Salivary microbiome of periodontitis-phenotype differs in Indian and Chinese cohorts

Abstract

Objectives: To determine salivary microbiome configurations and indicator taxa of a chronic periodontitis phenotype in cohorts from two different populations; Indian and Chinese. Methods: 51 Indian and 39 Hong Kong Chinese (HK) adults (30-65 years), under supportive dental care, were evaluated. Subjects had been treated for dental caries and periodontal disease, and categorised based on initial diagnosis of chronic periodontitis into 'healthy' or 'periodontitis' categories. DNA from unstimulated whole saliva was subjected to 16S rRNA (V3-V4 region) gene-amplicon Illumina-MiSeq sequencing. Sequence data were analysed using 'QIIME'. A bipartite network was constructed in 'CoNet' to discern associations of specific genera with phenotype variables (age, gender, periodontal category, percentage of residual sites with bleeding on probing) and alpha-diversity for each cohort. Indicator OTUs of periodontits phenotype in each cohort were determined using the R package ‘Indicspecies’. Results: Samples clustered robustly according to population, but no clustering according to periodontitis-phenotype was seen in unsupervised ordination (beta diversity) plots. Bipartite network analysis in each cohort however, revealed different genera linked to age, BOP, periodontits-phenotype and phylogenetic diversity measures. In HK, Paludibacter positively correlated to periodontits-phenotype and negatively to alpha-diversity. Unclassified Lachnospiraceae postively linked to age and periodontits. In Indians, BOP, age, and alpha-diversity positively correlated to unclassified Aerococcacea, TM7-3-1025; Rs-045, Parvimonas, Peptostreptococcus and Mycoplasma. Here, the periodontitis-phenotype negatively associated with Desulfobulbus, Burkholderia, S 24-7 (Bacteriodetes), which associated with higher alpha-diversity. 25 significant OTUs in HK subjects and 5 in Indians were significant periodontitis-phenotype indicators. An OTU representing Porphyromonas (oral taxon 279) was a single strongest indicator in Indians with a coverage of 100%. Conclusions: Salivary microbiome configuration, indicator genera of periodontitis-phenotype, and genera linked with demographic traits, microbial-diversity, and gingival inflammation, seem population-specific. These differed for Indian and Chinese cohorts with similar clinical characteristics.