How should a previously healthy 15-year-old with community-acquired pneumonia be managed, including first-line antibiotics, criteria for hospitalization, and alternatives for penicillin allergy?

Management of Community-Acquired Pneumonia in a Previously Healthy 15-Year-Old

High-dose oral amoxicillin 90 mg/kg/day divided into two doses (maximum 4 g/day) for 5–7 days is the definitive first-line treatment for outpatient management of a previously healthy 15-year-old with community-acquired pneumonia. 1, 2

First-Line Antibiotic Selection

When Bacterial Pneumonia is Suspected

• Prescribe amoxicillin 90 mg/kg/day in two divided doses (not the lower 40–45 mg/kg/day dose, which is inadequate for pneumococcal resistance). 1, 3, 2
• This high-dose regimen provides optimal coverage against Streptococcus pneumoniae, the most common bacterial pathogen in this age group. 1, 2
• Treatment duration should be 5–7 days for uncomplicated cases. 2, 4

When Atypical Pathogens Cannot Be Excluded

• Add azithromycin 10 mg/kg on day 1 (maximum 500 mg), then 5 mg/kg once daily on days 2–5 (maximum 250 mg/day) if clinical features do not clearly distinguish bacterial from atypical pneumonia (Mycoplasma pneumoniae or Chlamydophila pneumoniae). 1, 5, 2
• Atypical pathogens are more common in school-aged children and adolescents compared to younger children. 5, 2
• Alternative macrolides include clarithromycin 15 mg/kg/day divided twice daily for 7–14 days (maximum 1 g/day) or doxycycline 200 mg once daily in patients older than 7 years. 1, 5, 2

For Isolated Atypical Pneumonia

• Azithromycin monotherapy with the same dosing regimen is appropriate when atypical pneumonia is strongly suspected based on gradual onset, prominent cough, and absence of high fever or lobar consolidation. 5, 2

Criteria for Hospitalization

Admit to the hospital if the patient meets any of the following criteria:

Major Criteria (Any One Requires ICU or Continuous Monitoring)

• Invasive mechanical ventilation required 1
• Fluid-refractory shock 1
• Acute need for noninvasive positive pressure ventilation (CPAP or BiPAP) 1
• Hypoxemia requiring FiO₂ > 0.50 or oxygen flow not feasible in general care 1
• Pulse oximetry < 92% on inspired oxygen ≥ 0.50 1
• Altered mental status due to hypercarbia or hypoxemia 1

Minor Criteria (Two or More Warrant Hospitalization)

• Respiratory rate higher than WHO age-specific thresholds 1
• Apnea episodes 1
• Increased work of breathing (retractions, dyspnea, nasal flaring, grunting) 1
• PaO₂/FiO₂ ratio < 250 1
• Multilobar infiltrates 1
• Presence of pleural effusion 1
• Hypotension 1
• Unexplained metabolic acidosis 1

Additional Hospitalization Indicators

• Inability to tolerate oral antibiotics or maintain hydration 4
• Significant respiratory distress 1, 4
• Failure to improve or clinical deterioration within 48–72 hours of appropriate outpatient therapy 1, 2

Management for Penicillin Allergy

Non-Severe Allergic Reactions (Rash Without Anaphylaxis)

• Oral cephalosporins such as cefpodoxime, cefprozil, or cefuroxime can be used under medical supervision, as cross-reactivity risk is low (1–3%). 3, 2
• Azithromycin (10 mg/kg day 1, then 5 mg/kg daily days 2–5; maximum 500 mg/250 mg) is a safe β-lactam-free alternative. 3, 2

Severe Allergic Reactions (Anaphylaxis, Angioedema)

• Levofloxacin is the preferred alternative: 8–10 mg/kg once daily for adolescents 5–16 years (maximum 750 mg/day). 1, 3, 2
• Linezolid may be used as an alternative: 20 mg/kg/day divided twice daily for children ≥ 12 years. 1, 3, 2
• Fluoroquinolones should generally be reserved for severe cases due to concerns about cartilage development, but they are acceptable when severe penicillin allergy precludes β-lactam use. 5, 3

Inpatient Antibiotic Regimens (If Hospitalization Required)

Fully Immunized, Low-Risk Patients

• Ampicillin 150–200 mg/kg/day IV every 6 hours or penicillin G 200,000–250,000 U/kg/day IV every 4–6 hours is preferred. 1, 2
• Ceftriaxone 50–100 mg/kg/day IV once daily (or every 12–24 hours) is an acceptable alternative. 1, 2

Not Fully Immunized or High-Risk Patients

• Ceftriaxone 50–100 mg/kg/day IV or cefotaxime 150 mg/kg/day IV every 8 hours to cover penicillin-resistant S. pneumoniae and β-lactamase-producing H. influenzae. 1, 3, 2

Suspected MRSA (Severe Pneumonia, Necrotizing Features, Empyema, Recent Influenza)

• Add vancomycin 40–60 mg/kg/day IV every 6–8 hours or clindamycin 40 mg/kg/day IV every 6 hours to the β-lactam regimen. 1, 3, 2
• Failure to consider MRSA in severe presentations with necrotizing infiltrates or empyema is a critical and potentially fatal pitfall. 3, 2

Clinical Monitoring and Treatment Failure

Expected Response

• Clinical improvement should occur within 48–72 hours of initiating appropriate therapy, including reduced fever, improved respiratory effort, and better oral intake. 1, 5, 2

If No Improvement or Deterioration Within 48–72 Hours

• Obtain blood cultures and consider pleural-fluid sampling if effusion is present. 1, 3, 2
• Reassess for complications: parapneumonic effusion, empyema, necrotizing pneumonia, or lung abscess. 1, 2
• Consider resistant organisms (MRSA, penicillin-resistant S. pneumoniae) or alternative diagnoses. 1, 2
• Escalate to intravenous antibiotics if the patient is still outpatient, or broaden coverage if already hospitalized. 3, 2

Diagnostic Testing

Outpatient Setting

• Routine chest radiographs are not necessary for confirmation of suspected pneumonia in patients well enough to be treated as outpatients. 1
• Pulse oximetry should be performed in all patients with suspected hypoxemia to guide site-of-care decisions. 1
• Blood cultures should not be routinely obtained in nontoxic, fully immunized adolescents managed as outpatients. 1

When to Obtain Chest Radiography

• Order chest radiographs (posteroanterior and lateral) if the diagnosis is uncertain, if hypoxemia or significant respiratory distress is present, or if the patient fails to improve within 48–72 hours. 1, 4

Inpatient Setting

• Chest radiographs should be obtained in all hospitalized patients to document infiltrates and identify complications. 1
• Blood cultures should be obtained in children requiring hospitalization for moderate to severe pneumonia. 1

Critical Pitfalls to Avoid

• Do not underdose amoxicillin: The high dose of 90 mg/kg/day (not 40–45 mg/kg/day) is required to overcome pneumococcal resistance. 3, 2
• Do not use macrolides as first-line monotherapy for presumed bacterial pneumonia; they lack reliable activity against S. pneumoniae. 3, 2
• Do not delay adding vancomycin or clindamycin in severe pneumonia with necrotizing features or empyema, as MRSA is life-threatening. 3, 2
• Do not continue inadequate therapy beyond 48–72 hours without reassessment; prompt escalation prevents treatment failure. 1, 2
• Do not use cefixime or cefdinir as first-line empiric therapy; they provide inadequate pneumococcal coverage compared with high-dose amoxicillin. 3, 2