The effect of Farnesol on sensitivity of microorganisms from bacterial-fungal biofilm to antimicrobial agents in vitro

Two microorganisms — Staphylococcus aureus and Candida albicans isolated from a mixed bacterial-­fungal biofilm of horse wound were studied. Resistance profile of these clinical strains to antimicrobial agents was determined using standard disc diffusion method on solid nutrient medium in the laboratory. Next, Farnesol was added to the disks at concentrations of 12.5…200 μM/ml (experiment) or physiologic saline solution (control). The experiments showed that in most cases addition of Farnesol increased sensitivity of microorganisms to antimicrobial drugs, and there were no cases of a negative effect of Farnesol on sensitivity. Moreover, the best results of synergism were observed in combination with antifungal drugs rather than with antibacterial drugs. There were also unique indicators: sensitivity of C. albicans to Nystatin and Miconazole doubled after the addition of Farnesol at a concentration of 25…200 µM/ml. Furthermore, it was proved that the clinical strain of S. aureus was completely resistant to penicillin. And sensitivity appeared after the addition of Farnesol. A similar situation was with the Candida strain: resistance to Amphotericin B was initially observed, and in combination with Farnesol, this drug began to work even in small concentrations. In vivo data indicate that Farnesol has an adjuvant effect in combination with most antibiotics and/or antifungal drugs.