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Difficulty: MediumInfectious Diseases

A 45-year-old man is evaluated during hospital rounds. He was admitted 3 days ago for fever, productive cough, and pleuritic chest pain. A chest radiograph on admission showed a right lower lobe consolidation, and he was diagnosed with community-acquired pneumonia. Empiric therapy with intravenous ceftriaxone and oral azithromycin was initiated. He has no significant past medical history and takes no daily medications. He has no known drug allergies. Today, the patient reports feeling significantly better. His temperature is 37.1°C (98.8°F), blood pressure is 120/80 mmHg, pulse is 78/min, and respiratory rate is 16/min. Oxygen saturation is 98% on room air. Blood cultures obtained on admission are now growing *Streptococcus pneumoniae*. Susceptibility testing indicates the isolate is highly susceptible to penicillin, ceftriaxone, and levofloxacin, but resistant to macrolides. The patient is tolerating a regular diet without difficulty. Which of the following is the most appropriate next step in pharmacotherapy?

  1. Switch to oral amoxicillinAnswer
  2. B
    Switch to oral levofloxacin
  3. C
    Switch to oral amoxicillin-clavulanate
  4. D
    Continue intravenous ceftriaxone
  5. E
    Switch to oral cefdinir

Answer

The most appropriate next step is to switch the patient to oral amoxicillin.
The correct course of action is to transition the patient to oral amoxicillin. This patient has met the criteria for IV-to-PO transition: he is clinically improving, hemodynamically stable, afebrile, and able to tolerate an oral diet. Because the blood cultures confirmed a diagnosis of *Streptococcus pneumoniae* bacteremia that is highly susceptible to penicillin, the empiric regimen should be de-escalated. Amoxicillin is the first-line oral agent for penicillin-susceptible *S. pneumoniae*, adhering to the core principles of antimicrobial stewardship by using the narrowest effective spectrum.

Step-by-Step Solution

1
Assess the patient's current clinical stability for transition of care.
The patient is afebrile, hemodynamically stable, improving clinically, and tolerating oral intake.
These are the standard criteria for transitioning a patient from intravenous to oral antimicrobial therapy.
2
Analyze the culture and susceptibility results to guide de-escalation.
The pathogen is S. pneumoniae, which is highly susceptible to penicillin.
Culture data should always be used to narrow antibiotic coverage from empiric broad-spectrum regimens to targeted therapy.
3
Select the most appropriate targeted oral agent.
Oral amoxicillin is selected.
Amoxicillin is the preferred narrow-spectrum oral agent for penicillin-susceptible S. pneumoniae, avoiding collateral damage to the microbiome.

Key Concept

Antimicrobial stewardship dictates de-escalating to the narrowest effective oral antibiotic once a patient is clinically stable and susceptibility data are available.
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Topics

Infectious Diseases

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