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Difficulty: MediumGeneral Internal Medicine

A 62-year-old man is evaluated on the general medical ward on his third day of hospitalization. He was initially admitted for fever, right-sided flank pain, and leukocytosis. Blood and urine cultures were drawn, and he was started on empirical intravenous piperacillin-tazobactam for suspected complicated pyelonephritis. His past medical history is notable for benign prostatic hyperplasia and diet-controlled type 2 diabetes mellitus.

The patient has been afebrile for the past 24 hours, and his flank pain has largely resolved. He is currently kept strictly nil per os (NPO) in preparation for an elective esophagogastroduodenoscopy (EGD) scheduled in 2 hours to evaluate chronic dyspepsia.

Both the admission blood and urine cultures are now positive for *Klebsiella pneumoniae*. The susceptibility report for the isolate is as follows:

Ampicillin: Resistant
Cefazolin: Susceptible
Ceftazidime: Susceptible
Ceftriaxone: Susceptible
Ciprofloxacin: Susceptible
Meropenem: Susceptible
Piperacillin-tazobactam: Susceptible

Which of the following is the most appropriate next step in the patient's pharmacologic management?

  1. A
    Continue intravenous piperacillin-tazobactam
  2. B
    Switch to intravenous meropenem
  3. C
    Switch to oral ciprofloxacin
  4. Switch to intravenous cefazolinAnswer
  5. E
    Switch to intravenous ceftazidime

Answer

The most appropriate next step is to switch the patient's antibiotic to intravenous cefazolin.
The correct answer is to switch to intravenous cefazolin. This patient is clinically improving on empirical broad-spectrum therapy for complicated pyelonephritis and bacteremia. With culture results showing a pansensitive *Klebsiella pneumoniae* isolate, standard antibiotic stewardship principles dictate de-escalating to the narrowest-spectrum effective agent. Cefazolin, a first-generation cephalosporin, is highly effective for susceptible Enterobacteriaceae and has a much narrower spectrum than piperacillin-tazobactam, thereby reducing the risk of collateral damage. Because the patient is strictly NPO for an impending EGD, an intravenous formulation is required at this time, making IV cefazolin the ideal choice.

Step-by-Step Solution

1
Evaluate the patient's clinical trajectory and current regimen.
The patient is clinically stable, afebrile, and improving on empirical piperacillin-tazobactam therapy.
Clinical stability indicates that stepping down or de-escalating therapy can be safely considered once definitive pathogen data is available.
2
Analyze the culture and susceptibility results to identify de-escalation options.
The pathogen is Klebsiella pneumoniae, which is susceptible to multiple narrow and broad-spectrum agents, including cefazolin.
Identifying the susceptibility profile allows the clinician to discontinue overly broad empirical agents.
3
Select the most appropriate targeted therapy based on spectrum and patient-specific constraints.
Intravenous cefazolin is chosen.
Cefazolin is the narrowest-spectrum effective agent available, minimizing collateral damage. The intravenous route is required because the patient is strictly NPO for a procedure in 2 hours.

Key Concept

Antibiotic stewardship requires de-escalating from empirical broad-spectrum therapy to the narrowest-spectrum effective agent once culture and susceptibility data are available, while accounting for patient-specific constraints such as NPO status.
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General Internal Medicine

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