Longitudinal impact of oral bacteria and endotoxin on lung function.

Chronic respiratory diseases are on the rise globally, and growing evidence shows that lungs whether healthy or diseased harbor bacterial communities that primarily originate from the oral cavity. Despite this, longitudinal studies examining how oral bacteria influence respiratory health trajectories in the general population are lacking. This study aimed to explore the influence of oral bacteria on lung function (LF) outcomes measured 6 years later in a community-based Norwegian population. Analyses included measurements of endotoxin load and lipid A profiling to assess the inflammatory potential of oral bacterial communities. Saliva samples and spirometry data were collected from 75 participants in the RHINESSA study (Bergen, Norway) at baseline (2014-2015). Spirometry was repeated at follow-up (2020-2021). Bacterial community composition and endotoxin lipid A profiling were determined by targeted sequencing of the 16S rRNA gene (V3-V4 region). Associations between baseline salivary microbiota and lung function at follow-up were assessed using multivariate linear regression. The relative abundance of Selenomonas, Mogibacterium, Tannerella, and Prevotella was positively associated with both forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC), while Kingella, and Anaerococcus showed negative associations. Endotoxin load was positively associated with FEV1 and FVC. A negative association was observed between the proinflammatory hexa-acylated lipid A variant and LF outcomes, whereas a positive association was found for the penta-acylated lipid A variant. Salivary bacterial community characteristics were associated with LF outcomes measured 6 years later. Our findings suggest that the oral microbiota may represent a potential target for disease prevention or intervention strategies, warranting further investigation.