Pneumonia

Microbiology of Pneumonia
Clinical Setting Etiologies
Community-acquired (CAP) (NEJM 2014;371:1619 & 373:415; Lancet 2015;386:1097) No pathogen identified in 50–60%, virus alone in ~25%, bacteria alone in ~10%, virus-bacteria coinfection in <5%
Viruses: influenza, RSV, hMPV, rhinovirus (unknown significance), parainfluenza virus, coronavirus
S. pneumoniae (most common bacterial cause)
S. aureus (esp. postinfluenza)
Mycoplasma, Chlamydia (esp. in young & healthy)
H. influenzae, M. catarrhalis (esp. in COPD)
Legionella (esp. in elderly, smokers, ↓ immunity, TNF inhibitors)
Klebsiella & other GNR (esp. in alcoholics & aspiration)
Hospital-acquired or ventilator-assoc. (HAP/VAP)