A 53-year-old man is evaluated in the hospital for fever. He underwent elective coronary artery bypass graft surgery 2 days ago. An indwelling urinary catheter was inserted in the operating room. Medical history is unremarkable, and he takes no medications.

On physical examination, temperature is 38.4 °C (101.1 °F), blood pressure is 130/84 mm Hg, pulse rate is 88/min, and respiration rate is 18/min. Lungs are clear to auscultation. The sternotomy incision site is clean and dry. He has mild suprapubic tenderness but no costovertebral angle or flank tenderness.

Urinalysis reveals 10 to 20 leukocytes/hpf. Urine culture grows 104 colony-forming units of gram-negative rods. Chest radiograph shows no infiltrate.

In addition to removing the urinary catheter, which of the following is the most appropriate management?