This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Which of the following is a virulence factor for streptococci? \nSelect and explain. \nA. Hemolysin, B. M protein, C. Hyaluridase, D. Carbohydrate', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The cell wall antigens include capsular polysaccharide (C-substance), peptidoglycan and lipoteichoic acid (LTA), R and T proteins, and various surface proteins, including M protein, fimbrial proteins, fibronectin-binding proteins (eg, protein F), and cell-bound streptokinase. The C-substance may have a role in increased invasive capacity. The R and T proteins are used as epidemiologic markers and have no known role in virulence. Another virulence factor, C5A peptidase, destroys the chemotactic signals by cleaving the complement component of C5A. M protein, the major virulence factor, is a macromolecule incorporated in fimbriae present on the cell membrane projecting on the bacterial cell wall. It is the primary cause of antigenic shift and antigenic drift among group A streptococci.', 'role': 'assistant'}]