Abstract / Summary
Background Airway microbiome composition in bronchiectasis extends beyond conventional microbiology, but its clinical implications remain unclear. Aim This study evaluated the airway bacteriome and mycobiome in bronchiectasis, examining their associations with clinical characteristics, inflammatory patterns and disease aetiology. Methods This study reports the pre-specified baseline cross-sectional analysis from a prospective multicentre cohort of 153 adults with non-CF bronchiectasis studied during clinical stability. Airway bacterial and fungal communities were characterised using 16S rRNA (V3–V4) and ITS2 sequencing. Samples were stratified by dominant bacterial genus, associations with clinical features, inflammatory biomarkers and aetiological subgroups were assessed. LEfSe was used as an exploratory method to identify bacterial genera with differential relative abundance across dominance groups. Results Pseudomonas -dominant bacteriomes showed the lowest α-diversity, and the strongest associations with disease severity, including poorer lung function, higher BSI scores and elevated sputum inflammatory markers. Haemophilus -dominant communities also correlated with reduced diversity and airway inflammation, although were associated with milder clinical severity compared with Pseudomonas . In contrast, Streptococcus -dominant bacteriomes demonstrated the highest bacterial diversity, enrichment of commensal genera, lower inflammatory marker levels and more favourable clinical features. The mycobiome also contributed to airway ecology: Ascomycota abundance correlated with higher bacterial diversity and lower inflammatory biomarker levels, whereas Basidiomycota dominance was associated with reduced diversity and a pro-inflammatory pattern. Distinct taxa were associated with specific aetiologies, including Rothia and Porphyromonas in immunodeficiencies and Staphylococcus in primary ciliary dyskinesia. Conclusion Airway microbiome dominance is associated with distinct clinical characteristics and inflammatory patterns in bronchiectasis. In a well-characterised multicentre cohort, integration of bacteriome and mycobiome data with inflammatory and remodelling markers provides external validation of previous observations and may contribute to a better characterisation of disease heterogeneity.