Modelling the number of viable vegetative cells of Bacillus cereus passing through the stomach

Aims: Model the number of viable vegetative cells of B. cereus surviving the gastric passage after experiments in simulated gastric conditions. Materials and Methods: The inactivation of stationary and exponential phase vegetative cells of twelve different strains of Bacillus cereus, both mesophilic and psychrotrophic strains isolated from food and faeces from healthy and ill individuals, in simulated gastric conditions was determined using decimal reduction times at low pH (DpH). Subsequently inactivation rates were calculated. Inclusion of the inactivation rates into models describing the course of the gastric pH after the consumption of meal of solid food and the transfer of food from the stomach to the small intestine resulted in numbers of viable Bacillus cereus vegetative cells able to pass the stomach. Conclusions: According to the model, 3¿26% of the ingested vegetative cells from Bacillus cereus may survive the gastric passage, dependent on the growth phase of the vegetative cells, the type of strains, and the age of the consumer. Significance and Impact of the Study: Vegetative cells of Bacillus cereus may be involved in the onset of diarrhoeal disease to a greater extent than expected since up to 26% of the ingested cells survive simulated gastric conditions.