Vancomycin Soaking Reduces Bacterial Growth During Direct Exposure but Does Not Protect Against Subsequent Graft Contamination: An Ex Vivo and In Vivo Study

PURPOSE: To evaluate, using ex vivo and in vivo controlled contamination models, the antibacterial effect and mechanism of vancomycin presoaking against coagulase-negative staphylococci. METHODS: colony-forming units) and soaked for 5 minutes in control (untreated), saline, or vancomycin (5 mg/mL) to distinguish between a saline dilution effect and a direct antibacterial effect of vancomycin. Second, allografts were presoaked and then contaminated to assess the effect of vancomycin release from the presoaked graft. Each group included 11 grafts. Ex vivo, grafts (n = 11 per group) were immediately cultured. In vivo, grafts (n = 11 per group) prepared under the same experimental conditions were implanted intra-articularly in Sprague-Dawley rats and cultured on postoperative day 7. The primary outcome was positive bacterial culture, and the secondary outcome was semiquantitative grade of bacterial growth. RESULTS: In the ex vivo model, there was a significant overall difference in culture positivity (P < .01) and bacterial growth grade (P < .01) among groups. Vancomycin soaking after contamination was associated with lower culture positivity compared with controls (54.5% vs 100%) and reduced bacterial growth grades. No difference was observed when contamination occurred after soaking (100% vs 100%, P > .99; grade distribution, P > .99). In the in vivo model, no bacterial growth was detected in any group (0% vs 0%, P > .99). CONCLUSIONS: Vancomycin soaking after contamination was associated with reduced culture positivity and bacterial growth, with no protective effect against contamination occurring after presoaking. Its antibacterial effect may be related to direct exposure during the soaking process rather than sustained release from the graft. CLINICAL RELEVANCE: Vancomycin presoaking may reduce graft contamination during the presoaking process, suggesting a potential role as an adjunctive strategy for infection prevention.