Updated: 4/13/2020

Vibrio cholerae

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Snapshot
  • A 40-year-old man presents to a local emergency room. He is currently on a medical mission in India. He reports sudden-onset nausea, vomiting, and copious amounts of watery diarrhea. His blood pressure is 93/65 mmHg and pulse is 114/min. On physical exam, he has sunken eyes, decreased skin turgor, and dry mucous membranes. He is given intravenous rehydration with the goal of rapid rehydration.
Introduction
  • Classification
    • Vibrio cholerae
      • a comma-shaped, flagellated, and gram(-) rod 
      • oxidase + and produces cholera toxin
    • transmission
      • fecal-oral via water or uncooked food
  • Epidemiology
    • incidence
      • rare in the United States
    • demographics
      • endemic in developing countries
      • most severe in children
    • risk factors
      • raw seafood
      • contaminated water
      • travel
  • Pathogenesis
    • acid-labile enterotoxin activates Gs and overactivates adenylate cyclase, causing ↑ cAMP 
      • requires large inoculum or decreased acidity in the host’s stomach
      • causes ↑ chloride secretion, resulting in secretory diarrhea and water efflux
      • this results in loss of potassium and bicarbonate
  • Prevention
    • live-attenuated oral cholera vaccine
      • indication
        • adults traveling to endemic areas
        • > 10 days prior to travel
  • Prognosis
    • if untreated, mortality is > 50%
    • if treated, mortality is < 1%
Presentation
  • Symptoms
    • may be asymptomatic
    • acute onset
      • painless rice-water secretory diarrhea
      • nausea
      • vomiting
  • Physical exam
    • dehydration
      • sunken eyes
      • dry mucous membranes
      • decreased skin turgor
Studies
  • Labs
    • stool culture in alkaline media
      • definitive diagnosis but not always necessary
      • no white blood cells in stool
    • electrolyte abnormalities
      • hypokalemia
      • hyponatremia
      • metabolic acidosis
  • Making the diagnosis
    • most cases are clinically diagnosed
Differential
  • Norovirus diarrhea
    • distinguishing factors
      • often associated with cruise ships, child care centers, or other crowded condition
      • typically self-limited
      • no association with geographic endemic locations
  • Campylobacter jejuni-associated diarrhea
    • distinguishing factors
      • bloody diarrhea
      • comma-shaped, but does not grow in alkaline media
      • white blood cells in stool
Treatment
  • Management approach
    • management is centered around rapid rehydration
  • Conservative
    • oral rehydration
      • indication
        • all patients
    • intravenous hydration
      • indication
        • severe dehyration
  • Medical
    • antibiotics
      • indication
        • severe dehydration
      • drugs
        • doxycycline
        • tetracycline
        • ciprofloxacin
Complications
  • Rapid dehydration
  • Hypovolemic shock
  • Death
 

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(M1.MC.14.1) A stool sample was taken from a 19-year-old male who presented with profuse watery diarrhea. He recently returned from a trip to Central America. A microbiologist identified the causative agent as a gram-negative, oxidase-positive, comma-shaped bacteria that is able to grow well in a pH > 8. Which of the following is a mechanism of action of the toxin produced by this bacteria? Tested Concept

QID: 106331
1

Degradation of cell membranes by hydrolysis of the phosphilpids

0%

(0/32)

2

Overactivation of adenylate cyclase by activation of Gs subunit by ADP-ribosylation

81%

(26/32)

3

Overactivation of adenylate cyclase by inhibition of Gi subunit by ADP-ribosylation

12%

(4/32)

4

Inactivation of the 60S ribosomal subunit by cleaving an adenine from the 28S rRNA

0%

(0/32)

5

Overactivation of guanylate cyclase

6%

(2/32)

L 1 D

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