Distribution of cereulide-producing Bacillus cereus in raw milk in Hokkaido, Japan, and evaluation of cereulide production

It is important to understand the distribution of strains of Bacillus cereus that produce the emetic toxin, cereulide, in raw milk, and to evaluate their impact on the safety of milk and dairy products. The distribution of cereulide-producing B. cereus was investigated for isolates from raw milk in Hokkaido, Japan, and the ability of strains to produce cereulide in milk was also studied. Only one of 393 isolates had the cereulide-producing gene, indicating very low presence of cereulide-producing strains in milk in Hokkaido. This isolate produced cereulide in milk stored at 12 and 30 °C, but not at 10 °C. It was concluded that keeping storage temperatures below 10 °C reduces the possibility of accumulation of cereulide in milk and dairy products pasteurised at temperatures at which B. cereus spores survive. Hence the possibility of occurrence of cereulide-associated vomiting by ingestion of dairy products of Hokkaido, is very low.