Descriptive, Exploratory Analysis of Microbial Community Composition Across Stages of Canine Periodontal Disease Revealed by 16S rRNA Sequencing in Dogs

Periodontal disease (PD) is one of the most prevalent oral conditions in dogs, yet the microbial dynamics underlying its progression remain incompletely understood. This exploratory study aimed to describe the canine oral microbiome across four clinical stages using 16S rRNA gene sequencing. Dogs were categorized as Healthy (Stage 0), Gingivitis (Stage 1), Early Periodontitis (Stage 2), and Moderate–Advanced Periodontitis (Stages 3–4) according to American Veterinary Dental College (AVDC) criteria. Pooled subgingival plaque samples from the groups were analyzed for microbial diversity, taxonomic composition, and ecological patterns. Alpha diversity differed among the four pooled profiles, with the highest observed richness in the Early Periodontitis (Stage 2) pool and the lowest in the Moderate–Advanced Periodontitis (Stages 3–4) pool. Beta diversity analyses showed separation among the pooled profiles, particularly between the healthy and severe groups. Taxonomic profiling identified higher relative abundances of sequences assigned to Porphyromonas gingivalis and Treponema denticola in the more advanced disease stage pools, while Fusobacterium nucleatum reached its highest relative abundance in the Early Periodontitis (Stage 2) pool. Visualization of abundance profiles across the four pooled libraries revealed concordant trends among selected treponeme taxa and Fusobacterium nucleatum, as well as inverse trends for other taxa. These findings provide a descriptive, group-level characterization of microbial community differences across AVDC-defined stages of canine periodontal disease based on pooled samples and generate hypotheses for future individual-level studies.