What is the latest clinical practice guideline for managing community‑acquired pneumonia in adults?

Community-Acquired Pneumonia in Adults: Latest Clinical Practice Guidelines

The most current evidence-based approach to managing community-acquired pneumonia (CAP) in adults comes from the 2025 American Thoracic Society (ATS) guideline update and the 2019 ATS/IDSA comprehensive guideline, which together provide a structured framework for diagnosis, site-of-care decisions, empiric antibiotic selection, and adjunctive therapies. 1, 2

Diagnostic Approach

Clinical Diagnosis

• CAP diagnosis requires both clinical signs/symptoms of pneumonia AND radiographic confirmation 2
• Lung ultrasound is now recommended as an alternative diagnostic modality to chest radiography, particularly when rapid diagnosis is needed or chest X-ray is unavailable 1

Microbiological Testing

• Expanded microbiological testing is recommended for patients suspected of drug-resistant infections, including those with risk factors for MRSA or Pseudomonas aeruginosa 3
• Blood cultures and sputum cultures should be obtained in hospitalized patients, particularly those with severe CAP 2
• Respiratory viral testing should be performed, as a positive viral test does not exclude bacterial co-infection and should not automatically preclude antibacterial therapy 1

Biomarkers

• Procalcitonin and other biomarkers have refined indications for guiding antibiotic decisions, though their routine use remains context-dependent 4

Site-of-Care Determination

Use validated severity-of-illness scores (PSI/PORT or CURB-65) to guide admission decisions 2:

• Outpatient management: Low-risk patients without hypoxemia or hemodynamic instability
• Hospital ward admission: Moderate-risk patients with comorbidities or abnormal vital signs
• ICU admission: Patients meeting severe CAP criteria (requiring vasopressors or mechanical ventilation, or having ≥3 minor criteria) 2

Empiric Antibiotic Therapy

Outpatient Treatment

For previously healthy patients without risk factors for drug-resistant pathogens 2, 3:

• Amoxicillin monotherapy is now recommended as first-line therapy (major change from 2007 guideline)
• Alternative: Doxycycline or a macrolide (azithromycin/clarithromycin) if beta-lactam allergy

For patients with comorbidities (chronic heart, lung, liver, or renal disease; diabetes; alcoholism; malignancy; asplenia) 2:

• Combination therapy: Amoxicillin-clavulanate or cephalosporin PLUS a macrolide
• Alternative: Respiratory fluoroquinolone (levofloxacin, moxifloxacin) monotherapy

Hospitalized Non-ICU Patients

Standard empiric regimen 2:

• Beta-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) PLUS a macrolide
• Alternative: Respiratory fluoroquinolone monotherapy

Severe CAP (ICU Patients)

Combination therapy is mandatory 2, 5:

• Beta-lactam (ceftriaxone or cefotaxime) PLUS either azithromycin OR a respiratory fluoroquinolone

For patients with risk factors for Pseudomonas aeruginosa (structural lung disease, recent hospitalization, recent antibiotics) 2, 4:

• Anti-pseudomonal beta-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) PLUS ciprofloxacin or levofloxacin (750 mg)
• Alternative: Anti-pseudomonal beta-lactam PLUS aminoglycoside PLUS azithromycin or respiratory fluoroquinolone

For patients with risk factors for MRSA (prior MRSA infection, recent IV drug use, severe necrotizing pneumonia) 2:

• Add vancomycin or linezolid to the above regimens

Key Change: Healthcare-Associated Pneumonia Category Eliminated

The healthcare-associated pneumonia (HCAP) category has been removed from treatment algorithms, as it led to unnecessary broad-spectrum antibiotic use without improving outcomes 3, 6

Antibiotic Duration

Minimum effective duration is 5 days for most patients who are clinically stable and afebrile for 48-72 hours 1, 4:

• Shorter courses (5-7 days) are preferred over traditional 10-14 day regimens
• Longer duration may be needed for complications (empyema, bacteremia with slow response, or infection with S. aureus or Pseudomonas) 2

Adjunctive Corticosteroid Therapy

Routine use of systemic corticosteroids is NOT recommended for all CAP patients 1, 3:

• The 2025 ATS update reinforces that corticosteroids should not be used routinely
• Consider corticosteroids only in patients with severe CAP and refractory septic shock, following standard sepsis protocols 1, 5
• The evidence remains mixed, with potential benefits in severe cases offset by risks of hyperglycemia and secondary infections 2

Follow-Up and Imaging

Routine follow-up chest imaging is not necessary for patients who achieve clinical stability 2:

• Repeat imaging at 6-12 weeks is recommended for patients with persistent symptoms, high-risk features (age >50, smoking history), or initial imaging concerning for underlying malignancy
• Chest CT may be indicated for complicated pneumonia, suspected abscess, or empyema 4

Common Pitfalls to Avoid

• Do not withhold antibacterial therapy solely because a respiratory virus test is positive—bacterial co-infection is common 1
• Avoid fluoroquinolone monotherapy in outpatients without comorbidities—reserve for appropriate indications to minimize resistance 2
• Do not use HCAP criteria to guide broad-spectrum therapy—this outdated category increases unnecessary antibiotic exposure 3, 6
• Do not routinely prescribe corticosteroids—evidence does not support benefit in most CAP cases and may cause harm 1

Target Pathogens

The major treatable bacterial pathogens remain 2:

• Streptococcus pneumoniae (most common)
• Haemophilus influenzae
• Mycoplasma pneumoniae
• Staphylococcus aureus (including MRSA in specific populations)
• Legionella species
• Chlamydia pneumoniae
• Moraxella catarrhalis
• Pseudomonas aeruginosa (in patients with risk factors)

Long-Term Considerations

CAP is no longer viewed as solely an acute illness—recognize long-term complications including 7:

• Cardiovascular events (myocardial infarction, stroke)
• Persistent respiratory impairment
• Cognitive decline in older adults
• Routine cardiovascular screening and rehabilitation after severe CAP should be considered 7