Prevalence of
Enterohemorrhagic E. coli (EHEC) in
Marler and Clark Retail Ground Beef
Baseline Study: Phase 3
Mansour Samadpour
Introduction
• IEH has been commissioned by
Marler and Clark to conduct a
baseline study to determine the
prevalence of non-O157 EHEC in
ground beef.
• The project involves analysis of 5000
ground beef samples purchased at
retail markets throughout the country.
• IEH accepted the project with the
condition that the names of the
manufacturing establishments would
not be released.
Enterohemorrhagic (EHEC):
Pathogenic Shiga Toxin Producing
E. coli (pSTEC)
• Several other serotypes of EHEC
have been associated with HC, and
HUS
• These serotypes are difficult to test
for, mainly due to lack of convenient
markers to allow for their detection
• Another impediment is lack of
regulatory definition for the target
organisms
Challenges in Defining EHEC/pSTEC
• Up to 20% of ground beef samples at retail can
contain E. coli that produce Stx, great majority of
these STEC strains lack the ability to cause
illness in humans:
 Stx is phage borne, generic E. coli can
get infected with the phage
 Stx alone is not sufficient to produce
illness other factors such as eae, or
subtilase are needed
 All major serotypes of EHEC also
contain EPEC members
The IEH Definition
• An E. coli strain is deemed to be
EHEC/pSTEC if it:
 Carries/produces at least one form of Stx
 The strain should also be eae or Subtilase
positive
 All isolates will be serotyped to determine if
they belong to one of the common
serotypes in the USA (O26, O45, O111,
O121, O145)
 Other serotypes will also be considered to
be EHEC/pSTEC if they possess the
appropriate virulence factors
Retail Ground Beef baseline Study
Phase III
Human isolates of non-O157 STEC,
by serogroup, 1983-2002
% of isolates
N = 940 isolates
70%
Brooks, JID 2005;192:1422
55 O groups,
each <1%
E. coli Serotypes in Retail Ground Beef Survey
35
31.6
30
Incidence (%)
25
20
15
11.6
10.5
10
9.5
6.3
5
5.3
4.2
3.2
2.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
0
U
nk
O
O
O
O
O
O
1 2 O8 : O1 3 9 1 1 4 1 1 1 0 O1 1
1 5 O1 5 O1 6 O1 7 O1 8 O5 : O6 :
3 9 O7 9 ON ON OR
T
T:
ou
H
H
H
no
3
1
:
5
1
4
3
3
0
6
6
5
9
1
(
H
:H :H :H
H
:H :H NM 34 :H 4 :H 7 :H
(n
( n 1 9 :H
(n
( n :H :H
gh
( n n=
1
w
1
2
49
=9 =6 (n 11 4 ( =2 =1 7 ( NT 25 25 25 8
1
n
8
(n 9 (
(n 9
:H
(
(
(n =11 0)
n=
=5
)
)
)
(n
( n n= )
(n
( n n=
(n n= =1 n= =1 (n= (n= 28
(
=3 )
n
1)
1)
= 4 3)
)
)
)
= 1 = 1 = 1 = 1 1) = 1 1)
1)
1)
(n
0)
)
)
)
)
)
=1
)
)
O
10
O
26
O
11
O
Incidence of Non O157 EHEC in Retail Ground Beef Survey (n=4,841)
7
6.22
6
Incidence (%)
5
4
3
1.96
2
1
0
Total IR (n=301)
Total Confirmed (n=95)
Incidence of Non O157 EHEC in Retail Ground Beef Survey (n=4,841)
7
6.22
6
Incidence (%)
5
4
3
1.96
2
1
0.62
0
Total IR (n=301)
Total Confirmed (n=95)
O26, O45, O111, O121, O145, O103 (n=30)
Incidence of Salmonella in Retail Ground Beef Survey (n=4,841)
3
2.85
3
Incidence (%)
2
1.74
2
1
1
0
Total IR (n=138)
Total Confirmed (n=84)
Conclusions regarding Phase III
• Substantial number of positives have the
Subtilase/Stx genotypes
• We have found some of the more pathogenic
serotypes which are not included in the CDC6
• From a public health point of view the CDC-6
approach is flawed
• The results of the current study are based on
N=1 sampling plan, as such, the data is an
underestimation of the burden of the target
organisms
Effective use of the pSTEC
group
•
•
•
•
Process control
Process control
Process control
Our failure to control pathogens in
ground beef is due to:
 Lack of understanding the
microbiological aspects of the process
 Insufficient verification
 Lack of process control
Frequency of Positive Signals
in Carcasses, Ground Beef, Trim, and Variety Meats
O157
STEC
2.0
E
Percent Positive Samples
Ground Beef
Trim
20
G
Carcass
Carcass
25
Percent Positive Samples
30
Variety Meats
15
10
5
Ground Beef
1.5
Trim
Variety Meats
1.0
0.5
0.0
0
Jan
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Feb Mar
Apr May
Jun
Jul
Aug Sep
Oct
Nov Dec
Dec
EHEC
Salmonella
6
10
H
F
Percent Positive Samples
Percent Positive Samples
Ground Beef
Trim
6
Carcass
5
Carcass
8
Variety Meats
4
2
Ground Beef
Trim
4
Variety Meats
3
2
1
0
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec