This patient's dysentery is most likely caused by Vibrio parahaemolyticus gastrointestinal infection. Bloody stools, fever, and vomiting commonly occur with Vibrio infection. The fact that other diners developed a gastrointestinal illness suggests a common source associated with the shared meal. Vibrio species are widespread in salt or brackish water, and human infections are associated with ingestion of contaminated seafood, particularly shellfish. In a large case series of V. parahaemolyticus infections reported to the U.S. Centers for Disease Control and Prevention, bloody diarrhea was noted in 29% of cases. Chronic liver disease is a risk factor for severe infection with this organism, and sepsis is a common and often fatal complication in this population. Vibrio species do not grow well on traditional stool culture media, so when this diagnosis is being considered, the laboratory should be notified to allow plating onto saline-enriched agar.

Clostridium difficile colitis has a similar presentation with diarrhea, fever, and abdominal pain and cramping, but gross blood in the stool is uncommon. C. difficile infection is not a foodborne illness, and therefore a clustering of cases following a shared meal would not be expected.

Norovirus is the leading cause of foodborne outbreaks in the United States, with spread through fecal-oral contamination. This virus causes a watery stool, often with associated vomiting; however, fever is uncommon and grossly bloody stools would exclude this diagnosis.

Yersiniosis typically occurs following ingestion of contaminated food or water. Outbreaks of Yersinia enterocolitica have been traced to consumption of chitterlings (pork intestines). Yersinia gastroenteritis is clinically indistinguishable from other forms of inflammatory diarrhea and is most commonly identified in young children. It does not cause grossly bloody stools. In some cases, diarrhea may be absent with bacteria localizing to lymphoid tissue in Peyer patches and associated mesenteric lymph nodes. This presentation may mimic appendicitis clinically.