Prevalence and expression of enterotoxins in Bacillus cereus and other Bacillus spp., a literature review

Members of the Bacillus genus are ubiquitous soil microorganisms and are generally considered harmless contaminants. However, a few species are known toxin producers, including the foodborne pathogen, B. cereus. This species produces two distinct types of foodborne illness, the emetic (vomit-inducing) syndrome, associated with consumption of toxin in cooked rice dishes, and the diarrheal illness seen occasionally following consumption of contaminated meats, sauces, and certain dairy products. In the latter case, illness results from the production of enterotoxins by vegetative cells in the small intestine of the host. In dairy products, the occurrence of Bacillus spp. is inevitable, and the spore-forming ability of this organism allows it to easily survive pasteurization. Many strains have been shown to grow and produce enterotoxin in dairy products at refrigeration temperatures. Evaluation of toxin gene presence and toxin expression in Bacillus spp. other than B. cereus has not been thoroughly investigated. However, the presence of natural isolates of Bacillus spp. harboring one or more enterotoxin gene(s) and subsequent demonstration of conditions which may support toxin expression holds crucial importance in the food safety arena.