Antifungal Activity of the Frog Skin Peptide Temporin G and Its Effect on Candida albicans Virulence Factors

The increasing resistance to conventional antifungal drugs is a widespread concern, and a search for new compounds, active against different species of fungi, is demanded. Antimicrobial peptides (AMPs) hold promises in this context. Here we investigated the activity of the frog skin AMP Temporin G (TG) against a panel of fungal strains, by following the Clinical and Laboratory Standards Institute protocols. TG resulted to be active against (i) Candida species and Cryptococcus neoformans, with MIC(50) between 4 µM and 64 µM after 24 h of incubation; (ii) dermatophytes with MIC(80) ranging from 4 to 32 µM, and (iii) Aspergillus strains with MIC(80) of 128 µM. In addition, our tests revealed that TG reduced the metabolic activity of Candida albicans cells, with moderate membrane perturbation, as proven by XTT and Sytox Green assays, respectively. Furthermore, TG was found to be effective against some C. albicans virulence factors; indeed, at 64 µM it was able to inhibit ~90% of yeast–mycelial switching, strongly prevented biofilm formation, and led to a 50% reduction of metabolic activity in mature biofilm cells, and ~30–35% eradication of mature biofilm biomass. Even though further studies are needed to deepen our knowledge of the mechanisms of TG antifungal activity, our results suggest this AMP as an attractive lead compound for treatment of fungal diseases.