Characteristics of Subgingival Plaque Microbiome in Japanese Older Adults With Healthy Gingiva

To elucidate the characteristics of the subgingival plaque microbiome in older adults without gingival inflammation.

Subgingival plaque from 180 participants was collected and analysed using 16S rRNA sequencing. Based on the clinical parameters at the sampling sites, participants were categorised as healthy (gingival index [GI] = 0, maximum probing pocket depth [PPD_max] ≤ 2.0 and gingival recession [GR] = 0) or non-healthy (GI > 0, or PPD_max > 2.0 or GR > 0). Each group was further stratified by age into younger (< 65 years) and older (≥ 65 years) subgroups. We performed diversity and linear discriminant effect size (LEfSe) analyses to elucidate microbiome characteristics of healthy older adults.

We observed differences in α-diversity and β-diversity between younger and older individuals only in the healthy group. Healthy older individuals showed a lower α-diversity index, indicating a healthy-like profile shift and also a significantly greater difference in β-diversity from the non-healthy group than the healthy younger subgroup. LEfSe analysis indicated that six amplicon sequence variants (ASVs), such as Rothia dentocariosa , Neisseria perflava and Actinomyces sp. HMT-448, were predominant in the healthy older subgroup.

Maintaining lower α-diversity, with an abundance of R. dentocariosa and N. perflava, which are possible nitrate-reducing bacteria, may contribute to lifelong healthy gingiva by preventing microbial dysbiosis.