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

Treatment for Community-Acquired Pneumonia

Outpatient Treatment (Previously Healthy, No Comorbidities)

For previously healthy outpatients without risk factors for drug-resistant pathogens, start with a macrolide (azithromycin 500 mg Day 1, then 250 mg daily Days 2-5) or high-dose amoxicillin (1 g every 8 hours). 1, 2, 3

• Macrolide monotherapy provides coverage against typical and atypical organisms including Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila 1, 2
• Doxycycline 100 mg twice daily (with first dose 200 mg) is an acceptable alternative first-line option 2
• The American Thoracic Society specifically recommends amoxicillin 1 g every 8 hours for outpatients under 40 years without comorbidities 2

Outpatient Treatment (With Comorbidities or Recent Antibiotic Use)

For outpatients with comorbidities (diabetes, heart/lung/liver/renal disease) or recent antibiotic exposure, use either a respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) OR combination therapy with a β-lactam plus a macrolide. 1, 2

• Respiratory fluoroquinolones remain justified despite FDA warnings due to their excellent performance, low resistance rates, coverage of typical and atypical organisms, oral bioavailability, and convenience of monotherapy 2
• Critical pitfall: Patients with recent exposure to one antibiotic class must receive treatment from a different class due to increased bacterial resistance risk 2
• Reserve fluoroquinolones for patients with β-lactam allergies or specific indications to prevent resistance development 2

Hospitalized Non-ICU Patients

For hospitalized non-severe CAP patients, use combination therapy with a β-lactam (ceftriaxone 1-2 g every 24 hours) PLUS a macrolide (azithromycin or clarithromycin). 1, 2, 4

• This combination provides coverage for Streptococcus pneumoniae (including multi-drug resistant strains), atypical organisms, and other common pathogens 1, 5
• Alternative option: respiratory fluoroquinolone monotherapy (levofloxacin or moxifloxacin) 1, 2
• The first antibiotic dose must be administered while still in the emergency department, as early administration is associated with improved outcomes 2
• Ceftriaxone combined with azithromycin for a minimum of 3 days is specifically supported by recent high-quality evidence 4

Severe CAP/ICU Patients

For ICU patients without Pseudomonas risk factors, use a β-lactam (ceftriaxone or cefotaxime) PLUS either azithromycin OR a respiratory fluoroquinolone (levofloxacin 750 mg daily). 1, 2

When Pseudomonas Risk Factors Present:

Use an antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, or meropenem) PLUS either:

• Ciprofloxacin or levofloxacin (double-dose: 750 mg), OR
• Aminoglycoside (gentamicin, tobramycin, or amikacin) plus azithromycin 2

Pseudomonas risk factors include: structural lung disease (bronchiectasis, COPD), recent hospitalization, recent broad-spectrum antibiotic use 2

MRSA Coverage

Add vancomycin or linezolid when community-acquired MRSA is suspected based on: 2

• Prior MRSA infection
• Recent hospitalization
• Recent antibiotic use
• Severe necrotizing pneumonia with hemoptysis
• Concurrent influenza infection

Duration of Therapy

Treat for a minimum of 5 days, ensuring the patient is afebrile for 48-72 hours and has no more than 1 sign of clinical instability before discontinuation. 1, 2

• For uncomplicated S. pneumoniae pneumonia: 7-10 days is typically sufficient 2
• For severe pneumonia or specific pathogens (Legionella, staphylococcal, Gram-negative enteric bacilli): extend to 14-21 days 2
• Treatment generally should not exceed 8 days in a responding patient 2
• FDA-approved levofloxacin regimens include both 5-day and 7-14 day options depending on pathogen and severity 5

IV to Oral Transition

Switch from intravenous to oral therapy when the patient is hemodynamically stable, clinically improving, and has been afebrile for 24 hours. 1, 2

• The oral route is preferred for non-severe pneumonia when no contraindications exist 2
• Switching to oral therapy facilitates earlier discharge but does not guarantee it 2

Pathogen-Directed Therapy

Once the etiology is identified through reliable microbiological methods, narrow antimicrobial therapy to target the specific pathogen. 1, 2

• Appropriate culture and susceptibility tests should be performed before treatment when possible 5
• Local antimicrobial susceptibility patterns should guide empiric therapy choices, as resistance varies by region 2
• S. pneumoniae macrolide resistance ranges 30-40% and often co-exists with β-lactam resistance in patients with recent hospitalization, chronic diseases, or prior antibiotic exposure 2

Critical Pitfalls to Avoid

• Inadequate atypical coverage: Failure to cover Mycoplasma, Chlamydophila, and Legionella significantly reduces clinical success, particularly for Legionella pneumonia 2
• Overreliance on fluoroquinolones: Reserve for specific indications to prevent resistance development 2
• Delayed antibiotic administration: Associated with increased mortality, particularly in severe pneumonia 2
• Failure to adjust therapy: Once culture results return, continuing broad-spectrum therapy unnecessarily promotes resistance 2

Special Populations

• Renal insufficiency: No levofloxacin dose adjustment needed for GFR >10 mL/min; exercise caution with GFR <10 mL/min 5
• Hepatic insufficiency: No specific azithromycin dose adjustment recommendations available 3
• Severe CAP with ARDS: Systemic corticosteroid administration within 24 hours may reduce 28-day mortality 4

Follow-up

Clinical review should be arranged for all patients at approximately 6 weeks, either with their general practitioner or in a hospital clinic. 1