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Vibrio and Related Organisms

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Title: Vibrio and Related Organisms


1
Vibrio and Related Organisms
2
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

3
Gram stain of Vibrio cholera
4
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

5
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
6
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
7
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

8
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
9
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

10
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)

11
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

12
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

13
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).

14
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

15
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

16
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

17
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
18
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.

19
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
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