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Difficulty: Very hardPediatric Infectious Diseases

A 33-year-old girl is evaluated in the hospital on day 44 of admission for acute mastoiditis. She initially presented to the emergency department with a 33-day history of high fever, severe left ear pain, and outward displacement of the left auricle. On admission, she underwent tympanostomy tube placement and was empirically started on intravenous vancomycin and ceftriaxone. Cultures of the purulent middle ear fluid obtained during the procedure grew Streptococcus pneumoniae. Susceptibility testing reveals the organism has a penicillin minimum inhibitory concentration (MIC) of 0.060.06 μ\mu g/mL (highly susceptible). It is also susceptible to clindamycin, ceftriaxone, and levofloxacin. Currently, the patient has been afebrile for 4848 hours, the postauricular erythema has resolved, and she is tolerating a regular diet. The medical team plans to discharge her today to complete a 1414-day total course of antimicrobial therapy as an outpatient. Which of the following is the most appropriate oral pharmacotherapy to prescribe for discharge?

  1. Oral amoxicillinAnswer
  2. B
    Oral amoxicillin-clavulanate
  3. C
    Oral clindamycin
  4. D
    Oral cefdinir
  5. E
    Outpatient intravenous ceftriaxone via a peripherally inserted central catheter

Answer

Oral amoxicillin
The correct decision is to prescribe oral amoxicillin. This patient has achieved clinical stability (afebrile for 4848 hours, improving local signs, tolerating PO), making the transition to oral therapy the safest and most appropriate next step. The culture grew Streptococcus pneumoniae that is highly susceptible to penicillin. The cornerstone of antimicrobial stewardship is narrowing the antibiotic spectrum once a pathogen is identified. Oral amoxicillin is the narrowest-spectrum, most targeted agent available for this infection. It has excellent oral bioavailability and achieves therapeutic concentrations in middle ear and mastoid tissues.

Step-by-Step Solution

1
Evaluate the clinical status for transition to oral therapy.
The patient is afebrile for 4848 hours, shows clinical resolution of mastoiditis signs, and tolerates a regular diet.
Clinical stability and the ability to take oral medications mandate stepping down from intravenous to oral therapy to reduce line-associated risks.
2
Analyze the microbiological data and susceptibility profile.
The causative pathogen is Streptococcus pneumoniae with a penicillin MIC of 0.060.06 μ\mu g/mL, indicating it is highly susceptible.
Susceptibility data drives the de-escalation of empiric broad-spectrum therapy to targeted therapy.
3
Select the narrowest spectrum, most efficacious oral agent based on the pathogen's resistance mechanisms.
Oral amoxicillin is selected over amoxicillin-clavulanate or clindamycin.
S. pneumoniae does not produce beta-lactamase; therefore, clavulanate offers zero added benefit. Amoxicillin provides excellent bioavailability and tissue penetration with the narrowest effective spectrum.

Key Concept

Antimicrobial stewardship dictates transitioning clinically stable pediatric patients to the narrowest-spectrum, highly bioavailable oral antibiotic. For penicillin-susceptible S. pneumoniae, amoxicillin is preferred over amoxicillin-clavulanate because pneumococcal resistance is mediated by altered PBPs, not beta-lactamase.
Estimated Time:1m 30s
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Topics

Pediatric Infectious Diseases

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