In-Vitro Activity of Three Propolis on Oral Microorganisms and Biofilm
Objectives: Natural products are discussed as alternatives to the commonly used chemicals in antimicrobial therapy. The study was aimed to investigate the antimicrobial activity of propolis originating from two different regions on microbial species being associated with caries, periodontal disease and with Candida infections.
Methods: Commercially available ethanolic extracts of propolis (EEP) originating from South America (Brazilian red propolis, Brazilian green propolis), and Central Europe (European) and as controls a chlorhexidine digluconate solution, an ethanolic solution were used. The minimal inhibitory concentrations (MIC) of propolis and controls against 8 microbial strains were determined before SEM and TEM images visualized the effect of propolis on microorganisms. Then, the activity on three different multi-species biofilms (both formation and existing biofilms) was assessed.
Results: All MIC values of the Brazilian EEPs were low against the tested oral species (<=0.1 mg/ml – 3.13 mg/ml propolis (Candida albicans)). The EEP European seemed to be slightly less active than the Brazilians EEPs. The SEM and TEM images suggest an interaction of propolis with the microbial cell wall. EEP European most retarded biofilm formation; after 4 h and 24 h of formation, 1% propolis reduced the total microbial counts (cfu) of the cariogenic biofilm by 2.21 log10 and 5.78 log10 vs. control. Applying 10% propolis of EEP Brazilian green or Brazilian red to already formed biofilms resulted in no (cariogenic biofilm), less than 1 log10 (periodontal biofilm) or less than 2 log10 (Candida biofilm) cfu in biofilms.
Conclusions: The antimicrobial and anti-biofilm activities underline the potential of propolis as an adjunct in oral health care products. Further research is needed to get better knowledge about the anti-inflammatory activity of propolis related to oral diseases.