Efeito da terapia fotodinâmica antimicrobiana com a associação de fluconazol e azul de metileno em Candida albicans

Abstract

Antimicrobial Photodynamic Therapy (APDT) has been used to treat localized infections and the constant exposure of antimicrobials presents an increasing number of cases of microbial resistance. The aim of this study was to evaluate the effects of the association of fluconazole and APDT with methylene blue in fungal suspension. Candida albicans ATCC 90028 was grown on Sabouraud agar and inocula were prepared at yeast density of 1x106 CFU/mL. Methylene blue (MB) was used as photosensitizer at final concentrations of 1 and 100 µM, and fluconazole was used at concentration of 0.05 µg/mL (minimal inhibitory concentration). Yeast cells were incubated for 10 min in 24-well plate and then irradiated by LED (660 nm; 690 mW; A= 2.7 cm2; I= 250 mW/cm2) with radiant exposure of 30, 60, and 120 J/cm2. The same APDI setup was used with 2 hours fluconazole (0.5 µg/mL) incubation. The comparison between groups was performed using One-way ANOVA followed by Bonferroni post hoc test. A UV–visible optical absorption spectroscopy was achieved following fractionated irradiation up to 960 s. There were substantial differences in the killing effect following MB-mediated APDI and C. albicans was eradicated in the both APDI groups. The fluconazole combined to APDI delayed the complete inactivation of the yeast (p<0.05). While PDT caused total eradication of cells in 4 min, the PDT combined to fluconazole still exhibited only 2 log reduction (p<0.05). Spectroscopy showed a decrease in absorption following irradiation for all absorption peaks. APDI presented an antagonist effect on fluconazole treated C. albicans. Furthermore