No abstract

The colonization of S. mutans serotypes on different tooth surfaces of the rat was investigated. Fissures appeared to be the main habitat. In the presence of a serotype c strain, S. mutans serotype d could only be established when sucrose-containing diets were supplied. However, the serotype c strain was always present in higher proportions. The production of a bacteriocin for which the serotype d strain was sensitive appeared to be responsible for the observed predominance of the serotype c strain.

Summary-Five successive experiments, with rats fed ad libitum on diets containing sucrose or Lycasin" 80/55, were carried out. In experiment I, the rats were inoculated with Streptococcus mutans alone or with Strep. mutans in combination with Actinomyces uiscosus. In three successive transmission experiments (II, III, IV), the rats were inoculated with plaque of the rats of the preceding experiment. The rats of experiment V were inoculated with the original strains or with plaque derived from experiment IV. After five successive transmissions of the plaque flora, no alterations were demonstrated in the numbers and percentages of Strep. mutans and A. uiscosus or in the fermentation rate of Lycasin by the plaque flora in vitro. Lycasin@ 80/55 was virtually non-cariogenic compared with sucrose @ < 0.001) irrespective of whether the rats were inoculated with Strep. murans alone or in combination with A. uiscosus, with the original strains or with plaque from the preceding experiments with rats on a Lycasina 80/55_containing