This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
Virulence factor of the group A beta-hemolytic streptococcus is 
Select and explain. 
A. Protein M, B. Protein T, C. Protein R, D. Lipotechoic acid
A: Protein M
Answer: A: Protein M 
Explanation: 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