Synergistic antibacterial effect of silver-containing hydroxyapatite coating and vancomycin against haematogenous orthopaedic implant-associated infection in rat femur.

Abstract

BACKGROUND: Orthopaedic implant-associated infection (OIAI) is a significant complication following orthopaedic procedures, and one treatment strategy includes debridement, antibiotics, and implant retention (DAIR). The synergistic antibacterial effect of the implant and antibiotics is important for successful treatment. Silver-containing hydroxyapatite (Ag-HA) coating and vancomycin (VCM) have previously been reported to exhibit synergistic antibacterial effects on subcutaneous infection in rats. However, this synergistic effect on implant-based infections in the bones remains unknown. The present study aimed to report the effects of Ag-HA coating and VCM against haematogenous infection caused by methicillin-resistant Staphylococcus aureus (MRSA) in rat femurs. METHODS: Sprague-Dawley rats were assigned to four groups of treatment: titanium (Ti) rods injected with phosphate-buffered saline (PBS) (Ti PBS); Ti rods injected with VCM (Ti VCM); Ag-HA-coated Ti rods injected with PBS (Ag-HA PBS); and Ag-HA-coated Ti rods injected with VCM (Ag-HA VCM). Thirteen rats per group were used for measurements. After inserting the rods into both femurs of rats, an MRSA suspension was injected intravenously into the tail vein to induce OIAI. The rats subsequently received a subcutaneous injection of VCM. VCM was administered every 12 h from postoperative day 10-13 (eight doses in total), simulating therapeutic intervention. On the 14th postoperative day, the rats were euthanised, and the femurs were dissected to calculate the viable MRSA cell count. RESULTS: The viable counts in the Ag-HA PBS group were lower than those in the Ti PBS group (p = 0.0012). Furthermore, the viable counts in the Ag-HA VCM group were lower than those in the Ti PBS group (p < 0.0001). CONCLUSIONS: The combination of Ag-HA coating and VCM exhibited a synergistic antibacterial effect against haematogenous infection caused by MRSA in the rat femur. The combination of Ag-HA coating and VCM may be advantageous in the treatment of OIAI with DAIR.