Vibrio parahaemolyticus
Summary
Vibrio parahaemolyticus is a halophilic, gram-negative curved rod that causes acute gastroenteritis after consumption of raw or undercooked seafood, especially oysters. It presents with watery diarrhea, abdominal cramps, nausea, and vomiting, typically self-limited within 3 days. It can also cause wound infections in individuals exposed to warm seawater.
Detail
Vibrio parahaemolyticus is a gram-negative, comma-shaped (curved) rod, oxidase-positive, and halophilic (requires salt for growth), distinguishing it from Vibrio cholerae. It is found in warm marine and estuarine waters worldwide and is a leading cause of seafood-associated gastroenteritis, particularly linked to raw or undercooked shellfish (oysters, shrimp, crab). Pathogenesis involves a thermostable direct hemolysin (TDH, Kanagawa phenomenon) and TDH-related hemolysin (TRH), which cause pore formation in intestinal epithelial cells leading to secretory diarrhea; it also has a type III secretion system contributing to cytotoxicity. Clinically, it causes acute watery diarrhea (occasionally dysenteric with blood/mucus), abdominal cramps, nausea, vomiting, and low-grade fever, usually self-limited (2-3 days) and managed with supportive care and rehydration; antibiotics are reserved for severe or prolonged cases. It can also cause wound infections and, rarely, septicemia in immunocompromised hosts or those with liver disease (similar to Vibrio vulnificus but less severe). Diagnosis is via stool culture on thiosulfate-citrate-bile salts-sucrose (TCBS) agar, where it produces green colonies (differentiating it from V. cholerae, which produces yellow colonies due to sucrose fermentation). Key USMLE associations: halophilic Vibrio, raw seafood/oysters, self-limited gastroenteritis, TCBS agar green colonies, Kanagawa phenomenon.
Sources
- First Aid for the USMLE Step 1
- Sherris Medical Microbiology
- CDC Vibrio parahaemolyticus fact sheet
- Harrison's Principles of Internal Medicine
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