Which of the following microorganisms is typically responsible for the majority of shellfish-related illnesses?

Vibrio vulnificus is primarily associated with shellfish-related illnesses, particularly those linked to the consumption of raw or undercooked shellfish, such as oysters. This bacterium is found naturally in warm seawater, which makes it prevalent in marine environments. When humans ingest contaminated shellfish, particularly during warmer months, they can contract severe gastrointestinal illnesses or even serious systemic infections. The health risks are especially pronounced for individuals with weakened immune systems, liver disease, or other underlying health conditions.

While other microorganisms can cause foodborne illnesses, they are typically not linked specifically to shellfish. For instance, Escherichia coli and Salmonella enteritidis are more commonly associated with contaminated meats, dairy products, and vegetables, rather than seafood. Campylobacter jejuni is generally found in poultry and unpasteurized milk rather than in shellfish. Therefore, Vibrio vulnificus stands out as the microorganism most directly tied to the risks associated with shellfish consumption.