Association of the salivary microbiome with asthma exacerbations

Abstract

Introduction: The human microbiome of different body sites is related to asthma exacerbations, which are the major contributor to the global asthma burden. However, no study so far has investigated the role of the salivary microbiome in asthma exacerbations. Aims and objectives: To study whether changes in the salivary microbiome are associated with asthma exacerbations. Methods: Saliva samples were collected from adults and children diagnosed with asthma (Global Initiative for Asthma) from the GEMAS study. Cases/controls were defined by the presence/absence of asthma exacerbations in the past 6 months (oral corticosteroids use). The microbiome composition and diversity were inferred by sequencing the V3-V4 region of the 16S ribosomal ribonucleic acid gene. Bioinformatic analyses were conducted using QIIME2 and R (phyloseq). Differences between groups were evaluated through logistic regression models and PERMANOVA, as appropriate, correcting for age, sex, and antibiotics use. Results: 239 patients were retained after quality control. Sequencing depth was normalized to 10,000 reads. Cases showed lower salivary microbiome richness (observed Operational Taxonomic Units) and diversity (Shannon and Faith indexes) in comparison with controls (p<0.04). Differences in the average bacterial composition (unweighted UniFrac distance) were observed between groups (p_PERMANOVA=0.002; p_PERMIDSP=0.412). The relative abundance of Rothia spp. was found to be increased in cases compared to controls (6.0% vs 4.9%, p=0.007). Conclusion: The development of asthma exacerbations in the past 6 months is associated with changes in diversity and composition of the salivary microbiome. Funding: Funded by SAF2017-83417R MINECO/AEI/FEDER, UE.