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Microbiology · Other Gram-negative rods

Vibrio cholerae !

  • Bacterium
  • Gram-negative
  • Contact
  • Exam priority: high

A bacterium in contaminated water that causes cholera: watery diarrhea so heavy it can kill by dehydration within hours.

Updated 2026-11-01

Also called: cholera vibrio

At a glance

Gram
Gram-negative
Shape
Comma-shaped curved rod
Oxygen
Facultative anaerobe
Family
Vibrionaceae
Stain
Gram: curved red rods

Morphology

  • Comma-shaped Gram-negative rod with one polar flagellum: fast "darting" motility
  • Oxidase-positive
  • Grows on alkaline media: TCBS agar with yellow colonies (ferments sucrose)
  • Only serogroups O1 and O139 cause epidemics

Transmission

  • Water or food contaminated with feces, raw shellfish
  • Outbreaks where safe water and sanitation are lacking (disasters, camps)
  • Contact (on top of standard) for diapered or incontinent patients

Reservoir: Humans; Brackish and coastal water (linked to plankton)

Isolation precautions

What the care team adds to standard precautions.

Contact
Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.

Virulence factors

  • Cholera toxin (A-B): the A subunit activates Gs, raises enterocyte cAMP and drives massive chloride and water loss
  • Toxin-coregulated pilus (TCP): colonizes the small bowel
  • Flagellum and mucinase: cross the mucus
  • Acid-sensitive: needs a large inoculum

Diseases it causes

  • Cholera: acute watery diarrhea with severe dehydration Cholera →

Clinical picture

  • Onset from a few hours to 5 days after exposure
  • Large, bloodless, "rice-water" stools with a fishy smell
  • Vomiting, cramps, hypovolemia, acidosis and shock
  • Many infected people have no symptoms but shed the bacterium

Diagnosis

  • Stool culture in alkaline peptone water and on TCBS agar
  • Rapid stool antigen tests for outbreak screening
  • Confirmation and serotyping at the reference laboratory

Treatment

Fluid replacement is the core: oral rehydration salts for most patients and intravenous fluids for severe cases. Antibiotics (doxycycline, azithromycin or ciprofloxacin) are given in severe cases to shorten diarrhea; mass antibiotic prophylaxis is not recommended.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Safe water, sanitation and hygiene
  • Inactivated oral vaccines in endemic areas, humanitarian crises and outbreaks
  • Cooking shellfish and handwashing

Vaccine: WHO-prequalified inactivated oral vaccines; because of the global shortage, campaigns use a single dose. They are not part of Colombia's PAI.

Test yourself

Think of the answer, then tap the question to see it.

How does cholera toxin work?

Its A subunit permanently activates Gs, raises cAMP in the enterocyte and causes massive chloride and water secretion.

What is the most important treatment for cholera?

Rehydration: oral rehydration salts and, in severe cases, intravenous fluids.

On which selective medium does Vibrio cholerae grow, and what color are its colonies?

TCBS agar, with yellow colonies because it ferments sucrose.

Which serogroups cause epidemic cholera?

O1 and O139.

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← Back to the group: Other Gram-negative rods

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: Cholera (WHO, 2026); Understanding Cholera: Causes, Symptoms, and Treatment (PAHO, 2026); Fichas y Protocolos (Instituto Nacional de Salud (INS), Colombia, 2026).

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Representative model, for educational purposes only.