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
[{'content': 'Virulence factor of the group A beta-hemolytic streptococcus is \nSelect and explain. \nA. Protein M, B. Protein T, C. Protein R, D. Lipotechoic acid', 'role': 'user'}, {'content': "Answer: A \nExplanation: 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", 'role': 'assistant'}]