Bacillus cereus

Background Bacillus cereus is widely distributed in the environment and is not a contaminant of food. It is found in rice and other natural foods, such as herbs and spices, cream, and dry foods.

Growth and survival Unlike the staphylococci, B. cereus is a spore-forming organism that survives prolonged boiling. It causes two fairly distinct types of food poisoning, emetic and diarrheic. The diarrheal toxin is heat labile and, like Clostridium perfringens, formed in the gut. The foods commonly associated with it are 'proteinaceous' and, like C. perfringens, associated with meats, stews, desserts, and sauces. The emetic type is 'farinaceous,' associated mainly with cooked rice, and produces an illness similar to SFP. Different serotypes of B. cer-eus cause these two different forms of FP, and the toxins are different also. Other members of Bacillus sp. are discussed later. Some strains will grow at refrigeration temperatures in milk and other foods.

Clinical features and characteristic sequence of events The emetic type of B. cereus FP is caused by preformed toxin (cereulide) in food, usually rice that has cooled slowly. This usually happens when a large bulk of rice, as in Chinese restaurants, is allowed to cool at room temperature for many hours, often overnight. The center of the mass will stay warm for a long enough period for the spores of the bacillus to germinate and form toxin. The toxin is heat stable and will survive the quick frying given to it in a Chinese restaurant. The incubation period is usually short (1-6 h), and the symptoms, predominantly vomiting, tend to be milder than those for SFP, which it otherwise resembles.

The diarrheal form of B. cereus FP is similar to that caused by C. perfringens. The toxin, unlike the emetic type, is an enterotoxin formed in the intestine and is heat labile. The predominant symptoms are diarrhea and abdominal colic. The incubation period, as expected for an organism that multiplies in the intestine and then produces its toxin, is also longer (8-16h). This type of B. cereus FP can be caused by a wide variety of foods, including meat, vegetables, and dairy products.

Diagnosis The mere presence of B. cereus in a food is insufficient because it is a normal contaminant of many natural foods. The diagnosis is confirmed by the finding of the organism in high concentrations [106-108/g, minimum 105] in cooked rice, or other food for the diarrheic type, and obtaining it from the stool or vomit of cases. Alternatively, the same serotype should be present in food and patient specimen. Detection of the toxin in the food may also be sufficient.

Baby Sleeping

Baby Sleeping

Everything You Need To Know About Baby Sleeping. Your baby is going to be sleeping a lot. During the first few months, your baby will sleep for most of theday. You may not get any real interaction, or reactions other than sleep and crying.

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