American Journal of Respiratory and Critical Care Medicine

Rationale: Although inflammation and infection are key disease drivers in bronchiectasis, few studies have integrated host inflammatory and microbiome data to guide precision medicine.

Objectives: To identify clusters among patients with bronchiectasis on the basis of inflammatory markers and to assess the association between inflammatory endotypes, microbiome characteristics, and exacerbation risk.

Methods: Patients with stable bronchiectasis were enrolled at three European centers, and cluster analysis was used to stratify the patients according to the levels of 33 sputum and serum inflammatory markers. Clusters were compared in terms of microbiome composition (16S ribosomal RNA sequencing) and exacerbation risk over a 12-month follow-up.

Measurements and Main Results: A total of 199 patients were enrolled (109 [54.8%] female; median age, 69 yr). Four clusters of patients were defined according to their inflammatory profiles: cluster 1, milder neutrophilic inflammation; cluster 2, mixed-neutrophilic and type 2; cluster 3, most severe neutrophilic; and cluster 4, mixed-epithelial and type 2. Lower microbiome diversity was associated with more severe inflammatory clusters (P < 0.001), and β-diversity analysis demonstrated distinct microbiome profiles associated with each inflammatory cluster (P = 0.001). Proteobacteria and Pseudomonas at phylum and genus levels, respectively, were more enriched in clusters 2 and 3 than in clusters 1 and 4. Furthermore, patients in cluster 2 (rate ratio [RR], 1.49; 95% confidence interval [CI], 1.16–1.92) and cluster 3 (RR, 1.61; 95% CI, 1.12–2.32) were at higher risk of exacerbation over a 12-month follow-up compared with cluster 1, even after adjustment for prior exacerbation history.

Conclusions: Bronchiectasis inflammatory endotypes are associated with distinct microbiome profiles and future exacerbation risk.

Correspondence and requests for reprints should be addressed to James D. Chalmers, M.B. Ch.B., Ph.D., Division of Molecular and Clinical Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK. E-mail: .

Supported by the European Respiratory Society through the European Multicentre Bronchiectasis Audit and Research Collaboration 3 (EMBARC3) consortium. EMBARC3 is supported by project partners Armata, AstraZeneca, Boehringer Ingelheim, Chiesi, CSL Behring, Grifols, Insmed, Janssen, Lifearc, and Zambon. J.D.C. is supported by the Asthma and Lung UK Chair of Respiratory Research.

Author Contributions: Study conception and design: H.C., F.B., M.S., S.A., O.S., A.S., and J.D.C. Data collection: H.R.K., Y.H.G., L.P., H.R., E.C., J.P., S.F., S.A., O.S., A.S., and J.D.C. Laboratory work: H.R.K., Y.H.G., L.P., H.R., E.C., J.P., S.F., S.A., O.S., A.S., and J.D.C. Data analysis: H.C., S.R., A.J.D., J.T.J.H., S.A., O.S., A.S., and J.D.C. Writing of the manuscript: H.C. and J.D.C. Critical revision for important intellectual content and final approval: all authors.

This article has a related editorial.

This article has an online supplement, which is accessible from this issue’s table of contents at

Originally Published in Press as DOI: 10.1164/rccm.202303-0499OC on September 28, 2023

Author disclosures are available with the text of this article at

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American Journal of Respiratory and Critical Care Medicine

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