Chitosan-based sleeves loaded with silver and chlorhexidine in a percutaneous rabbit tibia model with a repeated bacterial challenge

Various strategies have been explored to prevent pin tract infections (PTI), including the use of antibacterial sleeves. However, an ideal animal model to evaluate the efficacy of antibacterial strategies is still lacking. This study aimed to construct an animal model with a consistent induction of infection after bacterial challenge. Further, the efficacy of silver and chlorhexidine loaded chitosan sleeves was evaluated to prevent PTI around a percutaneous implant. Titanium pins wrapped with sleeves were implanted in anterior lateral rabbit tibia. After 2 weeks, Staphylococcus aureus suspensions (1 × 10⁶ CFU) were injected weekly to the exit site, and the clinical infection status was recorded. After 6 weeks, all rabbits were euthanized to evaluate the bacterial colonization microbiologically and histomorphometrically. Results showed that the implant screw bilaterally penetrated the tibia and kept the implant stable. A rod length of twice the thickness of the soft-tissue layer was necessary to maintain the percutaneous penetration of the implants. A 100% infection rate was obtained by the bacterial inoculation. Silver loaded sleeves reduced significantly the bacterial density and reduced the inflammatory symptoms of the percutaneous pin tract. However, the addition of chlorhexidine to the sleeves had no added value in terms of further reduction of bacteria and inflammation. In conclusion, a consistent animal model was designed to evaluate strategies to prevent PTI. In addition, the use of silver loaded chitosan sleeves can be pursued for further (pre-)clinical exploration for the prevention of PTI. STATEMENT OF SIGNIFICANCE: This study constructed a bacterial challenged percutaneous rabbit tibia model to evaluate the potential of antibacterial strategies for the prevention of pin tract infections. The model was applied to evaluate a silver and chlorhexidine loaded membranes as an antibacterial sleeve. Our results demonstrate that the rabbit tibia model is suitable to evaluate antibacterial strategies for the prevention of pin tract infection as evidenced by the stable, bone fixed percutaneous implant and a 100% infection rate of the percutaneous pin tract. Silver loaded sleeves can lower the bacterial density of the percutaneous pin tract, but the addition of chlorhexidine to the silver-loaded sleeves does not contribute to an enhanced antibacterial effect. Such experiments are of considerable interest to those in the research community, industry, and clinicians involved the occurrence of infection of skin penetrating medical devices.