Community-acquired pneumonia

Microbiology

• Bacteria
  • Typical organisms
    • Streptococcus pneumoniae
    • Haemophilus influenzae
    • Staphylococcus aureus
    • Group A streptococci
    • Moraxella catarrhalis
    • Anaerobes and aerobic gram-negative bacteria
      • Klebsiella pneumonia
      • Pseudomonas aeruginosa
      • Acinetobacter baumannii
  • Atypical organisms
    • Legionella spp.
    • Mycoplasma pneumoniae
    • Chlamydia pneumoniae
    • Chlamydia psittaci
  • Others
    • Coxiella burnetti
• Viral
  • Influenza virus
  • Parainfluenza virus
  • RSV
  • Adenovirus
  • Human metapneumovirus
  • Middle East respiratory syndrome virus (MERS-CoV)
  • Rhinovirus
• Fungi
  • Cryptococcus spp.
  • Histoplasma capsulatum
  • Coccidioides
• Clinically-important but uncommon organisms
  • Legionella species
  • Influenza A and B, including avian influenza A H5N1 and avian influenza A H7N9
  • MERS-CoV and severe acute respiratory syndrome coronavirus (SARS-CoV)
  • Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA)

Clinical Presentation

• If effusion, consider Legionella

Investigations

• Always add Legionella testing in immunocompromised, critical illness, recent travel, significant alcohol, and consider when pleural effusion is present

Further Reading

• IDSA CAP guidelines 2007
• HQO CAP guidelines 2014