Vibrio

• Gram-Negative Bacteria (GIT Infections)


  • Vibrio cholera
  • Helicobacter pylori
  • Campylobacter jejuni
• Vibrio cholera


  • Comma-shaped, curved
  • Facultatively anaerobic
  • Catalase and oxidase positive
  • Motile by monotrichous flagella
  • Vibrios can grow within a broad temperature range (14–40°C)
  • Require sodium chloride (NaCl) for growth (halophilic)
• Vibrio cholera serogroups O1 and O139


  Cause epidemic and pandemic cholera in humans
• Selective agars for Vibrio cholera

  • Thiosulfate-citrate-bile salts-sucrose (TCBS) agar
  • Produces yellow colonies (sucrose fermented)

  
• Vibrio cholera growth characteristics

  • Grow at a very high pH (8.5–9.5)
  • Rapidly killed by acid
• Vibrio cholera pathogenesis


  1. Enterotoxin/Choleragen: A subunit (Action) attached to five B subunits (Binding)

  2. A subunit activates intracellular cAMP

  3. Results in active secretion of Na and Cl as well as the inhibition of Na and Cl reabsorption

  4. Electrolyte-rich diarrhea occurs with as much as 20–30 L/day, resulting in dehydration, shock, acidosis, and death
• Cholera causes death by dehydration
• Infectious dose of Vibrio cholera

  (102–104) depends on stomach acid condition
• Medication (eg, proton-pump inhibitors) or condition that decreases stomach acidity makes a person more susceptible to infection with V. cholerae
• Clinical findings of Vibrio cholera infection

  1. Incubation period of 12 hours to 3 days

  2. Sudden onset of nausea and vomiting, followed by profuse diarrhea with abdominal cramps

  3. Stools resemble "rice water" and contain mucus, epithelial cells, and large numbers of vibrios
• Mortality rate of Vibrio cholera without treatment

  Between 25% and 50%, can be as high as 70%
• Mortality rate of Vibrio cholera with fluid replacement

  1% or less
• Vibrio parahaemolyticus is a marine bacterium that causes gastroenteritis after ingestion of uncooked seafood (sushi)
• Vibrio parahaemolyticus is the leading cause of diarrhea in Japan
• Helicobacter pylori


  • Formerly called Campylobacter pylori
  • Most common cause of duodenal ulcers and chronic gastritis, cancer
  • Spiral, curved, or fusiform rod-shaped Gram-negative bacteria
  • Motile with lophotrichous flagella
  • Usually grows within 3–6 days when incubated at 37°C in a microaerophilic and humid atmosphere, incubation up to 14 days may be necessary
  • Grows on chocolate agar and blood agar
  • Oxidase, catalase and urease positive

  
• Helicobacter pylori pathogenesis


  1. Urease located on the bacterial cell surface

  2. Mucinase and phospholipase

  
• Campylobacter jejuni is a zoonotic disease found in domestic animals and poultry
• Clinical findings of Campylobacter jejuni infection

  1. Fever and headache, followed after half a day by abdominal cramps and a bloody, loose diarrhea

  2. Organism invades the lining of the small intestine and spreads systemically

  3. Secretes an LT toxin which destroys mucosal cells