Mayhew D, et al. - Alterations in the composition of the lung microbiome associated with adverse clinical outcomes, known as dysbiosis, have been implicated with disease severity and exacerbations in COPD. Herein, longitudinal changes in the lung microbiome in the AERIS study (Acute Exacerbation and Respiratory InfectionS in COPD), as well as their link with associated COPD outcomes, were examined. Over time, distinct bacterial compositions and stabilities were noted in subtypes of COPD. Some exacerbation subtypes had non-random probabilities of repeating those subtypes in the future. Also, the association of bacterial genera, including Haemophilus and Moraxella, with disease severity, exacerbation events and bronchiectasis was also confirmed. Findings are informative regarding the identification of bacterial targets in the lung and biomarkers to classify COPD subtypes and to determine appropriate treatments for the patient.