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Difficulty: MediumInfectious Diseases

A 74-year-old man residing in a skilled nursing facility is evaluated on hospital day 33 for a complicated urinary tract infection. He was initially brought to the emergency department for altered mental status and a new fever. On admission, his temperature was 38.9∘C38.9^\circ\text{C} (102.0∘F102.0^\circ\text{F}), and his long-term indwelling urinary catheter was found to be obstructed with purulent sediment. The catheter was promptly removed, and he was started empirically on intravenous vancomycin and piperacillin-tazobactam. Today, the patient is afebrile, his mental status has returned to baseline, and he is tolerating an oral diet. Blood cultures obtained on admission show no growth. A urine culture obtained via straight catheterization prior to antibiotic initiation grows >100,000 CFU/mL>100,000\text{ CFU/mL} of Escherichia coli. Susceptibility testing reveals the organism is susceptible to ceftriaxone, ciprofloxacin, and trimethoprim-sulfamethoxazole, but resistant to ampicillin. Which of the following is the most appropriate next step in management?

  1. A
    Discontinue vancomycin and continue intravenous piperacillin-tazobactam.
  2. B
    Discontinue vancomycin and piperacillin-tazobactam, and begin oral nitrofurantoin.
  3. Discontinue vancomycin and piperacillin-tazobactam, and begin oral trimethoprim-sulfamethoxazole.Answer
  4. D
    Continue both intravenous vancomycin and piperacillin-tazobactam to complete a 7-day course.
  5. E
    Discontinue all antimicrobial therapy as the patient is now asymptomatic following catheter removal.

Answer

Discontinue vancomycin and piperacillin-tazobactam, and begin oral trimethoprim-sulfamethoxazole.
The correct action demonstrates the core principles of antimicrobial stewardship: narrowing the antibiotic spectrum based on culture data and transitioning from intravenous to oral therapy when clinically appropriate. The patient presented with a complicated, catheter-associated urinary tract infection accompanied by systemic symptoms, necessitating empiric broad-spectrum coverage (vancomycin and piperacillin-tazobactam). Now, with source control achieved (catheter removal) and clinical stability established (afebrile, tolerating oral intake), the empiric regimen must be adjusted. The culture shows E. coli susceptible to trimethoprim-sulfamethoxazole, a highly bioavailable oral agent with excellent penetration into the urinary tract and renal parenchyma. Discontinuing the broad intravenous agents and starting oral trimethoprim-sulfamethoxazole provides optimal targeted therapy.

Step-by-Step Solution

1
Evaluate the patient's clinical response to initial empiric therapy.
The patient is clinically stable, afebrile, has returned to his baseline mental status, and is tolerating oral intake.
Determines if the patient has achieved source control and is physiologically eligible for transition from intravenous to oral antibiotics.
2
Analyze the microbiological data and susceptibility results.
Urine culture confirms a single pathogen, Escherichia coli, which is susceptible to trimethoprim-sulfamethoxazole, ceftriaxone, and ciprofloxacin.
Identifies the specific pathogen to allow for de-escalation from empiric broad-spectrum therapy to targeted, narrow-spectrum therapy.
3
Select the most appropriate targeted therapy for a complicated urinary tract infection.
Oral trimethoprim-sulfamethoxazole is chosen.
It provides excellent systemic and renal tissue penetration (unlike nitrofurantoin), strictly targets the isolated pathogen without overly broad coverage, and utilizes the oral route.

Key Concept

Antibiotic de-escalation involves transitioning clinically stable patients from broad-spectrum intravenous empiric antibiotics to narrow-spectrum targeted oral therapy once culture and susceptibility data are available.
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Topics

Infectious Diseases

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