Inhibitory effects of alkyl‐galactosides on the coaggregation of Fusobacterium nucleatum and oral bacteria

Coaggregation and coadhesion are important mechanisms for oral bacteria to colonize the oral cavity and exert pathogenic effects. Fusobacterium nucleatum has been reported to coaggregate with various oral bacteria. Some of the coaggregation are inhibited by D‐galactose. D‐galactose, however, will be metabolized by oral bacteria when applied to the oral cavity, resulting in the acid generation that causes dental caries. In the present study, we developed a novel material, alkyl‐galactosides, that inhibits the coaggregation of F. nucleatum and is not metabolized by oral bacteria.Acid production from alkyl‐galactoside by Streptococcus mutans was determined by pH lowering during liquid culture. Antibacterial activity was measured using the minimum inhibitory concentration test, and coaggregation inhibitory effects were evaluated based on the relative coaggregation ratio between F. nucleatum and several oral bacteria using absorbance measurements.D‐galactose was rapidly metabolized by S. mutans, resulting in a decreased pH. Alkyl‐galactoside, however, was not metabolized by the bacterium at 1 mM. Minimum inhibitory concentration of alkyl‐galactoside against S. mutans is 1–4 mM. Alkyl‐galactoside inhibited coaggregation between F. nucleatum and several oral bacteria almost to the same extent as D‐galactose.Alkyl‐galactoside inhibits coaggregation between F. nucleatum and oral bacteria and is not assimilated by oral bacteria suggesting to be a potent novel material for prevention of dental plaque formation.