Question

A $62$-year-old man comes to the emergency department complaining of severe, worsening lower back pain for the past $3$ weeks. The pain is constant, wakes him up at night, and is not relieved by rest or over-the-counter analgesics. He reports feeling warm at times but denies any leg weakness, numbness, or loss of bowel and bladder control. His medical history is significant for type 2 diabetes mellitus and end-stage renal disease, for which he receives hemodialysis via a right internal jugular venous catheter. Temperature is $37.9^\circ\text{C}$ ($100.2^\circ\text{F}$), blood pressure is $135/85 \text{ mm Hg}$, and pulse is $88/\text{min}$. Physical examination reveals exquisite tenderness to percussion over the L3 and L4 spinous processes. Neurologic examination of the lower extremities shows $5/5$ strength, normal sensation to pinprick and light touch, and $2+$ deep tendon reflexes symmetrically. Anal sphincter tone is normal. Laboratory studies show a leukocyte count of $9,500/\text{mm}^3$, an erythrocyte sedimentation rate of $88 \text{ mm/hr}$, and a C-reactive protein of $65 \text{ mg/L}$. Two sets of blood cultures are drawn. Magnetic resonance imaging of the lumbar spine reveals increased fluid signal in the L3-L4 intervertebral disc space with adjacent vertebral body marrow edema, consistent with pyogenic spondylodiscitis. There is no evidence of an epidural abscess or spinal cord compression. Which of the following is the most appropriate next step in the management of this patient?