Abstract
Summary
Non-type specific resistance to Group A streptococcal variants was demonstrated by in vivo challenges of germ free and conventional mice. The presence of type specific anti-M antibodies was excluded by long chain and indirect bactericidal tests on the animals'sera. Both germ free and conventional mice were equally resistant to Group A strains lacking both M protein and capsule. The presence of either M protein or capsule increased virulence equally in germ free and conventional mice. However, strains containing both M and capsule in moderate amounts were significantly more virulent for germ free than for conventional animals. Both germ free and conventional mice were highly susceptible to a strain with maximal M protein and capsule. Resistance due to cross reacting antibody was superseded by requirements for anti-M antibody only when the infecting organism contained very large amounts of M protein and capsule.
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