepared as to be filtrable through a membrane filter.
One hundred and eighty five soil and 98 vegetable samples from 88 fields and 205 vegetable and shredded vegetables samples from retail shops were examined for Bacillus cereus and Bacillus thuringiensis (Bt). In regard to the field samples, B. cereus was found in 91% of soil and 55% of vegetable samples; the positive samples contained viable populations of 102-107 cfu/g and 102-105 cfu/g, respectively. Among the vegetable samples on the market, only 20% contained B. cereus in 102 to 105 cfu/g. On the other hand, Bt was found only in two soil and four chinese cabbage samples from fields and two vegetable samples from markets. The presumptive contents of Bt in those positives ranged 102-103 cfu/g. Among 407 isolates of B. cereus from various sources, 93% had starch hydrolyzing activities, and only 4% were grouped into Taylor and Gilbert's H-serovars including serovar 5, 10, 11, 13, 14, 17 and 18, all of which were starch hydrolysis positive. Thirty-seven percent of the isolates tested for diarrheal toxigenecity produced more than 2μg/ml of enterotoxin. The toxigenic activity of the starch hydrolyzing isolates was generally higher than that of nonhydrolyzing isolates. In addition, all Bt isolates were starch hydrolyzers, and some of these isolates also produced more than 2μg/ml of enterotoxin.