Characteristics of Bacillus cereus emetic toxin.

摘要

Cereulide, an emetic toxin produced by strains of B. cereus neither degrades starch nor can it ferment salicin and shows weak haemolysis. It is a cyclic low molecular (1.2 kDa) ring shaped peptide. Cereulide is resistant to heat (121 degrees C/90 minutes), digestive enzymes trypsin, and pepsin. Pathological symptoms evoked by cereulide are nausea and vomiting which may occur 1 to 5 hours after ingestion of a contaminated food product and continued for 24 hours. Cereulide causes in hepatic cell mitochondria that eventually leads into liver damage. The toxic dose for an adult is 400-500 micro g of cereulide. Due to its widespread presence in the environment, there is a high risk of Bacillus cereus mediated food poisoning (from boiled of fried rice, and food rich in starch such as pasta). Since the condition has a short duration, cases of emetic type of food poisoning provoked by cereulide are frequently not reported to health authorities and are therefore highly underestimated in official statistics. The presence of L-leucine and L-valine amino acids in a product markedly intensifies the process of emetic toxin produce by B. cereus. Cereulide synthesis is also affected by the presence of oxygen. The optimum temperature for cereulide formation ranges from 15 to 20 degrees C, however its production is at 8-10 degrees C or up to 35 degrees C.