Impact of intestinal microbiota and gastrointestinal conditions on the in vitro survival and growth of Bacillus cereus

Ingestion of B. cereus can result in diarrhea, if these bacteria survive gastrointestinal passage and achieve growth and enterotoxin production in the small intestine. The gastrointestinal survival of vegetative cells and spores of the diarrheal food poisoning strain B. cereus NVH 1230-88 was investigated during in vitro batch experiments simulating the stomach, duodenum and ileum using simulation media and competing intestinal microbiota. All spores and approx. 30% of the vegetative B. cereus cells survived the 2 h incubation in gastric medium with pH 4.0. Sterile intestinal medium induced germination of spores and enabled outgrowth of vegetative cells to approx. 7 log CFU/mL. The behavior of B. cereus in the intestinal environment with competing intestinal bacteria was determined by their relative concentrations. Besides the numbers of intestinal bacteria, the nutrition and composition of the intestinal community were also very important for the growth inhibition of B. cereus.