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
Which of the following factor is mainly respon-sible for virulence in Streptococcus : 
Select and explain. 
A. Carbohydrate, B. Streptokinase, C. Streptodornase, D. M protein
D: M protein
Answer: D: M protein 
Explanation: M Protein

It is major virulence factor of group A Strep. pyogenes.
It is hair like projection of cell wall.
It is of 80 types (basis of Griffith classification) so immunity is type specific.
M protein is also found in Group G streptococci.

Remember :

Carbohydrate is used as the basis of Lancefields classification.
Streptokinase or fibrolysin and streptodornase or DNAse liquefy pus so used in enzymatic debridement