Vibrio

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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
  • gastroenteritis
  • cholera – a devastating diarrheal disease
  • wound – simple to necrotizing fasciitis 
  • septicemia 
• 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