Infectious exacerbations of chronic bronchitis: diagnosis and management

Chronic bronchitis is an increasing cause of significant morbidity and mortality. Despite treatment, respiratory tract infection is the most common identifiable cause of death for patients with chronic obstructive pulmonary disease. Repeated infectious exacerbations may ultimately cause acute and chronic lung injury. The most common bacterial aetiologies of acute exacerbations of chronic bronchitis (AECB) include Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae. Pseudomonas aeruginosa is often a nosocomial pathogen and is becoming more prevalent in patients with severe underlying disease. Viruses are responsible for approximately one-third of acute exacerbations overall. Atypical pathogens are causative pathogens in < 10% of episodes. The diagnosis of AECB is often based on clinical impression, although suspicion of bacterial infection can be enhanced by quantitative Gram's stains from appropriately obtained sputum specimens. However, a specific microbiological diagnosis is only needed in certain specific situations. Management of AECB involves non-drug interventions (e.g. smoking cessation) and antibiotic treatment. Recommendations for antibiotic use in patients with known or highly suspected AECB are still evolving. The selection of an antibiotic for treatment of an infectious episode must consider underlying patient co-morbidities, likely pathogens, resistance issues and individual antibiotic properties. Cephalosporins, beta-lactam/beta-lactamase inhibitor combinations and macrolides are all reasonable choices. However, due to the increasing prevalence of resistance to standard antibiotics among common respiratory pathogens, and increased incidence of Pseudomonas spp., fluoroquinolones should be a first-line treatment for AECB in patients who have chronic bronchitis complicated by co-morbid illness, severe obstruction (FEV1 < 50%), old age (> 65 years) or have recurrent exacerbations. In patients who do not have these risk factors (i.e. those with simple chronic bronchitis), agents such as co-trimoxazole remain useful.