Which of the following pathogens is associated with fecal leukocytes and bloody diarrhea?

Campylobacter jejuni is a well-known pathogen that causes gastroenteritis, particularly characterized by symptoms such as diarrhea, which can be bloody, abdominal pain, and fever. The presence of fecal leukocytes indicates an inflammatory response in the intestines, which is a hallmark of bacterial infections that disrupt the intestinal mucosa. Campylobacter jejuni is often transmitted through undercooked poultry and contaminated water, and it typically leads to more severe symptoms, including the presence of blood in the diarrhea due to its ability to invade the gastrointestinal lining.

The other pathogens listed do not commonly present with fecal leukocytes or bloody diarrhea in the same way. Staphylococcus aureus typically causes food poisoning characterized by acute vomiting and diarrhea but is not usually associated with fecal leukocytes. Vibrio cholerae causes profuse watery diarrhea, known as "rice-water stools," and does not usually involve leukocytes or blood. Bacillus cereus can lead to a range of gastrointestinal symptoms, but its diarrheal disease is also not typically associated with fecal leukocytes or the presence of blood. Therefore, Campylobacter jejuni is the most fitting choice when considering the nature of the diarrhea and the associated immune response.