Studies of the mechanism of sucrose-associated colonization of Streptococcus mutans on teeth of conventional rats.

The mechanism of the colonization of S mutans strain 6715 on teeth in the presence of sucrose has been investigated using conventional Sprague-Dawley rats. Experiments were performed using rats fed diets with 56% sucrose or 56% glucose; oral inoculations with sucrose-grown, extracellular glucan-coated cells and glucose-grown, uncoated cells; and teeth treated with dextran 2000 via its incorportation in the diet, or teeth left untreated. In all instances, sucrose was required for satisfactory colonization of the test strain. Preformed extracellular glucan, whether associated with the bacterial cell or with the tooth surface, did not facilitate bacterial colonization when compared with cells or teeth devoid of extracellular glucan under the conditions used. The evidence suggests that glucan-mediated attachment of S mutans strain 6715 in the presence of sucrose involves an initial phase in which the cells are relatively weakly associated with the tooth surface and a subsequent phase during which firmer attachment occurs via new glucan synthesis.