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Question

Difficulty: MediumInfectious Diseases

A 65-year-old male is reevaluated during bedside rounds on his third day of hospitalization. He originally presented to the emergency department with high fever, left-sided costovertebral angle tenderness, and dysuria. Due to a history of recurrent urinary tract infections and a recent skilled nursing facility admission, he was empirically started on intravenous vancomycin and piperacillin-tazobactam. His clinical condition has markedly improved; he has been afebrile for 24 hours, and his flank pain has resolved. Blood and urine cultures drawn on admission now demonstrate growth of Enterococcus faecalis. The isolate is susceptible to ampicillin, vancomycin, linezolid, and daptomycin. Which of the following is the most appropriate next step in pharmacotherapy?

  1. Initiate intravenous ampicillin monotherapyAnswer
  2. B
    Maintain therapy with vancomycin and cease piperacillin-tazobactam
  3. C
    Maintain the current antimicrobial combination
  4. D
    Switch therapy to oral linezolid
  5. E
    Cease vancomycin and maintain piperacillin-tazobactam

Answer

The most appropriate step is to de-escalate the antibiotic regimen to intravenous ampicillin monotherapy.
The correct action is to initiate intravenous ampicillin monotherapy. When definitive culture and susceptibility data become available, antimicrobial stewardship principles mandate de-escalating from broad-spectrum empiric regimens to the narrowest-spectrum effective agent. Enterococcus faecalis is classically susceptible to ampicillin, which serves as the drug of choice. Compared to vancomycin, ampicillin has superior bactericidal activity against susceptible enterococci and does not drive vancomycin resistance. Because the patient's bacteremia and urinary tract infection are caused solely by this isolate, broad Gram-negative and anaerobic coverage is no longer indicated.

Step-by-Step Solution

1
Evaluate the patient's current clinical status.
The patient is clinically improving, hemodynamically stable, and afebrile, indicating the initial therapy was effective.
Clinical stability allows for safe narrowing and optimization of antimicrobial therapy based on culture results.
2
Analyze the culture and susceptibility data.
Blood and urine cultures are growing Enterococcus faecalis that is pan-susceptible, specifically to ampicillin.
Identifying the specific pathogen and its susceptibility profile is required to transition from empiric to definitive targeted therapy.
3
Apply principles of antimicrobial stewardship to select the definitive agent.
Ampicillin is selected over vancomycin, piperacillin-tazobactam, and linezolid.
Ampicillin provides the narrowest effective coverage, has superior bactericidal activity against susceptible enterococci compared to vancomycin, and prevents the development of multi-drug resistant organisms.

Key Concept

Antimicrobial stewardship dictates de-escalating to the narrowest, most effective agent once culture and susceptibility data are available; intravenous ampicillin is the preferred treatment for susceptible Enterococcus faecalis.
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Topics

Infectious Diseases

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