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Difficulty: MediumInfectious Diseases

A 68-year-old man is evaluated in the hospital on day 3 of admission for community-acquired pneumonia. His medical history is significant for hypertension and osteoarthritis. On admission, he presented with a temperature of 38.9°C (102.0°F), a productive cough, and a right lower lobe consolidation on chest radiography. He was started on empiric therapy with intravenous ceftriaxone and oral azithromycin.

Sputum and blood cultures obtained on admission have now finalized, both growing *Streptococcus pneumoniae*. Susceptibility testing of the isolate demonstrates the following:

AntimicrobialInterpretation
PenicillinSusceptible (MIC 0.03 mcg/mL)
AmoxicillinSusceptible
CeftriaxoneSusceptible
LevofloxacinSusceptible
AzithromycinResistant

Today, the patient reports feeling much better. He has been afebrile for the past 28 hours. His heart rate is 78/min, blood pressure is 128/82 mmHg, and respiratory rate is 16/min. Oxygen saturation is 96% on room air. He is tolerating a regular diet without difficulty. Which of the following is the most appropriate next step in his antimicrobial management?

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

Answer

Transition to oral amoxicillin
The correct decision is to transition to oral amoxicillin. This patient was initially treated appropriately with an empiric broad-spectrum regimen for community-acquired pneumonia. On day 3, he demonstrates excellent clinical improvement (afebrile for >24 hours, normalized vital signs, resolving symptoms) and is able to tolerate an oral diet. These factors fulfill the standard criteria for transitioning from intravenous to oral antibiotics. A fundamental principle of antimicrobial stewardship is 'de-escalation', which means narrowing the antibiotic spectrum as soon as a causative pathogen and its susceptibilities are known. Because the isolated *Streptococcus pneumoniae* is highly susceptible to penicillin, amoxicillin is the preferred narrow-spectrum, targeted oral agent.

Step-by-Step Solution

1
Assess the patient's clinical stability for transition from intravenous to oral therapy.
The patient is hemodynamically stable, afebrile for >24 hours, improving clinically, and tolerating an oral diet, making him a candidate for oral transition.
Transitioning to oral therapy reduces the risk of catheter-related complications and facilitates hospital discharge.
2
Review the finalized culture and susceptibility data.
Cultures demonstrate Streptococcus pneumoniae that is highly susceptible to penicillin and amoxicillin, but resistant to azithromycin.
Empiric broad-spectrum therapy must be tailored and narrowed once definitive culture data is available.
3
Select the most appropriate, narrow-spectrum oral agent.
Oral amoxicillin is selected.
Amoxicillin provides excellent targeted coverage for susceptible S. pneumoniae without the unnecessary broad-spectrum effects of levofloxacin or amoxicillin-clavulanate.

Key Concept

Clinically stable hospitalized patients with community-acquired pneumonia should be transitioned to a targeted, narrow-spectrum oral antibiotic (such as amoxicillin for susceptible S. pneumoniae) as soon as culture data permits and they are tolerating oral intake.
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Topics

Infectious Diseases

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