What is the recommended treatment for community-acquired pneumonia (CAP)?

Treatment for Community-Acquired Pneumonia

For outpatients without comorbidities, use amoxicillin 1 g every 8 hours or a macrolide (azithromycin 500 mg Day 1, then 250 mg Days 2-5); for hospitalized non-ICU patients, use a β-lactam (ceftriaxone 1-2 g daily) plus a macrolide (azithromycin or clarithromycin) for a minimum of 5 days. 1, 2

Outpatient Treatment Algorithm

Previously Healthy Adults (No Comorbidities)

• First-line therapy: Amoxicillin 1 g every 8 hours is the preferred option for patients without comorbidities 2
• Alternative first-line: Macrolide monotherapy (azithromycin 500 mg Day 1, then 250 mg Days 2-5, or clarithromycin) is appropriate for previously healthy adults, particularly those under 40 years old 1, 2, 3
• Second alternative: Doxycycline 100 mg twice daily (with first dose of 200 mg for rapid serum levels) 2

Outpatients with Comorbidities or Recent Antibiotic Use

• Preferred regimen: Respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) OR β-lactam plus macrolide combination 1, 2, 4
• Critical consideration: Patients with recent exposure to one antibiotic class should receive treatment from a different class due to increased resistance risk 2
• Fluoroquinolone justification: Despite FDA warnings about adverse events, fluoroquinolones remain justified for adults with comorbidities due to their performance in studies, low resistance rates, coverage of typical and atypical organisms, oral bioavailability, and convenience of monotherapy 2

Hospitalized Non-ICU Patients

• Standard regimen: β-lactam (ceftriaxone 1-2 g every 24 hours) PLUS macrolide (azithromycin or clarithromycin) 1, 2, 5
• Alternative monotherapy: Respiratory fluoroquinolone alone (levofloxacin or moxifloxacin) 1, 2
• Timing priority: First antibiotic dose should be administered while still in the emergency department, as early administration is associated with improved outcomes 2

Severe CAP/ICU Patients

Without Pseudomonas Risk Factors

• Recommended: β-lactam PLUS either azithromycin or respiratory fluoroquinolone 1, 2
• Alternative: Moxifloxacin or levofloxacin ± non-antipseudomonal cephalosporin III 2

With Pseudomonas Risk Factors

• Option 1: Antipseudomonal β-lactam PLUS ciprofloxacin or levofloxacin 1, 2
• Option 2: Antipseudomonal β-lactam PLUS aminoglycoside (gentamicin, tobramycin, or amikacin) PLUS azithromycin 1, 2
• Option 3: Antipseudomonal β-lactam PLUS aminoglycoside PLUS antipneumococcal fluoroquinolone 2

Duration of Therapy

• Minimum duration: 5 days for most patients with CAP 1, 2
• Discontinuation criteria: Patients must be afebrile for 48-72 hours AND have no more than 1 CAP-associated sign of clinical instability before stopping therapy 1, 2
• Uncomplicated S. pneumoniae: 7-10 days is typically sufficient 2
• Severe pneumonia or specific pathogens: Extend treatment to 14-21 days when Legionella, staphylococcal, or Gram-negative enteric bacilli are suspected or confirmed 2
• General guideline: Treatment should generally not exceed 8 days in a responding patient 2

Switching from IV to Oral Therapy

• Timing: Switch when patients are hemodynamically stable, clinically improving, and temperature has been normal for 24 hours 1, 2
• Typical timeframe: Usually occurs within 72 hours (3 days) after admission when patient defervesces clinically 2

Special Considerations

MRSA Coverage

• Add vancomycin or linezolid when: Community-acquired MRSA is suspected based on prior MRSA infection, recent hospitalization, or recent antibiotic use 2

Pathogen-Directed Therapy

• Once etiology identified: Antimicrobial therapy should be directed at the specific pathogen using reliable microbiological methods 1, 2
• Culture importance: Appropriate culture and susceptibility tests should be performed before treatment to isolate organisms and determine susceptibility 4

Corticosteroids

• Severe CAP: Systemic corticosteroid administration within 24 hours of development of severe CAP may reduce 28-day mortality 5

Critical Pitfalls to Avoid

• Macrolide resistance: S. pneumoniae resistance to macrolides ranges 30-40% and often co-exists with β-lactam resistance in patients with recent hospitalization, chronic diseases, or prior antibiotic exposure 2
• Fluoroquinolone overuse: Reserve respiratory fluoroquinolones for patients with β-lactam allergies or specific indications to prevent resistance development 2
• Inadequate atypical coverage: Ensure coverage for Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila, as clinical success is significantly higher for Legionella when atypical antibiotics are used 2
• Delayed antibiotic administration: Delaying antibiotic administration is associated with increased mortality, particularly in severe pneumonia 2
• Local resistance patterns: Local antimicrobial susceptibility patterns should guide empiric therapy choice, as resistance patterns vary by region 2

Follow-up

• Clinical review: Should be arranged for all patients at around 6 weeks, either with their general practitioner or in a hospital clinic 1
• Failure to improve: Conduct careful review of clinical history, examination, prescription chart, and all available investigation results; consider repeat chest radiograph, CRP, white cell count, and further microbiological testing 2