Polycationic peptides as prophylactic agents against methicillin-susceptible or methicillin-resistant Staphylococcus epidermidis vascular graft infection

Several polycationic peptides isolated from animals, plants, and bacterial species possess a broad spectrum of antimicrobial activity. A rat model was used to investigate the efficacies of two peptides, ranalexin and buforin II, in the prevention of vascular prosthetic graft infections. The effect o f peptide soaked collagen-sealed Dacron was compared to that of rifampin so aked collagen-sealed Dacron in the rat model of graft infection caused by m ethicillin-susceptible rifampin-susceptible Staphylococcus epidermidis and methicillin-resistant rifampin-susceptible S. epidermidis. Graft infections were established in the back subcutaneous tissue of 240 adult male Wistar rats by implantation of 1-cm(2) Dacron prostheses, followed by topical inoc ulation with 2 x 10(7) CFU of S. epidermidis. The study included a control group (no graft contamination), two contaminated groups that did not receiv e any antibiotic prophylaxis, two contaminated groups to which perioperativ e intraperitoneal cefazolin prophylaxis (30 mg/kg of body weight) was admin istered, six contaminated groups that received a peptide- or rifampin-soake d graft, and six contaminated groups that received a peptide- or rifampin-s oaked graft and perioperative intraperitoneal cefazolin prophylaxis (30 mg/ kg). The grafts were sterilely removed 7 days after implantation, and the i nfection was evaluated by using sonication and quantitative agar culture. O verall, the efficacies of the polycationic peptides against the methicillin susceptible and methicillin resistant strains were not significantly diffe rent from that of rifampin. Nevertheless, the combinations of ranalexin- an d buforin II-coated grafts with cefazolin treatment demonstrated efficacies significantly higher than that of the combination of rifampin coated graft s and cefazolin treatment against the methicillin resistant strain.