Community-acquired pneumonia: Difference between revisions

Latest revision as of 17:30, 19 September 2024

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
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%)
- Pneumocystis jirovecii
- Cryptococcus species
- Histoplasma capsulatum
- Coccidioides
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

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.

@@ Line 1: / Line 1: @@
-== Microbiology ==
+== Background ==
+* See also [[Respiratory infection in an immunocompromised person]] and [[Respiratory infection in unimmunized hosts]]
-* Bacteria
+=== Microbiology ===
+* Bacteria (15-30%)[[CiteRef::gadsby2022th]]
 ** Typical organisms
-*** ''[[Streptococcus pneumoniae]]''
+*** [[Streptococcus pneumoniae]] (5-15%)
-*** ''[[Haemophilus influenzae]]''
+*** [[Haemophilus influenzae]] (1-7%)
-*** ''[[Staphylococcus aureus]]''
+*** [[Staphylococcus aureus]] (2-5%)
-*** Group A streptococci
+*** [[Group A streptococcus]]
-*** ''[[Moraxella catarrhalis]]''
+*** [[Moraxella catarrhalis]]
 *** Anaerobes and aerobic gram-negative bacteria
-**** ''[[Klebsiella pneumonia]]''
+**** [[Klebsiella pneumonia]]
-**** ''[[Pseudomonas aeruginosa]]''
+**** [[Pseudomonas aeruginosa]] (1-3%)
-**** ''[[Acinetobacter baumannii]]''
+**** [[Acinetobacter baumannii]]
 ** Atypical organisms
-*** ''[[Legionella]]'' spp.
+*** [[Legionella]] species (1-6%)
-*** ''[[Mycoplasma pneumoniae]]''
+*** [[Mycoplasma pneumoniae]] (1-10%)
-*** ''[[Chlamydia pneumoniae]]''
+*** [[Chlamydia pneumoniae]] (1-3%)
-*** ''[[Chlamydia psittaci]]''
+*** [[Chlamydia psittaci]]
 ** Others
-*** ''[[Coxiella burnetti]]''
+*** [[Coxiella burnetti]]
+*** [[Nocardia]]
-* Viral
-** [[Influenza virus]]
+*** [[Mycobacteria]]
+* Viruses (25-60%)
-** [[Parainfluenza virus]]
-** [[RSV]]
+** [[Rhinovirus]] (8-17%)
-** [[Adenovirus]]
+** [[Coronavirus]] (3-13%)
-** [[Human metapneumovirus]]
+** [[Influenza virus]] (1-6%)
+** [[Human metapneumovirus]] (1-8%)
-** [[Middle East respiratory syndrome coronavirus]] (MERS-CoV)
-** [[Rhinovirus]]
+** [[Parainfluenza virus]] (1-8%)
+** [[RSV]] (1-8%)
-* Fungi
-** ''[[Cryptococcus]]'' spp.
+** [[Adenovirus]] (1-8%)
+* Fungi (1-3%)
-** ''[[Histoplasma capsulatum]]''
-** ''[[Coccidioides]]''
+** [[Pneumocystis jirovecii]]
+** [[Cryptococcus]] species
+** [[Histoplasma capsulatum]]
+** [[Coccidioides]]
+* No cause identified (46-66%)
 * Clinically-important but uncommon organisms
-** ''[[Legionella]]'' species
+** [[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 ==
+== Clinical Manifestations ==
 * Acute onset cough, dyspnea, and fever
@@ Line 46: / Line 54: @@
 * Per IDSA guidelines[[CiteRef::metlay2019di]], severe CAP includes either ''one major'' criterion or ''three or more minor'' criteria
 * '''Minor criteria'''
-** Respiratory rate ≥ 30 breaths/min
+** Respiratory rate ≥ 30 breaths/min
-** PaO2/FiO2 ratio ≤ 250
+** PaO2/FiO2 ratio ≤ 250
-** Multilobar infiltrates
+** Multilobar infiltrates
-** Confusion/disorientation
+** Confusion/disorientation
-** Uremia (blood urea nitrogen level ≥ 20 mg/dl)
+** Uremia (blood urea nitrogen level ≥ 20 mg/dl)
-** Leukopenia not due to chemotherapy (white blood cell count < 4,000 cells/μl)
+** Leukopenia not due to chemotherapy (white blood cell count < 4,000 cells/μl)
-** Thrombocytopenia (platelet count < 100,000/μl)
+** Thrombocytopenia (platelet count < 100,000/μl)
-** Hypothermia (core temperature < 36°C)
+** Hypothermia (core temperature < 36°C)
-** Hypotension requiring aggressive fluid resuscitation
+** Hypotension requiring aggressive fluid resuscitation
-* '''Major criteria'''
+* '''Major criteria'''
-** Septic shock with need for vasopressors
+** Septic shock with need for vasopressors
-** Respiratory failure requiring mechanical ventilation
+** 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
+* Always add ''[[Legionella]]'' testing in immunocompromised, critical illness, recent travel, significant alcohol, and consider when pleural effusion is present
-== Management ==
-== Prognosis ==
 == Further Reading ==