Recommended Antibiotics for Community-Acquired Pneumonia (CAP)
First-line antimicrobial therapy for community-acquired pneumonia should include a β-lactam plus either azithromycin or a respiratory fluoroquinolone, as recommended by the Infectious Diseases Society of America. 1
Initial Antibiotic Selection Algorithm
Outpatient Treatment
- Standard regimen: β-lactam (amoxicillin) + macrolide (azithromycin preferred)
- Penicillin-allergic patients: Respiratory fluoroquinolone (levofloxacin 750 mg daily for 5 days)
Inpatient Treatment (non-ICU)
- Standard regimen: Intravenous β-lactam (ceftriaxone) + macrolide (azithromycin)
- Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin)
ICU Treatment
- Standard regimen: β-lactam + either azithromycin or respiratory fluoroquinolone
- Pseudomonas risk: Antipseudomonal β-lactam + either ciprofloxacin/levofloxacin or aminoglycoside + azithromycin
- MRSA risk: Add vancomycin or linezolid to standard regimen
Pathogen-Specific Treatment Options
| Pathogen | Treatment Options |
|---|---|
| Streptococcus pneumoniae | β-lactams (amoxicillin, cefotaxime, ceftriaxone) [1] |
| Mycoplasma pneumoniae | Macrolide (azithromycin preferred) [1] |
| Legionella spp. | Levofloxacin (preferred), moxifloxacin, or macrolide ± rifampicin [1] |
| Chlamydophila pneumoniae | Doxycycline, macrolide, levofloxacin, or moxifloxacin [1] |
| Haemophilus influenzae | β-lactams, respiratory fluoroquinolones [2] |
Dosing Recommendations
Levofloxacin
- Standard regimen: 500 mg once daily for 7-14 days 2
- High-dose, short-course: 750 mg once daily for 5 days 2, 3
Azithromycin
- Standard regimen: 500 mg on day 1, followed by 250 mg once daily on days 2-5 5
- Alternative regimen: 500 mg once daily for 3 days 5
Duration of Therapy
- Minimum of 5 days of antibiotic therapy 1
- Patient should be afebrile for 48-72 hours and have no more than 1 CAP-associated sign of clinical instability before discontinuation 1
- Standard treatment duration is 7-10 days for most pathogens 1
- Extended duration (14-21 days) may be needed for:
- Atypical pathogens like Legionella
- Pseudomonas infections
- Slow clinical response
- Severe immunosuppression
- Complicated pneumonia 1
Transition to Oral Therapy
Transition from IV to oral therapy when the patient:
- Is hemodynamically stable
- Shows clinical improvement
- Can ingest medications
- Has normal GI function 1
Common Pitfalls to Avoid
- Delayed antibiotic administration: First dose should be given while still in the ED 1
- Inadequate initial coverage: Ensure coverage for both typical and atypical pathogens 1
- Failure to recognize treatment failure: Consider treatment failure if no improvement after 72 hours 1
- Inappropriate duration: Not extending therapy for complicated infections or when initial therapy was not active against the identified pathogen 1
- Not considering resistance patterns: S. pneumoniae resistance to macrolides and β-lactams is increasing 6
Special Considerations
- For patients with Pseudomonas risk, combination therapy with an antipseudomonal β-lactam plus either a fluoroquinolone or aminoglycoside plus azithromycin is essential 1
- The combination of a third-generation cephalosporin and a macrolide has shown excellent efficacy against S. pneumoniae compared to fluoroquinolone monotherapy 7
- Fluoroquinolones should be reserved for patients with contraindications to first-line agents or in areas with high resistance patterns to preserve their effectiveness 6
Remember that early, appropriate antibiotic therapy significantly reduces morbidity and mortality in patients with CAP, making the initial antibiotic selection crucial for optimal patient outcomes.