2.2. Exposure assessment
Except for the fact that the biodiversity of spore-forming bacteria makes hazard identification difficult, exposure assessment is also strongly affected by the diversity of their physiological properties.
The biodiversity can be expressed from the initial contamination of foods since the pathogenic strains are not equally distributed in foods. Crouch and Golden (2005) estimated that the fraction of type A cpe-positive C. perfringens isolates was 0.6% in meats but 2.9% in spices. Afchain et al. (2008) estimated that the genetic group II of B. cereus was prevailing in raw vegetables, that the genetic groups III was prevailing in milk proteins whereas group IV prevailed in milk proteins and starch. (Guinebretière et al., 2008).