Association between oral bacteria and respiratory health

<bold>Introduction:</bold> The oral microbiome may be associated with respiratory health, but knowledge of this association in populations is limited. <bold>Objectives:</bold> To explore the association between oral bacteria and asthma in a general population sample at three geographically different locations. We further investigated if the association differed by sensitisation status of the individual. <bold>Methods:</bold> Subgingival samples from 330 participants in Bergen (Norway), Melbourne (Australia) and Tartu (Estonia) underwent metagenomic sequencing as part of the third follow-up in the European Community Respiratory Health Study (ECRHS). Asthma status was derived from questionnaires, and sensitisation from allergen specific IgE/skin prick tests. The association between α diversity, the relative abundance of specific bacteria and asthma (never/ever/active) was evaluated using multinominal logistic modelling, adjusted for smoking and study centre. <bold>Results:</bold> Preliminary results show increased bacterial richness was associated with increased reports of active asthma (estimate 0.03, p-value <0.01). This association was only evident among non-sensitised (estimate 0.03, p-value <0.01 vs estimate 0.02, p-value 0.11). No association was found between α diversity and asthma ever. Relative abundance of two genera was found to be statistically significantly associated with asthma (ever/active), with opposing directions, <italic>Haemophilus</italic> (estimates -0.12/-0.09, p-values <0.01) and <italic>Prevotella</italic> (estimates 0.13/0.13, p-values <0.01). The association with the relative abundance of specific bacteria differed with sensitisation status. <bold>Conclusion:</bold> There were significant associations between oral bacteria and asthma across three geographical locations, modified by sensitisation status.