Oral purified bacterial extracts in chronic bronchitis and COPD: systematic review.

Oral lyophilized extracts of bacteria species have been used since the early 1970s to improve symptoms and to prevent exacerbations in COPD patients. The value of these treatments, which are thought to be immunomodulating, is poorly understood. Our aim was to quantify the efficacy of oral bacteria extracts in patients with chronic bronchitis and COPD.