The relationship between the detection of thermostable direct hemolysin gene (tdh) -positive Vibrio parahemolyticus from environmental samples (estuarine water and estuarine mud) and Rock Oysters, and the emergence of V. parahaemolytics infection was investigated in a district of Akita prefecture in 2000 and 2001. A selective isolation method employing PCR for tdh, an immunomagnetic separation technique, and direct inoculation of tdh-positive enrichment broth onto a Wagatsuma agar, was used in the examination of the environmental samples and Rock Oysters. The number of cases V. parahaemolyticus infection decreased between 2000 and 2003, which was due to a decrease in the number of V. parahaemolyticus O3: K 6 (tdh+) patients. The period in which V. parahaemolyticus infection was observed in Honjyo city coincided with that in which Rock Oysters were retailed, and tdh-positive V. parahaemolyticus was isolated from both of the environmental samples and Rock Oysters obtained in that period, suggesting that Rock Oyster was one source of V. parahaemolyticus infection in Honjyo city. However, whether all Rock Oysters containing tdh-positive V. parahaemolyticus could cause human diarrhea was unclear, because the infectious dose of tdh-positive V. parahaemolyticus has not been established, and the number of tdh-positive V. parahaemolyticus in Rock Oysters was not measured. We propose from our findings that the temperature of Rock Oysters at retail stores should be kept low enough to prevent proliferation of tdh-positive V. parahaemolyticus, which should prevent V. parahaemolyticus infection. This is the first report showing a relationship between the detection of tdh-positive Vibrio parahemolyticus from the environmental and food samples, and the emergence of V. parahaemolytics infection in a particular district. In order to elucidate epidemiology of V. parahaemolyticus infection, further studies should be conducted in the different districts of Japan.
Penicillium expansumO-385-10 produces glucose oxidase and catalase but showed poorgrowth in medium containing glucose as a sole carbon source. In this culture, gluconate wasaccumulated, the pH of the culture medium decreased during incubation, and growth wasremarkably inhibited. Glucose oxidase and catalase were purified as electrophoreticallyhomogeneous proteins from the culture in which the pH was adjusted using calcium carbonate.The molecular weights of glucose oxidase and catalase were estimated at about 130 kDa (homodimer) and 300 kDa (homotetramer). Glucose oxidase and catalase showed about 80%and 50% activity at pH 3, respectively. The catalase was remarkably activated by 1mM Ca2+and 1mM Ba2+. When glucose oxidase and catalase were simultaneously incubated withsmall pieces of apple, the fruit tissue browned remarkably. No browning reaction occurredwhen each enzyme was incubated independently.
The VIDAS Listeria monocytogenes 2 (LMO 2) is an enzyme-linked fluorescent assay (ELFA) system which is a fully automated ELISA technology to detect Listeria monocytogenes. This system is a powerful tool for the food industry because assay results following a 48 hr enrichment procedure can determine the presence or absence of L. monocytogenes within 70 min. The aim of this study is to compare the ELFA method with the conventional cultural method for detecting L. monocytogenes in natural cheese. We confirmed 33 samples (19 types) of natural cheese tested were not naturally contaminated by L. monocytogenes using both detecting methods. L. monocytogenes was then inoculated into the cheese samples at a concentration of 1cfu/g. Twenty of 33 samples showed 100% positive by the culture method. Twenty-seven samples showed 100% positive by the ELFA method. The overall positive rate of 33 samples of natural cheese were 83% and 89% for the culture method and ELFA method, respectively. Two samples of Blue cheese and one sample of Camembert cheese produced a poor positive rate by the ELFA method due to low numbers of L. monocytogenes cells after the enrichment procedure. These results show that the ELFA method could be used satisfactorily, except for particular cheeses, as a rapid method for the detection of L. monocytogenes in natural cheese inspection.