RNAIII-inhibiting peptide and/or nisin inhibit experimental vascular graft infection with methicillin-susceptible and methicillin-resistant Staphylococcus epidermidis.

OBJECTIVE: To investigate the efficacy of RNAIII-inhibiting peptide (RIP) and nisin as prophylactic agents in a rat model of vascular graft infection. DESIGN: Prospective, randomized, controlled animal study. MATERIALS: Two hundred and twenty adult male Wistar rats. Staphylococcus epidermidis ATCC 12228 and one clinical isolate of methicillin-resistant S. epidermidis. Drugs: RIP, nisin and rifampin. METHODS: Graft infections were established in the dorsal subcutaneous tissue by implantation of 1 cm(2) sterile Dacron grafts, followed by topical bacterial inoculation: grafts were retrieved at 7 days. The study included a control group (without inoculation) and two series composed of five groups for each staphylococcal strain: one contaminated group that did not receive any antibiotic prophylaxis, three contaminated groups that received grafts soaked with 10 mg/l RIP, 10 mg/l nisin, 10 mg/l rifampin, or RIP+nisin. The main outcome measure was the extent of bacterial at graft harvest. RESULTS: The bacterial counts for methicillin-resistant S. epidermidis on explanted grafts were 6.1+/-2.8x10(2), 7.8+/-3.0x10(3) and 5.5+/-2.9x10(4) for RIP, nisin and rifampin, respectively. RIP and nisin used in combination reduced the bacterial count to <10. The results for S. epidermidis were similar. CONCLUSIONS: RIP and nisin could be used in combination to coat medical devices to prevent drug resistant S. epidermidis infections.