Porphyromonas gingivalis and Treponema denticola induced Mixed microbial Periodontal Disease

Periodontal diseases are complex, multifactorial, polymicrobial immunoinflammatory infections. A prominent pathogenic consortium in subgingval biofilms in human periodontitis includes Porphyromonas gingivalis (Pg), Treponema denticola (Td), and Tannerella forsythia (Tf). Objective: This study was designed to evaluate and compare monobacterial and mixed-microbial periodontal disease in rats using P. gingivalis and T. denticola. Methods: Adult rats were infected with Pg 381 and Td ATCC 35404 at 1 x 10¹⁰ mixed with 2% carboxymethylcellulose. Infections were induced either as monobacterial (Pg, Td) or mixed-microbial (Pg+Td). Oral bacterial samples were collected and colonization/infection assessed by PCR. Rats were sacrificed at 6 and 12 weeks after infection. Serum IgG and IgM antibody responses to the mono- or mixed microbial infections are being evaluated by ELISA. The jaws were removed, prepared for histology (routine microscopic examination, immunohistochemistry), and histomorphometry (Osteoclast-TRAP staining). Defleshed rat jaws were also evaluated for morphometric (horizontal bone resorption) and digital radiographic (vertical bone resorption) analysis of alveolar bone resorption (ABR). Results: PCR detected P. gingivalis amplicons in nearly all animals throughout the experimental interval whereas T. denticola amplicons was detectable in fewer animals. Preliminary histomorphologic examination reveals mild to moderate chronic gingival inflammation in infected animals with slight increase in subepithelial vasculature and mild hyperplasia of the non-keratinized crevicular epithelium. Statistical analysis of histologic findings, histomorphometry, antibody titers and ABR measurements are in progress. Conclusions: This is the first study of an animal model using P. gingivalis and T. denticola as mixed microbial infectious agents in the induction of periodontal disease in rats. Supported by U24 DE016509 from the NIH, NIDCR.