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Vibrio

Vibrio_cholerae_01

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General Characteristics :

  • primarily found in aquatic environments
  • pandemics of cholera caused by Vibrio cholerae have occurred since 1817
  • occur primarily in Southeast Asia, India, the Middle East, and Africa, but also found in the Mediterranean and occasionally the U.S. Gulf Coast
  • infections are associated with consumption of seafood or contact with coastal waters
  • can be isolated from a variety of clinical specimens
  • spectrum of clinical infections
  • four species most often seen in labs :
    • V. cholerae (serogroup 01 & non-o1)
    • V. parahaemolyticus
    • V. vulnificus
    • V. alginolyticus
  • infrequently isolated – good medical hx of :
    • recent ingestion of raw seafood
    • recent foreign travel
    • gastroenteritis with rice-water stools
    • accidental trauma during contact with fresh marine water, or products

Cell Morphology :

  • gram negative rods
  • polar, sheathed flagella with grown in broth, but have peritichous, unsheathed flagella when grown on solid media
  • “curved” gram negative rods – usually only seen on the initial gram stain of the specimen
  • facultatively anaerobic
  • oxidase positive
  • most species are halophilic

Vibrio cholerae :

  • causative agent of cholera or epidemic cholera
  • major public health issue in developing countries
  • mainly spread through contaminated water
  • portal of entry : mouth
  • incubation period : 8 to 48 hours
  • organisms reside in small intestine and produce cholera toxin
  • symptoms :
    • vomiting
    • severe, explosive, watery diarrhea
    • dehydration and electrolyte loss
    • “rice watery stools”
    • 10-30 per days

Other Vibrio Infections :

  • causative agents : Halophilic vibrios
  • V. parahaemolyticus
    • diarrheal illness less severe than cholera
    • occurs approximately 24 to 48 hours after ingestion of contaminated seafood – particularly oysters
  • V. vulnificus
    • causes primary septicemia and wound infections
    • predisposing risk factors include liver dysfunction and conditions that produce high serum levels of iron
    • some type of traumatic injury involving water
  • V. alginolyticus
    • common inhabitant of marine waters – least likely to be isolated in lab
    • involved in eye,ear, and woundd infections associated with contact with sea water

Media Selection :

  • culture media should include noninhibitory media and selective media such as thiosulfate citrate bile salts (TCBS) sucrose agar
  • enrichment media (alkaline peptone broth with 1% NaCl) may be added
  • positive oxidase test differentiates these organisms from the Enterobacteriaceae
  • all Vibrio species are susceptible to vibrostatic compound 0/129
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