Listeria

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Listeria

• Presented by Hoang Thanh Van
• ID No. 452-5385

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Listeria

• Gram positive
• Non-sporeforming
• Non-acid fast rods
• Grow well in many common media such as trypticase
  soy tryptose broths
• Grow best in pH range 6-8

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Species of Listeria

• L.monocytogenes
• L.innocua
• L.seeligeri
• L.welshimeri
• L.ivanovii
• L.grayi
• L.murrayi

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Listeria monocytogenes

• Gram positive, short, non-sporing rods
• Catalase positive and facultatively anaerobic
• Motile at 25oC but non-motile at 35oC
• Colonies have bluish grey appearance

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• Grow in simple media
• Heat resistance among vegetative Gram positive
  bacteria
• Exhibits resistance to gamma irradiation
• Large pH range from pH 4.6 to pH 9.2
• Grow well at 37oC but also able to grow at
• Frozen conditions 18oC in various food
  substrates
• 0oC in sterile foods having neutral pH
• 4oC in ground beef

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L. monocytogenes has the ability to multiply at
low temperatures. The bacteria may therefore grow
and accumulate in contaminated food stored in the
refrigerator. So listeriosis is usually
associated with ingestion of milk, meat or
vegetable products that have been held at
refrigeration temperatures for a long period of
time.
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Intracellular cell
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Listeria attaches to a cell and there's a
microbial gene product called internalin that
aids in that process.
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Listeria is enclosed within a vacuole, a
phagocytic vacuole initially A very important
virulence factor, Listeriolysin-O or LLO, causes
the lysis of this membrane
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Listeria divides in the cytoplasm and begins to
polymerize host cell actin. A gene product called
Act-A is involved in this process
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A comet-like tail forms that propels the Listeria
through the cell and into the adjacent cell
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The double-walled membrane is disrupted by both
listeriolysin-O and phospholipases that are
elaborated by the bacteria.
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The cycle is then repeated.Listeria can get into
a cell, then into the cytoplasm, then into
another cell without ever being in contact with
the external environment. 
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Sources of Listeris monocytogenes

• Listeria monocytogenes is ubiquitous in the
  environment.1
• animals, birds, insects, soil and wastewater, and
  vegetation.
• In raw milk, supposedly pasteurized fluid milk,
  cheeses (particularly soft-ripened varieties),
  ice cream, raw vegetables, fermented raw-meat
  sausages, raw and cooked poultry, raw meats (all
  types), and raw and smoked fish.

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Listeriosis

• Symptoms fever, muscle aches, sometimes
  gastrintestinal symptoms such as nausea or
  diarrhea
• If it spreads to the nervous systems, symptoms
  headache, stiff neck, confusion, loss of balance
  or convulsions

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The main target populations for listeriosis are

• pregnant women/fetus
• persons immunocompromised by corticosteroids,
  anticancer drugs, graft suppression therapy, AIDS
• cancer patients
• the elderly
• normal people who used the foodstuff was heavily
  contaminated with the organism.

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Outbreaks

• Germany (1953) Pregnant woman who drank raw milk
  from cow with mastitis gave premature birth to
  stillborn twins.
• Sweden (1959) 4 cases3 infants, 1 adults, 1
  infant deaths.
• New Zealand (1980) 22 cases who ate shellfish and
  raw milk
• Los Angeles (1985) 142 cases who used
  Mexican-style cheese contaminated with raw milk.
• Philadelphia (1986-1987) 36 cases ice cream,
  salami or vegetables suspected.

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Consumers

• Avoid eating raw or improperly cooked foods of
  animal origin
• Avoid cross contamination between raw and cooked
  foods
• Raw vegetables should be thoroughly washed before
  eating
• Foods should be used before best before code on
  the package
• Maintain the clean refrigerator