A 34-year-old woman arrives at the emergency department complaining of severe nausea, vomiting, and diarrhea that began approximately four hours ago. She describes eating several dishes at a family potluck earlier in the day, including potato salad, deviled eggs, and cream-filled pastries. The patient notes that the food was left out for several hours in warm weather before it was served. Her symptoms started abruptly after she returned home, with significant nausea and repeated episodes of vomiting, followed by watery diarrhea. She denies any blood in her stool or fever but reports mild abdominal cramping. The patient has no significant medical history and does not take any regular medications. She denies recent travel, antibiotic use, or contact with anyone experiencing similar symptoms. She lives with her husband and two children, who have not yet shown any signs of illness. She does not smoke or drink alcohol and works as an administrative assistant. On examination, the patient appears mildly dehydrated but is alert and oriented. Her vital signs are stable, with a temperature of 98.8°F (37.1°C), heart rate of 90 beats per minute, blood pressure of 115/70 mm Hg, and respiratory rate of 16 breaths per minute. Abdominal examination reveals mild diffuse tenderness without rebound or guarding, and bowel sounds are hyperactive. There are no signs of peritonitis or other abnormalities on physical examination. Given the rapid onset of symptoms following the ingestion of improperly stored food and the absence of systemic signs such as fever, a clinical diagnosis of Staphylococcus aureus gastroenteritis is made. Which of the following best describes the mechanism of illness in this patient?
