Antibiotic-bonded PTFE vascular grafts: the effect of silver antibiotic on bioactivity following implantation

Use of an infection-resistant vascular prosthesis has appeal for grafting in sites of potential contamination or to replace graft segments involved in low-grade infections caused by coagulase-negative staphylococci (CNS). In this study, antibiotic retention on polytetrafluoroethylene (PTFE) grafts prepared using three antibiotic-bonding methods was compared following implantation into the arterial circulation. Ciprofloxacin or silver-ciprofloxacin was bonded to PTFE surfaces by surfactant-mediated or direct bonding methods. Antibiotic-bonded grafts of each type (n = 8) or control grafts (n = 2) were used to replace the carotid or femoral arteries of 10 dogs. Duplicate grafts segments (0.5 x 0.5 cm) were explanted at various time intervals ranging from 1 hr to 14 days later and imprinted onto culture plates of Klebsiella pneumonia. Antibiotic retention (micrograms/ml) was determined by measuring zones of inhibition and correlated with known disc concentrations of ciprofloxacin. Antibacterial bioactivity of grafts bonded with silver-antibiotic complexes was superior (P less than 0.02) to bonding of antibiotic alone at 3 and 24 hr following implantation. Ciprofloxacin retention in excess of the minimum bactericidal concentration (0.5 microgram/ml) of Staphylococcus epidermidis was demonstrated on all silver-antibiotic-bonded grafts after 14 days of implantation. At 7 and 14 days following implantation, the bioactivity of all antibiotic-bonded grafts exceeded 0.125 micrograms/ml of ciprofloxacin, the minimum inhibitory concentration of S. epidermidis. Bonding of silver-ciprofloxacin on PTFE grafts provided an effective source of local antibiotic release at levels which may be useful for bypass grafting in contaminated wounds or for in situ replacement of grafts infected by CNS.