CLOTTING ACTIVITY IN STAPHYLOCOCCUS-SCHLEIFERI SUBSPECIES FROM HUMAN PATIENTS

Staphylococcus schleiferi subsp. schleiferi is a coagulase-negative st aphylococcus, usually present as a contaminant in human specimens. A n ear relative, S. schleiferi subsp. coagulans, possesses coagulase acti vity but has not been reported from humans. We here describe three iso lates of pseudocoagulase-positive S. schleiferi subsp. schleiferi and one isolate of S. schleiferi subsp. coagulans from human patients. The pseudocoagulase from the S. schleiferi subsp. schleiferi isolates dif fers from S. aureus staphylocoagulase by being sensitive to a combinat ion of protease inhibitors (aprotinin, N-ethylmaleimide, and heparin). These isolates could all easily be confused with S. aureus in a typic al clinical laboratory, since they all possess a heat-stable DNase and promote clotting formation. Moreover, S. schleiferi subsp. coagulans produces protein A, and S. schleiferi subsp. schleiferi expresses a cl umping factor (fibrinogen affinity factor). Southern blot hybridizatio n with an S. aureus coa-specific probe revealed no sequence related to the coa gene in any of the S. schleiferi isolates, and their riboprob e profiles and biochemical characteristics were typical of S. schleife ri subspecies, not of S. aureus. This study demonstrates that both sub species of S. schleiferi can promote clotting of rabbit plasma in the standard tube test for coagulase.