Stage‐Associated Subgingival Dysbiosis Across the Periodontal Disease Spectrum in a Thai Cohort

ABSTRACT Aims This cross‐sectional study aimed to investigate the subgingival microbiota and predict functional profiles across the 2018 EFP/AAP periodontal disease spectrum in a Thai clinical cohort. Materials and Methods Subgingival plaque from 100 participants (gingivitis, n = 30; Stage II–IV periodontitis, n = 70) was analysed by 16S rRNA gene sequencing with taxonomic assignment using the Human Oral Microbiome Database. Results Peptostreptococcaceae ‐related taxa, Dialister pneumosintes , Shuttleworthia satelles , Prevotella sp. HMT‐304, and Bacteroidetes G‐3 bacterium HMT‐280 were recurrently identified across differential abundance and penalised regression analyses. Penalised regression models showed limited stage‐discriminative performance (multinomial AUC 0.68–0.78), with gingivitis achieving the highest classification accuracy (63%) and Stage IV the lowest, consistent with overlapping microbial profiles across stages. Nonetheless, some stage‐enriched taxa included Campylobacter species in Stage III and Porphyromonas gingivalis with Odoribacter bacterium HMT‐516 in Stage IV. Stage‐enriched taxa correlated with anaerobic fermentation pathways, while co‐occurrence networks became less dense but broader across stages. Conclusion Stage‐associated microbiome shifts were detectable using a gingivitis reference group, with a disease‐associated core and accompanying anaerobic functional enrichment. The findings suggest that subgingival dysbiosis across periodontitis stages does not follow a simple linear trajectory and that clinical stage is not determined by microbiome composition alone.