Paper I
Question
Halophilic Vibrios
Answer
Halophilic vibrios are Vibrio species that require (or tolerate) elevated salt (NaCl) concentrations for growth, reflecting their natural habitat in marine and estuarine waters — distinguishing them from Vibrio cholerae, which is non-halophilic.
Important examples:
- Vibrio parahaemolyticus — a leading cause of seafood-associated acute gastroenteritis, presenting with watery or, in severe cases, dysenteric (bloody) diarrhoea. Pathogenic strains show the Kanagawa phenomenon (beta-haemolysis on a special high-salt blood agar).
- Vibrio vulnificus — associated with severe wound infections (seawater exposure) and, in patients with chronic liver disease, a fulminant septicaemia with high mortality, often following consumption of raw shellfish.
- Vibrio alginolyticus — a less virulent halophilic vibrio, mainly causing wound and ear infections after seawater exposure.
Laboratory features: require salt-supplemented media; grow on TCBS agar, the selective medium used for vibrios generally.
Prevention: thorough cooking of seafood, avoiding contamination of wounds with seawater.