Virulence factor of the group A beta-hemolytic streptococcus is: (A) Protein M, (B) Protein T, (C) Protein R, (D) Lipotechoic acid
Answer is A. The virulence factors of group A streptococcus or Streptococcus pyogenes: 1. Capsule 2. Carbohydrate antigen 3. Protein antigen M, T, R proteins 4. Pili M protein - acts as virulence factor by inhibiting phagocytosis. Heat and acid stable but susceptible to tryptic digestion. Antibody to M proteins promote phagocytosis of cocci and is protective. Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 213