M antigens among group A streptococci isolated from skin lesions.

Three new provisional types of Group A streptococci have been identified among strains isolated from skin infections of American Indian children. A previously established type, Type 41, was also recognized among the pyoderma strains. Most of the skin streptococci with T-agglutination pattern 3/13/B3264 could be identified as Type 41 or as one of two new provisional types, Schoenborn (Type 52) and Hanson (proposed Type 53). Strains of the third new provisional type, Kingbird (proposed Type 54), agglutinated as 15/17/19/23/47, a T pattern not associated with skin infections in studies of other populations. Approximately half of the pyoderma strains examined were found to produce an M antigen; the proportion of M-typable strains from skin infections was found to be similar to that currently found in throat cultures of children with pharyngitis. The demonstration of M antigens in streptococci from skin lesions provides evidence of their potential virulence and should facilitate their classification in subsequent epidemiological studies.