Antibacterial effects of Listerine on oral bacteria.

To evaluate the efficacy of Listerine, a solution for washing the oral cavity consisting of essential oils (thymol, methanol, eukalyptol) and methyl salicylate, minimum concentrations inhibiting the growth of various microorganisms in the oral cavity and the bactericidal effects on bacteria in the saliva and dental plaque were evaluated in vitro. Listerine inhibited the growth of microorganisms over a very broad range. The minimum concentration inhibiting growth of Listerine was a 4 to 32 fold dilution, 2-4 times as potent as the solution after elimination of active ingredient components, in 38 of 54 bacterial strains, indicating the efficacy of the active ingredient in the inhibition of the growth of microorganisms. Bactericidal action of Listerine against from bacteria isolated from saliva and dental plaque from 5 healthy normal subjects was tested. Listerine exhibited a potent bactericidal effect on bacteria in saliva and dental plaque. Most of the bacteria died after a 30 second exposure to Listerine. According to these results, Listerine appears to be effective as a solution used for cleansing the oral cavity and dentures.