Table 1.

Microbial pathogens in COPD

Microbe	Role in Exacerbations	Role in Stable Disease
Bacteria
H influenzae	20%–30% of exacerbations	Major pathogen
Streptococcus pneumoniae	10%–15% of exacerbations	Minor role
Moraxella catarrhalis	10%–15% of exacerbations	Minor role
Pseudomonas aeruginosa	5%–10% of exacerbations, prevalent in advanced disease	Likely important in advanced disease
Enterobacteriaceae	Isolated in advanced disease, pathogenic significance undefined	Undefined
Haemophilus haemolyticus	Isolated frequently, unlikely cause	Unlikely
Haemophilus parainfluenzae	Isolated frequently, unlikely cause	Unlikely
Staphylococcus aureus	Isolated infrequently, unlikely cause	Unlikely
Viruses
Rhinovirus	20%–25% of exacerbations	Unlikely
Parainfluenza	5%–10% of exacerbations	Unlikely
Influenza	5%–10% of exacerbations	Unlikely
Respiratory syncytial virus	5%–10% of exacerbations	Controversial
Coronavirus	5%–10% of exacerbations	Unlikely
Adenovirus	3%–5% of exacerbations	Latent infection seen, pathogenic significance undefined
Human metapneumovirus	3%–5% of exacerbations	Unlikely
Atypical Bacteria
Chlamydophila pneumoniae	3%–5% of exacerbations	Commonly detected, pathogenic significance undefined
Mycoplasma pneumoniae	1%–2%	Unlikely
Fungi
Pneumocystis jiroveci	Undefined	Commonly detected, pathogenic significance undefined

From Sethi S, Murphy TF. Infection in the pathogenesis and course of chronic obstructive pulmonary disease. N Engl J Med 2008;359:2356; with permission.