Community-Acquired Pneumonia Treatment
For outpatient treatment of healthy adults without comorbidities, amoxicillin 1 gram three times daily is the first-line antibiotic choice, while hospitalized patients should receive combination therapy with a β-lactam (such as ceftriaxone) plus a macrolide (such as azithromycin) for at least 3 days. 1, 2, 3
Outpatient Treatment Regimens
Healthy Adults Without Comorbidities
- First-line therapy: Amoxicillin 1 gram three times daily (strong recommendation, moderate quality evidence) 1, 2
- Alternative options include:
Adults With Comorbidities
Important caveat: Recent antibiotic use within 3 months is a risk factor for drug-resistant Streptococcus pneumoniae and should guide selection away from recently used antibiotic classes 2
Inpatient Treatment (Non-ICU)
Preferred Regimen
- β-lactam (ampicillin/sulbactam, cefotaxime, ceftriaxone, or ceftaroline) PLUS a macrolide (azithromycin or clarithromycin) 1, 2, 3
- This combination has been shown to reduce length of stay compared to other regimens 4
Alternative Regimen
- Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin) 1, 2
- While convenient, fluoroquinolone monotherapy led to higher rates of documented adverse events (adjusted OR: 1.23) compared to macrolides in outpatient settings 4
Critical timing consideration: The first antibiotic dose should be administered within 8 hours of hospital arrival, ideally while still in the emergency department, as delayed administration increases mortality 5, 1, 2
Severe CAP Requiring ICU Care
Patients WITHOUT Pseudomonas Risk Factors
- Non-antipseudomonal β-lactam (ceftriaxone or cefotaxime) PLUS either a macrolide OR a respiratory fluoroquinolone 5, 1, 2
- Current data do not support fluoroquinolone monotherapy in ICU patients 5
Patients WITH Pseudomonas Risk Factors
- Antipseudomonal β-lactam (cefepime, ceftazidime, piperacillin-tazobactam, or meropenem) PLUS either: 5, 1, 2
Risk factors for Pseudomonas infection include: severe structural lung disease (bronchiectasis), recent antibiotic therapy, or recent hospitalization (especially ICU) 2
Special Populations and Pathogens
MRSA Coverage
- Add vancomycin or linezolid for patients with MRSA risk factors 5, 1, 2
- Obtain cultures and nasal PCR to allow de-escalation 1, 2
- In nosocomial pneumonia studies, vancomycin was added to treatment in approximately 40% of patients 6
β-Lactam Allergic Patients
- Without Pseudomonas risk: Respiratory fluoroquinolone with or without clindamycin 2
- With Pseudomonas risk: Aztreonam plus levofloxacin or aztreonam plus moxifloxacin, with or without an aminoglycoside 5, 2
Atypical Pathogens
- For suspected or confirmed Legionella: Respiratory fluoroquinolone (levofloxacin preferred) or macrolide (azithromycin preferred) ± rifampin 1
- For Mycoplasma or Chlamydophila: Macrolide, doxycycline, or respiratory fluoroquinolone 1
- Clinical success rates for atypical pneumonia due to Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila were 96%, 96%, and 70%, respectively 6
Multi-Drug Resistant Streptococcus Pneumoniae (MDRSP)
- Levofloxacin was effective for MDRSP with 95% clinical and bacteriologic success 6
- MDRSP isolates are resistant to two or more of: penicillin (MIC ≥2 mcg/mL), 2nd generation cephalosporins, macrolides, tetracyclines, and trimethoprim/sulfamethoxazole 6
Duration of Therapy
- Minimum duration: 5 days (level I evidence) 5, 1, 2
- Patients should be afebrile for 48-72 hours before discontinuing antibiotics 5, 2
- Patients should have no more than 1 CAP-associated sign of clinical instability before discontinuation 5
- Procalcitonin levels may guide shorter treatment duration 1, 2
- Longer duration may be needed if: initial therapy was not active against the identified pathogen or if complicated by extrapulmonary infection (meningitis, endocarditis) 5
Transition to Oral Therapy and Discharge
Criteria for switching from IV to oral therapy: 5
- Hemodynamically stable and improving clinically 5
- Able to ingest medications 5
- Normally functioning gastrointestinal tract 5
- Afebrile (<100°F) on two occasions 8 hours apart 5
- White blood cell count decreasing 5
- Improvement in cough and dyspnea 5
Patients can be discharged on the same day as oral therapy is started if other medical and social factors permit 5
Common Pitfalls and Caveats
- Avoid changing initial antibiotic therapy in the first 72 hours unless there is marked clinical deterioration 5
- Up to 10% of CAP patients will not respond to initial therapy, requiring diagnostic evaluation for drug-resistant or unusual pathogens, non-pneumonia diagnosis, or pneumonia complications 5
- Overuse of fluoroquinolones should be avoided to prevent development of resistance; recent fluoroquinolone use should dictate selection of a non-fluoroquinolone regimen 1, 2
- Macrolide resistance is reported in 20-30% of S. pneumoniae isolates 2
- Procalcitonin should not be used to withhold initial antibiotic therapy in patients with clinically suspected and radiographically confirmed CAP 1
- Inadequate coverage of causative pathogens is associated with worse outcomes 1
- Only 38% of hospitalized CAP patients have a pathogen identified, with viruses identified in up to 40% of those cases and S. pneumoniae in approximately 15% 3
- All patients with CAP should be tested for COVID-19 and influenza when these viruses are common in the community 3
Adjunctive Therapy for Severe CAP
- Systemic corticosteroid administration within 24 hours of development of severe CAP may reduce 28-day mortality 3
- Patients with persistent septic shock despite adequate fluid resuscitation should be considered for treatment with drotrecogin alfa activated within 24 hours of admission 5
- Hypotensive, fluid-resuscitated patients should be screened for occult adrenal insufficiency 5