Do airway bacteria cause COPD exacerbations?

Although noninfectious stimuli are capable of stimulating airway inflammation in chronic obstructive pulmonary disease (COPD) and contributing to exacerbations, infectious agents, including bacteria, viruses, and atypical pathogens are currently implicated in up to 80% of acute exacerbations, with bacteria likely playing a role in 50% of exacerbations (1). However, the precise role of bacterial infection in COPD has been a source of controversy for several decades (2,3). Opinion has ranged from a pre-eminent role (along with mucus hypersecretion) as embodied in the British hypothesis in the 1950s and 1960s to bacterial infection being regarded as a mere epiphenomenon in the 1970s and 1980s. In the last two decades, enhanced knowledge of microbial pathogenesis and application of new research tools have transformed our understanding of the role of infections in COPD, especially bacterial infections.