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The long-term antimicrobial prophylaxis of chronic bronchitis exacerbations.

Infectious exacerbations are the major cause of mortality in patients with chronic bronchitis, particularly in elderly subjects. Considering that the preventive use of antibiotics has provided no clear-cut evidence of real efficacy, it has become quite common to use treatments potentially able to stimulate the immune system for prevention of exacerbations of chronic bronchitis. This treatment, based on the oral administration of bacterial extracts, should, at least in theory, stimulate the immune defenses and reduce the incidence of recurring respiratory tract infections. Although during the last few years a good effort to define better the real efficacy and role played by bacterial extracts in chronic bronchitis has been made, their clinical effectiveness is still the subject of debate and the results of some clinical trials are controversial. Particularly, its mechanism of action remains poorly understood, although a huge effort has been made in this direction.