Pro: antibiotics for chronic bronchitis with exacerbations.

Abstract

Over the years, there has emerged a considerable body of evidence supporting the importance of antimicrobial therapy in exacerbations of chronic bronchitis. The following lines of evidence suggest that most acute exacerbations are caused by bacterial infection: (1) the individual with chronic bronchitis is susceptible to bacterial infection as a consequence of local damage from prolonged cigarette smoking; (2) subtle defects in the local immune system can be shown, including impaired particle transport, defective immunoglobulin A production, chronic mucous impaction, and defective neutrophil phagocytosis; (3) acute bronchitic exacerbations are associated with a proliferation of pathogenic bacteria in the lower respiratory tract, based on quantitative culture data obtained by bronchoscopy with a protected specimen brush; (4) viral respiratory infections, which were once linked to over 50% of purulent exacerbations, probably account for only a minority of bronchitic exacerbations; (5) some "culture negative" exacerbations may be caused by bacteria susceptible to antibiotics such as Mycoplasma pneumoniae or Chlamydia pneumoniae. There are also secondary effects of bacteria that are potentially amenable to antibiotic therapy. Bacteria that colonize the respiratory tract of chronic bronchitics cause direct damage to the respiratory epithelium. Lipooligosaccharide, a major component of the outer membrane of Haemophilus influenzae, is an endotoxin-like mediator of respiratory cell damage. The host inflammatory response to bacterial proliferation is ineffective and may be potentially harmful; the enzyme neutrophil elastase is released by the host during phagocytosis of bacteria and may lead to progressive airway damage. In addition, bacterial superinfections may complicate viral exacerbations of chronic bronchitis. Clinical trials examining the efficacy of antibiotic therapy in mild to moderate exacerbations of chronic bronchitis have yielded conflicting results, caused in part to fundamental differences in study design. The major double-blinded and placebo-controlled studies suggest a trend in favor of antimicrobial therapy, although the effect is modest. For the individual patient, the risks of antimicrobial therapy are small compared with the potential benefits of returning to work earlier and avoiding the rare case of respiratory decompensation.