Photodynamic Antimicrobial Chemotherapy (PACT) using methylene blue inhibits the viability of the biofilm produced by Candida albicans.

BACKGROUND: Candida albicans is an opportunistic fungus, an etiological agent of human infections, presenting high rates of morbidity and mortality. The resistance of C. albicans to conventional therapies has been reported due to the extensive use of conventional antifungals. Photodynamic antimicrobial chemotherapy (PACT) is a technique that combines a visible light with a specific wavelength and a photosensitizer, producing ROS and permanent damages in the treated cells. METHODS: In this work, the effects of PACT, using Methylene Blue (MB), as a photosensitizer, on C. albicans development were studied. RESULTS: Significant reduction in both cell growth and biofilm formation after PACT were observed, in a dependent manner on both MB concentration and fluence. In the presence of MB 0.02 mg/mL, it was observed inhibition in biofilm formation of ˜58, 70 and 74%, using fluences of 10, 20 and 30 J/cm2, respectively. Also, it was observed inhibition of 54, 66 and 55% in the presence of MB 0.01, 0.02 and 0.05 mg/mL, respectively in the viability of biofilm produced by C. albicans. The number of both yeast and filaments present in the structure of biofilm were reduced after PACT. Furthermore, PACT changed the growth kinetics of C. albicans. Interestingly, we demonstrated increase in the extent of lag phase and an alteration in the profile of the exponential phase after PACT. CONCLUSIONS: Taken together, these results indicate the potential PACT effects using MB to decrease the C. albicans development.

Photodynamic Antimicrobial Chemotherapy (PACT), using Toluidine blue (TBO) inhibits both growth and dimorphism in Paracoccidioides brasiliensis by a mechanism involving reactive oxygen species (ROS) production.

BACKGROUND: The thermo-dimorphic fungus Paracoccidioides brasiliensis is the pathogen of Paracoccidioidomycosis, an important public health problem in Latin American with prevalence in Brazil. Photodynamic Antimicrobial Chemotherapy (PACT) is a process that combines a photosensitizer and light, producing reactive oxygen species (ROS) that can promote damages to treated cells. METHODS: In this work was study the effect of PACT, using Toluidine blue (TBO) on both yeast and mycelial cells of P. brasiliensis. RESULTS: It was observed that PACT decreased P. brasiliensis yeast growth, in a dependent manner of both TBO concentrations and fluence. In the presence of TBO 0.005 mg/mL, PACT reduced P. brasiliensis yeast growth in 63, 62 and 86%, using fluences of 20, 30 and 40 J/cm2, respectively. After PACT, ROS production increased 2.80, 4.64 and 7.90 times, in the presence of TBO 0.001, 0.002 and 0.005 mg/mL, respectively. It was observed that after PACT, the cells are predominantly in mycelia form, indicating that mycelial cells irradiated in the presence of TBO, maintained their filamentous form and absence and/or decreased presence of transition structures. CONCLUSIONS: These results demonstrated the potential of PACT, using TBO to inhibit both yeast and mycelium development of P. brasiliensis.