Community Acquired Pneumonia

The following is a summary of the 2019 American Thoracic Society and Infectious Diseases Society of America Guidelines1. (Full Text) The guidelines recommend abandoning the “health care associated pneumonia” categorization of patients and instead recommend the following empiric therapy. Treatment for MRSA and Pseudomonas Aeruginosa is based on prior positive culture, nasal PCR, or presence of “locally validated risk factors”.

Antibiotic Selection

  • Amoxicillin 1 g TID (strong recommendation, moderate quality of evidence)


  • Doxycycline 100 mg BID (conditional recommendation, low quality of evidence)


  • Macrolide – only in areas with pneumococcal resistance to macrolides <25% (conditional recommendation, moderate quality of evidence). Note: Most areas in the US have already exceeded this threshold.
    • azithromycin 500 mg on first day then 250 mg daily or 
    • clarithromycin 500 mg BID or clarithromycin extended release 1,000 mg daily 
Combination Therapy
  • Amoxicillin/clavulanate 500 mg/125 mg TID or 
  • Amoxicillin/clavulanate 875 mg/125 mg BID or
  • Amoxicillin/clavulanate 2,000 mg/125 mg BID or
  • Cefpodoxime 200 mg BID or
  • Cefuroxime 500 mg BID


  • Azithromycin 500 mg day one, then 250 mg daily or
  • Clarithromycin 500 mg BID or
  • Clarithromycin extended release 1,000 mg once daily or
  • Doxycycline 100 mg twice daily (conditional, low quality of evidence)

Strong recommendation, moderate quality of evidence 

  • Levofloxacin 750 mg daily or
  • Moxifloxacin 400 mg daily or
  • Gemifloxacin 320 mg daily

Strong recommendation, moderate quality of evidence

Combination Therapy
  • Ampicillin + sulbactam 1.5–3 g every 6 h or
  • Cefotaxime 1–2 g every 8 h or
  • Ceftriaxone 1–2 g daily or
  • Ceftaroline 600 mg every 12 h 


  • Azithromycin 500 mg daily or 
  • Clarithromycin 500 mg BID

Strong recommendation, high quality of evidence

Patient who have contraindications to both macrolides and fluoroquinolones may substitute doxycycline 100 mg twice daily (conditional recommendation, low quality of evidence).

  • Levofloxacin 750 mg orally or IV daily or
  • Moxifloxacin 400 mg orally or IV daily

Strong recommendation, high quality of evidence

Previous MRSA isolation, add one of the following:
  • Vancomycin 15 mg/kg every 12 hours, adjust based on levels
  • Linezolid 600 mg every 12 hours
Previous evidence of Pseudomonas aeruginosa, add one of the following:
  • Piperacillin-tazobactam 4.5 g every 6 hours 
  • Cefepime 2 g every 8 hours
  • Ceftazidime 2 g every 8 hours
  • Imipenem 500 mg every 6 hours
  • Meropenem 1 g every 8 hours
  • Aztreonam 2 g every 8 hours

Miscellaneous Recommendations

Test / Therapy


Sputum Cultures

Recommended in patients with severe disease as well as in all inpatients treated for MRSA or Pseudomonas aeruginosa

Blood Cultures

Recommended in patients with severe disease as well as in all inpatients treated for MRSA or Pseudomonas aeruginosa

Procalcitonin Level

Not to be used to determine need for initial antibiotic therapy


Not recommended. Possible role in refractory shock

Healthcare Associated Pneumonia

Recommend abandoning this classification. Instead, use local epidemiology, risk factors, prior hx of MRSA or Pseudomonas, and de-escalation if cultures are negative

Routine follow up chest imaging

Not recommended

Treatment Duration

At least 5 days for CAP and 7 days if treating MRSA or Pseudomonas. Should be extended if clinical stability not achieved within 5-7 days.

Influenza Positive

Recommend antiviral therapy in addition to antibiotics if pneumonia present clinically or radiographically


The guidelines recommend use of a risk scoring system to guide disposition. Recommended options include: 

Who needs to be admitted? 

Admit to inpatient floor or ICU?

Further Reading

Community-Acquired Pneumonia in the Emergency Department (Infectious Disease CME) Date Release: Feb 2021 Recommendations on risk stratification, imaging, testing, and drug therapies for CAP are evolving continuously. This issue reviews the latest evidence on managing CAP in the ED.

Pediatric Community-Acquired Pneumonia: Diagnosis and Management in the Emergency Department (Pharmacology CME and Infectious Disease CME) Date Release: Apr 2019 Distinguishing bacterial pneumonia from viral pneumonia is critical to providing effective treatment but remains a significant challenge. This issue provides guidance for the management of pediatric community-acquired pneumonia as well as associated complications including pleural effusion/empyema.

FOAMed – Risk Management Pitfalls for Community-Acquired Pneumonia in the ED

FOAMed – Management of Community-Acquired Pneumonia: Clinical Pathway

FOAMed – Clinical Pathway for Management of Pediatric Patients With Community-Acquired Pneumonia


  1. Metlay JP, Waterer GW, Long AC, Anzueto A, Brozek J, Crothers K, Cooley LA, Dean NC, Fine MJ, Flanders SA, Griffin MR, Metersky ML, Musher DM, Restrepo MI, Whitney CG. 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. Am J Respir Crit Care Med. 2019 Oct 1;200(7):e45-e67. PubMed
  2. Jones BE, Jones J, Bewick T, Lim WS, Aronsky D, Brown SM, et al. CURB-65 pneumonia severity assessment adapted for electronic decision support. Chest 2011;140:156–163. PubMed

Last Updated on January 24, 2023

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