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Difficulty: MediumGastroenterology and Hepatology

A hospital medicine team is evaluating a 65-year-old woman on the third day of her admission for acute cholangitis. On presentation to the hospital, she had a temperature of 39.2°C (102.6°F), pronounced scleral icterus, and right upper quadrant abdominal tenderness. Two sets of blood cultures were drawn, and empiric intravenous piperacillin-tazobactam was initiated. Later that same day, she underwent an uncomplicated endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy and successful extraction of a 1.5-cm common bile duct stone.

Today, the patient is clinically much improved. Her temperature is 37.1°C (98.8°F), her abdominal pain has entirely resolved, and her leukocyte count has decreased from 18,000/mm³ on admission to 8,500/mm³. The admission blood cultures are now growing *Escherichia coli* in both sets. The laboratory's antimicrobial susceptibility report indicates the isolate is resistant to ampicillin but susceptible to ceftriaxone, ciprofloxacin, meropenem, and piperacillin-tazobactam.

Which of the following is the most appropriate next step in pharmacotherapy for this patient?

  1. Change to intravenous ceftriaxoneAnswer
  2. B
    Continue intravenous piperacillin-tazobactam
  3. C
    Change to intravenous meropenem
  4. D
    Add intravenous vancomycin
  5. E
    Discontinue all antimicrobial therapy

Answer

Change to intravenous ceftriaxone
The correct answer is changing to intravenous ceftriaxone. This vignette describes a patient who presented with severe acute cholangitis and appropriately received source control (ERCP) and broad-spectrum empiric antibiotics (piperacillin-tazobactam). Now that the blood culture has resulted with a single pathogen (*E. coli*) and its susceptibility profile is known, the core principle of antimicrobial stewardship dictates de-escalation. De-escalation involves narrowing the antibiotic spectrum to target the specific organism identified. Piperacillin-tazobactam provides broad Gram-negative, anaerobic, and anti-pseudomonal coverage. Because the isolated *E. coli* is susceptible to ceftriaxone (a third-generation cephalosporin without anti-pseudomonal activity), switching to ceftriaxone provides adequate definitive coverage while minimizing collateral damage to the patient's microbiome and reducing the risk of resistant organism emergence.

Step-by-Step Solution

1
Evaluate the patient's clinical status and source control.
The patient is afebrile, asymptomatic, and has normalizing labs after a successful ERCP.
Confirms that the initial management was effective and the patient is stable enough to adjust medications.
2
Analyze the microbiological data.
Blood cultures confirm *E. coli* bacteremia susceptible to multiple agents, including ceftriaxone.
Guides the transition from empiric therapy to targeted therapy.
3
Apply the principles of antimicrobial stewardship.
Identify the antimicrobial with the narrowest spectrum that effectively covers the isolated pathogen.
Prevents the development of antimicrobial resistance and reduces the risk of adverse effects like Clostridioides difficile infection.
4
Select the appropriate targeted agent.
Ceftriaxone is chosen over continuing piperacillin-tazobactam.
Ceftriaxone adequately covers the susceptible *E. coli* without unnecessary anaerobic or anti-pseudomonal activity.

Key Concept

Antimicrobial de-escalation in acute cholangitis
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Topics

Gastroenterology and Hepatology

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