INCIDENCE AND DIARRHEGENIC POTENTIAL OF BACILLUS CEREUS IN PASTEURIZED MILK AND CEREAL PRODUCTS IN THAILAND

Abstract

ABSTRACTBacillus cereus, bacteria that commonly occur in foods, can potentially cause foodborne illness. Two important factors that contribute to the illness are the number of B. cereus in food and the ability of the organism to produce enterotoxins. This study investigated the number of B. cereus cells in dairy and cereal products in Thailand, using the plate count method and the presence of diarrheal‐enterotoxin genes in the isolates through the polymerase chain reaction (PCR). The genes encoding hemolysin BL (hblA, hblC, hblD), nonhemolytic enterotoxin (nheA, nheB, nheC), cytotoxin K (cytK) and enterotoxin FM (entFM) were the targets of the PCR. B. cereus was found in all pasteurized milk samples and in 37.7% of the cereal product samples, ranging from 50 to 1.7 × 103 cfu/g. PCR results revealed that each gene occurred in more than half of the foodborne isolates tested. A large proportion (96%) of the isolates harbored enterotoxin genes and is considered to be potentially diarrhegenic.PRACTICAL APPLICATIONSSignificant frequency of Bacillus cereus contamination in pasteurized milk and cereal products, and the large proportion of diarrhegenic strains among foodborne B. cereus indicate the high risk of foodborne illness that could be caused by consumption of these foods in Thailand. This suggests that B. cereus should not be disregarded in its significance in disease control and prevention programs. Also, as complete elimination of this organism from pasteurized milk and most of the cereal products through the processing steps is not possible, proper handling and storage of these foods should be strictly applied by the food industry. This is necessary in order to prevent the growth of the organism to levels that can cause foodborne illness. This research is also relevant to other developing countries having similar situations as Thailand, where data concerning the number of B. cereus in foods, frequency of contamination and proportion of enterotoxigenic B. cereus are limited, and where B. cereus gastroenteritis could be underestimated.