Microorganisms residing in all parts of the human GIT are adapted to particular conditions such as the extremely low pH of the stomach or the presence of bactericidal substances like bile in
the intestines. The indigenous intestinal microflora perform metabolic activities but also offer protection by forming a kind of barrier against exogenous microflora, including pathogenic microorganisms. Lactic acid bacteria (LAB), mainly the Lactobacillus species, prevent the growth of pathogens through their production of lactic acid and bacteriocins. The studies of the effect of LAB on B. cereus growth confirmed the inhibiting influence of LAB on the growth of vegetative cells and the germination of spores, which was attributed to the high pH of the environment induced by thesebacteria [77,78]. Coconnier et al. [79] showed that antimicrobial compounds produced by the Lactobacillus acidophilus strain LB protect the intestinal epithelium cells against intestinal pathogens, e.g., B. cereus, irrespectively of their production of lactic acid.The bacteriostatic effect of the indigenous intestinal microflora also expresses itself through their occupation of the small intestinal epithelium. In this way, the microflora deprive the pathogens of favourable conditions for growth