In Vitro Antimicrobial Properties of Propolis against Caries-Associated Microorganisms

Natural products have attracted much attention in recent years as a useful substance used in medicine and dental products. Propolis is a lipophilic resinous mixture collected from various plant sources by honeybees. It has been known for many biological activities including antimicrobial properties. Objective: To evaluate the in vitro antimicrobial activity of propolis against caries-associated microorganisms, Streptococcus mutans, Lactobacillus casei and Candida albicans. Materials and methods: The antimicrobial activity was initially screened using agar disc diffusion and then the minimum lethal concentrations (MLCs) were determined using broth dilution technique. Chlorhexidine (0.2%) and dimethyl sulfoxide (5%) were used as positive and negative controls, respectively. Results: Propolis exhibits the zones of inhibition ranged from 15 to 18 mm for S. mutans, and from 10 to 12 mm for L. casei, but presented no activity against C. albicans. The MLC against S. mutans was 2.86 mg/mL and those against L. casei were 11.44 mg/mL and 12.87 mg/mL. Conclusion: Propolis shows a potent antimicrobial effect against S. mutans and L. casei. This could provide a scientific basis to its application of usage in oral care products for the prevention of dental caries. However, further studies are necessary to evaluate other biological activities and molecular mechanisms of action as well as its cytotoxic effect.