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Difficulty: EasyInfectious Diseases

A 39-year-old man is evaluated in the hospital on hospital day 3. He was admitted for community-acquired pneumonia after presenting with a high fever, productive cough, and right lower lobe consolidation on chest radiography. On admission, he was empirically started on intravenous ceftriaxone and oral azithromycin. Over the past 48 hours, his fever has resolved, his respiratory symptoms have significantly improved, and he is eating a regular diet. His temperature is 37.1 C (98.8 F), blood pressure is 124/82 mm Hg, pulse is 76/min, and respiratory rate is 14/min. Sputum and blood cultures obtained on admission both grow Streptococcus pneumoniae. Antimicrobial susceptibility testing reveals the isolate is susceptible to amoxicillin, ceftriaxone, levofloxacin, and linezolid. Which of the following is the most appropriate next step in pharmacotherapy?

  1. A
    Transition to oral levofloxacin
  2. B
    Continue intravenous ceftriaxone and oral azithromycin
  3. Transition to oral amoxicillinAnswer
  4. D
    Transition to oral amoxicillin-clavulanate
  5. E
    Transition to oral linezolid

Answer

Transition to oral amoxicillin
The correct action is to transition the patient to oral amoxicillin. This patient was admitted with community-acquired pneumonia and appropriately started on empiric broad-spectrum therapy (ceftriaxone and azithromycin). After 3 days, he is clinically stable, afebrile, and tolerating an oral diet, satisfying all standard criteria for IV-to-PO step-down therapy. Furthermore, cultures have returned positive for Streptococcus pneumoniae that is susceptible to amoxicillin. According to the core principles of antimicrobial stewardship, once a pathogen is identified and susceptibilities are known, empiric therapy should be immediately de-escalated to the narrowest effective, targeted agent. Oral amoxicillin is the ideal narrow-spectrum choice for susceptible S. pneumoniae.

Step-by-Step Solution

1
Assess the patient's clinical trajectory and criteria for intravenous to oral (IV-to-PO) transition.
The patient is afebrile for 48 hours, hemodynamically stable, showing clinical improvement, and tolerating oral intake.
Meeting these criteria indicates the patient can safely be transitioned from intravenous to oral antibiotics.
2
Evaluate the microbiology results and susceptibility data.
Cultures definitively identified Streptococcus pneumoniae, which is susceptible to narrow-spectrum beta-lactams (amoxicillin, ceftriaxone) as well as broader agents.
Identifying the specific pathogen allows for de-escalation from empiric broad-spectrum therapy to targeted therapy.
3
Select the most appropriate targeted oral agent based on antibiotic stewardship principles.
Oral amoxicillin is selected as the definitive therapy.
Amoxicillin provides excellent coverage for susceptible S. pneumoniae with the narrowest possible spectrum, minimizing collateral damage to the patient's microbiome and reducing the risk of resistant organisms.

Key Concept

Antibiotic Stewardship: De-escalation of Therapy
Estimated Time:1m 0s
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Topics

Infectious Diseases

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