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Infections in acute exacerbation of chronic bronchitis: what are they and how do we know?

Acute exacerbations of chronic bronchitis can be due to many factors. The most commonly recognized factor is infection, with bacterial infection being identified in about fifty percent of patients with chronic bronchitis. The causative agent can be detected by several different methods. The most common is sputum examination; however, more invasive techniques have been studied. These include transtracheal aspirates and bronchoscopic samples. The most widely studied bronchoscopic sample has been the protected brush specimen (PBS). Despite the wide array of sampling techniques, the pathogens which have been identified have been relatively consistent. The three most common pathogens have been H. influenzae, S. Pneumoniae, and B. catarrhalis. Other pathogens, including gram negative enteric organisms, are seen in patients with more advanced disease. The information obtained by the diagnostic studies has allowed clinicians to develop treatment strategies for AECB. These diagnostic studies will be needed to help upgrade treatment guidelines as new bacteria and bacterial resistance patterns change.