Antifungal effect of a metabolite of Pseudomonas aeruginosa LV strain on azole-resistant Candida albicans

Candida albicans remains the most common agent of candidiasis worldwide. This yeast is generally sensitive to most antifungals, however, the emergence of azole-resistant C. albicans has been reported. In addition, this microorganism can form biofilms on various surfaces, making it difficult to treat infections. In this study, the effect of secondary metabolites of Pseudomonas aeruginosa strain LV on planktonic and sessile cells of C. albicans, with different genotypes and susceptibility profile to fluconazole and voriconazole, was evaluated. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of the semi-purified fraction F4a ranged from 1.56 to 6.25 μg/mL and 6.25 to 25 μg/mL, respectively. Fluopsin C appears to be the antifungal component of F4a. The semi-purified fraction and fluopsin C showed fungicidal activity, dose and time dependent. F4a caused severe damage to the morphology and ultrastructure of planktonic fungal cells, and significantly reduced the viability of 24-hour biofilms, with MIC for sessile cells from 12.5 to 25.0 μg/mL. However, cytotoxicity was detected in mammalian cells for F4a and fluopsin C at concentrations that showed antifungal activity. These results indicate that fluopsin C may be a prototype for the development of new antifungals for C. albicans.