Shiga toxins (Verocytotoxins)

Abstract

Shiga toxins (Stxs) also called Verocytotoxins (Vtxs) and Shiga-like toxins (SLTs), are bacterial toxins produced by some members of the Enterobacteriaceaeparticulary Shigella dysenteriae and Escherichia coli 0157:H7 as well asAcinetobacter spp (Moraxellaceae), Enterobacter cloacae and Aeromonas hymophilus. The toxin is made of two moieties, the B-moiety that is responsible for its binding to cell surface receptors, and the A-moiety which enters the cytosol and inhibits protein synthesis enzymatically. Their pathological effect in humans is mainly as a result of inhibition of cellular protein synthesis. Shiga toxins are haboured mainly by ruminants, principally cattle as well as sheep, buffaloes, pigs, goats, dogs, cats and pigeons. The two major groups of the toxin, Stx1 and Stx2 are associated with mild or bloody diarrhea to hemorrhagic colitis (HC), hemolytic uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) and also, nosocomial infections in humans. Predisposing factors to infection with Shiga toxin producing bacteria includes old age, immunosupression, malnutrition, under developed immunity in neonates, poor hygiene, lack of portable water and excreta contamination of existing traditional water sources. Transmission is through consumption of contaminated food and water, person-to-person and animal contact. High rate of antibiotic resistance amongst Stxs-producing bacteria is causing concern all over the world, therefore improved personal and food hygiene and the provision of portable drinking water appears to be the best preventive measure against the infection.