Effects of Long-Chain Fatty Acids and Fatty Alcohols on the Growth of Streptococcus mutans

Minimal inhibitory concentrations (MICs) of a series of fatty acids and fatty alcohols against a cariogenic bacterium, Streptococcus mutans, were determined by a tube dilution technique. Among saturated fatty alcohols, tetradecanol and pentadecanol had the highest activity (MIC, 1.56μg/ml), while among monounsaturated fatty alcohols, 10Z-pentadecenol had the strongest activity (MIC, 0.78μg/ml). Saturated fatty acids showed relatively weak activity; tridecanoic acid had the highest activity among them (MIC, 12.5μg/ml). Among unsaturated fatty acids, 10Z-heptadecenoic 6Z-octadecenoic, 11Z-octadecenoic and 9Z,12Z-octadecadienoic acids had potent activity (MIC, 3.13 μg/ml). The antibacterial activities of methyl-branched and hydroxyl fatty acids as well as long chain dicarboxylic acids were also investigated.