Salmonella

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					E. coli O157:H7

Kang, Dong-Hyun
Associate Professor
Department of Food Science and Human Nutrition
Washington State University
Foodborne illness processes


 Infection
 Intoxication
 Toxicoinfection
Infections

   A disease state caused by the presence
    of viable, usually multiplying organisms
    at the site of inflammation
Intoxication

   A disease state caused by exposure to
    a toxic chemical
Toxicoinfection

   A disease state that is caused by
    exposure to a toxic chemical produced
    by the presence of viable, usually
    multiplying organisms at the site of
    inflammation
    Major Foodborne Pathogens
   E. coli O157:H7
   Listeria monocytogenes
   Salmonella
   Campylobacter
   Shigella
   Vibrio
   Yersina
   Staphylococcus
   Clostridium botulinum perfringens
   Bacillus cereus
   E. coli




    Major Foodborne
Pathogens in E. coli Group
Taxonomy
 Biochemical tests
   Production of indole (indole positive)
   Use of citrate (citrate positive)

 Serological tests
   Pathogenic strains is partially based on serology
  with 173 O (somatic), 56 H (flagella), and 80 K
  (capsular) antigen
   E. coli



    Major Foodborne
Pathogens in E. coli Group
             ETEC
             EPEC
             EHEC   E. coli O157:H7

             EAEC
             EIEC
Serotypes of pathogenic E.coli
 Table 1. Serotypes characteristic of the pathogenic E. coli categories




                                                aO   antigen untypeable by conventional methods.
Enterohemorrhagic E. coli
    E. coli O157:H7


Escherichia coli O157:H7

   Major Outbreaks

    2007
    E. coli O157:H7 in ground beef from the
    Topps Meat Company in Elizabeth, New
    Jersey. As of 2007, it is the second-largest
    beef recall in United States history
    E. coli O157:H7


Escherichia coli O157:H7

   Major Outbreaks

    2006
    E. coli O157:H7 from Taco Bell in South
    Plainfield, New Jersey and Long Island.
    They suffered from hemolytic uremic
    syndrome - 39 people in central New Jersey
    and on Long Island were sickened
    E. coli O157:H7


Escherichia coli O157:H7

   Major Outbreaks

    2006
    E. coli O157:H7 in bagged spinach
    packaged by Natural Selection Foods and
    most likely supplied by Earthbound Farm in
    San Juan Bautista. 3 dead, and 198 people
    reported sickened by the outbreak across 25
    US States
    E. coli O157:H7


Escherichia coli O157:H7
   Major Outbreaks

    2002
    E. coli O157:H7 in ground beef from ConAgra. 19
    people became ill in California, Colorado,
    Michigan, South Dakota, Washington and
    Wyoming as a result of eating tainted hamburger.
    The company recalled over 19 million pounds of
    ground beef it had manufactured, in the third
    largest recall in history
    E. coli O157:H7


Escherichia coli O157:H7

   Major Outbreaks

    1997
    E. coli O157:H7 in ground beef from
    Hudson Foods Company of Rogers,
    Arkansas.
    The company recalled over 25 million
    pounds of ground beef it had manufactured,
    in the second largest recall in history.
    E. coli O157:H7


Escherichia coli O157:H7

   Major Outbreaks

    1996
    E. coli O157:H7 in unpasteurized apple
    juice from Odwalla
    E. coli O157:H7


Escherichia coli O157:H7

   Major Outbreaks

    1993
    E. coli O157:H7 in undercooked
    hamburgers from Jack in the Box. Four
    people died and hundreds of others became
    sick in the Seattle area and other parts of the
    Pacific Northwest.
E. coli O157:H7
    E. coli O157:H7


Escherichia coli O157:H7

 Gram negative bacillus, generally motile
  Non-sporeforming bacteria
 73,480 cases/year – 500 deaths
 Relatively high toxicity as <10-100 bacteria
  can cause illness
 E. coli O157:H7




 Temperature:   rapid growth between
  30°C and 42°C, poor to no growth
  at >44°C
 survive well during freezing
 pH: optimum near neutrality, but
  tolerant of a number of conditions,will
  grow well down to 4.5
    E. coli O157:H7


Mode of Infection
 Once ingested, the organisms make
  their way to the large intestine, where
  they cause inflammation.
 Adhere to intestinal epithelium
 Adhering bacteria destroy the villi of the
  intestinal epithelial cells
 create a lesion – severe diarrhea
    E. coli O157:H7


Mode of Infection
   When the lesion becomes deep enough,
   Break the lamina propria – affect the
    underlying blood vessels – Hemorrhage and
    bloody stools

   Outpouring of a toxin into the blood
    circulation – leading to damage of small blood
    vessels in the kidneys, brain, other organs
   E. coli O157:H7


 Mode of Infection (Toxin)
The Shiga-like toxins - general class of AB toxins. -

The B component binds to molecules on the surface
of target cells.

The toxins are then taken up into the target cells by
endocytosis, at which point the A component enters
the cytoplasm and carries out some toxic enzymatic
reaction inside the cell.

Structural division between the cell-surface
recognition function (B subunit) and toxic enzymatic
action.
 E. coli O157:H7


Mode of Infection (Toxin)

The A component attacks the 28 S
ribosomal RNA, deaminates a single
adenine at position 4342. by clipping a
particular nucleotide from one of the
ribosomal RNAs. This blocks protein
synthesis and leads to the death of the
cell.
Pathogenesis

               Three-stage model of EPEC
               pathogenesis. (A) The first
               stage is characterized by initial,
               relatively distant interaction of
               bacteria with the enterocyte
               layer. This initial attachment is
               thought to be mediated by the
               bundle-forming pilus. (B) In
               the second stage, eae and other
               genes are activated, causing
               dissolution of the normal
               microvillar structure. (C) In the
               third stage, the bacterium binds
               closely to the epithelial
               membrane via the protein
               intimin. Other bacterial gene
               products mediate further
               disruption of the cytoskeleton
               and phosphorylation of cellular
               proteins.
Pathogenesis
   Virulence factors (BFP)




                   BFP
Pathogenesis
   Pedestal-like structure
EHEC
                   A toxin
Shiga Like Toxin                  Glycolipid
                   B toxin



                        28 S ribosomal RNA
    E. coli O157:H7


Illness
   Onset: 3 - 9 days, average 4 days
   Duration: 2 - 9 days
   Symptoms: abdominal cramps, watery diarrhea,
    grossly bloody diarrhea described as "all blood
    and no stool", abdominal pain described as equal
    in intensity to labor pains
   Hemolytic Uremic Syndrome (HUS)
   Thrombotic Thrombocytopenic Purpura (TPP)
Questions ?

				
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