Food poisoning with rice dishes

Staph and Bacillus cereus can cause acute food poisoning within 6 hours of ingestion of food. B. cereus is likely when rice is the culprit

·        B. cereus is able to persist in food processing environments due to its ability to survive at extreme temperatures as well as its ability to form biofilms and spores. 

·        B. cereus has been recovered from a wide range of foods, including rice, dairy products, spices, bean sprouts and other vegetables.

·        Fried rice is an important cause of emetic-type food poisoning associated with B. cereus

·        The organism is frequently present in uncooked rice, and heat-resistant spores may survive cooking. 

·        Cooked rice subsequently at room temperature can allow vegetative forms to multiply, and the heat-stable toxin that is produced can survive brief heating such as stir frying

·        Two distinct types of toxin-mediated food poisoning are caused by B. cereus, characterized by either diarrhea or vomiting, depending on which toxin is involved. The diarrheal toxin is produced by vegetative cells in the small intestine after ingestion of either bacilli or spores. The emetic toxin is ingested directly from contaminated food. Both toxins cause disease within 24 hours of ingestion.

·        The emetic syndrome is caused by direct ingestion of the toxin.

·        The number of viable spores and vegetative bacteria that produce diarrheal toxin is reduced by heating, although spores associated with emetic toxin are capable of surviving heat processing.

·        Cereulide is heat stable and resistant to gastric conditions. 

·        The ingested toxin itself may therefore cause disease despite sufficient heating to kill B cereus.

·        The emetic syndrome is characterized by abdominal cramps, nausea, and vomiting. Diarrhea also occurs in about one-third of individuals. Symptom onset is usually within one to five hours of ingestion, but it can also occur within half an hour and up to six hours after ingestion of contaminated food.

·        Symptoms usually resolve in 6 to 24 hours. 

·        Rice-based dishes in particular have been implicated in emetic toxin mediated disease, usually as a result of cooling fried rice dishes overnight at room temperature followed by reheating the next day. 

·        The infective dose of cereulide required to cause symptoms is 8 to 10 micrograms per kilogram of body weight.