Introduction to Non-O157
STECs
James Marsden
Distinguished Professor
Food Safety and Security
Kansas State University
SteakExpert 2012
What we know about STECs
Emerging STECs (Shiga Toxin Producing
strains of E. coli)
 Six strains of STECs have been
associated with ¾ of the food safety
illnesses in the United States (O26, O45,
0103, O111, O121, and O145 -- termed
the “Big Six).
What we know about STECs
Illnesses associated with STECs are
identical to E. coli O157:H7
 Symptoms include diarrhea, bloody
diarrhea, HUS and death
 Increased reports of illnesses may be due
to a higher prevalence of possibly
improved surveillance
 FoodNet reported 575 STECs between
2000 – 2006 (209 in 2006)

What we don’t know about
STECs
No one really knows how prevalent these
STECs are in nature or in the food supply
 FSIS estimates that the incidence in dairy
cattle may be between 0-19% and the
incidence in beef cattle feces and hides
may be 19.4 – 56.3%; Pre-evisceration
beef carcasses – >50%; Retail Ground
Beef – 2-3%

What we don’t know about
STECs
 The beef industry has been successful in



reducing the incidence of E. coli O157:H7
We don’t know for certain whether the same
interventions that are effective on E. coli
O157:H7 will also inactivate STEC strains.
We don’t know enough about thermal
resistance, acid resistance, effect of Aw and
HPP
We don’t know to what extent STECs are
associated with beef
What we need to know about
STECs




The ideal approach to the challenges posed by STECs
would first involve a national baseline study and risk
assessment
Secondly, research is needed to identify and validate
effective interventions.
Thee beef industry has been focused on interventions for
E. coli O157:H7 since the 1993 Jack-in-the-Box outbreak
It’s possible that the food safety systems already in place
for control of E. coli O157:H7 are effectively controlling
nSTECs as well. However, that needs to be proven.
What we need to know about
STECs
We need to better understand the biology
of STECs
 We need to determine the thermal
resistance, acid resistance, effect of Aw
and HPP
 We need to identify modes of
contamination and whether they are
similar to E. coli O157:H7

Pathogenicity
Not all E. coli strains are pathogenic.
 To be pathogenic, a strain must have the
necessary properties to cause disease in
human.
 These properties are called “virulence
factors.”
 Exactly what virulence factors are required
is unknown.

Pathogenicity
•
E. coli can cause human disease when they
possess stx1 or stx2.
•
Individuals infected with strains producing stx2
are more likely to develop severe disease than
those infected with strains carrying Shiga toxin 1.
•
It is commonly thought that E. coli must contain
stx1 or stx2 and eae (intimin) and its substitutes to
have the highest chance of causing disease in
humans – of course there are always exceptions.
CDC Reports on STECs

According to the US Centers for
Disease Control and Prevention, nonO157 E. coli STECs (like O26, O45,
0103, O111, O121, and O145) cause
36,700 illnesses, 1,100 hospitalizations
and 30 deaths in America each year
Top Non-O157 Serotypes
(CDC)






O26
22% of non-O157 STEC
O111
16% of non-O157 STEC
O103
12% of non-O157 STEC
O121 9% of non-O157 STEC
O45
7% of non-O157 STEC
O145
5% of non-O157 STEC
Annual Submission of Non-O157 to
PulseNet
CDC
E. coli O157 vs. Non-O157 E. coli
Persons with non-O157 STEC USUALLY
have less severe illness
 Non-O157 STEC include many
serogroups, with varying virulence

some typically cause only mild diarrhea
 others can cause HUS and death


Non-O157 isolates predominantly have
shiga toxin 1
Food commodities implicated
outbreaks of non-O157 STEC
infections with known food commodity,
1990-2007
Commodity
Fruit-nuts
Number outbreaks
3
Dairy
2
Leafy vegetables
1
No outbreaks due to beef
Food items
Juice, apple
cider, berries
Cheese,
margarine
Lettuce
But it all changed in 2010 with
the recall of ground beef
because of human illness
associated with O26
contamination
Testing for STEC

E. coli O157
 Unusual
feature: does not ferment
sorbitol

Non-O157 STEC
 Lack
unusual features
 A group of organisms
USDA Approach
Top 6 serotypes
 Responsible for about 70% of non-O157
human illness.







O26
O111
O103
O121
O45
O145
22% of non-O157 STEC
16% of non-O157 STEC
12% of non-O157 STEC
9% of non-O157 STEC
7% of non-O157 STEC
5% of non-O157 STEC
How Do Pathogens Find Their Way
into Beef Supply?
Hide is the principal sources of these
pathogens.
 Inadequate dressing practices is
responsible for transferring generic and
pathogenic bacteria from hides onto the
carcass.
 Once on the carcass it is impossible to be
100% sure that you have eliminated them.

The Ability to Detect Pathogens
Hides
Carcass (right after hide is removed)
Carcass (after all interventions)
Trim
Ground Beef
Message: If it is on the carcasses after hide is removed, sooner
or later it will be on the subprimals, trim and ground beef.
Control
Hide is the principal source of most
pathogens. An effective control in order
of
significance is:
1st - Dressing practices
2nd - Effective interventions
– scientific support
 Works in your hands – validation
 Must make contact the potential pathogens
 Effective
3rd - Effective test and hold
Control of STECs

STEC are a natural part of the animal microflora.

Some Non-O157 STEC can cause severe disease in
humans.

Non-O157 STEC is found at high frequency in preharvest samples (feces and hides).

Non-O157 STEC is probably just as prevalent,
maybe more, than O157 STEC in pre-harvest
samples.

Interventions used at the processing plants affect
STECs similarly.
HACCP Reassessment Issues





Lack of information in incidence of Big 6 STECs
in beef
Lack of scientific documentation regarding
validation of interventions and their effect on Big
6 STECs
Questions about availability and relevancy of
supplier COAs
Questions about trim testing and finished
product testing
Test and Hold policy?
HACCP Reassessment Issues
According to the Federal Register Notice,
USDA FSIS is assuming that the slaughter
and processing interventions, testing
programs and COAs in effect to address
E. coli O157:H7 will apply directly to the
Big 6 STECs
There are potential problems with COAs
as they relate to non-E. coli O157:H7
STECs
Problems in Conducting
Reassessment
Without extensive testing for the
Big 6 STECS – will the packers
be willing to issue COAs and if
they, will they be meaningful?
Problems in Conducting
Reassessment
Another problem will be how to provide
scientific support for slaughter and processing
interventions
Many NAMP members use ambient
temperature control as a CCP for E. coli
O157:H7 – There is a need for scientific
documentation specifically to address the Big
6 STECs
Problems in Conducting
Reassessment
US Beef Processors use processing
interventions, including Sanova, organic
acids and UV – USDA FSIS in the Federal
Register assumes that interventions for
controlling E. coli O157:H7 will be effective
for the Big 6 STECs – In order for HACCP
plans to be valid, there should be real
scientific support for that assumption
Interim Reassessment Steps
1. Request updated COAs from suppliers to
address the Big 6 STECs
2. Assume all slaughter and processing
interventions in place to address E. coli O157:H7
are effective at controlling other STECs
3. Conduct some level of testing for STECs in raw
materials and finished product to verify the
effectiveness of HACCP plans
4. Continue to reassess and provide scientific
documentation as it becomes available
USDA Testing of Trimmings
for STECs
USDA Testing for non-E. coli O157:H7
STECs began earlier this month
 Expect about 4-10% of the sample to
be “potential positive” that is the
enrichment is eae + stx
 Expect to have about 10 times the
prevalence of that of E. coli O157:H7
 Effect on trim prices (tested negative
and positive)

Industry Initiative on nSTECs
Regardless of potential FSIS actions
on nSTECs, it is in the interest of the
beef industry to address the issue of
nSTECs before it explodes into a
major public health crisis.
Scientific Issues
Testing methods for the BIG 6 STECs are
available and will improve over time
USDA has funded research to answer
many of the outstanding questions about
the validity of slaughter and processing
interventions
These studies will eventually provide the
necessary scientific documentation to
support HACCP plans
Long Term Solution
Interventions designed to virtually
eliminate surface contamination on
beef carcass - Carcass Pasteurization
Post-Chill UV/Photohydroionization
 Staged Antimicrobial Treatments
 Thermal – Steam or Hot Water

The best outcome (sliver
lining)

Renewed focus on dressing practices
and process control.
Current E. coli O145 Outbreak
14 Confirmed cases in Southeastern US
 1 Death
 Appear to be a sporadic outbreak
 So far, the CDC has been unable to
identify the source of the outbreak
 This outbreak underscores the need to
address Non-E. coli O157:H7 STECs

Questions?