Community-acquired pneumonia: Difference between revisions

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== Microbiology ==
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== Background ==
   
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* See also [[Respiratory infection in an immunocompromised person]] and [[Respiratory infection in unimmunized hosts]]
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* Bacteria
  
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=== Microbiology ===
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* Bacteria (15-30%)<ref>Gadsby NJ, Musher DM. The Microbial Etiology of Community-Acquired Pneumonia in Adults: from Classical Bacteriology to Host Transcriptional Signatures. ''Clin Microbiol Rev''. 2022 Sep 27:e0001522. doi: [https://doi.org/10.1128/cmr.00015-22 10.1128/cmr.00015-22]. Epub ahead of print. PMID: [https://pubmed.ncbi.nlm.nih.gov/36165783/ 36165783].</ref>
 
** Typical organisms
  
** Typical organisms
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*** ''[[Streptococcus pneumoniae]]''
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*** [[Streptococcus pneumoniae]] (5-15%)
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*** ''[[Haemophilus influenzae]]''
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*** [[Haemophilus influenzae]] (1-7%)
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*** ''[[Staphylococcus aureus]]''
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*** [[Staphylococcus aureus]] (2-5%)
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*** Group A streptococci
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*** [[Group A streptococcus]]
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*** ''[[Moraxella catarrhalis]]''
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*** [[Moraxella catarrhalis]]
 
*** Anaerobes and aerobic gram-negative bacteria
  
*** Anaerobes and aerobic gram-negative bacteria
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**** ''[[Klebsiella pneumonia]]''
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**** [[Klebsiella pneumonia]]
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**** ''[[Pseudomonas aeruginosa]]''
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**** [[Pseudomonas aeruginosa]] (1-3%)
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**** ''[[Acinetobacter baumannii]]''
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**** [[Acinetobacter baumannii]]
 
** Atypical organisms
  
** Atypical organisms
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*** ''[[Legionella]]'' spp.
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*** [[Legionella]] species (1-6%)
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*** ''[[Mycoplasma pneumoniae]]''
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*** [[Mycoplasma pneumoniae]] (1-10%)
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*** ''[[Chlamydia pneumoniae]]''
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*** [[Chlamydia pneumoniae]] (1-3%)
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*** ''[[Chlamydia psittaci]]''
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*** [[Chlamydia psittaci]]
 
** Others
  
** Others
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*** ''[[Coxiella burnetti]]''
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*** [[Coxiella burnetti]]
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*** [[Nocardia]]
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* Viral
  
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** [[Influenza virus]]
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*** [[Mycobacteria]]
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* Viruses (25-60%)
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** [[Parainfluenza virus]]
  
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** [[RSV]]
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** [[Rhinovirus]] (8-17%)
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** [[Adenovirus]]
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** [[Coronavirus]] (3-13%)
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** [[Human metapneumovirus]]
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** [[Influenza virus]] (1-6%)
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** [[Human metapneumovirus]] (1-8%)
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** [[Middle East respiratory syndrome coronavirus]] (MERS-CoV)
  
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** [[Rhinovirus]]
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** [[Parainfluenza virus]] (1-8%)
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** [[RSV]] (1-8%)
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* Fungi
  
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** ''[[Cryptococcus]]'' spp.
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** [[Adenovirus]] (1-8%)
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* Fungi (1-3%)
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** ''[[Histoplasma capsulatum]]''
  
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** ''[[Coccidioides]]''
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** [[Pneumocystis jirovecii]]
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** [[Cryptococcus]] species
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** [[Histoplasma capsulatum]]
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** [[Coccidioides]]
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* No cause identified (46-66%)
 
* Clinically-important but uncommon organisms
  
* Clinically-important but uncommon organisms
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** ''[[Legionella]]'' species
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** [[Legionella]] species
 
** [[Influenza]] A and B, including avian influenza A H5N1 and avian influenza A H7N9
  
** [[Influenza]] A and B, including avian influenza A H5N1 and avian influenza A H7N9
 
** [[MERS-CoV]] and [[severe acute respiratory syndrome coronavirus]] (SARS-CoV)
  
** [[MERS-CoV]] and [[severe acute respiratory syndrome coronavirus]] (SARS-CoV)
 
** Community-associated methicillin-resistant [[Staphylococcus aureus]] (CA-MRSA)
  
** Community-associated methicillin-resistant [[Staphylococcus aureus]] (CA-MRSA)
   
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== Clinical Presentation ==
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== Clinical Manifestations ==
   
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* Acute onset cough, dyspnea, and fever
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* If effusion, consider ''Legionella''
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* If effusion, consider ''[[Legionella]]''
   
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== Investigations ==
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=== Severity ===
   
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* Per IDSA guidelines[[CiteRef::metlay2019di]], severe CAP includes either ''one major'' criterion or ''three or more minor'' criteria
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* Always add ''Legionella'' testing in immunocompromised, critical illness, recent travel, significant alcohol, and consider when pleural effusion is present
  
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* '''Minor criteria'''
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** Respiratory rate ≥ 30 breaths/min
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** PaO2/FiO2 ratio ≤ 250
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** Multilobar infiltrates
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** Confusion/disorientation
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** Uremia (blood urea nitrogen level ≥ 20 mg/dl)
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** Leukopenia not due to chemotherapy (white blood cell count < 4,000 cells/μl)
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** Thrombocytopenia (platelet count < 100,000/μl)
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** Hypothermia (core temperature < 36°C)
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** Hypotension requiring aggressive fluid resuscitation
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* '''Major criteria'''
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** Septic shock with need for vasopressors
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** Respiratory failure requiring mechanical ventilation
   
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== Management ==
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== Investigations ==
   
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* Always add ''[[Legionella]]'' testing in immunocompromised, critical illness, recent travel, significant alcohol, and consider when pleural effusion is present
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== Prognosis ==
  
   
 
== Further Reading ==
  
== Further Reading ==

Latest revision as of 22:17, 3 October 2022

Background

Microbiology

Clinical Manifestations

  • Acute onset cough, dyspnea, and fever
  • If effusion, consider Legionella

Severity

  • Per IDSA guidelines1, 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

  1. ↑ Gadsby NJ, Musher DM. The Microbial Etiology of Community-Acquired Pneumonia in Adults: from Classical Bacteriology to Host Transcriptional Signatures. Clin Microbiol Rev. 2022 Sep 27:e0001522. doi: 10.1128/cmr.00015-22. Epub ahead of print. PMID: 36165783.

References

  1. ^  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.

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