Inhibition of Candida albicans biofilm by lipopeptide AC7 coated medical-grade silicone in combination with farnesol

Biosurfactants affect interaction of microorganisms with material surfaces by altering interfacial properties, and have recently attract the attention of the scientific community for their use as anti-adhesive and anti-biofilm agents. The work studied the synergistic effect of a lipopeptide from Bacillus subtilis AC7 (AC7BS) combined with the quorum sensing molecule farnesol to counteract Candida albicans biofilms on silicone elastomer in simulated physiological conditions. The anti-adhesive and anti-biofilm properties of AC7BS, farnesol and their combination was evaluated after 1.5, 24 and 48 h by the viable count method on three C. albicans strains. Moreover, fungal biofilm was characterised by both scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). By combining the two molecules, a synergistic effect was observed with a significant reduction of C. albicans adhesion up to 74% at 1.5 h and of biofilm growth up to 93% at 24 h and 60% at 48 h. SEM and CLSM confirmed the synergistic anti-adhesive and anti-biofilm activity. Similar trends for the percentage of biofilm covered surface and biofilm mean thickness were observed. No cytotoxicity on eukaryotic cells was detected after exposures to AC7BS concentrations up to 0.5 mg ml−1. Results demonstrated that the combination of the two molecules significantly inhibit both C. albicans initial adhesion and biofilm growth on silicone. Biosurfactant AC7 in combination with farnesol is a hopeful coating to prevent C. albicans medical device-associated infection.