Immunity to staphylococcal infection in mice: effect of living versus killed vaccine, role of circulating antibody, and induction of protection-inducing antigen(s) in vitro.

Mice immunized by sublethal doses of living Staphylococcus aureus strains other than the Smith diffuse strain were significantly more resistant to challenge with the Smith diffuse strain than animals immunized with heat-killed organisms. The increased resistance observed was shown, by appropriate passive protection experiments with immune mouse sera, to be due to circulating antibody, probably of the IgM class. In addition, it was observed that strains of S. aureus other than the Smith diffuse strain, when cultured in a modified Staphylococcus 110 broth but not in Brain Heart Infusion, were capable of absorbing protective antibody from hyperimmune rabbit antiserum.