E. coli O157:H7 is a pathogenic strain of Shiga toxin-producing E. coli (STEC) that causes foodborne illness. It was implicated in a large 1993 outbreak linked to undercooked hamburgers from Jack in the Box restaurants that infected over 700 people and killed 4 children. Major sources of infection include undercooked ground beef and contaminated produce. Symptoms range from mild diarrhea to severe complications like hemorrhagic colitis and hemolytic uremic syndrome. Controls and prevention strategies target pre-harvest cattle management, slaughter and processing interventions, thorough cooking of meat, and proper hygiene.

1. E.coli O157:H7
Marie Schneiders| VM 811 | Michigan State University

2. E. Coli O157:H7 - part of a subset of gram negative STEC (Shiga Toxin Escherichia coli) bacteria called EHEC
Characteristics
• EHEC: Enterohemorrhagic
E. coli
• Characterized by production of
Stx 1 and/or 2 and presence of
LEE
• Facultative Anaerobe

3. Jack in the Box Incident of 1993
• Implicated in a McDonald’s out break in 1982 - at this time the organism was
considered rare
• 1993: 732 people infected after eating hamburgers at 73 Jack in the Box
restaurants in California, Idaho, Washington, and Nevada
• The majority of victims were children under the age of 10
• 4 children died
• 178 other victims were left permanently damaged

4.  The largest outbreak in
the world took place in
Japan in 1996
 The cause of the
outbreak was white
radish sprouts
 6,309 school children
and 92 school staff
members became ill
 By August 9,578 cases
were reported and 11
people died

5. Sources of E. coli O157:H7
Raw and undercooked ground beef (most commonly implicated)
Water (potable, well, and recreational)
Bagged lettuce, spinach, and alfalfa sprouts
Yogurt, mayonnaise, fermented sausages, cheese, unpasteurized fruit juices
Frozen cookie dough

6. Virulence Factors
Shiga Toxin
• Stx 1 nearly identical to that
produced by Shigella
dysenteriae Type I
• Stx 2 most often associated
with HUS (hemolytic uremic
syndrome) – characterized by
renal failure
Presence of
LEE
• “Locus for enterocyte
effacement”
• Encodes for intimin – a
protein that enables bacterial
attachment to epithelial cells
Other
• Horizontal gene transfer
• Several other putative
virulence factors, including
enterohemolysin
• role of these factors in
pathogenesis remains
undetermined

7.  Intimin receptor (Tir)
translocates into the
host cell and inserts
itself into the host-
cell plasma
membrane
 Receptor interacts
with intimin on the
bacterial surface
firmly anchoring the
bacterium to the
host cell

8. Human Exposure to E.coli O157:H7
• FSIS (Food Safety & Inspection
Service) estimates that 99.993% and
99.982% of cooked ground beef in
low and high prevalence seasons
respectively are not expected to have
surviving E. coli O157:H7 organisms
present
• FSIS estimates that in grinder loads
consisting of 2,000 lbs. raw trim
(combo) between 40% and 88% of
these loads contained one or more E.
coli O157:H7 in the low prevalence
season and 61% to 94% in the high
prevalence season

9. Frequency
• ~63,000 cases of EHEC infections in
the U.S. yearly according to the CDC
• Ground beef continues to be
implicated in most infections
• Contaminated produce is on the rise
as a cause of infection

10. Infectious dose, clinical signs, and symptoms.
Estimated to
be 10-100
cells
Infectious Dose
Symptoms
typically
appear in 3-4
day, but can
range 1-9
days
Incubation Period
asymptomatic,
to mild
diarrhea, to
severe
complications
Mild Symptoms
Hemorrhagic
colitis
Hemolytic
Uremic
Syndrome
Acute Symptoms

11. Hemorrhagic colitis and HUS
o Hemorrhagic Colitis
o Severe abdominal cramps, nausea, vomiting, diarrhea that is initially watery
o Diarrhea becomes bloody and may look like it consists entirely of blood and occurs every 15-30
minutes
o 3% - 7% of HC cases progress to HUS
o Duration of symptoms is 2-9 days with an average of 8
o HUS is the premature destruction of red blood cells which impede the filtering function of kidneys
o May cause kidney failure, but if properly treated in a healthy individual a full recovery may be
expected

12. Detection and Diagnosis
• In raw, ground beef:
• Real-time PCR with Immuno-
magnetic separation
• ELISA, VIP, chromogenic agars
• In symptomatic patients:
• Plate bloody stool sample on to
Phenol Red Sorbitol agar – O157
does not ferment sorbitol
• Serologically confirm isolates from
agar using O157 and H7 antigens

13. Host Defense
• Mucins, AMPs, and members of the intestinal microbiota
• Mucins create a dynamic physical barrier
• Anti-microbial peptites are effectors of the innate immune response
• Resident microbiota provide a microbial barrier against pathogens
• Bacteria that originated from the intestinal microbiota have the capacity for
interfering with or block the process of pathogenicity of enteric bacterial pathogens

14. Control: In-Vivo
• Competetive Exlclsuion
• No field trials yet
• Beta-agonists (Ractopamine)
• Illegal to use almost everywhere but in
the U.S. & questionable results
• Fasting
• Pre and Post Transportation
• Sudden feed switch to hay
• Results in lower slaughter weight
• Direct Fed Microbials (DFM)
• Probiotics

15. Control: Pre-harvest
• Clean water
• Clean feed
• Clean environment
• Separate housing of calves and
heifers or reduced animal
density
• Biosecurity – wildlife exclusion
to the fullest extent possible
• Bacteriophage sprayed on hide
of live cattle in holding pens

16. Control: Slaughter
• Sanitary Dress
• Sanitary Hide Removal
• Bunging
• Rodding the Weasand
• HACCP Program
• Interventions
• Steam cabinets
• Anti-microbial carcass wash

17. Control : Processing & Sampling
• N60 trim sampling - 60 slices per lot
• 1 Lot = 5 combos
• New single-combo “Shaver” sampling
• N60+
• 1 combo = 1 lot
• Mechanical coring of 5 sites in a single
combo using a drill and specialized drill
head
• Each combo tested at the lab using
RT-PCR
• Positive combos removed from food
supply - sold to cook or rendered.

18. Control: Consumer End
• Practice proper hygiene
• Cook meats thoroughly
• Prevent cross-
contamination
• Avoid consuming raw
or unpasteurized dairy
products or juices

19. References
• http://en.wikipedia.org/wiki/1993_Jack_in_the_Box_E._coli_outbreak
• http://www.mayoclinic.org/diseases-conditions/hemolytic-uremic-syndrome/basics/definition/con-20029487
• http://www.nature.com/nature/journal/v449/n7164/fig_tab/nature06247_F2.html
• http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1471992/
• http://www.fsis.usda.gov/OPPDE/rdad/FRPubs/00-023N/00-023NReport.pdf
• http://www.fsis.usda.gov/wps/wcm/connect/d5314cc7-1ef7-4586-bca2-f2ed86d9532f/Reducing-Ecoli-Shedding-
in-Cattle.pdf?MOD=AJPERES
• http://www.fsis.usda.gov/OPPDE/rdad/FSISDirectives/6410.1.pdf
• http://www.ncbi.nlm.nih.gov/pubmed/24751204
• http://www.cdc.gov/Features/EcoliInfection/