Antistaphylocoagulase in Experimental Staphylococcal Infections

A study has been made of the effects of anti-staphylocoagulase in acute staphylococcal infections of rabbits and mice. Rabbits actively immunized with coagulase were more resistant to intravenous challenge with coagulase-positive, but not coagulase-negative staphylococci. When mice were injected intraperitoneally with coagulase-positive staphylococci suspended in a clotting system (fibrinogen/co-factor), serum from rabbits immunized with coagulase diminished the virulence of these staphylococci provided it was allowed to come into contact with the challenge organisms for 30 minutes before the addition of the clotting system. The virulence of the organisms was also diminished under the same conditions by human serum containing coagulase-inhibiting antibodies. This diminution of virulence was not produced by alpha antitoxin or staphylococcal agglutinating serum, and was not demonstrable against coagulase-negative staphylococci. It is considered that the diminution of virulence observed in mice was due to the in vitro inhibition of coagulase activity, and that the active immunity observed in rabbits was probably associated with in vivo inhibition of coagulase activity.