Vibrio

• Oxidase-Positive


  Positive for oxidase test
• Fermentative


  Able to ferment glucose
• Bacilli


  Rod-shaped bacteria
• Organisms


  • Vibrio
  • Aeromonas
  • Plesiomonas
  • Chromobacterium
  • Similar Organisms

  
• CHAPTER 19 VIBRIONACEAE
• Aquatic environments where Vibrionaceae are found

  • Fresh water
  • Brackish or estuarine water
  • Marine or salt water
• Vibrionaceae


  • Temperature-sensitive – above 20°C vibrios can easily be isolated from: water, suspended particulate matter, algae, plankton, fish, shellfish
  • Numbers decline markedly in the winter months and generally found only in the sediments
  • Risk of infection from all Vibrio spp. can be reduced by the avoidance of eating raw or undercooked shellfish, particularly in warmer summer months

  
• Organisms discussed in this chapter are: Oxidase positive, Glucose fermenting, Grow on MacConkey agar
• Other halophilic organisms, such as Halomonas venusia and Shewanella algae, require salt but do not ferment glucose, as do the halophilic Vibrio spp.
• V. cholerae and V. mimicus are the only Vibrio spp. that do not require salt for growth

  
• Best indication of a possible Vibrio infection

  • Recent consumption of raw seafood (especially oysters)
  • Recent immigration or foreign travel
  • Gastroenteritis with cholera-like or rice-water stools
  • Accidental trauma incurred during contact with fresh, estuarine, or marine water or associated products (e.g., shellfish, oyster or clam shells, fishhooks)

  
• Vibrio spp.


  • Asporogenous
  • Typically curved gram-negative rods in the initial Gram stain of the clinical specimen
  • Most are motile with a polar flagella

  
• Physiology of clinically significant Vibrio spp.

  • Oxidase-positive (except for Vibrio metschinikovii)
  • Catalase-positive
  • Reduce nitrate to nitrite
• Most vibrio exhibit a positive string test observed as a mucoid "stringing" reaction after emulsification of colonies in 0.5% sodium desoxycholate
• All Vibrio species are halophilic, or salt-loving, and require the addition of Na+ for growth except for V. cholerae and V. mimicus

  
• Three major subgroups of Vibrio cholerae

  • Vibrio cholerae O1
  • Vibrio cholerae O139
  • Vibrio cholerae non-O1

  
• Serotypes of Vibrio cholerae O1

  • Ogawa or variant F
  • Inaba or original J
  • Hikojima or middle or intermediate

  
• Biotypes of Vibrio cholerae O1

  • Biotype cholerae
  • Biotype el tor

  
• Vibrio cholerae O139


  Phenotypically resembles Vibrio cholerae, does not agglutinate in O1 antisera, generally associated with large outbreaks, can cause extraintestinal infections such as cholecystitis, cellulitis, ear infections, and septicemia

  
• Vibrio cholerae O1 causes epidemic cholera or epidemic Asiatic cholera

  
• Vibrio cholerae


  • Small, facultative, gram-negative rods that are slightly curved or comma-shaped
  • Characteristic darting motility by monotrichous flagellum
  • Cell body assumes C or S shape
  • Tolerate 3% NaCl only

  
• Culture media for Vibrio cholerae

  • Cary and Blair transport media (pH 9-10)
  • 5% SBA
  • Alkaline peptone water (enrichment medium)
  • Nutrient agar bile salt sucrose (NABS)
  • Dieudonne's medium
  • Thiosulfate citrate bile salt sucrose (TCBS) agar
  • Tellurite Taurocholate Gelatin Agar (TTGA)

  
• Biochemical tests for Vibrio cholerae

  • Immobilization test
  • Hemagglutination test
  • Cholera red test (nitrous oxide reaction)
  • Pfeiffer's phenomenon (bacteriolysis test)
  • Hemolysis test (Grieg's test)
  • Polymyxin B test
  • String test

  
• Treatment and management of cholera

  • Best accomplished by the administration of copious amounts of intravenous or oral fluids to replace fluids lost from the severe diarrhea
  • The administration of antimicrobial agents can shorten the duration of diarrhea and thereby reduce fluid losses
  • Resistance to tetracycline and doxycycline has been reported, therefore administration of additional antimicrobials such as azithromycin and ciprofloxacin may be necessary

  
• Vibrio parahaemolyticus

  • Second most common Vibrio species implicated in gastroenteritis
  • A pandemic strain of V. parahaemolyticus serotype O3:K6 emerged and has since been implicated in numerous foodborne outbreaks
  • Halophilic, or salt-loving – requiring 1% to 8% NaCl

  
• Modes of transmission for Vibrio parahaemolyticus

  • Ingestion of raw or improperly handled seafood
  • Wounds or tissues contaminated with seawater

  
• Vibrio parahaemolyticus

  • Specimens: feces and rectal swabs
  • Stained smears
  • Culture (similar to Vibrio cholerae)
  • Kanagawa phenomenon - pathogenic strains produce β hemolysis on human erythrocytes on a special high salt medium (Wagatsuma Blood Agar) distinguishing them from the non-pathogenic strains

  
• Vibrio vulnificus

  • Found in marine environments on the Atlantic, Gulf, and Pacific coasts of North America
  • Causes the second most serious types of Vibrio-associated infections next to cholera
  • Identified by green colonies on TCBS (non-sucrose fermenter but is a lactose fermenter)

  
• Vibrio alginolyticus

  • Least pathogenic for humans and is the one most infrequently isolated
  • Common inhabitant of marine environments
  • Strict halophile – requiring at least 1% NaCl, tolerate up to 10% NaCl
  • Almost all isolates originate from extraintestinal sources, such as eye and ear infections or wound and burn infections
  • Can be an occupational hazard for people in constant contact with seawater, such as fishermen or sailors

  
• Vibrionaceae laboratory diagnosis

  • Not fastidious
  • Only a few special collection and processing procedures are necessary to ensure the recovery of vibrios from clinical material such as body fluids, pus, tissues, and swabs (if transported in an appropriate holding medium like Cary-Blair to prevent desiccation)
  • Buffered glycerol saline is not recommended as a transport or holding medium because glycerol is toxic for vibrios
  • Strips of blotting paper soaked in liquid stool and placed in airtight plastic bags are considered viable specimens for up to 5 weeks
  • Stool specimens should be collected as early as possible in the course of the illness and preferably before the administration of antimicrobial agents

  
• Culture media for Vibrionaceae

  • Nutrient agar or sheep blood agar (SBA)
  • On SBA or chocolate (CHOC) agar - produce medium to large colonies that appear smooth, opaque, and iridescent with a greenish hue
  • On MacConkey agar - the pathogenic vibrios usually grow as non-lactose fermenters
  • Vibrio vulnificus - lactose fermenter

  
• It is imperative to determine the oxidase activity of any suspicious Vibrio-like colony, as lactose-positive colonies from selective differential media can give false-positive oxidase reactions

  
• Growth on TCBS (Thiosulfate Citrate Bile salt Sucrose) agar

  • Sucrose fermenters - yellow colonies: V. cholerae, V. alginolyticus, V. fluvialis, V. furnissii, V. cincinnatiensis, V. metschnikovii, some V. vulnificus
  • On prolonged incubation TCBS colonies turn green (non-fermenters) especially if the organism is the el tor biotype: Vibrio mimicus, Vibrio parahaemolyticus, Plesiomonas damsela, most Vibrio vulnificus strains

  
• Other culture media for Vibrionaceae

  • Alkaline peptone water (1% NaCl, pH 8.5) - enrichment medium
  • CHROMagar Vibrio - isolation and identification of Vibrio cholerae, Vibrio parahemolyticus, Vibrio vulnificus

  
• Susceptibility to the vibriostatic agent O/129 (150 µg) and positive string test distinguishes Vibrionaceae from Aeromonas

  
• Inability to ferment inositol (except for V. cincinnatiensis and some strains of V. metschnikovii) separates Vibrionaceae from Plesiomonas

  
• Presumptive identification of Vibrionaceae

  • Positive oxidase reaction (except for V. metschnikovii) - separates them from the Enterobacteriaceae (excluding Plesiomonas shigelloides)
  • Carbohydrate fermentation metabolism - separates them from the oxidative Pseudomonas

  
• With the halophilic vibrios, add at least 1% NaCl to most biochemical media to obtain reliable reaction results
• Antimicrobial susceptibility of Vibrio cholerae

  • Ampicillin
  • Chloramphenicol
  • Tetracyclines
  • Trimethoprim
  • Doxycycline
  • Ciprofloxacin

  
• Previously, the genus Aeromonas resided in the family Vibrionaceae, but phylogenetic evidence from molecular studies has resulted in the proposal of a separate family, Aeromonadaceae