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

Feature	Acute Rheumatic Fever (ARF)	Post-Streptococcal GN (PSGN)
Immune Mechanism	Type II HSR (Molecular Mimicry)	Type III HSR (Immune Complex)
Preceding Infection	Pharyngitis ONLY	Pharyngitis or Skin (Impetigo)
Prevention with Antibiotics t	YES. Treat within 9 days.	NO (for the initial episode).