Characteristics of subgingival plaque microbiome in Japanese older adults with healthy gingiva

[Aim]In this study, we aimed to elucidate the characteristics of the subgingival plaque microbiome in older population without gingival inflammation.[Materials and Methods]Subgingival plaque from 180 participants was collected and analyzed using 16S rRNA sequencing. Based on the clinical parameters at the sampling sites, participants were categorized as Healthy (gingival index (GI) = 0, maximum probing pocket depth (PPDmax) 0, or PPDmax > 2.0 or GR > 0). Each group was further stratified by age into younger (= 65 years) subgroups. We performed diversity and linear discriminant analysis effect size (LEfSe) analyses to elucidate the microbiome characteristics of the Healthy-older adults.[Results]We observed differences in alpha-diversity and beta-diversity between younger and older individuals in the Healthy only. The Healthy-older individuals demonstrated a lower alpha-diversity index, indicating healthy-like profile shift, and showed a significantly greater difference in beta-diversity from the Non-Healthy than the Healthy-younger. LEfSe analysis indicated that 5 ASVs such as Rothia dentocariosa, Neisseria perflava, and Actinomyces sp. HMT-169 were predominant in the Healthy-older.[Conclusion]Maintaining lower alpha-diversity, with an abundant level of Rothia dentocariosa and Neisseria perflava, which are possible nitrate-reducing bacteria, may contribute to lifelong healthy gingiva by preventing microbial dysbiosis.