A 35-year-old woman presents to the emergency department with a history of profuse watery diarrhea, crampy abdominal pain, and vomiting several days after eating oysters. Her laboratory findings are normal except for a mildly elevated white blood cell count, sodium 129 mEq/L (129 mmol/L), chloride 85 mEq/L (85 mmol/L), and potassium 3.2 mEq/L. Stool cultures are positive. Which pathogen is likely associated with this presentation?