Altered Schaedler Flora Effects on Dental Caries in SPFOM Rats

Objective: With the goal of reducing background caries scores, preserving high levels of disease induction upon inoculation with known cariogenic bacteria, and augmenting sensitivity for detection of virulence differences among bacterial strains we re-derived our rat colony. Re-derivation was by Caesarian delivery of neonates from existing specific pathogen free rats [TAN:SPFOM(OM)BR] and foster feeding by gnotobiotic rats harboring the “altered Schaedler flora” (ASF) gut microorganisms: 2 lactobacilli, 4 fusiforms, one spirochaete, and one bacteroid. The resultant re-derived colony was re-named TAN:SPFOM(OMASF)BR. We already reported on the microbial integrity of this colony and the effects of the ASF on oral establishment of various streptococci of interest in plaque formation/caries. Now we report on caries induction in this OMASF colony, and compare it with previous data gotten under the same experimental conditions using the [TAN:SPFOM(OM)BR] colony. Methods: We inoculated groups of weanling OMASF rats eating powdered high sucrose diet with S. mutans wild type (wt) strains 10449S, LT11, BM71, BM71's ptsI mutant DC10, or S. gordonii Challis wt CH1, and CH1's gtfG mutant AMS12. One group remained uninoculated. We did bacterial recoveries and scored lesions (Keyes' method) blindly. Results: Re-derivation and implantation of the ASF reduced background caries scores to levels of 30 years ago. Challenge inoculants colonized to high levels on the teeth, except for the ptsI mutant of S. mutans and the gtfG mutant of S. gordonii. All wild type S. mutans strains expressed high cariogenicity, and low cariogenicity of S. gordonii CH1 was now detected. Conclusion: The TAN:SPFOM(OMASF)BR colony allows experiments with very low background caries in un-inoculated or certain mutant-inoculated rats. This model also facilitates detection of subtle cariogenicity traits of bacteria like S. gordonii CH1, and preserves ability to detect high cariogenicity of S. mutans wild types. Supported by HCRAC-UCHC, NIH DE-96038, and MRC Canada MT-3546.