Background: Bacterial biofilms, which are critical mediators of chronic wounds, remain difficult to treat with traditional methods. Bacteriophage therapy against biofilm has not been rigorously studied in vivo. The authors evaluate the efficacy of a species-specific bacteriophage against Staphylococcus aureus biofilm-infected wounds using a validated, quantitative, rabbit ear model.
Methods: Six-millimeter dermal punch wounds in New Zealand rabbit ears were inoculated with wild-type or mutant, biofilm-deficient S. aureus. In vivo biofilm was established and maintained using procedures from our previously published wound biofilm model. Wounds were left untreated, or treated every other day with topical S. aureus-specific bacteriophage, sharp débridement, or both. Histologic wound healing and viable bacterial count measurements, and scanning electron microscopy were performed following harvest.
Results: Wild-type S. aureus biofilm wounds demonstrated no differences in healing or viable bacteria following bacteriophage application or sharp débridement alone. However, the combination of both treatments significantly improved all measured wound healing parameters (p < 0.05) and reduced bacteria counts (p = 0.03), which was confirmed by scanning electron microscopy. Bacteriophage treatment of biofilm-deficient S. aureus mutant wounds alone also resulted in similar trends for both endpoints (p < 0.05).
Conclusions: Bacteriophages can be an effective topical therapy against S. aureus biofilm-infected wounds in the setting of a deficient (mutant) or disrupted (débridement) biofilm structure. Combination treatment aimed at disturbing the extracellular biofilm matrix, allowing for increased penetration of species-specific bacteriophages, represents a new and potentially effective approach to chronic wound care. These results establish principles for biofilm therapy that may be applied to several different clinical and surgical problems.