Abdel-Aziz MI, Brinkman P, Vijverberg SJH, et al. - Researchers investigated severe asthma phenotypes based on sputum microbiome profiles and examined their stability after 12 to 18 months. Further,they evaluated clusters’ robustness after inclusion of an independent cohort of patients with mild-to-moderate asthma. They conducted a longitudinal multicenter cohort study collecting sputum samples for microbiome profiling from a subset of the Unbiased Biomarkers in Prediction of Respiratory Disease Outcomes adult patient cohort at baseline and after 12 to 18 months of follow-up. For 100 individuals with severe asthma (median age 55 years; 42% males), data were available. Analysis revealed two microbiome-driven clusters, which were characterized by differences in asthma onset, smoking status, residential locations, percentage of blood and/or sputum neutrophils and macrophages, lung spirometry results, and concurrent asthma medications.  A commensal-deficient bacterial profile was detected in the cluster 2 patients that was associated with worse asthma outcomes than those of the cluster 1 patients. Longitudinal clusters revealed that those with severe asthma exhibit high relative stability after 12 to 18 months. Further inclusion of an independent cohort of 24 cases with mild-to-moderate asthma was consistent with the clustering assignments. This supports the value of the sputum microbiome as a biomarker for better characterizing asthma phenotypes.