A spore-forming bacterium that causes food poisoning, most famously from cooked rice left warm or cooled too slowly.
Rice commonly carries the spores, and cooked rice left warm or at room temperature lets them grow and produce a heat-stable toxin. Reheating does not destroy that toxin, so cooled rice held out is a classic source of illness.
The vomiting type usually starts within one to five hours, while the diarrhoeal type appears 8 to 16 hours after eating. Both are generally mild and clear up within about a day.
Not always. Reheating kills the growing bacteria but the vomiting toxin is heat-stable and survives, so rice must be cooled and chilled quickly in the first place rather than relied on being made safe by reheating.
Serve it hot straight away, hold it at 60 degrees or above, or cool it quickly in shallow containers and refrigerate at 5 degrees or below. Use leftover rice within a day or two and do not leave it out overnight.
Pasta and other starchy foods, sauces, cooked vegetables and dairy can also be involved. Any cooked food held in the temperature danger zone can support Bacillus cereus growth.