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February 20, 2013
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1
For the low level inoculum, a dPOD
C
value of 0.00 with 95% confidence intervals of (-0.27, 0.27) was
2
obtained between the reference and candidate method samples confirmed following both the
3
traditional and alternative confirmation procedures at both the 18 hour and 24 hour primary
4
enrichment time points. The confidence intervals obtained for dPOD
C
indicated no significant
5
difference between the two methods. A dPOD
CP
value of 0.00 with 95% confidence intervals of (-0.27,
6
0.27) was obtained between presumptive and confirmed results using either the traditional and
7
alternative confirmation procedures for both the 18 and 24 hour primary enrichment time points. The
8
confidence intervals obtained for dPOD
CP
indicated no significant difference between the presumptive
9
and confirmed results.
10
11
INDEPENDENT LABORATORY STUDY
12
The independent laboratory study was conducted at Aegis Food Testing Laboratories in North Sioux
13
City, SD. The study was conducted according to the methods described above for raw ground chicken
14
and pasteurized liquid whole eggs.
15
16
Raw Ground Chicken
17
All uninoculated control samples of ground chicken were confirmed negative for
Salmonella
. The samples
18
were inoculated
S. enterica
subsp. Enteritidis
(NCTC 5717),
with an estimated 0.031 cells/g as determined
19
by MPN. The 3M Petrifilm SALXSystem detected 13 suspect colonies of which12 samples were presumptive
20
when the confirmation disk was added. All 12 of the presumptive samples confirmed as positive by the
21
USDA/FSIS MLG 4.05 reference method. There were 11 ground chicken samples that were determined to
22
be positive by the reference method. When comparing the number of samples determined to be positive
23
by the 3M Petrifilm SALX System to that of the reference method, there was no statistical difference in the
24
results obtained (χ
2
<3.8, p<0.05). The number of samples that were presumptive positive from the 3M
25
Petrifilm SALX System was compared to the number confirmed as positive using probability of detection
26
(POD) and difference in probability (dPODcp). The 95% confidence interval for the dPOD for the 3M
27
Petrifilm SALX System presumptive positives compared to the confirmed positive contains zero. Therefore,
28
there was no significant difference in the results at the 5% level. The number of samples that were
29
confirmed positive from the 3M Petrifilm SALX System was compared to the number confirmed as positive
30
by the reference method using probability of detection (POD) and difference in probability (dPODc). The
31
95% confidence interval for the dPOD for the 3M Petrifilm SALX System confirmed positives compared to
32
the reference method confirmed positive contains zero. Therefore, there was no significant difference in
33
the results at the 5% level.
34
35
Pasteurized Liquid Whole Eggs
36
All uninoculated control samples of pasteurized liquid eggs were confirmed negative for
Salmonella
.
37
The samples were inoculated with an estimated 0.008 cells/g of
S. enterica
subsp. Enteritidis (ATCC
38
13076, heat stressed)
as determined by MPN. The 3M Salmonella Petrifilm System detected 7 suspect
39
colonies of which 7 samples were presumptive when the confirmation disk was added. All 7 of the
40
presumptive samples confirmed as positive by the USDA/FSIS MLG 4.05 reference method. There were
41
8 pasteurized liquid eggs samples that were determined to be positive by the reference method. When
42
comparing the number of samples determined to be positive by the 3M Petrifilm SALX System to that
43
of the reference method, there was no statistical difference in the results obtained (χ
2
<3.8, p<0.05).
44
The number of samples that were presumptive positive from the 3M Petrifilm SALX System was
45
compared to the number confirmed as positive using probability of detection (POD) and difference in
46
probability (dPODcp). The 95% confidence interval for the dPOD for the 3M Petrifilm SALX System
47