The basic behaviors of Clostridium botulinum type E at low temperatures in medium and food under anaerobic condition generated with deoxygenator “Datusansozai” were studied. This experiment was aimed at finding effects of various growth factors and growth behaviors of C. botulinum type E in various kinds of meat. Firstly, the growth of C. botulinum type E in GAM broth was recognized only in the anaerobic atmosphere created with carbon dioxide generated with deoxygeneator at 5°C. It suggests that carbon dioxide is essential for growth of C. botulinum type E at lower temperatures. Pseudomonas fragi promoted but Lactobacillus sp. inhibited the growth of C. botulinum type E in mixed cultures. At 5°C, the growth of C. botulinum type E was inhibited by addition of smaller quanities of ethylalcohol or sodium chloride than at 10°C. Similarly, the growth of C. botulinum type E at 5°C was inhibited under a less acidic condition than at 10°C. Secondary, C. botulinum type E didn't grow in ground pork, ground chicken, ground beef or sliced lamb at 5°C, but at 12°C, it grew in ground chicken and sliced lamb. In sliced lamb, it grew from a very small initial inoculum at 12°C.
According to the report by HUGHES et. al., a vacuolation activity affecting HEp-2 culture cells was detected in culture filtrate of Bacillus cereus in cooked rice suspension. Fourty-four (78.5%) out of 56 B. cereus strains associated with emetic-syndrome food poisonings and three out of 16 strains from commercial foods produced the vacuolation activity. Fourty-two out of 53 H-1 serotype strains and two H-12 strains were positive in the vacuolation activity. Strains BC1364 and BC1040 isolated from emetic-syndrome food poisoning and strain BC18 isolated from commercial food were tested for the producibility of the activity in various media other than cooked rice suspension, viz., suspensions of cooked spaghetti, tofu, croquette and skim milk, BHIG broth, plain sporulation broth, and that supplemented with each of starch, skim milk, egg york, lecithin and rice oil. In all media except tofu suspension and sporulation broth, strains BC1364 and BC1040 produced the vacuolation activity, but strain BC18 produced no activity in any medium. The vacuolation activity was detected in the culture filtrate after the initiation of spore formation under shaking culture condition at 32°C. The activity was found to be resistant against heating at 100°C for 120 min and 115°C for 60 min, acid, alkaline and proteases.
From May, 1991 to February, 1992, a total of 909 samples of seafoods and seafood products in Tokyo Metropolitan Central Wholesale Market, Tsukiji Market were examined for the presence of Listeria monocytogenes and other Listeria spp. by the combined use of Listeria selective agar (Oxford formulation: Oxoid) and Palcam-Listeria-Selective agar (Merck) after enrichment culture in UVM modified Listeria enrichment broth (Difco). The overall incidence of Listeria spp. was found to be 9.0% in raw seafoods (except shellfish), 9.8% in raw shellfish, 25.0% in boiled shellfish and 14.1% in seafood products. It was revealed that 1.8% of 16 isolates were identified as L. monocytogenes, 7.8% as L. innocua, 1.5% as L. welshimeri, 0.7% as L. seeligeri and 0.4% as L. ivanovii. L. monocytogenes was isolated from smoked salmon (26.7%), salmon flakes (12.5%), crab-meat flakes (8.3%), boiled egg cockles (5.6%), sea urchin roes (3.6%), pink prawns (2.5%) and suquillas, boiled and peeled (2.4%). The predominant serotype of 16 isolates of L. monocytogenes were 1/2a and 1/2b. Most of the seafoods and seafood products contaminated with Listeria spp. found in this study were processed and packed in manufacturing processing.
Escherichia coli in various food samples including seafood was confirmed rampidly by observing fluorescence in cultured media which was prepared by adding 4-metyl-umbelliferyl-β-D-glucuronide (MUG) to EC medium, Violet Red Bile Agar (VRB) and Tryptose-soy pepton Agar. A high false positive rate, 60.8%, was observed in seafood samples when MUG-EC medium was used, however, it was overcome by replacing MUG-EC medium with MUG-VRB agar. A few false positives and negatives were observed in cooked food samples in MUG-EC medium. It was also overcome by replacing MUG-EC medium with MUG-VRB agar. The MUG-VRB agar method was more effective than the MUG-EC method for testing food samples including seafood.