Bacillus cereus
Widely distributed in nature and may be readily isolated from soil, vegetables and a wide variety of foods including milk, cereals, spices, meat and poultry.
History:
Colonies of Bacillus cereus were originally isolated from an agar plate left exposed to the air in a cow shed.
Hosts: Humans, cattle
Morphology:
• Gram positive.
• Large (1 x 5-10 µm) motile rods, centrally located endospores can sometimes be seen as uncolored regions after Gram staining of cells from older cultures.
• An aerobe, facultative anaerobe.
• B. cereus is generally motile but non-motile strains may occur.
• Non-capsulated.
• Can produce protective endospores. It is not susceptible to gamma phage.
Not pathogenic to laboratory animals.
Cultural characteristics: Large, opaque, grey-yellow, granular, flat colonies (diameter 5-10 mm). Most strains produce a clear broad zone of hemolysis on blood agar.
B. cereus produces a wide zone of haemolysis around the colonies. It is a beta haemolytic bacterium.
Virulence factors: Include cereolysin and phospholysin C.
| Genus Bacillus | |
| Bacillus anthracis | |
| Bacillus subtilis | |
| Bacillus licheniformis |