Efeito in vitro da terapia fotodinâmica antimicrobiana sobre os fatores de patogenicidade de Candida spp

Abstract

This research aimed to evaluate the effect of Antimicrobial Photodynamic Therapy, using methylene blue as a photosensitizer, on the pathogenicity factors of Candida spp. An in vitro assay was performed on cell concentration in a spectrophotometer, fungal morphology quantified by area dimensions, chromatic density and numbers of reproductive shoots, rupture with the cell wall regeneration cycle, as well as the interaction of treatments with Ergosterol, a constituent of the plasma membrane of fungi. From the suspension of Candida albicans, tropicalis and krusei, represented by clinical isolates from patients with Acute Lymphocytic Leukemia and by ATCC and CBS strains, inoculums were prepared at a concentration of 1 x 106 and submitted to the following groups: G1 - Growth Control; G2 - Red Irradiation; G3 - Methylene Blue with 20 minutes exposure; G4 - PDTa with a pre-irradiation time of 15 minutes; G5 – TPDa with TPI of 20 minutes; G6 - Association of Nystatin and PDT with 15-minute TPI; G7 - Association of Nystatin and PDTa with TPI of 20 minutes; G8 - Nystatin. The light source used was the InGaAlP laser, with a wavelength of 660 nm, a power density of 3.57 W/cm² and an energy of 5.0 J and an energy density of 178.5 J/cm². The concentration of Methylene Blue was 0.1%. The results of the image tests were processed in the ImageJ program (1.51p) and, later, statistically analyzed in the SPSS Software (version 18), as well as the product of the other tests. Statistical analysis was performed using the One-way ANOVA and Two-way ANOVA parametric test, with a significance level of 5%. In all experiments, the clinical microorganisms showed greater resistance potential to the treatments submitted, when compared to the standardized ones, justified by the constant cyclical exposure to drugs and immunological resources of the host. As for cell concentration, Candida krusei expressed the highest color densities among the clinical microbiota treated, being the only microorganisms to present in the form of hyphae. Candida tropicalis was the species with the greatest potential to maintain the cell wall recovery cycle. PDTa was the most effective treatment among the groups, indicating the lowest indices of cell concentration, area, color density and formation of reproductive buds in clinical strains. Nystatin had unsatisfactory antimicrobial effects regarding the analyzed factors, mainly in clinical microorganisms, however, being the only therapy to bind to synthetic Ergosterol, which can develop action on the plasma membrane of the fungus. It is expected that the results pointed out by the study help in the consolidation of PDTa as an effective treatment for oral candidiasis and that its association with allopathic methods enable a greater microbial reduction in the microbiological pathways of Candida spp.