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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