Comparison of the affinities to bovine and human prothrombin of the staphylocoagulases from Staphylococcus intermedius and Staphylococcus aureus of animal origin.

Staphylocoagulases of Staphylococcus aureus (40 strains originally isolated from horses, dogs, cats, cows, sheep, opossums, pigs, humans, and a goat) and Staphylococcus intermedius (19 isolates from dogs and 1 pigeon strain) were tested for their affinity to prothrombins of either bovine or human origin. The tests used were the coagulase tube test (using human, bovine, or equine fibrinogen with either bovine or human prothrombin as the source of coagulase-reacting factor) and a chromogenic assay which enabled quantification of the amidolytic activity of the staphylocoagulase-prothrombin complex. S. intermedius showed weak specificity for human prothrombin, with 15% of the coagulases clotting human fibrinogen, 25% clotting equine fibrinogen, and 40% clotting bovine fibrinogen. However, 65% of coagulases clotted equine fibrinogen, 75% of coagulases clotted human fibrinogen, and 100% of coagulases clotted bovine fibrinogen when bovine prothrombin was used. The animal isolates of S. aureus displayed more diverse specificity toward prothrombin than S. intermedius strains. While 85% of coagulase preparations clotted human fibrinogen when human prothrombin was used, only 45% of preparations clotted bovine fibrinogen when bovine prothrombin was used. However, 62.5% of coagulases clotted human fibrinogen when bovine prothrombin was used and 85% of coagulases clotted bovine fibrinogen when human prothrombin was used. This may be a reflection of the diversity of the animal origins of S. aureus isolates.