Tissue integration and biomechanical behaviour of contaminated experimental polypropylene and expanded polytetrafluoroethylene implants

Background: Infection is one of the most devastating complications following implantation of a prosthetic material. The aim of this study was to compare the behaviour of two biomaterials contaminated with Staphylococcus aureus or Staphylococcus epidermidis, used to repair abdominal wall defects. Methods: Defects (7 x 5 cm) were created in the anterior abdominal wall of 60 white New Zealand rabbits and repaired using polypropylene or expanded polytetrafluoroethylene (ePTFE) prostheses. The site of repair had been previously inoculated with 10(6) colony-forming units/ml S. aureus or S. epidermidis. Seven and 30 days after implantation, prosthetic specimens were examined by light and scanning electron microscopy, and immunohistochemical and biomechanical analysis. Results: No significant differences with respect to controls were observed in the S. epidermidis groups. Two animals inoculated with S. aureus died. S. aureus induced the appearance of denuded areas exposing the filaments in the polypropylene prostheses, whereas the ePTFE prostheses showed zones of erosion, disorganized tissue, haemorrhage and necrosis. The biomechanical strength of the contaminated implants was unaltered. Conclusion: Integration within host tissue was affected in the setting of S. aureus infection but the tensile strength of contaminated prostheses was not significantly reduced.