ABSTRACT
Bacillus cereus is a species of the genus Bacillus, which belongs to the Bacillaceae family. This family includes several genera of bacteria, mostly with a Gram-positive type of cell wall. Originally the group B. cereus was composed of four species: Bacillus cereus, Bacillus thuringiensis, Bacillusanthracis and Bacillus mycoides. The production of colonies with a strong reaction of egg yolk, characterized by a large precipitation halo, is typical for bacilli of the B. cereus group. Colonies in solid media are easily recognizable: large, flat, ranging from circular to irregular, with smooth or wavy edges. To differentiate B. cereus from the other bacilli of the group, the tests to be used are those that verify, respectively, the following conditions: the production of intracellular toxin crystals, rhizoid growth, and hemolytic activity.
