Anticandidal effect of multiple sessions of erythrosine and potassium iodide-mediated photodynamic therapy.

Background: Erythrosine+potassium iodide-mediated photodynamic therapy has shown an anticandidal effect. Single session, however, has inadequate fungal inhibition.

Objectives: We aimed to examine the effects of multiple aPDT sessions on Candida albicans inhibition and singlet oxygen formation.

Methods: 220 μM erythrosine +/-100 mM potassium iodide was applied to C. albicans biofilms for 1 min prior to irradiation at 530±10 nm using a 250 mW/cm² light-emitting diode. Negative and positive controls were phosphate buffer saline and nystatin, respectively. Single, double and triple irradiation sessions with a 5 min resting time between sessions were performed. Post-treatment candidal counts were done at 0, 1 6 and 24 hr while log₁₀ colony forming unit/ml was calculated and compared using a Kruskal-Wallis with Dunn's post hoc test at a p<0.05 - Singlet oxygen amount was compared using one-way ANOVA with a post hoc test at a p< 0.05.

Results: Two and three irradiation sessions to erythrosine+potassium iodide could inhibit Candida albicans at 7.92 log₁₀CFU/ml (p < 0.001) . Singlet oxygen from a combination groups was significantly higher than for erythrosine (positive control). Moreover, the correlation coefficient (r) between singlet oxygen production and decreased Candida albicans counts was equal to 1.

Conclusion: Multiple sessions PDT of 220 μM erythrosine+100 mM potassium iodide effectively inhibited a Candida biofilm.