The Growth of Food Poisoning Bacillus cereus on Rice Medium : Morphological obeservation with VP-SEM

概要

論文の詳細を見る
Background Bacillus cereus causes two different types of foodbornei Ilness, diarrhea syndrome and emetic syndrome. The types of foods involved in emetic type have been almost entirely associated with consumption of cooked rice. To solve a mechanism of B. cereus food poisoning occurrence, we observed the B. cereus colonies on the nutrient agar and the growing process of this strain on raw rice or an autoclaved rice more naturally using the variable pressure scanning electron microscopy. Methods and Results A bacterial colony on nutrient agar was observed directly by the variable pressure scanning electron microscopy without conventional sample preparation, such as fixation, dehydration, drying, and metal coating. There were the bacterial cells on a raw rice and an autoclaved rice and in a rice the diarrhea-type No.6 strain decomposed starch particles. It was observed that the emetic-type SA-50 tended to form a spore earlier than the diarrhea-type No. 6, whether the same numbers of bacterial cells was inoculated to raw rice and autoclaved rice. Conclusion The SA-50 strain has produced the cytotoxin to HEp-2 cells (carcinoma human larynx cell) that is thought to be emetic toxin. And this cytotoxic activity appeared in late exponential phase to stationary phase and the spore count had also reached its approximate maximum. At this point, it is speculated that the cytotoxin production is related to spore formation.
茨城県立医療大学の論文