Relevance of lower airway bacterial colonization, airway inflammation, and pulmonary function in the stable stage of chronic obstructive pulmonary disease

Abstract

The objective of this investigation was to verify the hypothesis that the presence of lower airway bacterial colonization (LABC) can be a stimulating factor of airway inflammation, more frequent exacerbation, and impact on pulmonary function, independent of current tobacco smoking in the stable phase of chronic obstructive pulmonary disease (COPD). A total of 46 ex-smokers with moderate to severe COPD, 19 healthy non-smokers, and 17 ex-smokers without COPD were included in this study. Their sputum specimens were collected at the first baseline visit and at the second visit after a follow-up of one year. The samples were analyzed for bacterial growth by culture, and the levels of interleukin (IL)-6, IL-8, and tumor necrosis factor alpha (TNF-α) were measured by enzyme-linked immunosorbent assay (ELISA). The frequencies of exacerbations and pulmonary function were compared at visit 2. At visit 1, 37.0% (17/46) were found to have LABC with bacterial loads ≥10⁶ CFU/ml in their sputum specimens. Haemophilus influenzae was the predominant pathogenic organism isolated. IL-8, IL-6, and TNF-α in these patients' sputum were significantly higher than those without LABC (p < 0.05). It was the presence of LABC that contributed to the significantly elevated IL-8 and IL-6 at the 1-year period (p < 0.05). LABC was also associated with significantly increased frequencies of exacerbations and declined forced expiratory volume in 1 s (FEV₁) (p < 0.05). LABC was documented in a subpopulation of stable COPD patients; it may be responsible for the deterioration of pulmonary function of COPD patients by promoting airway inflammation and/or increased frequency of exacerbations independently of tobacco smoking.

COPD is associated with reduced pulmonary interstitial expression of pentraxin-3

“…Impaired immune defence mechanisms leading to lowgrade viral infections and bacterial colonisation in the small airways of patients with COPD could contribute to this process [6][7][8]. In addition, reduced clearance of apoptotic cells and autoimmune mechanisms could also play a role in maintaining destructive inflammation in the lungs of patients with COPD [9][10][11][12].…”

Colonization and Bronchiectasis in Patients with Advanced Chronic Obstructive Pulmonary Disease

“…In contrast sputum sampling is relatively straightforward in such patients, especially given the reported corroboration in our colonization rates for sputum and explanted lungs [21].…”

“…Similarly the detection of Aspergillus in eight patients (4%) is in line with advanced disease. Until now, little was known about Aspergillus colonization rates in advanced COPD, with previous studies making no reference to fungal colonization [13,21,22]. Aquino et al examined the association of COPD with Invasive Aspergillosis (IA) when new infiltrates occurred.…”

Acute Exacerbation of Chronic Obstructive Lung Disease: Etiology and Treatment.

“…5,8,11,12 Approximate frequency of causes of exacerbations are given in table 1. [19][20][21][22][23] However, during stable periods, in terms of exacerbation etiology, the colonization by these bacteria raises doubts. Although the lower airways of healthy people are sterile, airways of patients with stable COPD are known to be colonized by bacteria.…”

“…[17][18] From studies evaluating the parameters associated with bacterial colonization, a significant relationship was found between the frequency of exacerbations and increased colonization. 14,19 There are studies showing correlation between the decrease in FEV1 and the colonization. 16 As a result, in patients with frequent exacerbation, bacterial colonization seems to be more common.…”