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?

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 .