Toxicokinetics and Mechanism of Action of S. aureus and B. cereus
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S. aureus
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S. aureus is a facultative anaerobic Gram-positive coccus that may be single, paired or in a grape-like cluster.
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S. aureus does not form spores and thus contamination may be avoided by proper heat treatment of food to kill the bacteria.
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S. aureus is an important infective pathogen as well and can easily be found in the nostrils and on the skin of most mammals.
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Staphylococcal enterotoxins are water soluble, very heat resistant and resist most proteolytic
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enzymes, such as trypsin and pepsin, which make it possible for them to travel through the digestive tract to their site of action.
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They have a direct effect on the intestinal epithelium as well as on the vagus nerve to cause stimulation of the emetic centre as well as increasing peristalsis.
B. cereus
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B. cereus is in the family Bacillaceae which are all Gram positive rod-shaped bacteria which form endospores.
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The family has two main divisions: the anaerobic spore-forming bacteria of the genus Clostridium and the aerobic or facultatively anaerobic spore-forming bacteria of the genus Bacillus.
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B. cereus is a primary inhabitant of soils and contaminates almost all agricultural products and is routinely involved in the contamination and spoilage of food products.
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B. cereus can also be involved in wound, eye or systemic infections.
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B. cereus food poisoning is generally described as having two types of illness caused by different metabolites.
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The diarrheal type of illness is caused by one or several heat-labile high molecular weight proteins, while the vomiting (emetic) type of illness is believed to be caused by a low molecular weight, heat-stable peptide which has been named cereulide.
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Last modified: Sunday, 30 October 2011, 10:28 AM