FURTHER STUDIES ON THE ANTIBACTERIAL ACTIVITY OF HUMAN SERUM ON MICROCOCCUS PYOGENES AND ITS INHIBITION BY COAGULASE

Abstract

Further evidence was presented to indicate that the ability of coagulase-positive, pathogenic strains of M. pyogenes to grow luxuriantly in normal human serum is associated with their coagulase-producing properties. Coagulase-negative or weakly coagulase-positive strains are incapable of initiating growth in serum under identical conditions, but can be stimulated to do so by the addition of exogenous purified cell- free coagulase. The inhibition of serum-susceptible strains of M. pyogenes appears to be due to a protein or protein complex constituent of normal human serum which is not serologically specific since it can be absorbed from the serum by several species of organisms. The antibacterial factor of the serum alters the susceptible cells by contact with them in such a way that they are incapable of multiplication when inoculated into coagulase -inactivated serum. Coagulase does not protect the organisms by direct means, but appears to function by inactivating the antibacterial factor of the serum. It has been shown that the antibacterial reaction is Ca sensitive since removal of Ca from antibacterial serum abolishes its activity.