Airway Inflammation and Etiology of Acute Exacerbations of Chronic Bronchitis

Study objectives: The etiologic role of bacterial pathogens isolated from sputum culture in 40 to 50% of acute exacerbations of chronic bronchitis (AECB) is controversial. If bacterial pathogens cause these AECB, they should be associated with greater neutrophilic airway inflammation than pathogen-negative exacerbations. Design: This hypothesis was tested by comparing levels of interleukin (IL)-8, tumor necrosis factor (TNF)-a, and neutrophil elastase (NE) in 81 sputum samples obtained from 45 patients with AECB. Four groups were compared. In the first three groups, nontypeable Haemophilus influenzae (n 5 20), Haemophilus parainfluenzae (n 5 27), and Moraxella catarrhalis (n 5 14) were isolated as sole pathogens, respectively. In the fourth group, only normal flora was isolated (n 5 20). Paired samples, obtained from individual patients at different times, that differed in their culture results were also compared. Setting: An outpatient research clinic at a Veterans Affairs Medical Center. Patients: These patients were participating in a prospective, longitudinal study of the dynamics of bacterial infection in chronic bronchitis, for which they were seen in the study clinic on a monthly basis as well as when they were experiencing symptoms suggestive of AECB. Interventions: None. Measurements and results: H influenzae exacerbations were associated with significantly higher sputum IL-8, TNF-a, and NE. M catarrhalis exacerbations demonstrated significantly higher sputum TNF-a and NE when compared to pathogen-negative exacerbations. H parainfluenzaeassociated exacerbations had an inflammatory profile similar to pathogen-negative exacerbations. Sputum elastase level distinguished bacterial from nonbacterial AECB and correlated with clinical severity of the AECB. Conclusions: Increased airway inflammation associated with isolation of H influenzae and M catarrhalis supports an etiologic role of these pathogens in AECB. (CHEST 2000; 118:1557‐1565)