What Organisms Cause Community-Acquired Pneumonia in Adults?

We usually treat patients with community-acquired pneumonia (CAP) empirically, without knowing the responsible organism. In this study, investigators sought to identify the responsible pathogen in 2259 adults admitted to five hospitals (in Chicago and Nashville) with clinical and radiographic evidence of CAP. Nearly all patients provided specimens for blood cultures and urinary antigen tests for Streptococcus pneumoniae and Legionella pneumophila; polymerase-chain reaction testing of nasopharyngeal and oropharyngeal swabs was performed to identify a panel of viruses, mycoplasma, and Chlamydophila pneumoniae. Sputum specimens were obtained from 41% of patients and cultured, but only about one third of the specimens were deemed to be high qua…