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Microbiologists use many terms to describe Shiga toxin and differentiate more than one unique form. Many of these terms are used interchangeably. Shiga toxin type 1 and type 2 (Stx-1 and 2) are the Shiga toxins produced by some E. coli strains. Stx-1 is identical to Stx of Shigella spp. or differs by only one amino acid. [6]
Shiga-toxin directly activates the alternative complement pathway and also interferes with complement regulation by binding to complement factor H, an inhibitor of the complement cascade. Shiga-toxin causes complement-mediated platelet, leukocyte, and endothelial cell activation, resulting in systemic hemolysis, inflammation and thrombosis.
The verocytotoxin (shiga-like toxin) can directly damage renal and endothelial cells. Thrombocytopenia occurs as platelets are consumed by clotting. Hemolytic anemia results from intravascular fibrin deposition, increased fragility of red blood cells, and fragmentation.
Escherichia coli O157:H7 is a serotype of the bacterial species Escherichia coli and is one of the Shiga-like toxin–producing types of E. coli.It is a cause of disease, typically foodborne illness, through consumption of contaminated and raw food, including raw milk and undercooked ground beef.
As a powerful anticholinergic agent, BZ produces a syndrome of effects known as the anticholinergic toxidrome: these include both psychological and physiological effects, with the most incapacitating effect being a state of delirium characterized by cognitive dysfunction, hallucinations, and inability to perform basic tasks.
[2] [3] This classification, while fairly exhaustive, is not the only system used. Other systems for classifying or identifying toxins include: By organism generating the toxin; By organism susceptible to the toxin; By secretion system used to release the toxin (for example, toxic effectors of type VI secretion system)
Tests for toxin production can use mammalian cells in tissue culture, which are rapidly killed by shiga toxin. Although sensitive and very specific, this method is slow and expensive. [49] Typically, diagnosis has been done by culturing on sorbitol-MacConkey medium and then using typing antiserum.
Domain A1 (approximately 22kDa in cholera toxin or heat labile enterotoxins) is the part of the toxin responsible for its toxic effects. Domain A2 (approximately 5kDa in cholera toxin or heat labile enterotoxin) provides a non-covalent linkage to the B subunit through the B subunit's central pore. [ 5 ]