485 / 596
13
In the rare event of any unusual light output, the algorithm labels this as “Inspect.” 3M
1
recommends the user to repeat the assay for any Inspect samples. If the result continues to be
2
Inspect, proceed to confirmation test using your preferred method or as specified by local
3
regulations.
4
5
Results of Collaborative Study
6
7
For this collaborative study, the 3M Molecular Detection Assay (MDA) 2 -
Listeria
8
monocytogenes
method was compared to the USDA FSIS MLG 8.09 reference method for deli
9
turkey and raw chicken breast fillet. A total of 13 laboratories throughout the United Statesand
10
Canada participated in this study, with 11 laboratories submitting data for the deli turkey and 12
11
laboratories submitting data for the raw chicken breast fillet. See Table 1 for a summary of
12
laboratory participation for each matrix. Each laboratory analyzed 36 test portions for each
13
method per matrix: 12 inoculated with a high level of
Listeria monocytogenes
, 12 inoculated
14
with a low level of
Listeria monocytogenes
, and 12 un-inoculated controls.
15
A background screen of the matrix indicated an absence of indigenous
Listeria monocytogenes
in
16
both matrices.Ten (10) replicate test portions (randomly sampled from 50% of the total packages
17
used in the analysis) were screened for the presence of
Listeria monocytogenes
. All test portions
18
produced negative results for the target analyte.
19
Results for the heat stress analysis of the inoculum for the deli turkey are presented in Table 2.
20
The raw chicken breast fillet is not heat treated, therefore it was not necessary to injure the
21
cells.
Table 2016.1A and 2016.1B summarize the inter-laboratory results for all foods tested,
22
including POD statistical analysis. As per criteria outlined in Appendix J of the AOAC
23
Validation Guidelines, fractional positive results were obtained.Detailed results for each
24
laboratory are presented in Tables 2016.2A and 2016.2B. For each matrix, the level of
Listeria
25
monocytogenes
was determined by MPN on the day of initiation of analysis by the coordinating
26
laboratory. MPN results are presented in Tables 2016.2A and 2016.2B.The individual laboratory
27
and sample results are presented in Tables 1-2 of the Supplementary Materials. The APCresults
28
for each collaborating are presented in Table
35
of the Supplementary Materials.
29
30
Deli Turkey (125 g Test Portions)
31
32
Deli turkeytest portions were inoculated at a low and high level and were analyzed for the
33
detection of
Listeria monocytogenes
. Un-inoculated controls were included in each analysis.
34
Laboratories 8 and 10 received test portions but were unable to conduct the analysis and
35
therefore no data was submitted. All other laboratories submitted data for both methods
36
evaluated.The MPN levels obtained for this matrix, with 95% confidence intervals, were 0.63
37
CFU/test portion (0.49,0.80) for the low inoculum level and 4.52 CFU/test portion (3.19, 6.42)
38
for the high inoculum level.
39
For the low inoculum level, 69 out of 132 test portions (POD
CP
of 0.52) were reported as
40
presumptive positive by the 3M MDA 2 –
Listeria monocytogenes
method with 66out of 132 test
41
portions (POD
CC
of 0.50) confirming positive. For samples that produced presumptive positive
42
results on the 3M MDA 2 –
Listeria monocytogenes
method, 66out of 132 samples confirmed
43