Evaluating hop extract concentrations found in commercial beer to inhibit Streptococcus mutans biofilm formation

Aims: The purpose of this study was to compare the effect of hop extracts with diverse beta-acid concentrations on Streptococcus mutans biofilm formation. Methods and Results: Ten different hop extracts, with a-acid concentrations similar to those found in commercial beer products and beta-acid concentrations ranging from 2.6 to 8.1%, were added to distilled water to make standardized concentrations. S. mutans isolates were treated with hop extract dilutions varying from 1:2 to 1:256. The minimum inhibitory, minimum bactericidal and minimum biofilm inhibitory concentrations were determined and the optical density was evaluated. Live/dead staining confirmed the bactericidal effects. Biofilm formation of several strains of S. mutans was significantly inhibited by hop extract dilutions of 1:2, 1:4, 1:8, 1:16 and 1:32. Strong negative correlations were observed between alpha- and beta-acid concentrations of the hop extracts and S. mutans total growth and biofilm formation. Conclusions: The use of hop extracts prepared similarly to commercial beer decreased S. mutans biofilm formation. Significance and Impact of the Study: The inclusion of hops in the commercial beer products may provide beneficial health effects. Further studies arc warranted to determine an effect in vivo on the development of dental caries.