[Isolation, identification and characterization of Bacillus cereus in the dairy industry].

In order to determine the major contamination sources of milk with (psychrotrophic) Bacillus cereus, the incidence of vegetative cells and spores of B. cereus on dairy farms, at two dairy processing plants and in pasteurized milk in household refrigerators was investigated. On dairy farms the major contamination sources were soil and faeces. In winter, when the cows were housed, used bedding probably also participates in this contamination route. The udder will be contaminated, finally resulting in the presence of B. cereus in raw milk. The organism could be detected in 35% of the raw milk samples analyzed. During processing, an increase in the percentage of positive samples was observed. These results suggest that B. cereus can be introduced via sources other than raw milk; equipment may play an important role in this. Biochemical and molecular typing showed that selection of strains takes place in the milk production chain. It was demonstrated that some types were found in the raw milk, during processing and in the end products, indicating that raw milk is an important source of contamination. Other types could only be detected after the pasteurization step in the production process supporting the assumption that additional contamination occurs during processing. If stored under proper conditions, maximum storage temperature 7 degrees C, and consumed within the expiration date, the levels of B. cereus in pasteurized milk will, in general, not exceed 10(5) per ml and cause no problems for healthy adults.