Occurrence of the M Substance of Type 28 Group A in Streptococci of Lancefield Groups B, G and G

SUMMARY: Strains of streptococci belonging to Lancefield groups B, C and G were found to possess an antigen which is identical with the group A type 28 M antigen in its ability to absorb group A type 28 antibodies, and to stimulate the production of type 28 antibodies. The antigen also resembles the group A type 28 antigen in its sensitivity to pepsin and trypsin, being inactivated by pepsin but not by trypsin. The antigen does not appear to be the major type-specific antigen in some of the strains not belonging to group A.