Which is the most common pathogen causing community-acquired pneumonia (CAP)?

Updated: Oct 31, 2019
  • Author: Stephanie L Baer, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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Epidemiologic data may provide clues to the specific pathogen causing CAP, as follows:

  • The most common bacterial pathogen overall is S pneumoniae, although, in some settings, including in the United States, its incidence is decreasing, possibly owing to vaccination. [1]
  • Underlying chronic obstructive pulmonary disease (COPD) [2] : H influenzae or M catarrhalis
  • Recent influenza infection [3] : Staphylococcus aureus or S pneumoniae [4]
  • Alcoholic patient presenting with “currant jelly” sputum : Klebsiella pneumoniae [2]

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