Farnesol decreases biofilms of Staphylococcus epidermidis and exhibits synergy with nafcillin and vancomycin.

Biofilm infections are frequently caused by Staphylococcus epidermidis, are resistant to antimicrobial agents, and adversely affect patient outcomes. We evaluated farnesol (FSL), the Candida quorum-sensing molecule, on S. epidermidis biofilms, in vitro and in vivo. We evaluated ED50, ED75, and ED90 (drug concentrations causing 50%, 75%, and 90% inhibition, respectively) of FSL and evaluated synergy with nafcillin and vancomycin. FSL's effects on morphology of S. epidermidis biofilms were analyzed using confocal microscopy and real-time changes using a bioluminescent strain of S. epidermidis, Xen 43. In mice, effects of FSL treatment on s.c. catheter biofilms; cultures of blood, kidney, and catheter and pericatheter tissues; and bioluminescence in strain Xen 43 were evaluated. FSL inhibited biofilms (ED50 ranged from 0.625 to 2.5 mM) and was synergistic with nafcillin and vancomycin at most combination ratios. FSL significantly decreased biovolume, substratum coverage, and mean thickness of S. epidermidis biofilms. In mice, FSL significantly decreased viable colony counts of S. epidermidis from blood, kidney, and catheter and pericatheter tissues and decreased Xen 43 bioluminescence. We confirmed the antibiofilm effects of FSL both in vitro and in vivo, in a bioluminescent strain and its synergy with antibiotics. FSL may be effective against clinical S. epidermidis biofilm infections.