Atividade antifúngica e antibiofilme da fração Ag2 do extrato de Agelas dispar frente espécies de Candida

Abstract

Microbial biofilms are especially a structural barrier that hinders antimicrobial therapy, having a relevant role in human diseases. For yeasts of the genus Candida, biofilms are characterized as a complex three-dimensional arrangement, consisting of different cellular forms incorporated into a matrix of extracellular polymeric substance. In the last decades, the search for natural compounds for the treatment of microbial infections has grown in order to obtain new alternatives to the mechanisms of resistance to antimicrobials, including those induced by biofilms. The marine sponge, Agelas dispar (Family Agelasidae) has been mentioned as a bioactive source, due to its secondary metabolites, the alkaloid derivatives, which have significant pharmacological activity. In this context, the objective of this study was to determine the antifungal and antibiofilm activity of the Ag2 fraction of the A. dispar metanolic extract on biofilm-producing strains of the genus Candida. The biological activity of Ag2 was investigated in 13 species of Candida, evaluating the Minimum Inhibitory Concentration (MIC) by the broth microdilution technique and by the Minimum Fungicide Concentration (CFM) method. The quantification of the biofilm formation and antibiofilm activity of the extract was performed with the violet crystal and the obtained optical densities were measured. Antifungal activity was found for 13 strains, with MIC ranging between 2.5 mg/mL and 0.1562 mg/mL and CFM values ranging from 5.0 mg/mL to 0.3125 mg/mL against Candida species. The results of biofilm formation indicated that all strains were biofilm producers, with 10 (77%) weak producing strains and 3 (23%) moderate producing strains. 10 (77%) weak producing strains and 3 (23%) moderate producing strains. The species C. krusei, C. glabrata and C. parapsilosis were used to test the antibiofilm activity (in formation and mature), resulting in inhibition of cell viability (IC50%) ranging from 49.6% to 57.6%, 70 , 5% to 76.3% (biofilm in formation) and 42.8% to 67.2%, 63.3% to 78.8% (mature biofilm) when these strains were posttreated, respectively, with the concentrations of 1.25 mg/mL and 2.5 mg/mL of the Ag2 fraction. The Scanning Electron Microscopy (SEM), allowed the visualization of the antibiofilm activity, quantitative decrease of the microbial community, structural alteration and destruction at the cellular level in both the forming and mature biofilms. It was concluded that the Ag2 fraction of A. dispar methanolic extract showed antifungal activity and fungicide-like nature, reducing the microbial load, in addition to showing efficiency in inducing changes in the structural morphology of the yeasts involved in the biofilm, as observed in the SEM. The results suggest that Ag2 acts at the level of the plasma membrane and/or yeast cell wall and can be a promising antifungal and antibiofilm therapeutic strategy against the different species of Candida.