Treatment of oral candidiasis with methylene blue-mediated photodynamic therapy in an immunodeficient murine model.

Abstract Objective. The purpose of this study was to evaluate the efficacy of using methylene blue (MB)–mediated photodynamic therapy to treat oral candidiasis in an immunosuppressed murine model, mimicking what is found in human patients. Study Design. Seventy-five experimental mice with severe combined immunodeficiency disease were inoculated orally with Candida albicans by swab 3 times a week for a 4-week period. On treatment day, mice were cultured for baseline fungal growth and received a topical oral cavity administration of 0.05 mL MB solution at one of the following concentrations: 250, 275, 300, 350, 400, 450, or 500 μg/mL. After 10 minutes the mice were recultured and underwent light activation with 664 nm of diode laser light with a cylindrical diffuser. After photodynamic therapy the mice were cultured again for colony-forming units per milliliter and then killed, their tissue harvested for histopathology. Results And Conclusions. The results indicate an MB dose-dependent effect. Concentrations from 250 to 400 μg/mL reduced fungal growth but did not eliminate Candida albicans . MB concentrations of 450 and 500 μg/mL totally eradicated Candida albicans from the oral cavity, resulting in reductions from 2.5 log 10 and 2.74 log 10 to 0, respectively. These results suggest that MB-mediated photodynamic therapy can potentially be used to treat oral candidiasis in immunodeficient patients. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:155-60)