Method:
We initially established genetically identical germ free (GF) and Specific Pathogen Free (SPF) mouse colonies and characterised the oral microbiota of the SPF animals. Periodontal disease was induced by oral gavage of mice at age 10weeks with Porphyromonas gingivalis W50 on days 1, 3 and 5 followed by bone loss determinations on day 42. Bacterial samples were collected using oral swabs and bacterial identification was performed by 16s rDNA sequencing and MALDI-TOF mass spectrometry. P. gingivalis colonisation was assessed by anaerobic culture, PCR and immunofluorescence microscopy using a P. gingivalis-specific monoclonal antibody. Alveolar bone levels were assessed by a morphometric technique.
Result: Bone levels were lower in SPF mice compared to GF at baseline in 10week old animals. P. gingivalis was able to colonise both SPF and GF animals but only at low levels. Inoculation of SPF animals with P gingivalis led to quantitative and qualitative shifts in the normal oral flora. This was associated with significantly increased levels of periodontal bone loss. Conversely, GF animals inoculated with P gingivalis showed no significant difference in bone levels compared to ‘sham’ inoculated GF controls.
Conclusion: The commensal microbiota can induce periodontal bone loss in this mouse model. Inoculation with P gingivalis alters the nature and abundance of this commensal microbiota and leads to increased periodontal bone loss. An intact commensal flora is needed for this process.