BILE ACIDS IN LOWER AIRWAYS AS A NOVEL INDICATOR OF AIRWAY MICROBIOTA CHANGES IN CHRONIC OBSTRUCTIVE PULMONARY DISEASE

Background Chronic obstructive pulmonary disease (COPD) is a complex disorder with a high degree of interindividual variability. Gastrointestinal dysfunction is common in COPD patients and has been proposed to influence the clinical progression of the disease. Using the presence of bile acid(s) (BA) in bronchoalveolar lavage fluid (BAL) as a marker of gastric aspiration, we evaluated the relationships between BAs, clinical outcomes, and bacterial lung colonisation. Methods We used BAL specimens from a cohort of COPD patients and healthy controls. Bile acids were profiled and quantified in BAL supernatants using mass spectrometry. Microbial DNA was extracted from BAL cell pellets and quantified using qPCR. We profiled the BAL microbiota using an amplicon sequencing approach targeting the V3-V4 region of the 16S rRNA gene. Results Detection of BAs in BAL was more likely at earliest clinical stages of COPD and was independent of the degree of airway obstruction. BAL specimens with BAs demonstrated higher bacterial biomass and lower diversity. Likewise, the odds of recovering bacterial cultures from BAL were higher if BAs were also detected. Detection of BAs in BAL was not associated with either inflammatory markers or clinical outcomes. We also observed different bacterial community types in BAL, which were associated with different clinical groups, levels of inflammatory markers, and the degree of airway obstruction. Conclusion Detection of BAs in BAL was associated with different parameters of airway ecology. Further studies are needed to evaluate whether BAs in BAL can be used to stratify patients and for predicting disease progression trajectories.