Effectiveness of antimicrobial photodynamic therapy with a single treatment of RLP068/Cl in an experimental model of Staphylococcus aureus wound infection

Abstract

Background: Chronic leg ulceration is a common health problem. It is well known that a clinically relevant bacterial load in chronic cutaneous wounds interferes significantly with the normal process of healing. Staphylococcus aureus is the most important representative of the staphylococcal group which causes clinically relevant infections within immunocompetent patients. Objectives: To investigate the efficacy of a single treatment of antimicrobial photodynamic therapy (APDT) with RLP068/Cl in a mouse model of a surgical wound infection induced with a methicillin-resistant strain of S. aureus (MRSA). Methods: Wounds, established through the panniculus carnosus of BALB/c and CD1 mice, were inoculated with 5 × 107 c.f.u. of MRSA. Mice were randomized into four groups respectively receiving no treatment, APDT with placebo, APDT with a new phthalocyanine derivative (RLP068/Cl) and intraperitoneal teicoplanin. Results: On day 2 from infection, a strong reduction of bacterial counts (≈ 3 logs) was observed in mice treated with RLP068/Cl in comparison with infected untreated mice. On day 9 from infection, a comparable and significant (≈ 2 logs) reduction of bacterial counts was found in mice treated with RLP068/Cl or with teicoplanin. At this time, histological examinations revealed that wounds treated with RLP068/Cl showed a complete re-epithelialization with a continuous epithelial lining. Conclusions: The results of the in vivo study demonstrated that APDT with RLP068/Cl may be useful in the management of chronic infected wounds, accelerating the repair process through a significant bacterial inhibition. © 2011 British Association of Dermatologists.