How does the M protein enhance the virulence of Streptococcus pyogenes?

• A. By producing toxins that lyse red blood cells
• B. By facilitating the formation of endospores
• C. By inhibiting phagocytosis by host immune cells
• D. By increasing the rate of bacterial replication

Answer: (C)

Verified step by step guidance

1. Understand that virulence factors are molecules produced by pathogens that contribute to their ability to cause disease.
2. Recognize that the M protein is a surface protein found on Streptococcus pyogenes and is a key virulence factor.
3. Recall that the M protein enhances virulence primarily by interfering with the host's immune response, specifically by inhibiting phagocytosis.
4. Phagocytosis is the process by which immune cells, such as macrophages and neutrophils, engulf and destroy pathogens; by inhibiting this, the M protein helps the bacteria evade immune clearance.
5. Note that the other options (producing toxins that lyse red blood cells, forming endospores, or increasing replication rate) are not the primary mechanisms by which the M protein enhances virulence in Streptococcus pyogenes.