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
A boy with skin ulcer on leg, culture revealed beta hemolysis. School physician said that similar hemolysis was seen in organism from sorethroat, what is the similarity between both? 
Select and explain. 
A. A protein is same for both, B. C carbohydrate antigen is different, C. C carbohydrate antigen is the same, D. Strain causing both are same
C: C carbohydrate antigen is the same
Answer: C: C carbohydrate antigen is the same 
Explanation: Ans. (c) C-carbohydrate antigen is the same 13 hemolytic streptococci causing both skin infection and sore throat can be none other than Group A streptococci. The basis by which Lancefield classified streptococci in to groups A-H and K-V is c carbohydrate. So, different Group A streptococci have same c carbohydrate. In group A, c carbohydrate is rhannose - N-acetyl glycosamine. Based on the M protein Griffith divided Group A carbohydrate in to 80 subtypes. Sore throat strains and skin strains of streptococci differ in their M-protein. Skin infection is usually caused by M-types .