Propellant-free intrawound antibiotic foam for intraoperative antimicrobial prophylaxis

Intrawound vancomycin powder is the most widely used intraoperative prophylactic intervention against surgical site infections (SSIs). However, applying raw drug powder to irregular or small surgical cavities can result in uneven wound coverage, drug precipitation, and airborne drug particles. To address these issues, we developed a surfactant-based aqueous foam specifically for spine surgery, where deep incisions and instrumentation heighten SSI risks. A rat model of spinal implant-associated Staphylococcus aureus infection was developed to assess the antimicrobial efficacy of intrawound vancomycin foam. The compatibility of the blank foam and the antimicrobial efficacy of the vancomycin foam were assessed in vivo in Sprague Dawley rats. Biocompatibility was evaluated by applying the foam, dispensed from a propellant-free pump device to the dorsal spine wound bed. The antimicrobial efficacy of the vancomycin foam was evaluated through exposure of the dorsal spine of the animals, foreign body implantation and S. aureus inoculation, with comparisons made to vancomycin powder-treated and untreated groups. Using a propellant-free pump device delivers the foam easily, ensuring uniform coverage and drug retention without leaving any solid residues. The foam formulation significantly increases vancomycin solubility compared to water alone. In a rat model of spinal implant-associated Staphylococcus aureus infection, the vancomycin foam demonstrated antimicrobial efficacy comparable to the vancomycin powder, with no observed soft tissue damage or systemic toxicity. Here, we have demonstrated that propellant-free aqueous foams can be an effective and simple alternative to intrawound vancomycin powder for preventing SSIs in spine surgery.