A 64-year-old woman is evaluated in the hospital on the third day of her admission. She or… — USMLE Step 2 CK

A $64$ -year-old woman is evaluated in the hospital on the third day of her admission. She originally presented to the emergency department with a $2$ -day history of severe right upper quadrant abdominal pain, jaundice, and a temperature of $39.2^\circ\text{C}$ ( $102.6^\circ\text{F}$ ). She was diagnosed with acute ascending cholangitis and promptly started on empirical intravenous piperacillin-tazobactam. An emergent endoscopic retrograde cholangiopancreatography (ERCP) was performed, which successfully cleared a $1.2\text{ cm}$ stone from the common bile duct. Today, the patient is completely asymptomatic, afebrile for the past $24\text{ hours}$ , and tolerating a regular diet. Blood cultures drawn on admission are now positive for *Escherichia coli*. Susceptibility testing reveals the organism is susceptible to ceftriaxone, ciprofloxacin, and piperacillin-tazobactam, and is resistant to ampicillin. Which of the following is the most appropriate next step in the pharmacologic management of this patient?

Switch to oral ciprofloxacinAnswer
B
Continue intravenous piperacillin-tazobactam
C
Switch to intravenous meropenem
D
Switch to intravenous ceftriaxone
E
Add intravenous vancomycin to the current regimen

Answer

The most appropriate next step is to switch the patient to oral ciprofloxacin.

The correct answer is to switch to oral ciprofloxacin. In the management of acute ascending cholangitis, empirical broad-spectrum intravenous antibiotics (such as piperacillin-tazobactam) are initially indicated to prevent life-threatening sepsis. However, once adequate biliary drainage is achieved (e.g., via ERCP), the patient is clinically stable, and culture results are available, antimicrobial stewardship principles dictate de-escalating to the narrowest effective therapy. Because this patient is tolerating a regular diet and the isolated *E. coli* is susceptible to ciprofloxacin, transitioning to a highly bioavailable oral agent is the ideal next step. This strategy allows the patient to complete the recommended 4-to-7-day total course of antibiotics while facilitating safe and prompt hospital discharge.

Step-by-Step Solution

Assess the patient's clinical status and the adequacy of source control.

The patient is afebrile, asymptomatic, tolerating a regular diet, and has had definitive source control via ERCP with stone extraction.

Clinical stability and confirmed source control are the primary prerequisites for de-escalating therapy and transitioning from intravenous to oral antibiotics.

Analyze the blood culture and susceptibility results.

The cultures isolated Escherichia coli that is susceptible to ceftriaxone, ciprofloxacin, and piperacillin-tazobactam.

Identifying the specific pathogen and its sensitivities allows for the narrowing of antimicrobial therapy from empirical broad-spectrum agents to targeted, narrow-spectrum agents.

Determine the most appropriate definitive antimicrobial regimen.

Select oral ciprofloxacin to complete the remaining treatment course.

Oral ciprofloxacin provides excellent targeted coverage against the isolated E. coli with high oral bioavailability, allowing for the removal of intravenous access and facilitating prompt hospital discharge.

Key Concept

Antimicrobial stewardship and IV-to-PO de-escalation in acute cholangitis

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