Antimicrobial activity of hop resins

The antimicrobial activity of hop resins against Streptococcus salivarius, Staphylococcus aureus (two strains), Bacillus megaterium, Escherichia coli B, and Bacillus subtilis was investigated. However, resistance development was carried out on Streptococcus salivarius, Staphylococcus aureus (two strains), and Bacillus megaterium. The two hop resins used were iso-alpha resin and beta resin. Prior to resistance development, S. salivarius, S. aureus, and B. megaterium were all inhibited by the iso-alpha-hop resin in the 0.01 to 0.03% range. The beta-hop resin which, according to the literature, is more active than the iso-alpha resin initially inhibited these organisms at the 0.003 to 0.01% concentrations. The ease of resistance development varied between the different microbes, B. megaterium being the least prone to develop resistance