Coagulase-negative staphylococci are major pathogens in prosthetic implant infections, and the capability of certain strains to produce glycocalyx enhances their infectivity. We investigated the importance of glycocalyx in an animal model of prosthetic vascular graft infection. Coagulasenegative staphylococci (5×108) and 1 cm2 pieces of Dacron or polytetrafluoroethylene (PTFE) grafts were placed in subcutaneous pockets of adult Sprague-Dawley rats. Two strains of bacteria were used, one producing and the other not producing glycocalyx. At 5 days, uninfected grafts were incorporated into the surrounding tissues whereas infected grafts were surrounded by fluid. Grafts were excised and adherent bacteria dislodged by sonication and quantitated. Scanning electron microscopy confirmed the presence of bacteria and glycocalyx, and the efficiency of bacterial dislodgement by sonication. The bacterial adherence (CFU/cm2 mean ± SE) of glycocalyx-producing staphylococci was 3.7±1.1×107 and 3.5±1.0×105 to Dacron and PTFE, respectively (both < 0.05). Nonglycocalyx producing bacteria had decreased adherence to both Dacron (1.4±0.8×104) and PTFE (0.9±0.4±104). Antibiotic administration reduced the adherence of the nonglycocalyx producing strain by one log to both materials (p<0.05) but did not affect the glycocalyx-producing strain. These data demonstrate that glycocalyx production enhances the adherence of coagulase-negative staphylococci to prosthetic vascular graft materials. Prophylactic antibiotic administration does little to inhibit the adherence of glycocalyxproducing bacteria but does affect nonglycocalyx producing strains.