Microbiology For COMLEX Level 1 Practice Test

Scarlet fever stems from Streptococcus pyogenes strains that produce pyrogenic (erythrogenic) exotoxins. These toxins act as superantigens, triggering widespread T-cell activation and a surge of inflammatory cytokines that produce the fever and the diffuse, sandpaper-like rash seen in scarlet fever. The toxin’s erythrogenic effect also contributes to the characteristic facial flushing with a pale perioral area and the “strawberry tongue.” Other toxins listed come from different bacteria and aren’t responsible for scarlet fever. Diphtheria toxin targets host translation by ADP-ribosylating EF-2, alpha toxin from Clostridium species acts as a membrane-damaging phospholipase, and Exotoxin A from Pseudomonas inhibits host protein synthesis in a manner distinct from the streptococcal pyrogenic exotoxins.