Abstract
AIM: This study aimed to explore the composition of the tooth-surface plaque (subgingival with marginal supragingival) microbiome in dentate older adults residing in long-term care (LTC) facilities, stratified by clinically assessed oral disease burden (ODB). A total of 196 LTC residents aged ≥62 years underwent oral examinations and microbial sampling from each dentate quadrant. Microbial profiling was performed using 16S rRNA gene sequencing. RESULTS: Participants were more frequently categorized into Moderate (n = 95, 48%) than Low (n = 32, 16%) or High (n = 69, 35%) ODB groups. Those with High ODB were oldest and had lowest number of remaining teeth. Alpha diversity did not differ between the ODB groups, whereas beta diversity analysis revealed significant differences between groups (Bray-Curtis: P = 0.005; weighted Unifrac: P = 0.025). The Low and Moderate ODB groups were enriched with both commensals and disease-associated genera, such as Ottowia, Lactococcus, Pseudoramibacter, and Anaeroglobus. High ODB group exhibited an increased abundance of genera linked to both oral and systemic diseases, including Cardiobacterium, Leptotrichia, Stomatobaculum, and Pseudopropionibacterium. Among ODB groups, periodontitis was a stronger determinant of oral microbiome composition than caries, whereas caries had a stronger effect on bacterial diversity. CONCLUSION: These findings indicate a progressive shift toward a dysbiotic oral microbiome with increasing ODB.