|Bacillus cereus is a food borne pathogen, which causes gastroenteritis. Fatal and severe cases have been reported within the last few years. Virulence of B. cereus is only partly understood. Most strains are presumably innocuous or madly pathogenic whereas few are presumably highly virulent. No methods exist to distinguish virulent from non-virulent strains. The project proposes to investigate virulence mechanisms of B. cereus in order to identify determinants specific of highly virulent strains. From these results, methods to detect virulent strains will be designed and dose response curve will be improved. The diversity of virulence within B. cereus and the ecology of virulent strains will be investigated in order to identify the contamination routes of foods with virulent strains and to estimate the risk for their presence and development infolds.