Review Question - QID 108942

A 45-year-old male who recently returned from a business trip abroad presents to the emergency room complaining of several days of diarrhea. He has up to 10 voluminous watery stools per day accompanied by mild nausea and abdominal cramps. In addition, he recently noticed blood on his toilet paper after wiping but not in the toilet. His past medical history is notable for gout, peptic ulcer disease, and gastroesophageal reflux disease. He takes allopurinol and omeprazole. His temperature is 100.6°F (38.1°C), blood pressure is 120/75 mmHg, pulse is 105/min, and respirations are 18/min. On examination, he has dry mucous membranes and delayed capillary refill. He demonstrates mild tenderness to palpation in all quadrants of his abdomen. Figure A shows the gram stain for the organism that is isolated from stool culture. These organisms were also found to ferment lactose quickly. The mechanism that is most likely responsible for this patient's diarrhea is similar to that used by an organism with which of the following characteristics?