Efficacy of bacteriophages in propionibacterium acnes-induced inflammation in mice

Background: Bacteriophages have been introduced as living drugs for infectious diseases; thus, they may provide an alternative to conventional acne therapeutics in patients with non-responsive acne. Objective: We investigated the effect of bacteriophages using an acne mouse model with Propionibacterium acnes-induced inflammatory nodules by clinical examination, pathology, and immunohistochemical analysis. Methods: A human-isolated P. acnes suspension (10 ⁹ colony forming units/μl) was injected into the backs of HR-1 mice. Group A was used as a control, Group B was injected on the back with P. acnes 4 weeks following the initial P. acnes suspension injection, and group C was injected on the back with P. acnes and bacteriophages 4 weeks following the initial P. acnes suspension injection. Clinical and histopathological evaluations were performed. Results: Inflammatory nodule size decreased with time in all groups. Group C showed the greatest decrease in size, followed by group B and group A. The histopathological findings showed a decrease in epidermal thickness and the number and size of microcomedone-like cysts in groups B and C compared to group A. Immunohistochemistry revealed similar expression of integrin α6, the epidermal proliferation marker, infiltration of CD4/CD8 T cells and neutrophils, and expression of myeloperoxidase, interleukin-1β, toll-like receptor-2, LL-37, and matrix metalloproteinase-2/3/9 in all three groups. Conclusion: Using an acne mouse model with P. acnes-in-duced inflammatory nodules, we demonstrate that bacteriophages may constitute an alternative to conventional acne therapies. However, additional studies are needed for human applications.