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Difficulty: MediumInfectious Diseases

A physician evaluates a 68-year-old woman who is currently on hospital day 3 for the treatment of urosepsis. Upon admission to the intensive care unit three days ago, the patient was hypotensive and febrile. She received aggressive fluid resuscitation and was empirically started on intravenous vancomycin and cefepime. She was transferred to the general medical ward yesterday. Today, her vital signs are stable, she has been afebrile for 24 hours, and she is comfortably eating a regular diet. Initial blood and urine cultures now show growth of *Escherichia coli*. Antimicrobial susceptibility testing reveals the isolate is sensitive to ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole, but resistant to ampicillin. Which of the following is the most appropriate next step in antibiotic therapy?

  1. A
    Continue intravenous vancomycin and cefepime
  2. B
    Continue intravenous cefepime and discontinue vancomycin
  3. Transition to oral trimethoprim-sulfamethoxazoleAnswer
  4. D
    Switch to intravenous piperacillin-tazobactam
  5. E
    Switch to intravenous meropenem

Answer

Transition to oral trimethoprim-sulfamethoxazole
The correct answer is to transition the patient to oral trimethoprim-sulfamethoxazole. Antimicrobial stewardship principles dictate two major changes in this scenario: de-escalation and IV-to-PO transition. First, once a patient with a severe bacterial infection (such as urosepsis) is clinically stable, afebrile, and able to take oral medications, they should be transitioned from intravenous to highly bioavailable oral antibiotics. Trimethoprim-sulfamethoxazole has excellent oral bioavailability and achieves high concentrations in both the serum and urinary tract. Second, broad-spectrum empiric therapy (vancomycin and cefepime) must be de-escalated to targeted, narrow-spectrum therapy based on definitive culture and susceptibility results. Since the isolated E. coli is susceptible to trimethoprim-sulfamethoxazole, stepping down to this targeted oral agent is the most appropriate management.

Step-by-Step Solution

1
Assess the patient's current clinical stability and route of administration feasibility.
The patient is hemodynamically stable, has been afebrile for 24 hours, and is successfully tolerating a regular diet.
Patients with severe infections who have clinically improved and can absorb oral medications are excellent candidates for an intravenous-to-oral (IV-to-PO) transition.
2
Evaluate the microbiological data and susceptibility results.
Cultures isolated Escherichia coli that is susceptible to ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole.
Empiric broad-spectrum therapy must be de-escalated to targeted, narrow-spectrum therapy once susceptibilities are known to prevent resistance and reduce adverse effects.
3
Select the most appropriate definitive therapy.
Oral trimethoprim-sulfamethoxazole is chosen as the next step.
It provides targeted, narrow-spectrum coverage for the susceptible E. coli isolate, has excellent oral bioavailability for completing the treatment course, and avoids unnecessary intravenous access.

Key Concept

Antibiotic Stewardship: Intravenous to Oral Transition and De-escalation
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Topics

Infectious Diseases

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