Evaluation of the activity of crude extracts from semi-arid soil fungi against clinical yeasts and molds

Abstract

In recent years, the incidence and severity of fungal diseases has increased, particularly in populations with a broad list of immunocompromised conditions. Moreover, the emergence of azole resistance is arising. For these reasons and the small number of available antifungal agents, searching for new and effective compounds with antifungal activity is mandatory. The aim of this study was to evaluate the antifungal activity of crude extracts from semi-arid soil fungi against strains of clinical molds and yeasts. For screening purposes crude extracts of fifteen isolates, corresponding to ten fungal species, were preliminarily explored against Candida albicans ATCC6414 by diffusion methodology. Special focus was placed on Aspergillus tatenoi, Leiothecium ellipsoideum, Subplenodomus violicola and Trichoderma saturnisporum extracts because of their preceding antifungal performance. Crude extracts of these species were once more examined and assayed against 54 yeast and 24 molds including the genera Aspergillus, Candida and Cryptococcus. Antifungal susceptibility testing by microdilution methodology was performed. Activity, as the percentage of clinical strains inhibited by different extract concentrations, ranged from 60.5% to 100% for A. tatenoi, L. ellipsoideum and T. saturnisporum extracts. On the other hand, S. violicola extract was active against all the strains tested with MIC values ≤ 0.25 µg/mL. This study dealt with active crude extracts; particularly, the extract from S. violicola has shown a potent and promising antifungal activity. The composition of the active fractions and the mechanisms of action involved remain to be studied and warrant further investigations.