What is the recommended workup for an unvaccinated 6‑month‑old infant presenting with three days of fever and acute otitis media?

Workup for an Unvaccinated 6-Month-Old with Three Days of Fever and Acute Otitis Media

All infants under 6 months with confirmed acute otitis media require immediate antibiotic therapy—specifically high-dose amoxicillin 80–90 mg/kg/day divided twice daily for a full 10-day course—without the option of observation. 1, 2, 3

Immediate Clinical Assessment

Confirm the Diagnosis of Acute Otitis Media

• Perform pneumatic otoscopy to document all three required diagnostic criteria: (1) acute onset of symptoms (ear pain, irritability, fever), (2) presence of middle-ear effusion (impaired tympanic-membrane mobility, bulging, or air-fluid level), and (3) signs of middle-ear inflammation (moderate-to-severe bulging or new otorrhea). 1, 3
• Do not diagnose AOM based on isolated tympanic-membrane redness without effusion, as this does not warrant antibiotics. 1, 2
• If pneumatic otoscopy is equivocal, obtain tympanometry to confirm middle-ear effusion. 1

Assess for Severe Disease

• Severe AOM is defined by moderate-to-severe otalgia, otalgia persisting ≥48 hours, or fever ≥39°C (102.2°F). 1, 3
• In this 6-month-old with three days of fever, the duration alone suggests more significant disease requiring immediate treatment. 1

Fever Workup in the Context of Unvaccinated Status

Critical Consideration: Rule Out Serious Bacterial Infection

• An unvaccinated 6-month-old with three days of fever warrants heightened vigilance for invasive bacterial disease, particularly because lack of pneumococcal conjugate vaccine (PCV-13) increases risk for bacteremia and meningitis from Streptococcus pneumoniae. 1
• If the infant appears toxic, has persistent high fever (≥39°C), or shows signs of systemic illness beyond the ear infection, perform a full sepsis workup including complete blood count, blood culture, urinalysis with culture, and strongly consider lumbar puncture to exclude meningitis. 2
• The presence of AOM does not exclude concurrent bacteremia or meningitis, especially in unvaccinated infants. 1

When AOM Alone Explains the Fever

• If the infant is well-appearing, feeding adequately, and the fever is attributable to the confirmed AOM, proceed directly to antibiotic therapy without additional laboratory workup. 2, 3
• Pain control is mandatory regardless of antibiotic initiation; administer weight-based acetaminophen or ibuprofen immediately, as analgesics provide relief within 24 hours whereas antibiotics do not relieve symptoms in the first 24 hours. 1, 2

First-Line Antibiotic Therapy

Recommended Regimen

• Prescribe high-dose amoxicillin 80–90 mg/kg/day divided into two or three equal doses (maximum 2 grams per dose) for a full 10-day course. 1, 2, 3
• High-dose amoxicillin achieves middle-ear fluid concentrations adequate to eradicate penicillin-resistant S. pneumoniae, the most common pathogen in AOM. 1, 2
• Complete the full 10-day course even if symptoms improve earlier, to prevent recurrence and resistance. 2, 3

When to Use Amoxicillin-Clavulanate Instead

• Switch to amoxicillin-clavulanate (90 mg/kg/day amoxicillin component + 6.4 mg/kg/day clavulanate, divided twice daily) if the infant has received amoxicillin within the past 30 days, has concurrent purulent conjunctivitis (suggesting Haemophilus influenzae), or attends daycare with high prevalence of β-lactamase-producing organisms. 1, 2, 3
• Twice-daily dosing of amoxicillin-clavulanate causes significantly less diarrhea than three-times-daily dosing while maintaining equivalent efficacy. 1

Penicillin-Allergic Alternatives

• For non-severe (non-IgE-mediated) penicillin allergy, prescribe cefdinir 14 mg/kg/day once daily (preferred for convenience), cefuroxime 30 mg/kg/day divided twice daily, or cefpodoxime 10 mg/kg/day divided twice daily. 1, 2
• Cross-reactivity between penicillins and second- or third-generation cephalosporins is negligible (approximately 0.1%), making these agents safe in non-severe allergy. 1

Mandatory Reassessment Protocol

Follow-Up at 48–72 Hours

• Re-evaluate the infant at 48–72 hours if symptoms worsen or fail to improve. 1, 2, 3
• Confirm the AOM diagnosis with repeat pneumatic otoscopy and exclude alternative causes of persistent fever. 1, 2

Treatment-Failure Algorithm

• If amoxicillin fails, switch to amoxicillin-clavulanate 90 mg/kg/day. 1, 2, 3
• If amoxicillin-clavulanate fails, administer intramuscular ceftriaxone 50 mg/kg once daily for three consecutive days (superior to a single-dose regimen). 1, 2
• After multiple treatment failures, consider tympanocentesis with culture and susceptibility testing to guide further therapy. 1, 3

Post-Treatment Expectations

• Middle-ear effusion persists in 60–70% of infants at 2 weeks after successful treatment, declining to approximately 40% at 1 month and 10–25% at 3 months. 1, 2, 3
• Persistent effusion without acute symptoms (otitis media with effusion) requires monitoring but not additional antibiotics unless it persists beyond 3 months with documented hearing loss. 1, 3
• Consider follow-up examination at 10 days for infants under 6 months or those with recurrent AOM, although routine follow-up is not necessary for uncomplicated cases. 2, 3

Prevention Counseling

• Strongly recommend pneumococcal conjugate vaccine (PCV-13) and routine immunizations to prevent future episodes and reduce risk of invasive pneumococcal disease. 1, 2
• Encourage exclusive breastfeeding for at least 6 months, eliminate tobacco smoke exposure, reduce pacifier use after 6 months, and avoid supine bottle feeding. 1

Key Pitfalls to Avoid

• Do not observe without antibiotics in any infant under 6 months with confirmed AOM, regardless of severity or laterality. 1, 2, 3
• Do not use azithromycin or other macrolides as first-line therapy; pneumococcal macrolide resistance exceeds 40% in the United States, with bacterial failure rates of 20–25%. 1
• Do not use trimethoprim-sulfamethoxazole or erythromycin-sulfisoxazole for treatment failures due to substantial pneumococcal resistance. 1, 2
• Antibiotics do not prevent complications such as acute mastoiditis; 33–81% of children who develop mastoiditis had received prior antibiotics. 1