What are the recommended antibiotic regimens for community-acquired pneumonia (CAP)?

Recommended Antibiotic Regimens for Community-Acquired Pneumonia

For community-acquired pneumonia (CAP), treatment should be stratified based on patient setting (outpatient vs. inpatient), comorbidities, and risk factors for resistant pathogens, with specific antibiotic regimens tailored to each scenario. 1

Outpatient Treatment

Healthy Adults Without Comorbidities

• First-line options:
  • Amoxicillin 1 g three times daily (strong recommendation) 1
  • Doxycycline 100 mg twice daily (conditional recommendation) 1
  • Macrolide (azithromycin 500 mg on day 1, then 250 mg daily for 4 days) only in areas with pneumococcal resistance to macrolides <25% 1

Adults With Comorbidities

Comorbidities include: chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; or asplenia

• Preferred options:

  • Combination therapy:

    • β-lactam (amoxicillin/clavulanate 875 mg/125 mg twice daily OR cefpodoxime 200 mg twice daily OR cefuroxime 500 mg twice daily) PLUS
    • Macrolide (azithromycin 500 mg on day 1, then 250 mg daily) OR doxycycline 100 mg twice daily 1

  • Monotherapy alternative:

    • Respiratory fluoroquinolone (levofloxacin 750 mg daily, moxifloxacin 400 mg daily, or gemifloxacin 320 mg daily) 1, 2

Inpatient Treatment (Non-ICU)

• Preferred regimen:

  • β-lactam (ceftriaxone 1-2 g IV daily, cefotaxime 1-2 g IV q8h, or ampicillin-sulbactam) PLUS
  • Macrolide (azithromycin 500 mg IV/PO daily) 1, 3

• Alternative regimen:

  • Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg IV/PO daily or moxifloxacin 400 mg IV/PO daily) 1, 3, 2

ICU Treatment

• Standard regimen (when Pseudomonas is not a concern):

  • β-lactam (ceftriaxone, cefotaxime, ampicillin-sulbactam) PLUS
  • Either macrolide or respiratory fluoroquinolone 1, 3

• When Pseudomonas is a concern:

  • Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, meropenem) PLUS
  • Either ciprofloxacin or levofloxacin OR an aminoglycoside plus either a respiratory fluoroquinolone or macrolide 1, 3

• For patients with β-lactam allergy:

  • Aztreonam plus either levofloxacin or moxifloxacin, with or without an aminoglycoside 1, 3

Special Considerations

Penicillin Allergy

• For immediate-type hypersensitivity reactions: Respiratory fluoroquinolone monotherapy 3
• For non-immediate reactions: Aztreonam-based regimens for severe allergies 3

Suspected MRSA

• Add vancomycin or linezolid to standard regimens 3

Suspected Aspiration

• Add anaerobic coverage with clindamycin or metronidazole if using a fluoroquinolone that lacks anaerobic activity 3

Duration of Therapy

• Standard duration: 5-7 days for most patients 3, 4
• Minimum 5 days, with criteria for discontinuation including:
  • Afebrile for 48-72 hours
  • No more than one sign of clinical instability
  • Improvement in cough and dyspnea 3

Switching from IV to Oral Therapy

Patients can be switched from IV to oral antibiotics when they are:

• Hemodynamically stable
• Clinically improving
• Able to take oral medications
• Afebrile for 48-72 hours 3

Important Considerations

• Recent antibiotic use (within 3 months) increases risk for resistant organisms; avoid using the same class of antibiotics 1, 3
• β-lactam monotherapy has been shown to be non-inferior to β-lactam-macrolide combination or fluoroquinolone monotherapy for non-ICU hospitalized patients in some studies 5
• Multidrug resistance is increasingly common in CAP pathogens, particularly S. pneumoniae and K. pneumoniae 6
• The most common bacterial pathogens in CAP include S. pneumoniae, H. influenzae, atypical bacteria (M. pneumoniae, C. pneumoniae, L. pneumophila), and increasingly, resistant gram-negative organisms 4, 7

Pitfalls to Avoid

• Using macrolide monotherapy in areas with high pneumococcal resistance (>25%) 1
• Failing to consider recent antibiotic exposure when selecting empiric therapy 3
• Prolonging antibiotic therapy beyond 7 days in responding patients 3
• Using fluoroquinolones in patients who have received them within the past 3 months 3
• Delaying appropriate antibiotic therapy, which is associated with increased mortality 4

The 2019 ATS/IDSA guidelines represent the most current comprehensive recommendations for CAP management, with treatment decisions based on patient setting, risk factors, and local resistance patterns 1.