STUDIES ON ENTEROTOXIGENIC BACILLUS CEREUS IN RAW MILK AND SOME DAIRY PRODUCTS

ABSTRACT A total of 150 samples of raw milk, ice cream and yogurt (50 of each) were collected randomly in their packages from different localities in Beni‐Suef governorate, Egypt, to study the presence of Bacillus cereus in these products. B. cereus could be detected in 30, 48 and 2% of examined raw milk, ice cream and yogurt samples with a mean count of 9.11 × 102 ± 4.87 × 102, 6.37 × 103 ± 2.83 × 103 and 6 ± 5.9 cells/mL or g, respectively. All B. cereus isolates showed hemolytic activity; 95% of isolates showed vero cell toxicity and 27.5% of them killed adult mice. B. cereus could not be detected in artificially inoculated yogurt after 24 and 48 h. B. cereus was sensitive to pefloxacin, gentamycin, chloramphenicol and nalidixic acid, whereas all isolates were resistant to colistin sulfate. Public health significance and suggestive control measures are discussed. PRACTICAL APPLICATIONS The incidence of contamination of raw milk and ice cream by Bacillus cereus is fairly high, and nearly all of the isolates showed hemolysin and cytotoxic toxin activities, so the risk of food poisoning caused by B. cereus in such products should not be neglected. B. cereus rapidly dies in yogurt, so acidification is a common method of preservation, and as the acidity of fermented milk increased, B. cereus fails to survive. Pefloxacin, gentamicin and chloramphenicol are effective antibiotics against B. cereus infection. B. cereus is highly resistant to colistin sulfate.