Enterotoxin

An enterotoxin (not to be confused with endotoxin) is a protein toxin released by a microorganism in the intestine.

Enterotoxins are chromosomally encoded exotoxins that are produced and secreted from several bacterial organisms. They are often heat-stable, and are of low molecular weight and water-soluble. Enterotoxins are frequently cytotoxic and kill cells by altering the apical membrane permeability of the mucosal (epithelial) cells of the intestinal wall. They are mostly pore-forming toxins (mostly chloride pores), secreted by bacteria, that assemble to form pores in cell membranes. This causes the cells to die.

Clinical significance
Has a particularly marked effect upon the gastrointestinal tract, causing vomiting, diarrhoea, and abdominal pain. The action of enterotoxins leads to increased chloride ion permeability of the apical membrane of intestinal mucosal cells. These membrane pores are activated either by increased cAMP or by increased calcium ion concentration intracellularly. The pore formation has a direct effect on the osmolarity of the luminal contents of the intestines. Increased chloride permeability leads to leakage into the lumen followed by sodium and water movement. This leads to a secretory diarrhea within a few hours of ingesting enterotoxin. Several microbial organisms contain the necessary enterotoxin to create such an effect, such as Staphylococcus aureus and E. coli.

Organisms secreting enterotoxins
Examples of organisms secreting enterotoxins are:

Bacterial

 * Clostridium difficile
 * Escherichia coli O157:H7
 * Clostridium perfringens (Clostridium perfringens enterotoxin)
 * Vibrio cholerae (Cholera toxin)
 * Staphylococcus aureus (Staphylococcal Enterotoxin B)
 * Yersinia enterocolitica
 * Shigella dysenteriae (Shiga toxin)

Viral

 * Rotavirus (NSP4)