Community-acquired pneumonia
From IDWiki
Background
- See also Respiratory infection in an immunocompromised person and Respiratory infection in unimmunized hosts
Microbiology
- Bacteria (15-30%)1
- Typical organisms
- Streptococcus pneumoniae (5-15%)
- Haemophilus influenzae (1-7%)
- Staphylococcus aureus (2-5%)
- Group A streptococcus
- Moraxella catarrhalis
- Anaerobes and aerobic gram-negative bacteria
- Atypical organisms
- Legionella species (1-6%)
- Mycoplasma pneumoniae (1-10%)
- Chlamydia pneumoniae (1-3%)
- Chlamydia psittaci
- Others
- Typical organisms
- Viruses (25-60%)
- Rhinovirus (8-17%)
- Coronavirus (3-13%)
- Influenza virus (1-6%)
- Human metapneumovirus (1-8%)
- Parainfluenza virus (1-8%)
- RSV (1-8%)
- Adenovirus (1-8%)
- Fungi (1-3%)
- No cause identified (46-66%)
- 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 Manifestations
- Acute onset cough, dyspnea, and fever
- If effusion, consider Legionella
Severity
- Per IDSA guidelines2, severe CAP includes either one major criterion or three or more minor criteria
- Minor criteria
- Respiratory rate ≥ 30 breaths/min
- PaO2/FiO2 ratio ≤ 250
- Multilobar infiltrates
- Confusion/disorientation
- Uremia (blood urea nitrogen level ≥ 20 mg/dl)
- Leukopenia not due to chemotherapy (white blood cell count < 4,000 cells/μl)
- Thrombocytopenia (platelet count < 100,000/μl)
- Hypothermia (core temperature < 36°C)
- Hypotension requiring aggressive fluid resuscitation
- Major criteria
- Septic shock with need for vasopressors
- Respiratory failure requiring mechanical ventilation
Investigations
- Always add Legionella testing in immunocompromised, critical illness, recent travel, significant alcohol, and consider when pleural effusion is present
Further Reading
References
- ^ Joshua P. Metlay, Grant W. Waterer, Ann C. Long, Antonio Anzueto, Jan Brozek, Kristina Crothers, Laura A. Cooley, Nathan C. Dean, Michael J. Fine, Scott A. Flanders, Marie R. Griffin, Mark L. Metersky, Daniel M. Musher, Marcos I. Restrepo, Cynthia G. Whitney. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America. American Journal of Respiratory and Critical Care Medicine. 2019;200(7):e45-e67. doi:10.1164/rccm.201908-1581st.
