Coagulase and Hemolysin Tests as Measures of the Pathogenicity of Staphylococci

Abstract

Although the hemolytic titer of certain strains of staphylococci is a reliable index of their pathogenicity for rabbits, some pathogenic strains are non-hemolytic. Coagulation of citrated or oxalated plasma proved to be a reliable indicator of pathogenicity of these non-hemolytic strains. Hemolytic non-coagulating aureus strains were pathogenic; hemolytic non-coagulating albus strains were not. This stressed the importance of a careful differentiation on the basis of color of colonies. A few aureus strains were hemolytic and pathogenic for rabbits, but did not coagulate plasma, Therefore, it is necessary to use both reactions in a study of staphylococci. When 5 cc of dense suspensions of whole live cultures were injected intravenously into rabbits, most of the hemolytic aureus strains and/or coagulating albus and aureus strains killed rabbits in 1-8 days; most of the other strains had no demonstrable effect. When interpreted according to these findings, a combination of hemolysis and coagulase tests affords a reliable index of staphylococcic toxicity.