A rat model of polypropylene graft infection caused by Staphylococcus epidermidis

Background:  The aim of this study was to constitute a valid graft infection model with Staphylococcus epidermidis in rats. Methods:  Rats were divided into seven groups. In groups 1 and 2, 2 cm × 2 cm polypropylene grafts were incubated with 108 c.f.u./mL slime-positive S. epidermidis at 37°C for 2 and 24 h and were then placed subfascially to the groins of rats. In the third group, naive grafts were placed and 0.5 mL of 3 × 107 c.f.u. slime-positive S. epidermidis were injected on the inside of the wounds. Rifampicin (30 mg/kg) in group 4 and teicoplanin (20 mg/kg) in group 5 were applied i.p. to rats with 2-h incubated grafts for prophylaxis. The same prophylactic regimens were given to groups 6 and 7 in which rats were incubated for 24 h. At eighth day, rats were killed and wounds were assessed with macroscopic evaluation and cultures. Results:  No death occurred in any of the groups. In groups 1 and 2, 100% infection rates were achieved. However, graft infection was detected in only two (20%) of the rats in group 3 (P = 0.001). Prophylactic application of teicoplanin or rifampicin decreased the infection rates significantly in the short-incubation groups. Conclusion:  Incubation of polypropylene grafts with slime-producing S. epidermidis for 2 and 24 h in the pre-application period achieved the occurrence of a standardized graft infection. Prophylactic use of teicoplanin and rifampicin decreased the infection rates. We propose to use this reproducible and reliable animal model of graft infection in future studies.