Question

A 76-year-old woman is evaluated in the hospital on day 5 of her admission due to an episode of hypotension and altered mental status. She was initially admitted for a severe COPD exacerbation and has been receiving systemic glucocorticoids, nebulized bronchodilators, and prophylactic enoxaparin. An indwelling Foley catheter was placed on admission due to urinary retention and has remained in place.

Today (Day 5), her temperature is $38.3^\circ\text{C}$ ($100.9^\circ\text{F}$), blood pressure is $88/56\text{ mmHg}$, heart rate is $112\text{/min}$, and respiratory rate is $22\text{/min}$. Physical examination reveals a lethargic patient. The abdomen is soft and non-tender, and there is no costovertebral angle tenderness. Laboratory findings show a leukocyte count of $16,500\text{/mm}^3$. A urinalysis obtained from the Foley catheter port shows $25\text{ WBCs/hpf}$ and positive leukocyte esterase, but negative nitrites.

Blood and urine cultures are drawn. The patient receives intravenous fluid resuscitation, and empiric intravenous vancomycin and cefepime are initiated.

Two days later (Day 7), the patient is clinically improved, her mental status has returned to baseline, she is hemodynamically stable off fluids, and she is afebrile. Blood cultures show no growth at 48 hours. The urine culture grows $>10^5\text{ CFU/mL}$ of *Enterococcus faecalis*.

Antimicrobial susceptibility testing for the *E. faecalis* isolate demonstrates the following:
- Ampicillin: Susceptible
- Cefepime: Resistant
- Ciprofloxacin: Resistant
- Linezolid: Susceptible
- Vancomycin: Susceptible

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