Relationship between airway colonization, inflammation and exacerbation frequency in COPD

Summary

Rationale

To evaluate bacterial colonization and the airway inflammatory response, and its relationship to the frequency of exacerbation in patients with stable chronic obstructive pulmonary disease (COPD).

Methods

Quantitative bacteriologic cultures, neutrophil elastase, myeloperoxidase (MPO), tumor necrosis factor alpha (TNF-α) and interleukin (IL)-8 were measured in bronchoalveoler lavage (BAL) in 39 patients with stable COPD [19 with frequent exacerbation (⩾3/year), and 20 with infrequent] and in 18 healthy controls (10 smokers and 8 non-smokers).

Results

BAL revealed the microorganisms with potential pathogenicity above the established threshold (⩾10³ cfu/ml) in 68.4% of patients with frequent exacerbation, 55% of infrequent exacerbation, 40% of smokers and 12.5% of non-smokers controls ($P=0.05$). BAL MPO, IL-8 and TNF-α levels were found to be significantly higher in COPD as compared to controls ($P=0.001$). However, only IL-8 level was significantly higher in COPD patients with frequent exacerbation as compared to infrequent ($P=0.001$). Airway bacterial load correlated with levels of airway inflammation markers in COPD ($P<0.05$).

Conclusion

The bacterial load and airway inflammation contributes to each other in stable COPD. However, there is a link only between interleukine (IL)-8 and frequent exacerbations. Clearly, the relationship between bacterial colonization, airway inflammation and frequent exacerbations is of major importance in understanding of the COPD pathogenesis.