Virulence factors and resistances

• Toxins
  • Erythrogenic exotoxin A
  • Streptolysin O
  • Streptococcal pyrogenic exotoxins
    • Bridges MHC class II molecules on antigen-presenting cells and T-cell receptors on T cells outside of the normal binding sites
    • Results in a large release of IL-1, IL-2, IFN-γ, and TNF-α
• Enzymes
  • DNase: destroys neutrophils → potentiates infection and transmission
  • Streptokinase
  • Hyaluronidase
• Proteins
  • Protein F: fibronectin‑binding protein that mediates adherence to epithelial cells
  • M protein (virulence factor): prevents opsonization by C3b
• Hyaluronic acid capsule: inhibits phagocytosis

Associated conditions

• Head and neck
  • Pharyngitis
  • Tonsillitis
  • Peritonsillar abscess
  • Otitis media
• Skin and soft tissues (pyogenic)
  • Erysipelas
  • Cellulitis
  • Impetigo (“honey-crusted” lesions)
  • Necrotizing fasciitis
  • Perianal streptococcal dermatitis
• Toxin-mediated disease
  • Scarlet fever
  • Streptococcal toxic shock-like syndrome
• Immunologic complications (after primary infection)
  • Acute rheumatic fever
  • Poststreptococcal glomerulonephritis