Production of Bacillus cereus emetic toxin (cereulide) in various foods

Abstract

To determine the role of Bacillus cereus as a potential pathogen in food poisoning, the production of an emetic toxin (cereulide) by B. cereus was quantified in various food sources. The amount of emetic toxin in 13 of 14 food samples implicated in vomiting-type food poisoning cases ranged from 0.01 to 1.28 μg/g. A vomiting-type strain, B. cereus NC7401, was inoculated into various foods and incubated for 24 h at 20, 30, and 35 °C. In boiled rice, B. cereus rapidly increased to 10 7–10 8 cfu/g and produced emetic toxin at both 30 and 35 °C. In farinaceous foods, the production of emetic toxin was as high as that in the food samples implicated in food poisoning. Low levels of emetic toxin were detectable in egg and meat and their products and a small quantity of toxin was detectable in liquid foods such as milk and soymilk when not aerated. Bacterial growth and toxin production was inhibited in foods cooked with vinegar, mayonnaise, and catsup, supposedly by the decreased pH of acetic acid. This is the first report that has quantified emetic toxin of B. cereus in various foods.