Bacillus Cereus Testing

Bacillus cereus is an environmentally widespread Gram-positive, spore-forming, motile rod, which can cause gastrointestinal (e.g. diarrhea) as well as non-gastrointestinal diseases (e.g. septicemia, endocarditis, infections of the central nervous system) in humans. The illness is normally self-limiting and of short duration, although a few fatal cases have occurred. Reporting of Bacillus cereus food poisoning is not required, and thus, the relatively low number of registered cases is regarded as representing only about 1% of the actual cases. The frequency of cases also varies geographically, accounting for less than 1% of all food-related illnesses in some countries while more than 30% in others.

Bacillus cereus is isolated from foods relatively frequently, making it an important environmental indicator organism for the food industry. Foods bearing contamination risk include meat and milk products, vegetables, soups, spices and especially baby food.

Almost all Bacillus cereus strains possess the ability to produce one or more toxins. Cytotoxic enterotoxins are produced by almost 95% of isolates. Of these, non-haemolytic enterotoxin (NHE) is produced by 90% and haemolysin BL (HBL) by about 55% of toxin-producing isolates. The assumption is that HBL and NHE are formed in the gut after the consumption of foods contaminated by vegetative cells or spores of Bacillus cereus.

In addition to this, some Bacillus cereus strains produce a different, heat stable toxin known as Bacillus cereus emetic toxin. This toxin is assumed to be pre-formed in the food and is often associated with starchy products such as rice and pasta. For these reasons, it is becoming increasingly relevant to test foods for toxin-forming Bacillus cereus using reliable and rapid testing methods.