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Deli turkey test portions were inoculated at a low and high level and were analyzed
1
(Table 2) for the detection of
Listeria monocytogenes.
Fourteen laboratories participated in the
2
analysis of the deli turkey. Un-inoculated controls were included in each analysis.
3
Laboratory5did not submit results to the coordinating laboratory. Laboratory 8 reported a
4
deviation in the protocol (Enrichment of MDA test portions using UVM broth) and laboratory 10
5
reported the occurrence of cross contamination of their samples (8 confirmed positive
6
uninoculated reference method samples and 7 confirmed positive uninoculatedMDA method
7
samples). Results from these laboratories were excluded from the statistical analysis. The MPN
8
levels obtained for this test portion, with 95% confidence intervals, were 0.66 CFU/test portion
9
(0.51, 0.83) for the low level and 5.08 CFU/test portion (3.39, 7.63) for the high level.
10
For the high level, 132 out of 132 test portions (POD
CP
of1.00) were reported as presumptive
11
positive by the 3M MDA
Listeria monocytogenes
method with all 132 test portions (POD
CC
of
12
1.00) confirming positive.Based on the valid data submitted from each of the collaborating
13
laboratories, no false negative or false positive results were obtained resulting in 132 confirmed
14
positives (POD
C
of 1.00). For the low level, 66 out of 132 test portions (POD
CP
of 0.50) were
15
reported as presumptive positive by the 3M MDA
Listeria monocytogenes
method with 67 test
16
portions (POD
CC
of 0.51) confirming positive. Based on the valid data submitted from each of
17
the collaborating laboratories, 3 false negative results and 2 false positive results were obtained
18
resulting in 64 confirmed positives (POD
C
of 0.48).For the un-inoculated controls, 2 out of 132
19
samples (POD
CP
of 0.02) produced a presumptive positive result by the 3M MDA
Listeria
20
monocytogenes
method with one test portion(POD
CC
of 0.01) confirming positive. (Each
21
discrepant result was produced by a different laboratory. Based on the valid data submitted from
22
each of the collaborating laboratories, 2 false negative results and 1 false positive results were
23
obtained resulting in 64 confirmed positives (POD
C
of 0.00). Laboratories 4 and 6 produced 1
24
false positive result and laboratory 16 produced 1 false negative result). For test portions
25
analyzed by the USDA/FSIS-MLG Method, 132 out of 132 high inoculum (POD
R
of 1.00) and
26
66 out of 132 low inoculum test portions (POD
R
of 0.50) confirmed positive. For the un-
27
inoculated controls, 0 out of 132 test portions (POD
R
of 0.00) confirmed positive.
28
For the low level, a dLPOD
C
value of -0.02 with 95% confidence intervals of
29
(-0.14, 0.11) were obtained between the 3M MDA
Listeria monocytogenes
method and the
30
USDA/FSIS-MLG method. The confidence intervals obtained for dLPOD
C
indicated no
31
significant difference between the two methods. A dLPOD
CP
value of -0.01 with 95%
32
confidence intervals of (-0.13, 0.12) were obtained between presumptive and confirmed 3M
33
MDA
Listeria monocytogenes
results. The confidence intervals obtained for dLPOD
CP
indicated
34
no significant difference between the presumptive and confirmed results using either
35
confirmation process.
36
For the high level, a dLPOD
C
value of 0.00 with 95% confidence intervals of
37
(-0.03, 0.03) were obtained between the 3M MDA
Listeria monocytogenes
method and the
38
USDA/FSIS-MLG method. The confidence intervals obtained for dLPOD
C
indicated no
39
significant difference between the two methods. A dLPOD
CP
value of 0.00 with 95% confidence
40
intervals of (-0.03, 0.03) were obtained between presumptive and confirmed 3M MDA
Listeria
41
monocytogenes
results. The confidence intervals obtained for dLPOD
CP
indicated no significant
42
difference between the presumptive and confirmed results. Detailed results of the POD statistical
43
analysis are presented in Table 2014.2B and Figures 2A-2B of the Supplemenatary aterials.
44
45
46
Discussion
47
48
Candidates for 2016 Method of the Year
160