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Difficulty: EasyInfectious Diseases

During morning rounds, a physician evaluates a patient admitted two days ago for a severe lower respiratory tract infection. The patient, a 52-year-old non-smoker, initially presented with a high fever, productive cough, and lobar consolidation on chest radiography. At admission, he was empirically started on intravenous ceftriaxone and oral azithromycin. Today, he is completely afebrile, his respiratory rate is 16/min, his oxygen saturation is 97% on ambient air, and he is eager to go home. The microbiology laboratory reports that the admission sputum culture is growing *Streptococcus pneumoniae*. Susceptibility testing indicates the isolate is susceptible to penicillin, amoxicillin, ceftriaxone, levofloxacin, and vancomycin. Blood cultures remain sterile. The physician is writing discharge orders to complete a total 5-day course of therapy. Which of the following is the most appropriate oral antibiotic regimen for discharge?

  1. Oral amoxicillinAnswer
  2. B
    Oral amoxicillin-clavulanate
  3. C
    Oral levofloxacin
  4. D
    Oral cefpodoxime and oral azithromycin
  5. E
    Oral linezolid

Answer

Oral amoxicillin
The patient's culture data demonstrates an infection with *Streptococcus pneumoniae* that is susceptible to penicillin and amoxicillin. Once a pathogen is identified and susceptibilities are known, fundamental antibiotic stewardship principles dictate de-escalating to the narrowest-spectrum effective agent. Oral amoxicillin provides excellent, targeted coverage for susceptible *S. pneumoniae* without unnecessary broad-spectrum effects, making it the most appropriate choice to complete the treatment course.

Step-by-Step Solution

1
Analyze the patient's clinical trajectory and microbiology data.
The patient is clinically stable for discharge, and cultures have identified a specific pathogen (*Streptococcus pneumoniae*) that is susceptible to multiple narrow-spectrum antibiotics.
Establishing clinical stability and identifying the pathogen are prerequisites for safely transitioning from empiric intravenous therapy to targeted oral therapy.
2
Apply principles of antimicrobial stewardship.
Therapy must be de-escalated from broad-spectrum empiric coverage (ceftriaxone and azithromycin) to the narrowest-spectrum agent that is effective against the isolated pathogen.
De-escalation minimizes collateral damage to the patient's microbiome, reduces the risk of adverse effects (e.g., C. difficile infection), and prevents the emergence of antimicrobial resistance.
3
Select the appropriate targeted oral agent.
Amoxicillin is chosen as the discharge regimen.
Amoxicillin is a highly effective, narrow-spectrum oral beta-lactam that is the standard of care for fully susceptible S. pneumoniae.

Key Concept

Antimicrobial stewardship dictates that empiric broad-spectrum antibiotic therapy should be de-escalated to targeted, narrow-spectrum therapy once a pathogen is identified and susceptibility results are available.
Estimated Time:1m 0s
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Infectious Diseases

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