Catechol thwarts virulent dimorphism in Candida albicans and potentiates the antifungal efficacy of azoles and polyenes

Abstract

The present study was deliberately focused to explore the antivirulence efficacy of a plant allelochemical—catechol against Candida albicans, and attempts were made to elucidate the underlying mechanisms as well. Catechol at its sub-MIC concentrations (2–256 μg/mL) exhibited a dose dependent biofilm as well as hyphal inhibitory efficacies, which were ascertained through both light and fluorescence microscopic analyses. Further, sub-MICs of catechol displayed remarkable antivirulence efficacy, as it substantially inhibited C. albicans’ virulence enzymes i.e. secreted hydrolases. Notably, FTIR analysis divulged the potency of catechol in effective loosening of C. albicans’ exopolymeric matrix, which was further reinforced using EPS quantification assay. Although, catechol at BIC (256 μg/mL) did not disrupt the mature biofilms of C. albicans, their initial adherence was significantly impeded by reducing their hydrophobic nature. Besides, FTIR analysis also unveiled the ability of catechol in enhancing the production of farnesol—a metabolite of C. albicans, whose accumulation naturally blocks yeast-hyphal transition. The qPCR data showed significant down-regulation of candidate genes viz., RAS1, HWP1 and ALS3 which are the key targets of Ras-cAMP-PKA pathway -the pathway that contribute for C. albicans’ pathogenesis. Interestingly, the up-regulation of TUP1 (a gene responsible for farnesol-mediated hyphal inhibition) during catechol exposure strengthen the speculation of catechol triggered farnesol-mediated hyphal inhibition. Furthermore, catechol profusely enhanced the fungicidal efficacy of certain known antifungal agent’s viz., azoles (ketoconazole and miconazole) and polyenes (amphotericin-B and nystatin).