What is the recommended treatment for community-acquired pneumonia in patients less than 1 year old?

Treatment of Community-Acquired Pneumonia in Infants Less Than 1 Year Old

For infants under 1 year of age with community-acquired pneumonia, amoxicillin 90 mg/kg/day divided into 2 doses is the definitive first-line outpatient treatment, while hospitalized infants require intravenous ampicillin or penicillin G (if fully immunized) or ceftriaxone/cefotaxime (if not fully immunized or at high risk). 1, 2

Outpatient Management for Infants <1 Year

First-Line Treatment

• Amoxicillin 90 mg/kg/day divided into 2 doses is the recommended empiric therapy for presumed bacterial pneumonia in infants 6-12 months old who can be managed as outpatients 1, 2, 3
• The high-dose regimen (90 mg/kg/day rather than 40-45 mg/kg/day) is critical to overcome pneumococcal resistance—underdosing is a dangerous and common error 2
• Treatment duration should be 5 days based on recent evidence showing non-inferiority to longer courses 4, 5, 6, 7

Alternative Agents

• Amoxicillin-clavulanate (amoxicillin component 90 mg/kg/day in 2 doses) should be used if the infant is not fully immunized against Haemophilus influenzae type b or Streptococcus pneumoniae, as it provides coverage for β-lactamase-producing organisms 1, 2
• For suspected Staphylococcus aureus involvement, amoxicillin-clavulanate is preferred 2

Atypical Pathogen Coverage

• Macrolides are generally not indicated as first-line monotherapy for infants under 1 year, as typical bacterial pathogens (S. pneumoniae, H. influenzae) predominate in this age group 1, 2
• Azithromycin 10 mg/kg on day 1, followed by 5 mg/kg/day on days 2-5 can be considered if atypical pneumonia (Chlamydophila, Mycoplasma) is specifically suspected, though this is uncommon in infants 1, 8

Inpatient Management for Infants <1 Year

Fully Immunized, Low-Risk Infants

• Ampicillin 150-200 mg/kg/day IV every 6 hours OR penicillin G 100,000-250,000 units/kg/day IV every 4-6 hours is first-line therapy 1, 2, 3
• Alternative: Ceftriaxone 50-100 mg/kg/day IV every 12-24 hours OR cefotaxime 150 mg/kg/day IV every 8 hours 1, 2

Not Fully Immunized or High-Risk Infants

• Ceftriaxone 50-100 mg/kg/day IV OR cefotaxime 150 mg/kg/day IV every 8 hours is recommended to cover resistant organisms and β-lactamase-producing H. influenzae 1, 2, 9
• Add vancomycin 40-60 mg/kg/day IV every 6-8 hours OR clindamycin 40 mg/kg/day IV every 6-8 hours if community-associated MRSA is suspected (recent hospitalization, severe presentation, necrotizing infiltrates, empyema) 1, 2, 9

Risk Factors Requiring MRSA Coverage

• Recent hospitalization or antibiotic exposure 9
• Severe pneumonia with diffuse lung involvement 9
• Necrotizing infiltrates or empyema on imaging 2
• Recent influenza infection 2

Clinical Monitoring and Treatment Adjustment

Expected Response

• Clinical improvement should occur within 48-72 hours of initiating appropriate therapy 1, 2, 3
• If no improvement or clinical deterioration occurs, obtain chest radiography to evaluate for complications (parapneumonic effusion, empyema, lung abscess) 1, 9

Treatment Failure Management

• Send blood cultures and pleural fluid cultures (if effusion present) before changing antibiotics 9
• Consider resistant organisms, inadequate dosing, poor compliance, or alternative diagnoses 3
• Reassess antibiotic coverage—broaden to include MRSA if not already covered 2, 9

Critical Pitfalls to Avoid

• Never underdose amoxicillin: Using 40-45 mg/kg/day instead of the recommended 90 mg/kg/day is inadequate for resistant S. pneumoniae 2
• Do not use macrolides as monotherapy for presumed bacterial pneumonia in infants—they lack adequate coverage for S. pneumoniae 2, 3
• Do not overlook MRSA risk factors: Failure to add vancomycin or clindamycin in high-risk infants with severe pneumonia can lead to treatment failure 2, 9
• Avoid cefixime: This agent is explicitly not recommended for pediatric pneumonia due to inadequate coverage 2

Special Considerations for Infants <6 Months

• Safety and effectiveness of azithromycin for pneumonia have not been established in infants under 6 months of age 8
• These very young infants often require hospitalization and parenteral therapy due to higher risk of severe disease and complications 1
• Consider broader differential diagnosis including pertussis, viral etiologies, and congenital abnormalities in this age group 1