Causative Organisms in COPD Exacerbations

Bacterial Etiology

Streptococcus pneumoniae and Haemophilus influenzae are equally common causative organisms in COPD exacerbations in smokers, with S. pneumoniae typically listed first but H. influenzae being particularly associated with smoking and chronic obstructive pulmonary disease 1, 2, 3, 4
The European Respiratory Society recommends considering both Streptococcus pneumoniae and Haemophilus influenzae as the most common bacterial pathogens causing exacerbations in COPD patients 1, 2, 4, 5
Haemophilus influenzae is listed as the second most common organism, with particular prevalence in smokers, according to the European Respiratory Society 1, 2, 3, 4

Both typable and nontypable strains of H. influenzae are pathogenic primarily among smokers and patients with COPD, as stated by the Infectious Diseases Society of America 6
The American College of Chest Physicians notes that during stable periods, many patients with chronic bronchitis, especially current smokers, are colonized with S. pneumoniae, M. catarrhalis, and H. influenzae 3, 4
The American Thoracic Society states that the history of cigarette smoking increases the likelihood of H. influenzae infection, though S. pneumoniae remains a major pathogen 7

The European Respiratory Society recommends that first-line therapy should include coverage for both S. pneumoniae (including drug-resistant strains) and H. influenzae 1, 2, 5
The American College of Chest Physicians suggests that recommended regimens include amoxicillin, amoxicillin/clavulanic acid, or newer cephalosporins that cover both pathogens 1, 2
The American Thoracic Society notes that macrolides alone may be inadequate as erythromycin does not provide reliable H. influenzae coverage 7, 8