Soru

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?