parahaemolyticus

Parahaemolyticus, referring to Vibrio parahaemolyticus, is a Gram-negative, curved, motile bacterium in the family Vibrionaceae. It is halophilic and commonly found in marine and estuarine environments, including seawater, sediments, and seafood. It is routinely isolated from shellfish and other seafood products and can be present in coastal waters, especially during warmer months.

In humans, Vibrio parahaemolyticus is a leading cause of gastroenteritis associated with seafood consumption. Illness typically follows ingestion of raw or undercooked or otherwise contaminated seafood, particularly oysters. Most infections are self-limited, presenting with watery diarrhea, abdominal cramps, nausea, and sometimes fever or vomiting, resolving within a few days. In some individuals, especially those with underlying liver disease, diabetes, or immunocompromise, extraintestinal infections such as wound infections or septicemia can occur, though these are less common.

Virulence in V. parahaemolyticus is related to several factors, most notably the thermostable direct hemolysin (TDH) and the TDH-related hemolysin (TRH), as well as Type III secretion systems. The presence of tdh and/or trh genes is linked to virulence in clinical strains. A pandemic lineage, designated O3:K6, emerged in the 1990s and has contributed to widespread outbreaks.

Diagnosis is based on culture of stool or seafood samples, followed by biochemical tests and molecular assays for virulence genes. Treatment is usually supportive, with hydration and electrolyte management; antibiotics are reserved for severe or invasive disease and may include doxycycline or a fluoroquinolone. Prevention centers on proper handling and thorough cooking of seafood and avoiding cross-contamination.