Evaluation of bacteriophage efficacy against Pseudomonas aeruginosa in ex vivo and in vitro canine skin systems

Abstract Pseudomonas aeruginosa is an opportunistic pathogen responsible for chronic infections in both human and veterinary medicine, with biofilm formation and multidrug resistance posing major clinical challenges. The efficacy of two bacteriophages, JG003 and PTLAW1, alone and in combination, was evaluated. In vitro biofilms grown on abiotic 96-well plates showed significant reduction after treatment with individual bacteriophages or their combination, as confirmed by confocal microscopy. To better simulate physiological conditions, efficacy was assessed using an epidermal equivalent model and an ex vivo canine skin model. In the ex vivo system, bacteriophage treatment reduced bacterial load by 4 logs, as confirmed by scanning electron microscopy and immunofluorescence imaging. In the epidermal equivalent model, bacteriophage therapy decreased bacterial counts and CXCL8 levels without inducing cytotoxicity or disrupting the skin barrier. Integration of in vitro and ex vivo systems bridges the gap between traditional biofilm assays and in vivo studies. The use of Franz-type diffusion cells provides a physiologically relevant platform for evaluating topical bacteriophage delivery and skin permeation. These findings establish a reproducible preclinical framework for biofilm-targeted therapies, demonstrating that bacteriophage combinations effectively reduce Pseudomonas aeruginosa biofilms and inflammation on skin, supporting their potential for wound treatment in both human and veterinary medicine.