This 30-year-old dairy farmer was in good health until the day prior to admission, when he felt chilled and feverish. He developed nausea, vomiting, diarrhea, and lower abdominal discomfort and presented to the emergency room, where he was noted to be lethargic. His vital signs included temperature of 40ºC, blood pressure of 100/60 mmHg in the supine position and 80/69 mmHg sitting, and a pulse of 80 beats/min. His physical examination was remarkable for lower abdominal tenderness. A rectal examination revealed occult blood in the stool. The patient was lethargic but had no focal neurological deficits. Of note, his 3-year-old daughter had been discharged from the hospital 2 days previously with a similar history. The patient was treated with i.v. fluids and antibiotics, and his condition improved. A stool examination was fecal leukocytes was positive, and a stool culture was diagnostic. Biochemical examination of the organism revealed it to be a lactose nonfermenter on MacConkey agar, H2S negative, urease negative, and nonmotile. 1. Which organisms would be in your differential diagnosis of bloody diarrhea with fecal leukocytes? 2. On the basis of the biochemical reactions, which organism do you think it is? 3. How is dehydration in patients with diarrhea usually treated? Why could this therapy not be used in this case?