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

Recommended Antibiotics for Community-Acquired Pneumonia

For community-acquired pneumonia (CAP), the recommended initial antibiotic treatment is a β-lactam (ampicillin-sulbactam, cefotaxime, ceftriaxone, or ceftaroline) plus a macrolide (azithromycin or clarithromycin), or respiratory fluoroquinolone monotherapy (levofloxacin 750 mg or moxifloxacin 400 mg). 1

Treatment Approach Based on Setting and Severity

Outpatient Treatment

• Mild CAP (healthy patients with no risk factors):

  • First-line: Macrolide (azithromycin 500 mg on day 1, then 250 mg daily for days 2-5) 2
  • Alternative: Doxycycline

• Moderate CAP (comorbidities or risk factors for drug-resistant pathogens):

  • First-line: Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) 3, 4
  • Alternative: β-lactam (high-dose amoxicillin or amoxicillin-clavulanate) plus a macrolide 1

Inpatient Treatment (Non-ICU)

• Standard regimen: β-lactam (ampicillin-sulbactam, cefotaxime, ceftriaxone) plus a macrolide 1
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin or moxifloxacin) 1

Severe CAP (ICU)

• Standard regimen: β-lactam (ampicillin-sulbactam, cefotaxime, ceftriaxone, or ceftaroline) plus either a macrolide or a respiratory fluoroquinolone 1

Special Considerations

Drug-Resistant Streptococcus pneumoniae (DRSP)

• For suspected DRSP, use:
  • Respiratory fluoroquinolones (moxifloxacin, levofloxacin) 5, 3
  • High-dose β-lactams (ceftriaxone, cefotaxime) 5
  • Avoid older macrolides if high local resistance rates 1

MRSA Risk Factors

• For patients with prior MRSA infection/colonization or recent hospitalization:
  • Add MRSA coverage (vancomycin or linezolid)
  • Obtain cultures/nasal PCR to allow de-escalation 1

Pseudomonas Risk Factors

• For patients with structural lung disease, recent hospitalization, or frequent antibiotic use:
  • Add antipseudomonal β-lactam (piperacillin-tazobactam, cefepime)
  • Obtain cultures to guide therapy 1

Pathogen-Specific Treatment

• Streptococcus pneumoniae: β-lactams (amoxicillin, cefotaxime, ceftriaxone) 1
• Mycoplasma pneumoniae: Macrolide (azithromycin preferred) 1
• Legionella spp.: Levofloxacin (preferred), moxifloxacin, or macrolide 1
• Chlamydophila pneumoniae: Doxycycline, macrolide, levofloxacin, or moxifloxacin 1

Treatment Duration

• Standard treatment duration: 7-10 days 1
• May extend to 14 days for atypical pathogens such as Legionella 1
• Extended duration (14-21 days) for Pseudomonas infections, slow clinical response, severe immunosuppression, or complicated pneumonia 1

Monitoring and Response Assessment

• Monitor clinical response using:
  • Body temperature
  • Respiratory parameters
  • Hemodynamic stability
• Consider treatment failure if no improvement after 72 hours 1
• Switch from IV to oral therapy when clinically stable (usually within 3-5 days) 1

Common Pitfalls to Avoid

1. Inadequate initial coverage: Ensure appropriate spectrum based on risk factors
2. Delayed switch from IV to oral therapy: Transition when clinically stable
3. Inappropriate duration: Avoid unnecessarily prolonged courses
4. Failure to recognize treatment failure: Reassess if no improvement after 72 hours
5. Overuse of broad-spectrum antibiotics: De-escalate based on culture results 1

Evidence Quality and Considerations

Recent evidence from network meta-analyses suggests trends toward better clinical response and lower mortality with respiratory fluoroquinolones for empiric treatment of mild to moderate CAP, though confidence intervals were broad and partially overlapping 6. However, fluoroquinolone therapy has been associated with higher rates of adverse events compared to macrolides 7.

The choice between combination therapy (β-lactam plus macrolide) versus fluoroquinolone monotherapy should consider local resistance patterns, patient risk factors, and comorbidities. The American Thoracic Society guidelines recommend either approach as acceptable first-line therapy 1.