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 β-acid concentrations on Streptococcus mutans biofilm formation. Methods and Results Ten different hop extracts, with α-acid concentrations similar to those found in commercial beer products and β-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 α- and β-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 are warranted to determine an effect in vivo on the development of dental caries.