Organism

Community-acquired pneumonia

Neonate: E. coli (GNR), group A or B streptococcus (GPC), S. aureus (GPC), Pseudomonas sp (GNR), C. trachomatis.

Infant/child (<5 years): Virus, S. pneumoniae (GPC), H. influenzae (GNCB), S. aureus.

Age 5–40 years: Virus, M. pneumoniae, C. pneumoniae (formerly known as TWAR strain), C. psittaci, S. pneumoniae, Legionella sp.

Age >40 years without other disease: S. pneumoniae (GPDC), H. influenzae (GNCB), S. aureus (GPC), M. catarrhalis (GNDC), C. pneumoniae, Legionella sp. (GNR), S. pyogenes (GPC), K. pneumoniae (GNR), Enterobacteriaceae (GNR), viruses (eg, influenza).

Cystic fibrosis: P. aeruginosa (GNR), Burkholderia cepacia.

Elderly: S. pneumoniae (GPDC), H. influenzae (GNCB), S. aureus (GPC), Enterobacteriaceae (GNR), M. catarrhalis (GNDC), group B streptococcus (GPC), legionella (GNR), nocardia (GPR), influenza.

Aspiration: S. pneumoniae (GPDC), K. pneumoniae (GNR), Enterobacteriaceae (GNR), Bacteroides sp. and other oral anaerobes.

Fungal: H. capsulatum, C. immitis, B. dermatitidis.

Exposure to birthing animals, sheep: C. burnetii (Q fever), rabbits: F. tularensis (tularemia), deer mice: hantavirus, birds: C. psittaci.