Microbiology-of-Pneumonia

Clinical Setting: CAP

Etiologies

• No pathogen identified in 50–60%, virus alone in ~25%, bacteria alone in ~10%, virus-bacteria coinfection in <5%
• Viruses: influenza, RSV, hMPV, parainfluenza, rhinovirus, coronavirus
• S. pneumoniae (most common bacterial cause)
• S. aureus (espec. post-influenza)
• Mycoplasma, Chlamydia (espec. in young & healthy)
• H. influenzae, M. catarrhalis (espec. in COPD)
• Legionella (espec. in elderly, smokers, ↓ immunity, TNF inhibitors)
• Klebsiella & other GNR (espec. in alcoholics & aspiration)

Clinical Setting: HAP/VAP

S. aureus, Pseudomonas, Klebsiella, E. coli, Enterobacter, Acinetobacter, Steno. IV abx w/in 90 d risk factor for MDR. Viral ~20% cases.

Clinical Setting: Empyema

S. pneumo, S. aureus, E. coli, Klebsiella, H. influenzae, anaerobes

Clinical Setting: Lung abscess

Often polymicrobial, incl. oral flora. S. aureus, anaerobes, Strep (anginosus, GAS), GNR (Klebsiella, E. coli, Pseudomonas), Nocardia, Actinomyces, fungi, mycobacteria, Echinococcus

Clinical Setting: infxns in immunosuppressed hosts

Above + Pneumocystis, Cryptococcus, Nocardia, non-TB myco- bacteria (NTM), CMV, invasive molds