Vibrio cholerae

• What are the phenotypic and biochemical characteristics of Vibrio cholerae?

  Vibrio cholerae is a Gram-negative, comma-shaped bacillus that produces the cholera toxin, an AB toxin which increases cyclic AMP to disrupt intestinal water regulation.
• What are the phenotypic tests to confirm a diagnosis of Vibrio cholerae infection?

  • Microscopy (Gram stain shows Gram-negative curved rods)
  • Culture (preferred selective media like TCBS Agar or MacConkey agar)
  • Motility Test (observes characteristic “shooting star” motility)
• What are the preferred selective media for cultivating Vibrio cholerae?

  • Thiosulfate-Citrate-Bile Salts-Sucrose (TCBS) Agar
  • MacConkey agar
• What causes the yellow color of colonies on TCBS Agar when Vibrio cholerae grows?

  Sucre fermentation by Vibrio cholerae produces yellow colonies on TCBS Agar.
• How do colonies of Vibrio cholerae appear on MacConkey agar?

  They appear as pale colonies as Vibrio cholerae does not ferment lactose.
• What are the biochemical tests used to confirm Vibrio cholerae diagnosis?

  • Oxidase Test (positive for cytochrome oxidase)
  • Sucrose Fermentation (positive on TCBS Agar)
  • String Test (forms a mucoid string with sodium deoxycholate)
• In what situations would PCR testing be useful for diagnosing Vibrio cholerae infection?

  PCR is useful in outbreaks or regions with endemic cholera to detect the cholera toxin genes (ctxA or ctxB).
• What is the cornerstone of treatment for cholera?

  • Rehydration therapy (oral rehydration salts or IV fluids)
• Which antibiotics may be used to reduce the severity and duration of cholera in severe cases?

  Doxycycline or azithromycin.