A new approach for treatment of deep skin infections by an ethosomal antibiotic preparation: An in vivo study

Objectives: Dermal and subdermal bacterial infections, caused mainly by Staphylococcus aureus, are currently treated by systemic antibiotics. The aim of the present study was to investigate a new approach to treat deep skin and soft tissue bacterial infections by dermal application of erythromycin in an ethosomal carrier. Methods: A model for deep dermal S. aureus infection in mice was developed. The efficiency of ethosomal erythromycin applied to the skin-infected site was compared with intraperitoneal erythromycin administration and with local application of hydroethanolic erythromycin solution. The parameters evaluated were the development of dermal wound, histological sections and bacterial count of the infected tissue. Results: The in vivo experiments demonstrated a very efficient healing of S. aureus-induced deep dermal infections when the mice were treated with ethosomal erythromycin. Bacterial counts and histological evaluation of the skin treated with ethosomal antibiotic revealed no bacterial growth and normal skin structure. On the contrary, no subdermal healing was observed in infected animals treated with topical hydroethanolic erythromycin solution. In this group, animals developed deep dermal abscesses and the dermal structures were destroyed where S. aureus colonies were present. Bacterial counts of the infected tissues were 1.06 × 10⁷ and 0.27 × 10⁷ cfu/g of tissue, respectively, on days 7 and 10. Conclusions: Therapy with ethosomal erythromycin applied to the skin of S. aureus-infected mice was as effective as systemically administered erythromycin, suggesting a new possibility to treat deep dermal infections by local application of antibiotic in ethosomal carrier.