Management of Community-Acquired Pneumonia
Severity-Based Treatment Algorithm
Treatment of community-acquired pneumonia should be stratified by severity, with outpatients receiving amoxicillin or a macrolide, hospitalized non-severe cases receiving combination therapy with amoxicillin plus a macrolide, and severe ICU cases requiring IV ceftriaxone or cefotaxime plus a macrolide or respiratory fluoroquinolone. 1
Outpatient Management (Mild CAP)
First-line therapy:
- Amoxicillin at higher doses for 7 days remains the preferred first-line agent 1
- Macrolides (azithromycin, clarithromycin, or erythromycin) are the alternative for penicillin-allergic patients 1, 2
- Doxycycline or a respiratory fluoroquinolone with enhanced S. pneumoniae activity are additional options 2
Dosing for azithromycin: 500 mg as a single dose on Day 1, followed by 250 mg once daily on Days 2-5 3
Hospitalized Non-Severe CAP
Preferred regimen:
- Combined oral therapy with amoxicillin plus a macrolide 1
- Most hospitalized patients can be adequately treated with oral antibiotics rather than IV 1
Alternative regimens:
- Beta-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) plus a macrolide (clarithromycin or erythromycin) 2
- Respiratory fluoroquinolone monotherapy 2
Important consideration: Between 2000-2009, U.S. practice patterns shifted away from single-agent therapy (48.2% to 30.0%) toward combination regimens, with ceftriaxone plus azithromycin becoming the most common regimen by 2009 (18.5% of cases) 4
Severe CAP Requiring ICU Admission
Immediate IV antibiotics are required after diagnosis 1
Preferred regimen:
- IV ceftriaxone or cefotaxime plus a macrolide 1, 5
- Alternative: Second or third generation cephalosporin combined with a macrolide 1
- Alternative: Respiratory fluoroquinolone (levofloxacin, moxifloxacin) 1
Ceftriaxone dosing consideration: For patients requiring mechanical ventilation, ceftriaxone 2 g/day was associated with lower 30-day mortality (17.2% vs 20.4%) compared to 1 g/day, though overall adverse events were slightly higher 6
When Pseudomonas is suspected (COPD, bronchiectasis, recent antibiotics/steroids):
- Anti-pseudomonal beta-lactam (piperacillin/tazobactam, carbapenem, cefepime) plus anti-pseudomonal fluoroquinolone (high-dose ciprofloxacin) 5
- Alternative: Anti-pseudomonal beta-lactam plus aminoglycoside 5
When MRSA is suspected:
- Add vancomycin or linezolid 5
- Note: Vancomycin use in CAP nearly doubled from 13.1% to 23.3% between 2000-2009 4
Supportive Care
Oxygen therapy:
- Maintain oxygen saturation >92% and PaO2 >8 kPa 1
- High-concentration oxygen is safe in uncomplicated pneumonia 1
- For COPD patients with ventilatory failure, guide oxygen therapy by repeated arterial blood gases 1
Duration and Route of Therapy
Treatment duration:
- 7 days of appropriate antibiotics for uncomplicated non-severe CAP 1, 2
- Severe pneumonia: extend to 10-14 days 2
- Legionella or resistant bacteria: up to 21 days 2
IV to oral switch criteria:
- Clinical improvement occurs 1
- Temperature normalizes for 24 hours 1
- No contraindications to oral therapy exist 1
Short-course high-dose regimens:
- Levofloxacin 750 mg daily for 5 days demonstrated 90.9% clinical success, comparable to 500 mg for 10 days (91.1%) 7
- Azithromycin 500 mg Day 1, then 250 mg Days 2-5 is effective for mild CAP 3
Pathogen-Specific Efficacy
Multi-drug resistant S. pneumoniae (MDRSP):
- Levofloxacin achieved 95% clinical and bacteriologic success in MDRSP cases 7
- Respiratory fluoroquinolones demonstrate clinical success rates >90% for S. pneumoniae 8
Atypical pathogens:
- Clinical success rates: Chlamydophila pneumoniae 96%, Mycoplasma pneumoniae 96%, Legionella pneumophila 70% 7
Prevention
Vaccination recommendations:
- Influenza vaccination for high-risk groups: chronic lung/heart/renal/liver disease, diabetes, immunosuppression, age >65 years 1, 2
- Pneumococcal vaccination for those aged ≥2 years at increased risk (though evidence for CAP prevention in at-risk groups is limited) 1
Risk factor modification:
Common Pitfalls
Avoid monotherapy in severe CAP: Combination therapy is essential for ICU patients to cover both typical and atypical pathogens 1, 5
Don't delay antibiotics in severe cases: Immediate IV antibiotics after diagnosis are critical for severe pneumonia 1
Consider local resistance patterns: Rising resistance rates, particularly with S. pneumoniae, necessitate empirical coverage for both typical and atypical pathogens 8
Reassess non-responders: Patients not responding to treatment require diagnostic evaluation for resistant/unusual pathogens, non-pneumonic diagnoses, or complications 2