The basidiomycete mushroom Macrocybe titans has recently been reported in Brazil and there are few records in the literature about its antimicrobial potential. The present study aimed to verify the antifungal potential of aqueous extracts of this macrofungi on Candida tropicalis and Trichosporon spp. as well as the effects on the morphological aspects of these yeasts. It was used the ATCC 750 strain of C. tropicalis and a clinical isolate of Trichosporon spp. The aqueous extracts of the mushroom were from dry basidiomas, crushed and diluted in water at a concentration of 250 μg/μl. The extracts were kept for 24 hours at 4 o C and filtered through a sterile 0.45 μm and 0.22 μm PES filters. The antifungal effects of both extracts (MT-22 and MT-45) was evaluated by microdilution in broth and disk-diffusion method. It was found that the aqueous extract MT-22 showed the best minimal inhibitory concentration (MIC), compared to the extract MT-45. Through the CFM test (minimum fungicidal concentration) it was verified that the MT-22 extract showed fungistatic action on C. tropicalis, and fungicidal action for Trichosporon spp. The CFU/ml assay showed a reduction or inhibition in the amount of colony forming units of microorganisms when exposed to the MT-22 extract. Micromorphological aspects were analyzed by microculture on cornmeal agar with Tween 80 (1%), Fluorescence Microscopy using Calcofluor White and Scanning Electron Microscopy (SEM). In the microculture analysis it was possible
to observe complete inhibition of the growth of Trichosporon spp. in the oncentration of sub-MIC and MIC, and increased filamentation of C. tropicalis in the sub-MIC and MIC of M. titans extract. Through SEM, it was possible to observe morphological changes and significant damage on the surfaces of cells treated with the extract MT-22 in the concentrations referring to the MIC of the two yeasts. Fluorescence microscopy with Calcofluor White dye exhibited the presence of elongated structures when C. tropicalis cells were cultured in the sub-MIC concentration, and a considerable reduction in the cell number of Trichosporon spp. From the results presented in this study, it was possible to conclude that the aqueous extract of M. titans showed very promising behavior with regard to antifungal action, leading to significant morphological changes on the surface of C. tropicalis and Trichosporon spp.