Oral implantation of human strains of Streptococcus mutans in rats fed sucrose or glucose diets

Abstract

Conventional rats fed high sucrose or glucose diets were compared with respect to the establishment of Streptococcus mutans on their teeth. The minimum cell dose required for infection and the cell populations attained were determined. A number of streptomycinlabelled strains of human and animal origin belonging to different serogroups were tested. Groups of rats were inoculated once with decreasing cell numbers of each strain obtained via serial 10-fold dilution. For bacterial enumeration, rats were killed 5 weeks after inoculation; all molar teeth were extracted and ground in tissue grinders and suspensions were cultured on streptomycin-containing mitis-salivarius agar. The minimum infective dose for rats fed the two diets was comparable in all but one of the strains; the cell populations on the teeth of rats fed sucrose diet were generally higher than those on the teeth of rats fed a glucose diet. The findings support the concept that in man infection of the teeth by Strep. mutans can be initiated and sustained in the absence of sucrose.