Rifampin protection against experimental graft sepsis

The risk of infection in vascular prosthetic conduits appears to be greatest in the perioperative period and the organism most frequently found is Staphylococcus aureus. Previous work suggests that antibiotics must be chemically bonded to the material to resist rapid washout caused by the flow of blood through the graft. The exception to this is rifampin, which remains fixed in Dacron prostheses after passive addition of the agent to aliquots of blood used to clot the interstices of porous Dacron grafts. This characteristic of rifampin is presumed to be caused by its poor water solubility. This potential infection resistance was challenged in a standard model of a canine infrarenal aortic graft by intravenous infusion of S. aureus organisms (10(7)) in the perioperative period. The grafts of five animals were preclotted with 9 ml of autogenous blood plus 1 ml of rifampin (60 mg/ml). A second group had similar procedures with 1 ml of cefazolin (238 mg/ml) substituted for the rifampin, and a control group had 1 ml of saline solution added to the 9 ml aliquot of blood. The animals were killed at 3 weeks and examined for clinically apparent infection. Rings of the graft material were also removed aseptically and cultured. All five grafts preclotted with cefazolin had clinical and culture evidence of infection (S. aureus), as did the grafts of three of the five control dogs. None of the grafts preclotted with rifampin was infected (p less than 0.05). Addition of rifampin to the blood used to clot the graft interstices appears to be a simple way of imparting graft resistance to perioperative sepsis.