Antifungal activity of silver nanoparticles and simvastatin against toxigenic species of Aspergillus

Abstract

Aspergillus spp. are ubiquitous fungi that grow on stored grains. Some species produce toxins that can harm human and animal health, leading to hepato- and nephrotoxicity, immunosuppression and carcinogenicity. Major fungicides used to prevent fungal growth may be toxic to humans and their repeated use over time increases levels of resistance by microorganisms. Nanotechnology is an emerging field that allows use of antimicrobial compounds in a more efficient manner. In this study, was evaluated the antifungal activity of biogenic silver nanoparticles (AgNPs, synthesized by fungi) and simvastatin (SIM, a semi-synthetic drug), alone and in combination against three toxigenic species belonging to the genera Aspergillus section Flavi (Aspergillus flavus, Aspergillus nomius and Aspergillus. parasiticus) and two of section Circumdati (Aspergillus ochraceus and Aspergillus melleus). SIM exhibited a MIC50 of 78 μg/mL against species of Section Flavi and a MIC50 of 19.5 μg/mL against species of Section Circumdati. The MIC50 of AgNPs against Aspergillus flavus, Aspergillus nomius and Aspergillus parasiticus was 8 μg/mL, while the MIC50 was 4 μg/mL against Aspergillus melleus and Aspergillus ochraceus. Checkerboard assay showed that these compounds, used alone and in combination, have synergistic and additive effects against toxicogenic species of Aspergillus. Analysis by SEM gives an idea of the effect of SIM and AgNPs alone and in combination on spore germination and vegetative growth. Ultrastructural analysis revealed that spore germination was prevented, or aberrant hyphae were formed with multilateral branches upon treatment with SIM and AgNPs. These results reveal potential benefits of using combination of AgNPs and SIM to control fungal growth.