Streptococcus pyogenes expresses which antiphagocytic virulence factor?

Streptococcus pyogenes expresses which antiphagocytic virulence factor?

• A. M protein
• B. Protein A
• C. Exotoxin A
• D. Panton-Valentine leukocidin

Answer: (A)

Streptococcus pyogenes uses M protein on its surface to resist phagocytosis. This protein helps the bacterium avoid being engulfed by neutrophils and protects against opsonization by interfering with complement deposition, which allows the bacteria to survive in bloodstream and tissues. Other options come from different organisms: Protein A is from Staphylococcus aureus and binds the Fc portion of IgG to prevent opsonization; Panton-Valentine leukocidin is a leukocidal toxin produced by some S. aureus strains; Exotoxin A is associated with Pseudomonas aeruginosa. So the antiphagocytic factor in GAS is the M protein.

Streptococcus pyogenes uses M protein on its surface to resist phagocytosis. This protein helps the bacterium avoid being engulfed by neutrophils and protects against opsonization by interfering with complement deposition, which allows the bacteria to survive in bloodstream and tissues. Other options come from different organisms: Protein A is from Staphylococcus aureus and binds the Fc portion of IgG to prevent opsonization; Panton-Valentine leukocidin is a leukocidal toxin produced by some S. aureus strains; Exotoxin A is associated with Pseudomonas aeruginosa. So the antiphagocytic factor in GAS is the M protein.