Chronic Obstructive Pulmonary Disease and the Airway Microbiome: What Respirologists Need to Know

Abstract

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide. The lower airways contain a rich and diverse microbiome, which may play a significant regulatory role in both health and disease. In COPD, the microbiome becomes perturbed, causing dysbiosis. Increased representation of members in the Proteobacteria phylum and certain members in the Firmicutes phylum has been associated with increased risk of exacerbations and mortality. Therapies such as inhaled corticosteroids and azithromycin may modulate the airway microbiome or its metabolites in patients with COPD. This paper provides an up-to-date overview of the airway microbiome and its importance in the pathophysiology of COPD and as potential therapeutic target in the future.

Keywords: Airway Microbiome; Chronic Obstructive Pulmonary Disease; Dysbiosis; Sequencing.

Fig. 1.

An example of a taxonomic hierarchy of bacteria. The figure exemplifies a commonly used taxonomic hierarchical diagram for bacteria. With 16S sequencing, bacteria are identified to the level of genus. With metagenomics sequencing, species and occasionally strain identification is possible.

Fig. 2.

Bacterial composition at a phylum level of the microbiome in healthy persons. Members in Bacteroidetes, Firmicutes, and Proteobacteria phyla constitute the large majority of bacteria in the normal nasopharynx, oropharynx and the lower airways. In the nasopharynx, members in the Firmicutes phylum predominate, while in the oropharynx, members in the Bacteroidetes predominate, and in the lower airways, Bacteroidetes and Firmicutes predominate. The data are modified from Hilty et al [17].

Fig. 3.

Changes in the microbiome of chronic obstructive pulmonary disease (COPD) airways. In patients with COPD, the β-diversity of the lower airway changes with decreased representation of members in the Bacteroidetes phylum and increased representation of bacteria in the Firmicutes and Proteobacteria phyla. Increased representation of members in the Firmicutes or in particular Proteobacteria phylum in sputum has been associated with increased risk of mortality in patients with COPD [19]. Figure adapted from paper by Ramsheh et al [20].