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Community-acquired pneumonia in adults

ATS/IDSA-based adult CAP confirmation, site-of-care decisions, microbiology, empiric treatment, stability review and safety escalation.

JurisdictionUnited States
Source check2026-08-20
Clinical reviewiatroX editorial team 路 Clinical editorial review 路 reviewed 2026-08-20 路 due 2027-08-20
AudienceUnited States healthcare professionals
This is an iatroX educational summary of named United States sources, not an official guideline. It does not replace the complete source documents, local policy, specialist advice or clinical judgement. Use the named authority, current FDA labeling, applicable state law, payer rules and local protocol where relevant.

Scope of this summary

Immunocompetent adults with clinically suspected and radiographically confirmed community-acquired pneumonia. The 2019 ATS/IDSA guideline does not cover children, major immunocompromise, hospital-acquired or ventilator-associated pneumonia, aspiration syndromes as a single entity, or infections requiring a pathogen-specific pathway.
sources for this section:ATS/IDSA CAP 2019

The Bottom Line

  • Confirm CAP with a compatible clinical syndrome and chest imaging; a cough or abnormal auscultation alone does not establish the population addressed by this guideline.
  • Use a validated prognosis tool鈥攑referentially the Pneumonia Severity Index鈥攁longside clinical judgment, oral-intake ability, cognition, oxygen need, social support and comorbidity when deciding outpatient versus inpatient care.
  • Do not use a low procalcitonin result to withhold initial antibacterial treatment from an adult with clinically suspected and radiographically confirmed CAP.
  • Choose empiric antibiotics from illness severity, comorbidity, local pneumococcal resistance and validated risk factors for MRSA or Pseudomonas aeruginosa; the guideline removed the former healthcare-associated-pneumonia category.
  • Continue treatment until clinical stability is achieved and for no less than five days, then reconsider complications or an alternative diagnosis when stability is delayed.
sources for this section:ATS/IDSA CAP 2019

Practical clinical workflow

1
Assess vital signs, oxygenation, mental status, hydration, oral intake and sepsis features; obtain chest imaging and consider influenza, SARS-CoV-2 and geographically relevant fungal disease.
2
Determine site of care with the Pneumonia Severity Index plus judgment, and apply the guideline鈥檚 severe-CAP criteria when deciding higher-level monitoring or intensive care.
3
Reserve blood and sputum cultures for severe CAP and the source-defined MRSA or Pseudomonas situations; obtain microbiology before antibiotics when feasible without delaying urgent treatment.
4
Start a guideline-concordant regimen promptly, document allergy and interaction risks, and narrow or redirect therapy when reliable microbiology and clinical response permit.
5
Reassess stability, complications and adherence. Routine follow-up chest imaging is not recommended when symptoms resolve within five to seven days, while persistent or recurrent symptoms need targeted review.
sources for this section:ATS/IDSA CAP 2019

Safety boundaries and escalation

  • Hypoxemia, hypotension, confusion, severe respiratory distress, multilobar disease, rapidly worsening physiology or inability to maintain oral intake warrants urgent hospital-level assessment.
  • Suspected sepsis or shock requires immediate resuscitation and the relevant sepsis pathway; a severity score must not delay escalation.
  • Immunocompromise, recent resistant respiratory isolates, structural lung disease or unusual exposure can make the standard CAP pathway unsafe and should prompt specialist or pathogen-specific advice.
  • Antibiotic selection must account for local antibiograms, renal and hepatic function, pregnancy, QT risk, drug interactions and current FDA warnings rather than copying a generic regimen.
sources for this section:ATS/IDSA CAP 2019

Localization

Use the ATS/IDSA adult CAP guideline, local US antibiogram and current CDC pathogen and vaccination guidance. Antibiotic availability and resistance differ by location.
sources for this section:ATS/IDSA CAP 2019

Source documents

Use the linked source documents for complete recommendations, evidence grading, exclusions and implementation detail.

  1. American Thoracic Society and Infectious Diseases Society of AmericaDiagnosis and Treatment of Adults with Community-acquired Pneumonia: An Official Clinical Practice GuidelineDOI 10.1164/rccm.201908-1581ST 路 published 2019-10-01 路 accessed 2026-08-20
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