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Difficulty: MediumInfectious Diseases

A 65-year-old man is evaluated in the intensive care unit for recent fever. He was admitted 10 days ago for severe acute pancreatitis and required aggressive fluid resuscitation via a right internal jugular central venous catheter. Two days ago, he developed a temperature of 38.9∘C38.9^\circ\text{C} (102.0∘F102.0^\circ\text{F}) and tachycardia. The central catheter was removed, and peripheral blood cultures were drawn. Empiric intravenous vancomycin and cefepime were initiated. Today, the patient is afebrile and hemodynamically stable. Both sets of blood cultures are positive for *Enterococcus faecalis*. Susceptibility testing demonstrates that the isolate is susceptible to ampicillin, vancomycin, and daptomycin, but resistant to cefepime. Which of the following is the most appropriate next step in this patient's antimicrobial therapy?

  1. A
    Discontinue cefepime, and continue intravenous vancomycin
  2. B
    Discontinue vancomycin and cefepime, and start intravenous daptomycin
  3. Discontinue vancomycin and cefepime, and start intravenous ampicillinAnswer
  4. D
    Continue intravenous vancomycin and cefepime to complete a 14-day course
  5. E
    Discontinue vancomycin and cefepime, and start intravenous piperacillin-tazobactam

Answer

Discontinue vancomycin and cefepime, and start intravenous ampicillin
The most appropriate management for an ampicillin-susceptible Enterococcus faecalis bloodstream infection is to transition to intravenous ampicillin. This aligns with core antimicrobial stewardship principles, which dictate de-escalating from broad-spectrum empiric regimens to the narrowest effective targeted therapy once culture and susceptibility data are available. E. faecalis is intrinsically resistant to cephalosporins (including cefepime). While vancomycin is active against this isolate, its continued use when the pathogen is ampicillin-susceptible unnecessarily increases the risk of selecting for vancomycin-resistant Enterococcus (VRE) and other resistant Gram-positive organisms. Therefore, stopping both empiric medications and initiating ampicillin provides optimal, targeted treatment.

Step-by-Step Solution

1
Identify the causative pathogen and its susceptibility profile.
The pathogen is Enterococcus faecalis, which is susceptible to ampicillin, vancomycin, and daptomycin.
Guiding definitive antimicrobial therapy based on culture results is essential for effective treatment.
2
Evaluate the empiric regimen for appropriateness against the isolated pathogen.
Cefepime provides no coverage against Enterococcus species, and vancomycin provides unnecessarily broad Gram-positive coverage.
Empiric therapy must be de-escalated to targeted therapy to prevent antimicrobial resistance and reduce adverse effects.
3
Select the most appropriate targeted therapy based on antimicrobial stewardship principles.
Intravenous ampicillin is selected as the definitive therapy.
Ampicillin is the drug of choice for susceptible E. faecalis because it is highly active, narrow-spectrum, and minimizes the risk of selecting for vancomycin-resistant Enterococcus (VRE).

Key Concept

De-escalation of empiric antibiotics to targeted, narrow-spectrum therapy, specifically using ampicillin for susceptible Enterococcus faecalis bloodstream infections.
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Topics

Infectious Diseases

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