Impetigo, Erysipelas Throat infections --> Pharyngitis The streptococcus bacteria causing the two infections belongs to the same lancefield group they both have same carbohydrate A antigen in their cell wall but they have difference in their surface M protein, i.e. they belong to different strains of streptococcus A. -Base on M protein the streptococcal 'A' group is divided into 80 strains. - Different strains of streptococci are associated with different infections. The throat infection and the skin infection are caused by different strains of the same lancefield group of streptococci. - A paicular lancefied group is divided into different strains based on "M proteins". -The M protein in the strain causing pharyngitis is quite different from the strain causing impetigo. - But both these strains belong to the same lancefield group and contains the same carbohydrate (A) antigen. - Impetigo is caused by higher number of M types 49, 53-55 - Throat infection caused by lower number M types Serotypes 1, 12 The question asks about the similarity between the two bacterias which is the presence of same carbohydrate antigen in their cell wall.">