Frequency of pseudocoagulase production in Staphylococcus aureus.

Staphylocoagulase activity could only be separated from that of pseudocoagulase after addition of 4 inhibitors: 3 proteases inhibitors (EDTA, N-ethylmaleimid, aprotinin) and heparin. Of the 32 collection strains studied, only the strains 1503 and NCTC 10 345 (mutant of WOOD 46) exhibited pseudocoagulase activity alone. No other WOOD 46 strain had this isolated activity; on the other hand, 22% of them had simultaneous coagulase and pseudocoagulase activities. One out of 286 Staphylococcus aureus strains of human origin was found to be productive of pseudocoagulase alone, 32% of the strains having both activities. The search for staphylocoagulase coagulating activity in rabbit plasma is a valid test for the identification of Staphylococcus aureus; taxonomical implications are limited without use of a specific detection of coagulase.