Bactericidal activity of mastic resin against Staphylococcus pseudintermedius and Staphylococcus aureus and its therapeutic efficacy in experimental pyoderma/impetigo.

In recent years, inappropriate usage of antibiotics has led to a rapid increase in antimicrobial-resistant bacteria. Mastic is a natural resin obtained from the stems and leaves of Pistacia lentiscus trees. We previously demonstrated its anti-inflammatory potential for alleviating atopic dermatitis symptoms, however, its direct effects on Staphylococci are unclear. This study was performed to verify the bactericidal effects of mastic at different concentrations against staphylococcal species in vitro and to evaluate the preventive and therapeutic potential of mastic in a mouse model of pyoderma/impetigo. Mastic showed bactericidal effects against methicillin-resistant Staphylococcus pseudintermedius and Staphylococcus aureus based on counting of the bacterial colonies and measurement of the ATP content. The effects of mastic on cytotoxicity and inflammatory cytokine release induced by staphylococcal strains were monitored using a human keratinocyte cell line. A murine model of pyoderma/impetigo was developed through intracutaneous administration of staphylococci in BALB/c mice. Lesion size analysis, histological examination, bacterial count, and gene expression analyses were performed. Mastic exhibited significant bactericidal effects against both strains of staphylococci. Cellular cytotoxicity and cytokine production induced by both strains of staphylococci were significantly inhibited by mastic pre-treatment. Mastic pre-treatment of mice also significantly inhibited the development of pyoderma/impetigo induced by both strains of staphylococci. Pyoderma induced by S. pseudintermedius was also significantly alleviated by therapeutic treatment with 1 % mastic; however, this effect was less pronounced for S. aureus-induced symptoms. These findings indicate the potential of mastic administration as a preventive and therapeutic approach for managing Staphylococcus-associated skin diseases.