Enzymatic reduction of the colonization of Streptococcus mutans in human dental plaque

Abstract

The aim of the present study was to evaluate the significance of water-insoluble glucans, containing mainly α-1,3 glucoside linkages, in the colonization of Streptococcus mutans on human teeth in vivo, and furthermore to assess the influence of α-1,3 glucan hydrolase on the accumulation of dental plaque. Five dental students with excellent oral hygiene participated in the investigation. The experiment was divided into two sections, each consisting of an initial two week period of oral hygiene, followed by one week of rinsing either with a sucrose solution or with a solution of sucrose containing α-1,3 glucan hydrolase, synthesized by a strain of Aspergillus nidulans. Oral hygiene was discontinued during rinsing. The amount of plaque was estimated at intervals during the whole experiment, and it was found that the accumulation of dental plaque was roughly identical during rinsing with solutions of sucrose and sucrose containing enzyme, substantiating the expectation that numerous microorganisms colonize the teeth by mechanisms other than synthesis of α-1,3 glucan. However, after each rinsing period the dental plaque was examined bacteriologically, and the proportions of selected streptococcal species were calculated. This revealed that in all five subjects the proportion of Strep mutans was lower after rinsing with the sucrose solution containing enzyme than after rinsing with sucrose only, the average being less than 2.2% compared to 10.4%. Based on this finding it may be concluded that Strep mutans, at least in part, depends on glucans with mainly α-1,3 glucoside linkages for its colonization of the teeth in humans.