Effect of photodynamic therapy with 5‐aminolevulinic acid and EDTA‐2Na against mixed infection of methicillin‐resistant Staphylococcus aureus and Pseudomonas aeruginosa

Abstract

AbstractBackgroundThe increasing abundance of drug‐resistant bacteria is a global threat. Photodynamic therapy is an entirely new, non‐invasive method for treating infections caused by antibiotic‐resistant strains. We previously described the bactericidal effect of photodynamic therapy on infections caused by a single type of bacterium. We showed that gram‐positive and gram‐negative bacteria could be killed with 5‐aminolevulic acid and 410 nm light, respectively. However, clinically, mixed infections are common and difficult to treat.ObjectiveWe investigated the bactericidal effects of photodynamic therapy on mixed infections of methicillin‐resistant Staphylococcus aureus and Pseudomonas aeruginosa.MethodsWe compared bacterial growth with and without photodynamic therapy in vitro. Then, in vivo, we studied mixed infections in a mouse skin ulcer model. We evaluated the rates of ulcer area reduction and transitions to healing in treated and untreated mice. In addition, a comparison was made between PDT and existing topical drugs.ResultsWe found that photodynamic therapy markedly reduced the growth of both methicillin‐resistant Staphylococcus aureus and Pseudomonas aeruginosa, in culture, and it reduced the skin ulcer areas in mice. PDT was also more effective than existing topical medicines.ConclusionThis study showed that photodynamic therapy had antibacterial effects against a mixed infection of gram‐positive and gram‐negative bacteria, and it promoted skin ulcer healing. These results suggested that photodynamic therapy could be effective in both single‐ and mixed‐bacterial infections.