Occurrence of Bacillus cereus in milk and milk products in Egypt.

The presence of B. cereus spores in raw, pasteurized, and dry milk as well as in Damietta and processed cheese and in a baby food product was investigated, using three selective agar media for enumeration. The organism was detected in 70, 90, and 50% of milk, in processed and Damietta cheese samples, respectively. Spore counts varied from 10(2) to 10(6) and from 10 to 10(2)/ml of raw and pasteurized milk, respectively. In the two types of cheese and dried milk spore densities reached 10 to 10(3)/g. Egg yolk agar (E) gave better recovery rate of B. cereus when compared to the other two media, containing lithium chloride plus polymyxine B- sulphat (I) or polymyxin B-sulphate alone (KG). The latter agar medium favoured the development of larger colonies, surrounded by a more distinctive zone of precipitation.