Novel murine model for delayed wound healing using a biological wound dressing with Pseudomonas aeruginosa biofilms

Bacterial biofilms impair healing in 60% of chronic skin wounds. Various animal models (mice, rats, rabbits, and pigs) have been developed to replicate biofilm infected wounds in vivo. We developed a sustained wound infection model by applying preformed Pseudomonas aeruginosa biofilms on a wound dressing to full-thickness murine skin wounds. We bathed a commercially available wound dressing in P. aeruginosa for 48 h, allowing a biofilm to establish on the dressing prior to application to the wound. Dressings were removed from the wounds after 3 days at which time the wound beds contained ∼10⁸ bacterial cells per gram tissue. Significant numbers of P. aeruginosa persisted within the skin wounds for up to 21 days. Un-inoculated wounds reached closure between 9 and 12 days. In contrast, biofilm-inoculated wounds achieved closure between 18 and 21 days. Histologic analysis confirmed decreased re-epithelialization and collagen deposition, coupled with increased inflammation, in the biofilm-inoculated wounds compared to un-inoculated controls. This novel model of delayed healing and persistent infection of full-thickness murine skin wounds may provide a robust in vivo system in which to test novel treatments to prevent wound infection by bacterial biofilms.