Review Question - QID 210420

A 51-year-old police officer is brought to the emergency room after being shot in the abdomen. His wound was packed and bandaged by emergency medical services before he was transported to the hospital. His past medical history is notable for hypertension and diabetes. He takes metformin and lisinopril. He has a 20-pack-year smoking history and does not drink alcohol. His temperature is 98.6°F (37°C), blood pressure is 142/86 mmHg, pulse is 120/min, and respirations are 24/min. On exam, he appears uncomfortable but is able to answer questions appropriately. He has a 1 cm x 1 cm wound in the left upper quadrant. There is an exit wound in the left lower back. After undergoing the appropriate laboratory and imaging tests, he undergoes a diagnostic laparotomy. No involvement of the colon or small intestine is noted intraoperatively. He is placed on the appropriate antibiotic and pain control regimens. Three days later, he experiences several episodes of non-bloody diarrhea. His temperature is 101°F (38.3°C). Sigmoidoscopy reveals multiple pseudomembranous plaques in the sigmoid and descending colon. This patient's symptoms are most likely due to taking an antibiotic that inhibits which of the following enzymes?