Microbiome characterization in patients with bronchiectasis and its association with severity and bronchial inflammation. Bronchi-Omics Project

<b>Aims:</b> Characterize the microbiome (MB) in patients with non-cystic fibrosis bronchiectasis (BE) and its correlation with relevant clinical variables, bronchial and systemic inflammation. <b>Methods:</b> Observational, prospective, multicentre study involving 9 university hospitals. Clinical data, sputum and blood samples have been collected in stability. Bacterial and fungal MB has been determined by amplification and sequencing of 16S rRNA and&nbsp;Internal Transcribed Spacer (ITS). Bronchial inflammatory markers have been analysed by ELISA. Systemic inflammation was measured by C-reactive protein (CPR). <b>Results:</b> The analysis of the basal MB has detected 14 phyla dominated by Firmicutes and Proteobacteria, and 149 genera, dominated by <i>Streptococcus</i>, <i>Haemophilus</i> and <i>Pseudomonas</i>.&nbsp;Diversity loss is significantly associated with BE severity (p=0.002), airflow obstruction (p&lt;0.001), severe exacerbations (p=0.022), and sputum production (p=0.0003). However, no significant differences have been observed in this microbial diversity depending on the various BE aetiologies. Regarding the presence of dominant genera, the dominance of <i>Haemophilus</i> genera is associated with an increase in inflammatory interleukins in sputum, as well as an increase in systemic inflammation measured by CPR, which, however, is not related to variables of severity of the disease.&nbsp;Though, the dominance of the <i>Pseudomonas</i> genera&nbsp;is associated with&nbsp;increased levels of neutrophil elastase,&nbsp;and greater&nbsp;severity of BE. <b>Conclusions:</b> The characteristics of the respiratory MB in BE are significantly correlated with clinical markers of disease severity and with bronchial and systemic inflammation.