The inhibitory action of fatty acids on oral bacteria

Saturated and unsaturated fatty acids and fatty acid derivatives were examined for their growth-inhibitory effects towards three selected oral bacteria: Porphyromonas gingivalis, Selenomonas artemidis, and Streptococcus sobrinus. Of the 45 compounds surveyed, only one, myristoleic acid, was inhibitory towards S. artemidis at a concentration < 100 micrograms/ml. cis-Hexadecenoic and cis-octadecenoic acids were generally inhibitory towards P. gingivalis and S. sobrinus, but there was no correlation between the position of the double bond and the minimum inhibitory concentration. Supra-minimum inhibitory concentrations of palmitoleic acid did not promote leakage of intracellular materials from either P. gingivalis or S. sobrinus, nor was L-isoleucine uptake by S. sobrinus inhibited. Fatty acids and derivatives were also examined for prospective synergistic or antagonistic interactions with thymol vis-à-vis growth inhibition of the test strains. Lauric acid and myristic acid each behaved synergistically with thymol to inhibit the growth of at least one test strain, whereas cis-10-heptadecenoic acid and thymol were noticeably antagonistic towards the growth of S. sobrinus.