What is the recommended treatment for a patient with community-acquired pneumonia (PCAP)?

Treatment of Community-Acquired Pneumonia

For hospitalized patients with community-acquired pneumonia without risk factors for resistant organisms, initiate combination therapy with ceftriaxone 1-2 g IV daily plus azithromycin 500 mg daily for a minimum of 5 days, transitioning to oral therapy once hemodynamically stable. 1

Initial Assessment and Severity Stratification

Immediately assess severity to determine treatment location and antibiotic regimen:

• Evaluate for ICU-level severity indicators: respiratory rate >30/min, PaO₂/FiO₂ <250, multilobar infiltrates, confusion, uremia, hypotension requiring aggressive fluid resuscitation, or hypothermia 2, 1
• Obtain chest radiograph to confirm air space density consistent with pneumonia 3
• Test for COVID-19 and influenza when these viruses are circulating in the community, as positive results alter treatment strategy 3
• Obtain blood and sputum cultures before initiating antibiotics in all hospitalized patients 1

Antibiotic Selection by Clinical Setting

Non-ICU Hospitalized Patients (Standard Regimen)

Two equally effective first-line options exist with strong evidence:

• Preferred: Ceftriaxone 1-2 g IV daily plus azithromycin 500 mg daily 1, 3
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily) 1

For penicillin-allergic patients: Use respiratory fluoroquinolone monotherapy 1

ICU-Level Severe Pneumonia

Mandatory combination therapy for all ICU patients:

• β-lactam (ceftriaxone 2 g IV daily, cefotaxime 1-2 g IV every 8 hours, or ampicillin-sulbactam 3 g IV every 6 hours) PLUS either azithromycin 500 mg daily OR respiratory fluoroquinolone (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily) 1, 4

Special Populations Requiring Broader Coverage

Add antipseudomonal coverage when these risk factors are present:

• Structural lung disease (bronchiectasis, COPD with frequent exacerbations)
• Recent hospitalization with IV antibiotics within 90 days
• Prior respiratory isolation of Pseudomonas aeruginosa 1

Antipseudomonal regimen: Antipseudomonal β-lactam (piperacillin-tazobactam 4.5 g IV every 6 hours, cefepime 2 g IV every 8 hours, imipenem 500 mg IV every 6 hours, or meropenem 1 g IV every 8 hours) PLUS ciprofloxacin 400 mg IV every 8 hours OR levofloxacin 750 mg IV daily PLUS aminoglycoside (gentamicin 5-7 mg/kg IV daily or tobramycin 5-7 mg/kg IV daily) 1

Add MRSA coverage when these risk factors are present:

• Prior MRSA infection or colonization
• Recent hospitalization with IV antibiotics
• Post-influenza pneumonia
• Cavitary infiltrates on imaging 1

MRSA regimen: Add vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) OR linezolid 600 mg IV every 12 hours to base regimen 1

Critical Timing Considerations

Administer first antibiotic dose in the emergency department before hospital admission 2, 1

• While the 4-hour rule has been questioned by recent evidence showing no mortality benefit 5, guidelines still recommend prompt administration 2
• Prioritize patients based on severity, age, comorbidities, and clinical condition rather than applying a strict 4-hour threshold to all patients 5

Transition to Oral Therapy

Switch from IV to oral antibiotics when ALL of the following criteria are met:

• Hemodynamically stable (systolic BP ≥90 mmHg, heart rate ≤100 bpm)
• Clinically improving (decreased respiratory rate, improved oxygenation)
• Able to ingest oral medications
• Normal gastrointestinal function 2, 1

Typical transition occurs by day 2-3 of hospitalization 1

Oral step-down regimen: Amoxicillin 1 g orally three times daily plus azithromycin 500 mg orally daily 1

Duration of Therapy

Treat for a minimum of 5 days AND until the patient meets ALL stability criteria:

• Afebrile (temperature ≤37.8°C) for 48-72 hours
• No more than 1 CAP-associated sign of clinical instability:
  • Heart rate ≤100 bpm
  • Systolic BP ≥90 mmHg
  • Respiratory rate ≤24/min
  • Oxygen saturation ≥90% on room air
  • Able to maintain oral intake
  • Normal mental status 2, 1, 6

Typical duration for uncomplicated CAP: 5-7 days total 1, 3

Extended duration (14-21 days) required for:

• Legionella pneumophila
• Staphylococcus aureus
• Gram-negative enteric bacilli
• Extrapulmonary complications (empyema, endocarditis, meningitis) 2, 1

Management of Treatment Failure

If no clinical improvement by day 2-3, systematically evaluate:

• Obtain repeat chest radiograph, CRP, white blood cell count 1
• Obtain additional microbiological specimens (sputum culture, blood cultures, urinary antigen testing for Legionella and S. pneumoniae) 1
• Consider alternative diagnoses (pulmonary embolism, malignancy, inflammatory conditions) 2

Antibiotic modification strategies:

• For patients initially on β-lactam monotherapy: Add macrolide 1
• For patients on combination therapy: Switch to respiratory fluoroquinolone 1
• For severe pneumonia not responding: Consider adding rifampicin 1

Adjunctive Therapies for Severe CAP

Systemic corticosteroids:

• Administer within 24 hours of severe CAP development to potentially reduce 28-day mortality 3

Respiratory support:

• Trial noninvasive ventilation for hypoxemia or respiratory distress unless severe hypoxemia (PaO₂/FiO₂ <150) with bilateral infiltrates requires immediate intubation 2
• Use low-tidal-volume ventilation (6 mL/kg ideal body weight) for patients with diffuse bilateral pneumonia or ARDS 2

Hemodynamic support:

• Screen hypotensive, fluid-resuscitated patients for occult adrenal insufficiency 2

Follow-Up Care

Schedule clinical review at 6 weeks for all hospitalized patients 1, 4

Obtain follow-up chest radiograph at 6 weeks for:

• Persistent symptoms or physical signs
• Smokers and patients >50 years old (higher malignancy risk) 1, 4

Chest radiograph NOT required before hospital discharge in patients with satisfactory clinical recovery 1

Critical Pitfalls to Avoid

• Never use macrolide monotherapy for hospitalized patients—provides inadequate coverage for typical bacterial pathogens like S. pneumoniae 1
• Avoid cefuroxime, cefepime, piperacillin-tazobactam, or carbapenems as first-line empiric therapy unless specific risk factors for Pseudomonas or MRSA are documented 1
• Do not extend therapy beyond 7 days in responding patients without specific indications—increases antimicrobial resistance risk 1
• Never delay obtaining blood cultures before antibiotic administration—prevents pathogen-directed therapy 1
• Avoid diagnosing CAP without radiographic confirmation—the 4-hour antibiotic rule has led to overdiagnosis and inappropriate antibiotic use 7