Characterisation of the gut-lung axis microbiome in clinically stable patients with chronic obstructive pulmonary disease.

The microbiome in airway and stool samples was highly dissimilar both in patients with COPD and controls, with only 0.37% of microbial diversity associated with COPD.

• Prospective, multicentre, longitudinal and controlled study design
• Sample included n=60 stable COPD patients and n=30 controls
• 16S rRNA sequencing was performed on oropharyngeal swabs, sputum, bronchoalveolar lavage fluid (BALF), and stool
• Only 0.37% of microbial diversity was associated with COPD status across sample types

The microbiome taxa associated with COPD in oropharyngeal swabs and sputum were highly similar to each other but different from BALF, suggesting oropharyngeal swabs can serve as a surrogate sample for sputum.

• Comparison was made across four sample types: oropharyngeal swabs, sputum, BALF, and stool
• Taxa profiles in OP swabs and sputum showed high similarity in COPD-associated bacteria
• BALF showed a distinct microbial profile compared to upper airway samples
• The authors conclude that OP swabs can be 'a surrogate sample of sputum'

Weighted gene co-expression network analysis (WGCNA) identified modules of co-abundant bacteria in oropharyngeal swabs and sputum associated with FEV1 as well as exacerbations, dyspnoea, and inhaled corticosteroid use.

• 5 modules in oropharyngeal swabs were associated with FEV1
• 3 modules in sputum were associated with FEV1
• Some modules in both OP swabs and sputum were also associated with exacerbations, dyspnoea, and inhaled steroid (ICS) use
• WGCNA was employed in each sample type to identify modules of co-abundant bacteria associated with clinical traits

WGCNA identified modules of co-abundant bacteria in BALF associated with FEV1, dyspnoea, and inhaled corticosteroid use.

• 4 modules in BALF were associated with FEV1 and dyspnoea
• 2 modules in BALF were associated with inhaled corticosteroid (ICS) use
• BALF microbiome was distinct from upper airway microbiome in terms of COPD-associated taxa

WGCNA identified modules of co-abundant bacteria in stool associated with FEV1, exacerbation history, and inhaled corticosteroid use.

• 1 stool module was related to FEV1
• 1 stool module was related to exacerbations
• 3 stool modules were associated with ICS use
• These findings indicate the gut microbiome is clinically relevant in COPD despite being distinct from the lung microbiome

Both the gut and lung microbiomes in patients with COPD are clinically relevant, presenting bacterial associations with airflow limitation, exacerbation history, and inhaled corticosteroid use.

• Airflow limitation (FEV1) was associated with bacterial modules in all four sample types
• Exacerbation history was associated with bacterial modules in OP swabs, sputum, and stool
• ICS use was associated with bacterial modules across all four sample types (OP swabs, sputum, BALF, stool)
• The gut and lung microbiomes were distinct from each other but each independently showed clinical associations