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

Treatment for Community-Acquired Pneumonia

For outpatients without comorbidities or recent antibiotic use, treat with amoxicillin or a macrolide; for those with comorbidities or recent antibiotics, use a respiratory fluoroquinolone or combination β-lactam plus macrolide; hospitalized non-ICU patients require either a respiratory fluoroquinolone alone or β-lactam plus macrolide; ICU patients need a β-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) plus either azithromycin or a respiratory fluoroquinolone. 1, 2

Outpatient Treatment

Previously Healthy Patients

• Amoxicillin at higher doses (1 g three times daily) is the preferred first-line agent for patients without comorbidities or recent antibiotic exposure 1, 2
• A macrolide (azithromycin, clarithromycin, or erythromycin) serves as an alternative choice and is appropriate for penicillin-allergic patients 1, 2
• Doxycycline represents another acceptable alternative in this population 1

Patients with Comorbidities or Recent Antibiotic Use

• A respiratory fluoroquinolone (levofloxacin 750 mg, moxifloxacin, or gemifloxacin) is strongly recommended as monotherapy 1, 3
• Alternatively, use combination therapy with a β-lactam (high-dose amoxicillin 1 g three times daily, amoxicillin-clavulanate 2 g twice daily, ceftriaxone, cefpodoxime, or cefuroxime 500 mg twice daily) plus a macrolide 1
• In regions with high-level macrolide resistance (≥25% with MIC ≥16 mg/mL), avoid macrolide monotherapy and use the above alternatives 1

Suspected Aspiration with Infection

• Amoxicillin-clavulanate or clindamycin should be used to cover anaerobic organisms 2

Non-Severe Hospitalized Patients

Most non-severe inpatients can be treated with oral antibiotics from admission, which is a key cost-saving and safety consideration 2, 4

Preferred Regimens

• Combined oral therapy with amoxicillin plus a macrolide (erythromycin or clarithromycin) is the standard approach 2, 4
• A respiratory fluoroquinolone (levofloxacin) as monotherapy provides an effective alternative 1, 4

When Parenteral Therapy is Required

• Use intravenous ampicillin or benzylpenicillin together with erythromycin or clarithromycin 2
• A β-lactam (cefotaxime, ceftriaxone, or ampicillin) plus a macrolide is strongly recommended 1
• Ertapenem is acceptable for selected patients with risk factors for gram-negative pathogens (excluding Pseudomonas) 1

Severe CAP Requiring ICU Admission

Patients with severe pneumonia require immediate parenteral antibiotics upon diagnosis, as delays significantly worsen outcomes 2, 4

Standard Regimen

• A β-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) plus either azithromycin or a respiratory fluoroquinolone is the evidence-based combination 1, 4
• This dual coverage addresses both typical and atypical pathogens, which improves mortality in severe disease 1

Pseudomonas aeruginosa Coverage

When Pseudomonas is suspected or documented (structural lung disease, recent hospitalization, broad-spectrum antibiotic exposure):

• Use an antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) 1, 4
• Plus either ciprofloxacin or levofloxacin 750 mg 1, 4
• Alternatively, use the antipseudomonal β-lactam plus an aminoglycoside and azithromycin 1
• For penicillin allergy, substitute aztreonam for the β-lactam 1

MRSA Coverage

• Add vancomycin or linezolid when community-acquired MRSA is suspected or proven 1, 4
• Consider MRSA in patients with necrotizing pneumonia, cavitation, or severe illness following influenza 1

Duration of Therapy

Treat for a minimum of 5 days if the patient achieves clinical stability, defined as afebrile for 48-72 hours with no more than one CAP-associated sign of clinical instability 1, 2

Clinical Stability Criteria

Before discontinuing antibiotics, patients must be:

• Afebrile for 48-72 hours 1
• Hemodynamically stable 2
• Improving clinically with decreased cough and dyspnea 2
• Able to take oral medications 2

Duration by Clinical Scenario

• 3 days for non-severe or moderate CAP stabilized by day 3 5
• 5 days for patients stabilized by day 5 1, 5
• 7 days for uncomplicated CAP not meeting earlier stability criteria 1, 5
• 7 days for suspected or proven MRSA or P. aeruginosa 1
• 14-21 days for complicated pneumonia (empyema, lung abscess, Legionella, Staphylococcus aureus, or gram-negative enteric bacilli) 2

Switching from IV to Oral Therapy

Switch to oral antibiotics when the patient is hemodynamically stable, improving clinically, afebrile, and able to tolerate oral intake 2, 4

• Use the same agent or same drug class when switching 1
• Most patients achieve stability within 48-72 hours, allowing early transition 1
• The switch does not require waiting for complete symptom resolution, only clinical stability 2

Timing of First Antibiotic Dose

For patients admitted through the emergency department, administer the first antibiotic dose while still in the ED to minimize time to treatment and improve outcomes 1, 2

Microbiological Testing

Obtain respiratory tract samples for culture and susceptibility testing in hospitalized patients, particularly those with severe disease, risk factors for resistant pathogens, or failure of outpatient therapy 1

• This approach helps combat overuse of anti-MRSA and antipseudomonal therapy 1
• Blood cultures should be obtained before antibiotics in hospitalized patients 1
• Sputum Gram stain and culture are recommended when feasible 1
• Once etiology is identified, narrow therapy to pathogen-directed treatment 4

Common Pitfalls to Avoid

• Do not use macrolide monotherapy in regions with high macrolide resistance or in hospitalized patients 1
• Avoid the healthcare-associated pneumonia (HCAP) classification, which led to inappropriate broad-spectrum antibiotic overuse 1
• Do not routinely obtain follow-up chest imaging in patients whose symptoms resolve within 5-7 days 1
• Do not continue antibiotics beyond clinical stability unless complications exist 1, 5
• Always add an antipseudomonal β-lactam when treating Pseudomonas with a fluoroquinolone to prevent resistance development 1, 3