Review Question - QID 109674

A 24-year-old man presents to the emergency department for abdominal pain for the past day. He has had profuse, watery diarrhea and abdominal pain that is keeping him up at night. He sees blood on the toilet paper when he wipes and has lost 5 pounds recently. His past medical history is notable for IV drug use and a recent hospitalization for sepsis. His temperature is 99.5°F (37.5°C), blood pressure is 120/68 mmHg, pulse is 100/min, respirations are 14/min, and oxygen saturation is 98% on room air. The patient is clutching his abdomen in pain. An abdominal exam demonstrates hyperactive bowel sounds and diffuse abdominal tenderness. A cardiopulmonary exam is within normal limits. After appropriate workup, which of the following is the most appropriate treatment?