Patients with Chronic Obstructive Pulmonary Disease (COPD) suffer from frequent and recurrent acute exacerbations (AECB) which are associated with enormous healthcare expenditures and significant morbidity, specifically an increased risk of death, a decline in pulmonary function and a significant change in quality of life. Bacteria appear to have an important role in acute exacerbations in chronic bronchitis and COPD. Studies of acute exacerbations in COPD have shown a reduction in bacterial load with prolonged exacerbation-free interval. In addition, recent studies indicate that acquisition of a new strain of H. influenzae, M. catarrhalis, S. pneumoniae or P. aeruginosa are responsible for many of these exacerbations. Chronic inflammation and bacterial infection predispose many patients to frequent and recurrent acute exacerbations.