Bacillus cereus are bacteria that cause serious illness in humans. Many cases of illness related to Bacillus cereus are caused by eating contaminated foods. The recent tragic cases involving babies in neonatal units are extremely unusual, as it appears the infections were through intravenous fluids given as nutrition to the babies. This meant that the bacteria entered the blood stream of these already vulnerable babies directly, with tragic results. An investigation is now underway to determine how the Bacillus cereus got into the intravenous, but it would appear from this statement by Public Health England that this was down to an isolated incident in the strictly controlled manufacturing process. Bacillus cereus is commonly found in the environment, hence the need for the strictest conditions during production to keep harmful bacteria out.
The majority of cases of food poisoning by Bacillus cereus come from eating poorly prepared or stored food. The bacteria, and its spores, are found commonly in the environment, in soil, dust or on vegetation. Bacillus cereus spores can survive boiling and freezing, so although food processing can minimise the risk, food may be contaminated with low numbers of these bacteria. However, in the vast majority of cases, the bacteria don’t affect us, as they do not survive, and are killed off by our gut’s defence systems, or outcompeted by the trillions of other ‘good’ bacteria inside us. Food poisoning can happen when the food is stored or prepared in such a way that it encourages the growth and multiplication of the bacteria. In particular, special care must be taken in post cooking temperature control to minimise the chances of bacteria growth. Food should be thoroughly cooked, and if not immediately eaten kept at temperatures above 60°C, or rapidly cooled to below 10°C.
Rice is an important potential source of Bacillus cereus food poisoning, which is why special care needs to be taken in the way rice is served and stored, and why the advice is not keep rice warm for long periods before consumption. http://www.nhs.uk/chq/pages/can-reheating-rice-cause-food-poisoning.aspx