Synergistic combination of Sapindoside A and B: A novel antibiofilm agent against Cutibacterium acnes.

Sapindus saponins extracted from Sapindus mukorossi Gaertn. have been reported to exert antibacterial activity against Cutibacterium acnes (C. acnes). However, there are no reports about their potentials against its biofilm, which is a major contributor to the antibiotic resistance of C. acnes. This study aimed to investigate the synergistic antibiofilm activity and action of the combination of Sapindoside A and B (S) against C. acnes. S with sub-MICs significantly inhibited the early-formed and mature biofilm of C. acnes and decreased the adhesion and cell surface hydrophobicity (p < 0.05). Also, S greatly reduced the production of exopolysaccharide and lipase (p < 0.05), and the binding mode of S and lipase was predicted by molecular docking, via hydrogen bonds and hydrophobic interactions. Biofilm observed with electron microscopies further confirmed the high antibiofilm activity of S against C. acnes. Furthermore, a significant down-regulation of biofilm biosynthesis-associated genes was observed. The combination index explained the synergistic effects of S leading to the above results, and the contribution of S was greater than that of S. The current results showed that S had synergistic antibiofilm activity against C. acnes, and the Sapindoside A played a major role, indicating that S could be a natural antiacne additive against C. acnes biofilm-associated infections.