Staphylococcus aureus Induces Tissue Factor Expression in Cultured Human Cardiac Valve Endothelium

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Abstract
In vitro infection of cultured human cardiac valve endothelium (HCVE) with Staphylococcus aureus was used as a model to study potential mechanisms of vegetation formation in infective endocarditis. S. aureus was observed to adhere to and be ingested by HCVE. Infection for 8 h resulted in increased levels of procoagulant activity in HCVE, shown to be tissue factor by a specific assay. Mean activity in infected HCVE was 662 .+-. 149 (mU/105 HCVE .+-. 1 SD) versus 221 .+-. 78 in control HCVE; surface-expressed activity was 57 .+-. 25 in infected monolayers and undetectable (.ltoreq. 10) in controls. Bacteria alone had no activity. These results suggest that endothelium may have a functional role in the pathogenesis of S. aureus endocarditis and may provide one potential mechanism for activating coagulation to initiate vegetation formation on a colonized cardiac valve.