What is the most common bacterial 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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S pneumoniae remains the most common bacterial agent responsible for CAP. The incidence of S pneumoniae pneumonia varies according to the population studied. A 2015 study of 267 patients with CAP in Norway reported that S pneumoniae accounted for 30% of cases; this represented 48.5% of the cases in which an organism was identified. [35] A separate study of adults with CAP in the United States identified S pneumoniae as the etiologic agent in only 5% of total cases of CAP (13.5% of cases with an identified pathogen). [1] Declining tobacco smoking and widespread pneumococcal vaccination have been postulated as potential contributors to the decreased rates of S pneumoniae infection in the United States. [36]

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