Vibrio and Related Organisms

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Vibrio and Related Organisms
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General Characteristics

• The Vibrio family contains three clinically
  significant genera Vibrio, Aeromonas, and
  Pleisiomonas
• All are Gram-negative rods with some enteric-like
  properties
• Vibrio, Aeromonas, and Pleisiomonas are
  non-fastidious
• All three genera are glucose fermenters, as are
  the enterics
• Most species in the group are bile tollerant
  Mac, EMB, etc
• Some are intestinal pathogens
• But they are not enterics differences include
• Vibrio cells in fluid specimens or cultures
  sometimes appear to be curved. Vibrio means
  comma shaped
• Aeromonas, Pleisiomonas and all, but one species
  of Vibrio, are oxidase positive
• Vibrio species are halophilic or halotolerant but
  Aeromonas species or Pleisiomonas species are not
  

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Gram stain of Vibrio cholera
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General Characteristics

• Since cell and colony morphology is similar to
  the enterics and some of the non-fermenting
  Gram-negative rods (GNNF), the vibrio need to be
  preliminarily grouped using biochemical tests
• Vibrio infections are rare in the U.S.,
  especially in inland areas. Cholera is common in
  poor, highly populated areas of India, etc.
  Shellfish / seafood related Vibrio infection is
  more common near warm marine environments, such
  as the Gulf of Mexico.
• Vibrio has only been isolated once at LGH in the
  last 20 years. This patient had eaten raw gulf
  oysters on vacation.
• Aeromonas, primarily associated with diarrhea, is
  the most commonly isolated bacteria of this group
  at LGH
• Pleisiomonas, an organism associated with fresh
  water, is more often isolated at LGH than Vibrio

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Differentiating the vibrio group from Other
Non-fastidious Gram Negative Rods
Flagellar Arrangement Peri or none Polar
Polar Polar Polar or none
O/F Glucose F F F F O or NC
Organism Enteric GNR Vibrio Aeromonas Pleisiomona
s GNNF
KIA KorA/A KorA/A KorA/A KorA/A K/K
Oxidase Neg Pos Pos Pos Pos or Neg
Flagellar arrangements Peri, peritrichous
Polar, one flagellum on the end of the cell
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Differentiation within the vibrio Group
Physiological Tests

Growth in 5 NaCl - -
Sensitive to 01291 Vibriostat
-
Growth in 1NB with no added NaCl
-

Organism Vibrio cholera Other Vibrio Aeromonas Pl
eisiomonas

Growth On TCBS2 -
-
1Nutrient Broth 2150ug Disk 2Thiocitrate
bilesalts sucrose agar
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Vibrio cholera

• Vibrio cholera is the cause of epidemic or
  Asiatic cholera in humans, a severe diarrheic
  disease that has been the scourge of humanity for
  centuries.
• There have been seven recorded pandemics of
  cholera, the first was in 1816 and the last one
  in 1989. The majority of the morbidity and
  mortality associated with these pandemics
  occurred in India, although S.E. Asia was
  involved as well.
• Strains of Vibrio are subdivided according to
  somatic O antigen
• The pandemic strains are designated 01 because
  they agglutinate with 01 somatic typing serum and
  and the non-epidemic strains are designated
  non-01because they do not

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Characteristics of V. cholera
Methods of Classification Serogroups Biotypes Se
rotypes Toxin
Epidemic Associated 01 Classical, El
Tor Inaba, Ogawa, Hikojima Produce cholera toxin
Not Epidemic-Associated Non-01 Biotypes
not applicable to non-01 strains Serotypes not
applicable to non-01 strains Usually do not
produce cholera toxin, may produce other
toxins
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Cholera

• Cholera is the prototype of a diarrheal disease
  syndrome
• It is not caused by tissue invasion but through
  the production of enterotoxins - they interrupt
  normal intestinal exchange of water and
  electrolytes
• Cholera is most often spread by fecally
  contaminated water, or food contaminated with
  such water
• Foods involved in cholera outbreaks include fish
  and seafood, milk, ice cream, and unpreserved
  meats
• In acute cases cholera manifests itself as severe
  gastroenteritis accompanied by vomiting and
  diarrhea with up to 20L/day
• Stool samples of cholera patients are often
  described as rice water because they are
  liquid and contain flecks of mucous

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Cholera

• The number of stools can be as many as 10 to 30 a
  day
• If untreated cholera can result in such a rapid
  loss of fluids and electrolytes that it leads to
  dehydration, hypovolemic shock, metabolic
  acidosis, and death in a matter of hours
• Most of the symptoms are the result of a powerful
  enterotoxin known as the cholera toxin or
  choleragen
• Choleragen binds to a receptor called
  GM1-ganglioside
• Once inside the cell it stimulates the production
  of adenylate cyclase which leads to the
  production of cyclic adenine monophosphate (cAMP)
  (and loss of the ability to make ATP)
• This causes hyperexcretion of electrolytes
  followed by osmotic water loss (out of the cell
  and into the intestinal lumen)

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Vibrio parahaemolyticus

• V. parahaemolyticus is the second most common
  Vibrio associated with gastroenteritis
• It is the leading cause of summer diarrhea in
  Japan, and has been isolated from nearly every
  costal state in the United States
• It is found in aquatic environments, and is
  primarily associated with food outbreaks
  involving filter feeding seafoods oysters,
  clams, crabs, lobsters, scallops, sardines,
  shrimp, etc.
• In most outbreaks the seafoods are consumed raw
  or cooked for too short a time to kill V.
  parahaemolyticus

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Vibrio vulnificus

• V. vulnificus is found in marine environments on
  the Atlantic, Gulf, and Pacific coast of North
  America
• Eventhough it IS associated with the consumption
  of shellfish (especially raw oysters), it is NOT
  a diarrheic pathogen like the other Vibrio
  species, but rather it causes wound infections
  and septicemia - septicemia is presumed to occur
  via a GI route
• Patients with liver dysfunctions that result in
  increased serum iron levels (e.g. cirrhosis) are
  particularly predisposed
• Within hours of consuming contaminated food
  septicemia can develop
• The mortality rate is 40 to 50
• Patients with wound infections usually have a
  history of trauma near coastal waters

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Aeromonas species

• Aeromonas species are ubiquitous in fresh water,
  esturine, and marine environments worldwide
• They are often isolated from retail produce
  sources and animal meat products
• They cause a diverse spectrum of diseases among
  warm and cold-blooded animals including fish,
  reptiles, amphibians, mammals, and humans
• Various Aeromonas species cause red-leg disease
  in frogs
• There are 10 currently recognized Aeromonas
  species 7 have been isolated from human clinical
  specimens
• Aeromonas hydrophilia is the most commonly
  isolated species. It is an uncommon cause of
  wound infections and septicemia in
  immunocompromised humans, especially those with
  histories of liver dysfunction and
  myeloproliferative disorders (those of marrow,
  stems cells, and their products).

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Aeromonas species

• Aeromonas species are strongly associated with
  gastroenteritis, but recent reports suggest that
  A. hydrophilia can cause profuse respiratory
  pathology in immune suppressed patients as well
• Pediatric patients are at a greater risk than the
  general population
• One clue that a stool culture may contain
  Aeromonas species is that many are beta hemolytic
  on SBA
• Commercial kits used to identify enterics may or
  may not identify Aeromonas species
• An oxidase positive fermenter that does not key
  out properly on an enteric kit should be
  identified using additional tests that are
  usually available only at reference labs

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Pleisiomonas shigelloides

• P. shigelloides is the only species in this genus
• It is usually found in freshwater environments
• Like Aeromonas, Pleisiomonas is widely
  distributed among warm and cold blooded animals
  including dogs, cats, pigs, vultures, reptiles
  and shellfish
• Human infections are mostly intestinal (vomiting,
  diarrhea, etc)
• Individuals engaged in outdoor activities are at
  greatest risk of coming in contact with the
  organism, and therefore of infection
• Most commercial enteric identification kits
  include P. shigelloides in their data base and
  can identify this organism with a high degree of
  accuracy
• Since P. shigelloides is oxidase positive, it is
  confusing that some contributors to the 2004
  edition of the Manual of Clinical Microbiology
  have proposed to move P. shigelloides to the
  Enterobacteriaceae

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Lab Diagnosis

• As already mentioned, the Vibrio group are not
  fastidious
• They require no special collection and processing
  requirements except using Cary-Blair transport
  media for stool samples
• Peptone water, buffered to pH 8.5 and
  supplemented with 1 NaCl, works well as an
  enrichment medium for V. cholera
• Most isolates of Vibrio, Aeromonas, and
  Pleisiomonas grow well on MacConkey they are
  bile tollerant
• They are non-lactose fermenters with the
  exception of V..vulnificus which is lactose
  positive
• If a selective medium is warranted (i.e. locales
  near coastal waters) thiosulfate citrate bile
  salts sucrose (TCBS) works well
• Presumptive identification can be made using a
  few preliminary tests

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Differentiating the Vibrio Group
TESTS

Growth in 5 NaCl - -
Sensitive to 01291 Vibriostat
-
Growth in NB with no added NaCl
-

Organism Vibrio cholera Other Vibrio Aeromonas Pl
eisiomonas

Growth On TCBS2 -
-
1150ug Disk 2Thiocitrate bilesalts sucrose agar
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Lab Diagnosis

• The lab approach to the isolation of the vibrio
  group from GI (mainly fecal) specimens can follow
  one of several approaches
• Use normal procedures and make no specific effort
  to search for them since most are non-lactose
  fermenters and could be suspected in the process
  of ruling out Salmonella and Shigella
• Use normal procedures and search for oxidase
  positive colonies on SBA (this is LGHs approach)
• Incorporate TCBS in the battery of media
• Use alkaline peptone water as an enrichment
  (sub-cultured to TCBS)
• Use DNA probe, PCR, etc.

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Lab Diagnosis

• Definitive identification can usually be done
  with the same commercial products that identify
  enteric Gram negative rods (but do not forget the
  oxidase test it helps arrive at the code number
  and a positive result will differentiate the
  vibrios from the enterics)
• Recall that most commercial products may not
  satisfactorily identify Aeromonas species