Role of oral bacteria composition and functional gene profiles in respiratory diseases.

INTRODUCTION

The oral microbiome has been shown to be associated with respiratory health, primarily in adult case studies or among children. This relationship has been scarcely investigated in adult population-based cohorts.

OBJECTIVES

To investigate the association between oral microbiome and respiratory health, more specifically asthma, chronic rhinosinusitis (CRS), lung function and fractional exhaled nitric oxide (FeNO) in a population-based cross-continental multicentre study among adults.

METHODS

Subgingival samples from 355 adult European Community Respiratory Health Survey participants from Norway, Australia and Estonia underwent metagenomic sequencing. Respiratory disease was defined from questionnaires and sensitisation from specific immunoglobulin E (IgE)/skin prick tests. Spirometry and FeNO were measured. The associations between alpha diversity and disease status were evaluated in cross-sectional analyses using logistic regression adjusting for sex, smoking and study centre. Differential abundance analyses were performed using analysis of compositions of microbiomes with bias correction.

RESULTS

Alpha diversity differed by study centre and sensitisation status and was associated with non-allergic CRS (richness: 1.12, 95% CI 1.03 to 1.22). A similar though not statistically significant pattern was seen for forced vital capacity (FVC) below the lower limit of normal (LLN). Lachnospiraceae and Xanthomonas were more abundant in the oral microbiome of non-asthmatics and individuals without CRS, respectively, as compared with asthmatics and CRS patients. Several functional genes (1477-3391) and genera (54-98) were only present in the non-case groups, whereas individuals with affected respiratory health had 0-74 unique functional genes, but no unique genera present only in their respective groups.

CONCLUSION

Increased alpha diversity was associated with non-allergic CRS and a similar trend was seen for FVC below LLN. Bacterial composition and functional profiles of the oral microbiome differed by respiratory health status. This study is novel in exploring functional gene profiling in relation to asthma and FeNO.