Evaluation of Antifungal Efficacy of Three New Cyclic Lipopeptides of the Class Bacillomycin from Bacillus subtilis RLID 12.1.

New lipopeptide homologues (AF, AF, and AF) with antifungal activities against and spp. were purified from a cell-free supernatant of RLID 12.1. The lipopeptides AF, AF, and AF were identified with the same peptide sequence Asn-Pro-Tyr-Asn-Gln-Thr-Ser with variations in the fatty acid branching type and chain length (-C, -C, and -C, respectively). Upon comparing the three homologues for MICs against 81 ( = 64) and ( = 17) clinical isolates and their cytotoxicities, we found that AF was the most promising antifungal lipopeptide, since it demonstrated 100% inhibition at geometric mean MICs of 3.31, 3.41, 3.48, and 2.83 μg/ml against , , , and , respectively, with low hemolysis values (<6%) and 50% inhibitory concentrations (13.31 μg/ml). The additive effects among the homologues AF, AF, and AF were evaluated against three species, along with the cytotoxicity studies. Five combinations exhibited good additive interaction effects: AF/AF (at corresponding concentrations of 4 and 4 μg/ml [4/4 μg/ml]), AF/AF (4/4 μg/ml), AF/AF (2/4 μg/ml), AF/AF (4/4 μg/ml), and AF/AF (2/4 μg/ml) in planktonic cell inhibition and AF/AF (4/4 μg/ml), AF/AF (4/4 μg/ml), and AF/AF (2/4 μg/ml) in the inhibition of biofilm formation. However, combinations AF/AF and AF/AF, which showed >70% cell survival with low hemolysis (<5%), were found to be comparatively effective. We describe here the additive effects of lipopeptide homologues showing reduced cytotoxicity against mammalian cells; these combinations might serve as a potent antibiofilm-forming substitute.