Overview
Enterotoxins are secreted bacterial protein toxins that target the intestines, causing fluid secretion, electrolyte imbalance and diarrhoea. They interfere with host cellular signalling or act as superantigens to trigger vomiting and diarrhoea.
Explanation
Enterotoxins are a diverse group of proteins produced by Gram-negative and Gram-positive bacteria. Classical AB toxins, such as cholera toxin and the heat‑labile toxin of enterotoxigenic Escherichia coli, have enzymatic A subunits that ADP‑ribosylate host G proteins. This modification keeps adenylate cyclase permanently active, raising cyclic AMP and driving chloride secretion and water loss. The heat‑stable toxin of E. coli binds guanylate cyclase C receptors to increase cyclic GMP with a similar secretory outcome. Staphylococcal enterotoxins behave as superantigens; they cross‑link class II major histocompatibility complex molecules and T‑cell receptors, causing massive cytokine release that leads to vomiting and diarrhoea. Bacillus cereus and Clostridium perfringens produce pore‑forming enterotoxins that disrupt epithelial membranes. Molecular assays and immunoassays detect specific enterotoxin genes or proteins in clinical specimens, and vaccines targeting toxoids are being studied.
Notable toxins and diseases
Cholera toxin from Vibrio cholerae is the archetype enterotoxin and is responsible for the profuse watery diarrhoea of cholera. Enterotoxigenic E. coli produces heat‑labile and heat‑stable toxins that cause traveller’s diarrhoea and childhood diarrhoeal disease in developing countries. Staphylococcal enterotoxins (SEA–SEE) are associated with food poisoning; they resist cooking temperatures and trigger emesis via vagus nerve stimulation and superantigen activity. Bacillus cereus produces an emetic toxin and a separate diarrhoeal enterotoxin often linked to reheated rice dishes. Clostridium perfringens type A enterotoxin causes outbreaks of meat‑associated food poisoning by forming pores in intestinal epithelium. These examples highlight the varied mechanisms by which bacterial enterotoxins induce gastrointestinal illness.
Enterotoxins are significant virulence factors that exploit host signalling pathways or immune responses to disrupt intestinal function. Understanding their structure and mode of action informs diagnostics, outbreak investigations and the development of toxin‑based vaccines.
Related Terms: Exotoxin, Cholera toxin, Heat-labile toxin, Heat-stable toxin, Staphylococcal enterotoxin