[Infections in chronic obstructive pulmonery disease]

Infection plays an important role in COPD, particularly during exacerbations. The principal pathogens involved in exacerbations are viruses (influenza and parainfluenza virus, picornavirus, and respiratory syncytial virus). Bacteria (mainly Haemophilus influenzae, Streptococcus pneumoniae, Branhamella catarrhalis) are isolated from sputum in approximately 50% of exacerbations and 25% of patients with stable state. Recent data favor of a proinflammatory role of these bacteria in the natural history of the disease. The role of atypical pathogens like Chlamydia pneumoniae may be underestimated. Trials of antibiotic treatment have shown a slight but significant benefit, particularly in patients with recent-onset purulent sputum. The benefit is more significant in patients with stable severe obstructive disease. Guidelines have been published in industrialized countries on the use of antibiotics in this indication. The role of infections in the pathogenesis of obstructive lesions is controversial. Some authors have forwarded a "vicious circle" hypothesis, in which impairment of mucociliary clearance by tobacco smoke contributes to bronchial colonization by bacteria, and this further impairs mucociliary clearance and promotes airway epithelial injury. COPD is a major risk factor for community-acquired pneumonia.