Bacterial tissue tropism: an in vitro model for infective endocarditis

Since infective endocarditis may affect individuals without pre-existing valvar heart disease, and Staphylococcus aureus is the organism most commonly involved, the binding characteristics of S aureus to several components of normal vascular endothelium and subendothelium were studied. S aureus adhered specifically to endothelial monolayers (6.08(1.10)%; p less than 0.005), fibronectin (5.43(0.81)%; p less than 0.001), fibrinogen (7.13(1.43)%; p less than 0.001), and acid soluble calf skin collagen (2.38(0.90)%; p less than 0.001). S aureus also adhered specifically to Von Willebrand factor (1.62(0.28)%, p less than 0.001). Protein A containing (Cowan I) and deficient (Wood) strains of S aureus adhered similarly to all surfaces and substrates (NS). Escherichia coli adhered poorly. Immunofluorescence microscopy of preconfluent endothelial cells identified an extensive pericellular fibronectin network at regions of cell to cell contact. Light microscopy showed S aureus binding solely within these regions. Therefore, the ability of S aureus to infect valvar endothelium may be dependent on the presence of a fibronectin receptor. The existence of specific receptor for S aureus on the endothelial cell surface itself remains undetermined.