Antibiofilm and antifungal activities of medium‐chain fatty acids against Candida albicans via mimicking of the quorum‐sensing molecule farnesol

Candida biofilms are tolerant to conventional antifungal therapeutics and the host immune system. The transition of yeast cells to hyphae is considered a key step in C. albicans biofilm development, and this transition is inhibited by the quorum‐sensing molecule farnesol. We hypothesized that fatty acids mimicking farnesol might influence hyphal and biofilm formation by C. albicans. Among 31 saturated and unsaturated fatty acids, six medium‐chain saturated fatty acids, that is, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid and lauric acid, effectively inhibited C. albicans biofilm formation by more than 75% at 2 µg ml(−1) with MICs in the range 100–200 µg ml(−1). These six fatty acids at 2 µg ml(−1) and farnesol at 100 µg ml(−1) inhibited hyphal growth and cell aggregation. The addition of fatty acids to C. albicans cultures decreased the productions of farnesol and sterols. Furthermore, down‐regulation of several hyphal and biofilm‐related genes caused by heptanoic or nonanoic acid closely resembled the changes caused by farnesol. In addition, nonanoic acid, the most effective compound diminished C. albicans virulence in a Caenorhabditis elegans model. Our results suggest that medium‐chain fatty acids inhibit more effectively hyphal growth and biofilm formation than farnesol.