What are the treatment guidelines for Community-Acquired Pneumonia (CAP)?

Community-Acquired Pneumonia Treatment Guidelines

Initial Assessment and Site-of-Care Decision

Severity assessment should guide treatment location using validated tools, with the first antibiotic dose administered in the emergency department for hospitalized patients. 1, 2

• Use CURB-65 scoring or the Pneumonia Severity Index (PSI) to determine appropriate treatment setting 1, 2
• PSI risk classes I-III can be safely managed as outpatients, while classes IV-V typically require hospitalization 1
• For patients admitted through the ED, administer the first antibiotic dose while still in the ED to minimize time to treatment 3, 2
• Test all patients for COVID-19 and influenza when these viruses are circulating in the community, as results may affect treatment decisions 4

Outpatient Treatment Regimens

For previously healthy outpatients without recent antibiotic use, first-line therapy is amoxicillin 1g every 8 hours OR doxycycline 100mg twice daily. 1, 2

• Alternative regimens include macrolides: azithromycin 500mg on day 1, then 250mg daily for days 2-5, or clarithromycin 500mg twice daily 1, 5
• For patients with comorbidities or recent antibiotic therapy, use an advanced macrolide or respiratory fluoroquinolone 2
• For suspected aspiration pneumonia with infection, use amoxicillin-clavulanate or clindamycin 2

Non-Severe Inpatient Treatment (Medical Ward)

Standard therapy for non-severe hospitalized patients is combination oral therapy with amoxicillin plus a macrolide (azithromycin or clarithromycin). 2, 6

• Alternative regimen: respiratory fluoroquinolone alone OR β-lactam plus advanced macrolide 1, 2
• Most non-severe inpatients can be adequately treated with oral antibiotics 2, 6
• When oral treatment is contraindicated, use parenteral ampicillin or benzylpenicillin together with erythromycin or clarithromycin 2
• A recent high-quality study confirms β-lactam/macrolide combination (such as ceftriaxone combined with azithromycin) as effective first-line therapy 4

Severe CAP/ICU Treatment

Patients with severe pneumonia requiring ICU admission must receive immediate parenteral combination therapy: β-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) PLUS either an advanced macrolide OR respiratory fluoroquinolone. 1, 6

• For Pseudomonas risk factors, use an antipneumococcal, antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) plus either ciprofloxacin or levofloxacin 750mg 6
• For suspected community-acquired MRSA, add vancomycin or linezolid 6
• Systemic corticosteroids administered within 24 hours of severe CAP development may reduce 28-day mortality 4
• Patients with persistent septic shock despite adequate fluid resuscitation should be considered for drotrecogin alfa activated within 24 hours of admission 3, 6

Duration of Therapy

Treat CAP for a minimum of 5 days, with patients afebrile for 48-72 hours and no more than 1 sign of clinical instability before discontinuation. 3, 1, 6

• Extended duration of 14-21 days is required for Legionella, staphylococcal, or gram-negative enteric bacilli infections 1, 2
• Longer therapy may be needed if initial therapy was not active against the identified pathogen or if complicated by extrapulmonary infection (meningitis, endocarditis) 3, 6
• A recent 2024 study confirms that hospitalized patients can be treated for a minimum of 3 days with appropriate antibiotics 4

Switching from IV to Oral Therapy

Switch from intravenous to oral therapy when patients are hemodynamically stable, clinically improving, afebrile, able to ingest medications, and have a functioning gastrointestinal tract. 3, 2, 6

• Specific criteria include improvement in cough and dyspnea, decreasing white blood cell count, and adequate oral intake 2
• Inpatient observation while receiving oral therapy is not necessary; discharge as soon as clinically stable 3

Pathogen-Directed Therapy

Once the etiology is identified through reliable microbiological methods, switch to pathogen-directed therapy. 3, 6

• Only 38% of hospitalized CAP patients have a pathogen identified 4
• Of those with identified pathogens, up to 40% have viruses and approximately 15% have Streptococcus pneumoniae 4
• Early treatment within 48 hours of symptom onset is recommended 3, 6

Management of Treatment Failure

For patients not improving at 48-72 hours, perform systematic reassessment including careful review of clinical history, examination, prescription chart, and all investigations. 1, 2

• Consider bronchoscopy for patients under 55 years with multilobar disease who are nonsmokers 3
• Obtain additional testing: CT scan to evaluate for pleural fluid, nodules, or cavitation; serologic tests for Legionella, Mycoplasma, viral agents, and endemic fungi 3
• Legionella urinary antigen testing is positive in more than 80% of patients with Legionella pneumophila serogroup 1 infection 3

Special Considerations for Severe CAP

• Patients with hypoxemia or respiratory distress should receive a cautious trial of noninvasive ventilation unless immediate intubation is required (PaO₂/FiO₂ ratio <150 with bilateral infiltrates) 3, 6
• Use low-tidal-volume ventilation (6 mL/kg ideal body weight) for patients with diffuse bilateral pneumonia or ARDS 3, 6
• Screen hypotensive, fluid-resuscitated patients for occult adrenal insufficiency 3

Vaccination and Prevention

All appropriate at-risk patients should receive both pneumococcal and influenza vaccines. 3

• Pneumococcal polysaccharide vaccine is recommended for persons ≥65 years and those with high-risk conditions 3
• Health care workers should receive annual influenza immunization 3
• The intranasally administered live attenuated influenza vaccine is an alternative for persons 5-49 years without chronic diseases 3
• Smoking cessation is an important preventive strategy for CAP 3

Follow-Up

Clinical review should be arranged at 6 weeks with either the general practitioner or hospital clinic. 1, 2, 6

• Arrange chest radiograph at follow-up for patients with persistent symptoms, physical signs, or higher risk of underlying malignancy (especially smokers over 50 years) 2, 6