Effect of bronchial colonisation on airway and systemic inflammation in stable COPD

The recovery of potentially pathogenic microorganisms (PPMs) from bronchial secretions is associated with a local inflammatory response in COPD patients. The objective of this study was to determine the relationships between bronchial colonisation and both bronchial and systemic inflammation in stable COPD. In COPD patients recruited on first admission for an exacerbation, bacterial sputum cultures, interleukin (IL)-1β, IL-6 and IL-8 levels, and blood C-reactive protein (CRP) were measured in stable condition. Bronchial colonisation was found in 39 of the 133 (29%) patients and was significantly related to higher sputum IL-1β (median [percentile 25-75]; 462 [121-993] vs. 154 [41-477] pg/ml, p = 0.002), IL-6 (147 [71-424] vs. 109 [50-197] pg/ml, p = 0.047) and IL-8 values (15 [9-19] vs. 8 [3-15] (×10³) pg/ml, p = 0.002). Patients with positive cultures also showed significantly elevated levels of serum CRP (6.5 [2.5-8.5] vs. 3.5 [1.7-5.4] mg/l, p = 0.016). Bronchial colonisation by Haemophilus influenzae was associated with higher levels of IL-1β and IL-8 and clinically significant worse scores on the activity and impact domains of the St. George's Respiratory Questionnaire. In conclusion, bronchial colonisation is associated with bronchial inflammation and high blood CRP levels in stable COPD patients, being Haemophilus influenzae related to a more severe inflammatory response and impairment in health-related quality of life.