Enterotoxigenic profiles and polymerase chain reaction detection of Bacillus cereus group cells and B-cereus strains from foods and food-borne outbreaks

Bacillus cereus is one of the important food pathogens. Since B. cereus gro up cells, such as B. cereus, B. thuringiensis, B. anthracis and B. mycoides , share many phenotypical properties and a high level of chromosomal sequen ce similarity, it is interesting to investigate the virulence profiles for B. cereus group cells, including B. cereus strains isolated from foods and samples associated with food-poisoning outbreaks. For this investigation, t he presence of enterotoxin genes, such as those of haemolysin BL, B. cereus enterotoxin T and enterotoxin FM, were assayed by polymerase chain reactio n (PCR) methods. Meanwhile, their enterotoxin activities were assayed using the BCET-RPLA kit, haemolytic patterns on sheep blood agar and their cytot oxicity to Chinese hamster ovary (CHO) cells. Results showed that there wer e 12 enterotoxigenic profiles for the 98 B. cereus group strains collected. In addition, if any of the three types of enterotoxins was present in the B. cereus group cells, these cells were shown to be cytotoxic to the CHO ce lls. Similar enterotoxigenic profiles could be found among strains of B. ce reus, B. mycoides and B. thuringiensis. Thus, all B. cereus group strains m ay be potentially toxigenic and the detection of these cells in foods is im portant. We thus designed PCR primers, termed Ph1/Ph2, from the sphingomyel inase gene of B. cereus cells. These primers were specific for all B. cereu s group strains and could be used for the detection of B. cereus cells cont aminated in food samples.