What is the initial approach to managing community-acquired pneumonia (CAP)?

Community-Acquired Pneumonia Management

Initial Assessment: Determine Site of Care

The first critical decision in CAP management is determining whether the patient requires hospitalization, which should follow a structured 3-step process: (1) assess preexisting conditions compromising home safety, (2) calculate the Pneumonia Severity Index (PSI) or CURB-65 score, and (3) apply clinical judgment. 1, 2

• PSI risk classes I, II, and III can safely be treated as outpatients unless other factors contraindicate home care 1, 2
• CURB-65 scoring (Confusion, Urea, Respiratory rate, Blood pressure, age ≥65) provides an alternative severity assessment tool 3, 2
• Patients requiring ICU admission represent severe CAP and need immediate intensive monitoring 2

Key Severity Indicators for ICU Admission

Severe CAP requiring ICU care is defined by the presence of 2 of 3 minor criteria (systolic BP <90 mmHg, multilobar involvement, PaO2/FiO2 <250) OR 1 of 2 major criteria (mechanical ventilation need or septic shock). 4

Additional markers of severity include: 1, 4

• Acute respiratory failure
• Hemodynamic compromise
• Blood urea nitrogen >7 mM
• Multilobar radiographic infiltrates

Empirical Antibiotic Therapy by Clinical Setting

Outpatient Treatment (Non-Severe CAP)

For previously healthy adults without recent antibiotic use, first-line therapy is amoxicillin 1g three times daily OR a macrolide (azithromycin or clarithromycin) OR doxycycline. 1, 2

For patients with comorbidities (COPD, diabetes, renal/heart failure, malignancy) without recent antibiotic use, use an advanced macrolide OR a respiratory fluoroquinolone (levofloxacin, moxifloxacin). 1, 2

If recent antibiotic therapy occurred: 1

• Use a respiratory fluoroquinolone alone, OR
• Combine an advanced macrolide plus high-dose amoxicillin (or amoxicillin-clavulanate)

Hospitalized Patients (Medical Ward)

For non-ICU hospitalized patients, the preferred regimen is a β-lactam (ceftriaxone, cefotaxime, ampicillin-sulbactam, or ceftaroline) PLUS a macrolide (azithromycin or clarithromycin). 1, 2

Alternative acceptable regimen: 1

• Respiratory fluoroquinolone alone (levofloxacin, moxifloxacin, or gatifloxacin)

Critical timing consideration: The first antibiotic dose must be administered while still in the emergency department, ideally within 8 hours of hospital arrival to minimize mortality. 3, 2, 5

Severe CAP (ICU Patients)

For ICU patients WITHOUT Pseudomonas risk factors, use a non-antipseudomonal β-lactam (ceftriaxone or cefotaxime) PLUS either azithromycin OR a respiratory fluoroquinolone. 1, 2

For ICU patients WITH Pseudomonas risk factors (structural lung disease, recent hospitalization, recent broad-spectrum antibiotics), use an antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, ceftazidime, or meropenem) PLUS EITHER ciprofloxacin OR (aminoglycoside plus respiratory fluoroquinolone or macrolide). 1, 2

For β-lactam allergic patients with Pseudomonas risk: 1

• Aztreonam plus levofloxacin, OR
• Aztreonam plus moxifloxacin/gatifloxacin ± aminoglycoside

Special Pathogen Considerations

For suspected Legionella pneumophila, use a respiratory fluoroquinolone (levofloxacin preferred) OR azithromycin. 2, 6, 7

For Mycoplasma pneumoniae or Chlamydophila pneumoniae: 2, 6, 7

• Macrolide, doxycycline, or respiratory fluoroquinolone

For suspected aspiration with infection: 1

• Amoxicillin-clavulanate OR clindamycin

Duration and Transition to Oral Therapy

The standard duration of therapy is 5-7 days for patients showing clinical response. 2, 6

Switch from IV to oral therapy when the patient meets ALL of the following criteria: hemodynamically stable, clinically improving (reduced cough/dyspnea, afebrile), able to ingest medications, and has functioning GI tract. 3, 2

Specific switch criteria include: 2

• Decreasing white blood cell count
• Adequate oral intake
• Temperature normalization

Common Pitfalls and Critical Caveats

Delayed antibiotic administration significantly increases mortality—ensure timely treatment within the first hour of recognized severe infection. 2, 5

Inadequate pathogen coverage is associated with worse outcomes; empiric regimens must cover both typical bacteria (S. pneumoniae) and atypical pathogens (Legionella, Mycoplasma, Chlamydophila). 1, 2, 8

Up to 10% of CAP patients fail initial therapy—these patients require careful reassessment for drug-resistant pathogens, unusual organisms, non-pneumonia diagnoses, or complications (empyema, abscess). 2

Important monitoring considerations: 1, 2

• Obtain blood cultures before antibiotics when possible
• Sputum Gram stain/culture has limited utility for guiding initial therapy but may help in non-responders
• Clinical syndromes cannot reliably predict specific pathogens

Multi-Drug Resistant S. pneumoniae (MDRSP)

MDRSP (resistant to ≥2 of: penicillin, 2nd-gen cephalosporins, macrolides, tetracyclines, TMP-SMX) is effectively treated with respiratory fluoroquinolones or high-dose β-lactam combinations. 6

Levofloxacin 750mg daily for 5 days is FDA-approved for MDRSP CAP with 95% clinical success rates 6

Follow-Up and Prevention

Clinical review should occur at 6 weeks post-treatment, with chest radiograph for patients with persistent symptoms or higher malignancy risk. 2

Pneumococcal and influenza vaccination should be administered to appropriate at-risk populations prior to discharge. 2, 8