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A 24-year-old man presents to the emergency department for bloody stools. The patient states that he has had bloody diarrhea for the past 3 days without improvement. He recently returned from a camping trip where he drank stream water and admits to eating undercooked meats which included beef, chicken, pork, and salmon. The patient's father died at age 40 due to colon cancer, and his mother died of breast cancer at the age of 52. The patient lives alone and drinks socially. The patient has unprotected sex with multiple male partners. His temperature is 98.3°F (36.8°C), blood pressure is 107/58 mmHg, pulse is 127/min, respirations are 12/min, and oxygen saturation is 99% on room air. Laboratory values are ordered as seen below. Hemoglobin: 9.2 g/dL Hematocrit: 29% Leukocyte count: 9,500/mm^3 with normal differential Platelet count: 87,000/mm^3 Lactate dehydrogenase: 327 IU/L Haptoglobin: 5 mg/dL Serum: Na+: 139 mEq/L Cl-: 100 mEq/L K+: 5.9 mEq/L HCO3-: 19 mEq/L BUN: 39 mg/dL Glucose: 99 mg/dL Creatinine: 1.1 mg/dL Ca2+: 10.2 mg/dL Which of the following is the most likely cause of this patient's presentation?

A 34-year-old, previously healthy woman is admitted to the hospital with abdominal pain and bloody diarrhea. She reports consuming undercooked beef a day before the onset of her symptoms. Her medical history is unremarkable. Vital signs include: blood pressure 100/70 mm Hg, pulse rate 70/min, respiratory rate 16/min, and temperature 36.6℃ (97.9℉). Physical examination shows paleness, face and leg edema, and abdominal tenderness in the lower right quadrant. Laboratory investigation shows the following findings: Erythrocytes 3 x 106/mm3 Hemoglobin 9.4 g/dL Hematocrit 0.45 (45%) Corrected reticulocyte count 5.5% Platelet count 18,000/mm3 Leukocytes 11,750/mm3 Total bilirubin 2.33 mg/dL (39.8 µmol/L) Direct bilirubin 0.2 mg/dL (3.4 µmol/L) Serum creatinine 4.5 mg/dL (397.8 µmol/L) Blood urea nitrogen 35.4 mg/dL (12.6 mmol/L) E. coli O157: H7 was identified in the patient’s stool. Which toxin is likely responsible for her symptoms?