Biofilm formation of candida albicans exposed to ethanol extract of propolis

Objective: Propolis extract showed an excellent in vitro performance against yeast and was additionally found to be fungistatic and fungicidal. Propolis extract is also used for treatment and prevention of fungal infections. However, its effectiveness against Candida albicans biofilm formation requires investigation. The study evaluated the ability of propolis to inhibit C. albicans while the fungus is growing as a biofilm in vitro. Methods: Two reference strains, C. albicans ATCC 25923 and a clinical strain (laboratory stock), were used in this study. For the biofilm experiment, the fungi were cultured in Tryptic Soy Broth medium with 1% sucrose and incubated at 37°C for 24 h, and different concentrations of ethanol extract of propolis were used as the inhibitor agents. Biofilm assays were performed in 96-well microtiter plates, quantification of the total biofilm biomass was performed using a crystal violet staining method, and the Student’s t-test was chosen for statistical analyses. Results: Our data showed that 3 h incubation with propolis did not affect the biomass in the experimental group compared to the control. When the incubation time was extended to 18 h, the biomass increased significantly compared to the control. Conclusion: This study showed that several concentrations of propolis did not inhibit biofilm. However, in each incubation time, we observed no hyphal morphology in the biofilm mass. Propolis might attenuate the opportunistic virulence of fungus growing as a biofilm in vitro. Further studies are necessary to confirm this phenomenon.