Sputum microbiome and clinical profiles in Portuguese non-cystic fibrosis bronchiectasis patients

BACKGROUND: The global prevalence of bronchiectasis (BC) has been rising. This study aimed to characterise the sputum microbiome and correlate the microbiome with clinical data obtained from clinically stable Portuguese patients with BC. METHODS: Non-cystic fibrosis BC patients were enrolled. A single spontaneous sputum sample was collected and analysed by 16S rRNA gene sequencing. Taxonomic composition, α-diversity (Shannon index), and β-diversity (Bray-Curtis) were analysed and correlated with clinical, functional, and radiological variables. RESULTS: Fifty-eight patients (median age 58 years) were included. The sputum microbiome showed marked inter-patient variability and could be stratified into distinct subtypes dominated by Haemophilus (24%), Streptococcus (24%), Pseudomonas (14%), and an emergent Rothia/Streptococcus subtype (10%). Haemophilus and Pseudomonas subtypes displayed opposite clinical patterns, with Pseudomonas associated with more severe disease as shown by lower forced expiratory volume in 1 s (FEV1), higher bronchiectasis severity index (BSI), and diffuse radiological changes. α-diversity was significantly lower in BC patients with changes in the left lower lobe (LLL) and associated with extreme serum IgA values, while β-diversity showed significant associations with bronchiectasis severity index, body mass index, and LLL involvement. No association between α- or β-diversities and lung function was found. CONCLUSIONS: This first characterisation of the sputum microbiome in Portuguese BC patients revealed marked heterogeneity and distinct microbial subtypes associated with disease severity and radiological patterns. These results highlight the potential influence of host-microbiome interactions and anatomical factors in shaping BC phenotypes. Larger and longitudinal studies are warranted to confirm the subtype temporal stability.