The lung microbiome and exacerbations of COPD.

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Traditional culture methods have identified airway bacterial pathogens that cause acute exacerbations of chronic obstructive pulmonary disease (COPD), and contribute to airway inflammation and COPD progression. However, conventional microbiology is limited by low sensitivity and bias toward predetermined and predominant pathogens. Highly sensitive, unbiased microbiome techniques overcome these limitations. Here, we present recent lung microbiome data, specifically in the context of smoking, COPD, and exacerbations. In contrast to the sterile lung environment found with conventional microbiology, microbiome techniques demonstrate a lower respiratory tract microbiome in health. Alterations in the lung microbiome with smoking and COPD have been clearly demonstrated by culture techniques, however, the findings in microbiome studies are limited and controversial. Increasing COPD disease severity is associated with a reduction in microbial diversity. Though microbial community structure does not change with exacerbation, there are notable changes in its composition. Antibiotic and corticosteroid treatment of acute exacerbations of COPD have significant but opposing effects on microbiome composition. The composition of the lung microbiome changes with smoking, the severity of COPD, during acute exacerbations and with the use of steroids and/or antibiotics. Understanding the role of the microbiome in disease progression and development of exacerbations will lead to novel therapies.