Antimicrobial activity of herbal products against dental biofilm forming bacteria

Objective: To evaluate, in vitro, the antimicrobial effect of pollen and alcoholic and aqueous propolis extracts in their pure and diluted forms against reference strains Streptococcus mutans ATCC 25175, Streptococcus salivarius ATCC 7073, Streptococcus mitis ATCC 903 and Lactobacillus casei ATCC 9595, by determination of Maximum Inhibitory Dilution (MID). Methods: Chlorhexidine was used as a positive control and distilled water and 70% grain alcohol as negative controls. The alcoholic and aqueous propolis extracts were subjected to dilutions from 1:1 to 1:64 in 70% alcohol and distilled water, respectively. For being an apolar substance, pollen was diluted in alcohol at the concentrations of 5% (amount present in the chemical composition of propolis) and 50%. Each bacterial strain was reactivated in Brain Heart Infusion (BHI) broth and seeded onto plates with swabs, and the susceptibility tests were performed in duplicate by the agar diffusion method using the agar well technique. Next, the plates were incubated at 37øC in microaerophilia during 48 hours. Results: All dilutions of alcoholic propolis extract inhibited the bacterial growth while the aqueous propolis extract showed less efficient results, being effective only against S. mitis in its pure form and in the 1:1 to 1:4 dilutions. Pollen at 5% was efficient against all bacteria, but pollen at 5% had action only against S. mitis. The negative controls did not present antimicrobial activity. Conclusion: The antimicrobial activity of propolis and pollen against the reference strains was higher than that of placebo but lower than that of chlorhexidine.