Effect of Human Streptococcus Strain GS-5 on Caries and Alveolar Bone Loss in Conventional Mice and Rats

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Abstract
Streptococcal strain GS 5 was shown to be cariogenic and alveolar bone destructive in gnotobiotic rats. The purpose of this investigation was to determine the extent of establishment of this organism in the mouths of conventional CD mice and rats and whether the implanted organisms would accelerate alveolar bone loss. Human strain GS 5 was made resistant to 1 mg/ml of streptomycin. Twenty weanling mice and 21 weanling rats were maintained for 20 days on diet 585 to which 0.05% penicillin was added. Thereafter animals were maintained on the same diet without penicillin for 86 days. Streptomycin resistant strain GS 5 was swabbed intraorally in the mouths of 10 mice and 10 rats once a day for 5 successive days immediately after the animals were removed from the penicillin diet. Test swabs for establishment of organisms were taken 2, 42, and 80 days after the last inoculation. Organisms were established in the mouths of rats but not in the mice. The percentage of GS 5 in the total microbiota 80 days after inoculation varied from 1 to 41%. On the 81st days after final inoculation, the animals were sacrified and the jaws prepared for gross and histologic examination. None of the mice developed caries. Four of the 10 rats harboring the human streptococcus developed caries. None of the 11 control animals developed caries. Alveolar bone loss was scored on half jaws by method of Gupta and Shaw (1956). The mean was found to be 45.1 in the control mice versus 48.4 in the inoculated animals. This difference was not significant. However, the streptococcus inoculated rats developed significantly more alveolar bone loss (mean score 65.8) than uninoculated controls (mean score 42.6).