Strains of Staphylococcus aureus, isolated from the effluent of patients with peritonitis on CAPD (continuous ambulatory peritoneal dialysis), adhered well to both cultured human mesothelial cells and to fibronectin, but not to laminin or gelatin. Mesothelial cells grown in medium M199 exhibited more surface fibronectin compared to cells grown in MEM-Dval and demonstrated higher levels of S. aureus adherence. Soluble fibronectin concentrations up to 10 micrograms/ml increased the adherence of S. aureus to cultured mesothelial cells. The dose-response curve was consistent with the binding of fibronectin to a saturable receptor of apparent dissociation constant (KD) = 1.7 x 10(-10) M. This corresponds closely to the KD (2 x 10(-10) M) of the staphylococcal fibronectin-binding protein. S. aureus adherence was increased following the preincubation of mesothelial cell monolayers with interleukin-1 and was maximal after 6 h preincubation. Treating mesothelial cells with interferon-gamma for 48-72 h reduced the adherence of S. aureus.