Soru

A $68$-year-old woman with a history of poorly controlled type $2$ diabetes mellitus is evaluated on hospital day $3$. She originally presented to the emergency department with fever, right upper quadrant abdominal pain, and jaundice. On admission, her temperature was $39.2^{\circ}\text{C}$ ($102.6^{\circ}\text{F}$), blood pressure was $88/54\text{ mmHg}$, and heart rate was $118/\text{min}$. Laboratory studies showed a leukocyte count of $21,000/\mu\text{L}$, total bilirubin of $6.4\text{ mg/dL}$, and alkaline phosphatase of $450\text{ U/L}$. Blood cultures were drawn, and she was aggressively resuscitated with intravenous fluids and empiric intravenous piperacillin-tazobactam.

She subsequently underwent an emergent endoscopic retrograde cholangiopancreatography (ERCP), which revealed a common bile duct stone. A biliary sphincterotomy was performed, and the stone was successfully extracted, followed by the placement of a biliary stent.

Today, the patient is afebrile and hemodynamically stable. Her abdominal pain has resolved, and she is tolerating a regular diet. Her leukocyte count has decreased to $9,000/\mu\text{L}$. The admission blood cultures have grown *Escherichia coli*. The susceptibility report indicates the organism is sensitive to ampicillin, ceftriaxone, ciprofloxacin, and piperacillin-tazobactam.

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