Streptococcal pyrogenic exotoxin

Cartoon representation of the molecular structure of SPEA1.
Cartoon representation of the molecular structure of SpeA1.

Streptococcal pyrogenic exotoxins also known as erythrogenic toxins, are exotoxins secreted by strains of the bacterial species Streptococcus pyogenes.[1][2] SpeA and speC are superantigens, which induce inflammation by nonspecifically activating T cells and stimulating the production of inflammatory cytokines.[3] SpeB, the most abundant streptococcal extracellular protein, is a cysteine protease.[4][5] Pyrogenic exotoxins are implicated as the causative agent of scarlet fever and streptococcal toxic shock syndrome.[2] There is no consensus on the exact number of pyrogenic exotoxins. Serotypes A, B, and C are the most extensively studied and recognized by all sources, but others note up to thirteen distinct types, categorizing speF through speM as additional superantigens.[1][2][6][7] Erythrogenic toxins are known to damage the plasma membranes of blood capillaries under the skin and produce a red skin rash (characteristic of scarlet fever).[8] Past studies have shown that multiple variants of erythrogenic toxins may be produced, depending on the strain of S. pyogenes in question. Some strains may not produce a detectable toxin at all.[9] Bacteriophage T12 infection of S. pyogenes enables the production of speA, and increases virulence.[10]

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