In an outbreak of probable foodborne illness, a group of individuals develops watery diarrhea 48 hours after eating imported shellfish. The MOST likely causative organism is:
The CBIC Certified Infection Control Exam Study Guide (6th edition) highlights that consumption of raw or undercooked shellfish, particularly imported shellfish, is a well-recognized risk factor for waterborne and foodborne Vibrio infections, including Vibrio cholerae. The organism thrives in warm coastal waters and can contaminate shellfish harvested from endemic or inadequately regulated regions.
The clinical presentation described—profuse watery diarrhea occurring approximately 48 hours after exposure—is classic for Vibrio cholerae. The organism produces cholera toxin, which causes rapid fluid secretion into the intestinal lumen, resulting in large-volume watery stools. The incubation period typically ranges from a few hours to five days, making a 48-hour onset highly consistent with this pathogen.
The other options are less likely based on incubation period and symptom profile. Hepatitis A virus has an incubation period of weeks and presents with jaundice rather than acute watery diarrhea. Staphylococcus aureus food poisoning causes rapid onset (1–6 hours) due to preformed toxin and is commonly associated with vomiting. Listeria monocytogenes typically causes invasive disease rather than acute watery diarrhea and has a longer incubation period.
For CIC® exam preparation, recognizing shellfish-associated watery diarrhea with short incubation as characteristic of Vibrio cholerae is essential, particularly in outbreak investigations involving imported seafood.
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