Inhibitory effects of quaternary ammonium salts on water-insoluble glucan synthesis by cariogenic bacterium

Abstract

The effects of domiphen bromide (DB) and dequalinium chloride (DC), in comparison with cetylpyridinium chloride (CPC), on water-insoluble glucan (WIG) synthesis by glucosyltransferases (GTase) purified from S. sobrinu 6715 or S. mutans MT6R were determined. The morphological effects of the three drugs on WIG were observed under scanning and transmission electron microscopes. The production of total WIG (sum of adherent and nonadherent WIG) by strain 6715 GTase decreased by increasing the concentration of all three drugs. The decrease in adherent WIG was prominent as compared with that in nonadherent WIG. The inhibitory effects of the three drugs on WIG synthesis were in the following order: CPC≥DC>DB. On the other hand, the production of total WIG by strain MT6R GTase was decreased by all three drugs in a concentration-dependent manner. Almost complete inhibition of adherent WIG production was achieved by the three drugs even at low concentrations. The inhibitory effects of the three drugs on WIG synthesis were in the follwing order: DC>CPC≥DB. These results indicate that DC and DB have an inhibitory action on GTase of serotype c strain, the same as CPC does. Electron microscopic experiments showed that networks and clumps of WIG were decreased by all three drugs. From these results, DC and DB are expected to be used for prevention of dental caries as rinsing agents.