A group of students develops explosive watery diarrhoea six hours after eating undercooked prawns at a coastal resort. Stool culture on TCBS agar yields green colonies. The isolate grows only when the medium is supplemented with sodium chloride. This salt requirement reflects that the organism is:

• A Sucrose fermenting, producing acid colonies
• B Fastidious, requiring X and V factors
• C Microaerophilic, requiring reduced oxygen tension
• D Halophilic, requiring NaCl for growth ✓

Explanation

Vibrio parahaemolyticus is a halophilic marine vibrio that requires sodium chloride for growth and fails to grow on nutrient media lacking added salt. It produces green colonies on TCBS because it does not ferment sucrose, unlike Vibrio cholerae which forms yellow colonies. Its pathogenicity correlates with production of the thermostable direct haemolysin detected by the Kanagawa test. Fastidious X and V factor dependence describes Haemophilus, not vibrios.

Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.