Red propolis hydroalcoholic extract inhibits the formation of Candida albicans biofilms on denture surface

BACKGROUND: To evaluate the antifungal activity of the red propolis hydroalcoholic extract (RPHE) against Candida albicans biofilms. MATERIAL AND METHODS: The minimum inhibitory and fungicidal concentrations (MIC and MFC) of the RPHE were determined by the microdilution technique. C. albicans biofilms were formed on the surface of resin specimens preconditioned with artificial saliva (1h). The specimens (N=48) were equally divided according to the four solutions used for anti-biofilm evaluation (n=12 per group). After overnight incubation, biofilms were daily exposed (2x/day for 15 min) along 3 days with 3% RPHE, 0.12% chlorhexidine (CHX), 50,000 IU/mL nystatin (NYS) or saline (0.9% NaCl). Biofilms were analyzed regarding the number of viable microorganisms (CFU/mL), the metabolic activity (MTT assay) and the proportion of hyphae (optical microscopy). RESULTS: The MIC and MFC of RPHE were respectively 0.29 mg/mL (0.03%) and 1.17 mg/mL (0.12%). There was no difference in the microorganisms’ viability (CFU/mL) among groups treated with RPHE (4.92×103), CHX (3.33×102) or NYS (6.8×104), being all of them different from NaCl (3.93×107) (p<0.05). The CHX (0.133) had the lowest metabolic activity (p<0.05), followed by RPHE (0.292) and NYS (0.302) (p>0.05). All experimental groups had a mean proportion of hyphae <10%, lower than NaCl (70%). CONCLUSIONS: RPHE has antifungal activity against C. albicans biofilms, suggesting its use for the biofilm control on denture surfaces. Key words:Propolis, Candida albicans, biofilm, dentures, antifungal agents.