Chronic obstructive pulmonary disease (COPD) is an increasingly important health problem world-wide. Whereas most other leading diseases have shown a decline in the past decades, COPD morbidity and mortality is on a steady increase. Exacerbations are usually defined as an increase in cough, a change in the colour or quantity of sputum, and a worsening dyspnea. The role of bacterial infections and the efficacy of antimicrobial therapy in acute exacerbations of chronic bronchitis (AECD) is still controversial. Exacerbations of chronic bronchitis are a common occurrence in clinical practice and are a leading cause of antibiotic prescription among respiratory infections. It is still uncertain whether each new exacerbation may deteriorate the natural history of chronic bronchitis. Undoubtedly, every episode includes a temporary worsening in lung function and may therefore pose the threat of respiratory failure or death in more severely obstructed patients.

Chlamydia pneumoniae is now recognized as an important human pathogen. Chlamydia pneumoniae is involved in 5%-15% of community acquired pneumonias, and recent data indicate its relevance in severe pneumonia and as a respiratory pathogen in immunocompromised subjects. A causal role for Chlamydia pneumoniae in the initiation, exacerbations and promotion of asthma has been suggested. Approximately 5% of chronic bronchitis exacerbations have been attributed to Chlamydia pneumoniae infections, and chronic infection may facilitate access of other pathogens to the lower respiratory tract. Another field of potential great social impact is the possible involvement of Chlamydia pneumoniae in the pathogenesis of atherosclerosis and related cardiovascular diseases. This book presents the current state-of-the-art knowledge on Chlamydia pneumoniae infection and highlights future lines of research.