In Vivo Killing of Candida albicans by Photodynamic Therapy

Objectives: This study evaluated the effectiveness of Photodynamic Therapy (PDT) on Candida albicans inactivation in a murine model of oral candidosis. Methods: Forty-five immunosuppressed mice were anesthetized with chlorpromazine chloride and orally infected with C. albicans (10⁷CFU/mL). Tetracycline in drinking water was given to mice. Photogem^®, a hematoporphyrin derivate, was used as a photosensitizer (PS). Two handpieces having a blue (455nm) or red (630nm) light-emitting diode (LED) was used to irradiate the mice tongue. Animals were anaesthetized with ketamine 4 days after Candida infection. Then, 50µL of PS at concentrations of 400 or 500mg/L was pippeted onto the tongue dorsum. After 30min in the dark, the LED device (blue or red) was placed onto the tongue dorsum, which was illuminated for 20min (305J/cm²). The effect of PS alone (400 or 500mg/L) was tested in the absence of light. The groups that received light only (blue or red) were exposed to the same LED fluence. The control group did not receive either PS or light. Each experimental group consisted of five animals. Next, the tongue dorsum was swabbed with a cotton pad. Duplicate aliquots from the serial dilutions were spread over the surface of Agar Sabouraud Dextrose. After 48h at 37°C, colonies on plates were counted and the data [log(CFU/mL)] were statistically analyzed by one-way ANOVA and Holm-Sidak test. Results: The association of PS with LED light promoted significant reduction of CFU/mL of C. albicans from mice tongue. There was no significant difference between the PS concentrations and the light wavelengths. No difference was also observed among the control group and the groups that were treated only with PS or light. Conclusion: PDT was effective to reduce C. albicans in a murine model of oral candidosis.

Grant: FAPESP 2005/02193-4 and 2005/03226-3