Immunological properties of Staphylococcus aureus coagulase.

Using purified enzyme in agar gel precipitation, it was shown that staphylococci produce two types of coagulase different in biological action and immunological property. The homologous enzyme is specific for human fibrinogen in strains belonging to phage groups I, II, III and specific for bovine fibrinogen in strains of phage group IV. The heterologous enzyme acts upon bovine fibrinogen in case of strains belonging to phage groups I, II or III, and upon human fibrinogen if they belong to phage group IV. The complete enzyme produces with the serum of the homologous enzyme two precipitation bands in agar gel; one is unidentical, the other identical with the coagulase of strains belonging to any of the phage groups. In a heterologous system, the enzymes of every strain give a single band reaction. The strains isolated from bovine mastitis and typable with phage 116 of phage group II are an exception in that they give a precipitation band in both the homologous and the heterologous systems. These staphylocoagulases show in both systems antigenic identity with the homologous coagulase produced by strain of phage group IV.