415 / 596
(NC). A 20 µL aliquot was transferred to the NC and the Reagent Control (RC) tubes. A 20 µL
1
aliquot of a randomly picked sample was added to the Matrix Control tube, mixed, and recapped.
2
Using the 3M
™
software, prompts were followed to identify samples and controls. All samples
3
were loaded into the Speed Loader Tray, placed into the Molecular Detection System, and the
4
3M
™
MDA 2 -
Listeria
assay was initiated and results were obtained within 75 minutes.
5
6
Matrix Study Results
7
8
For each method, the probability of detection (POD) was calculated as the number of positive
9
outcomes divided by the total number of trials. [13] The following were calculated: the candidate
10
presumptive results, POD
CP
;
the candidate confirmatory results, POD
CC
; the difference in the
11
candidate presumptive and confirmatory results, dPOD
CP,
; the presumptive candidate results that
12
confirmed positive, POD
C
(=POD
CC
);
the reference method, POD
R
, and the difference in the
13
confirmed candidate and reference methods, dPOD
C
. POD analyses were conducted for the
14
MDA 2 -
Listeria
test points and compared to the appropriate reference method results. The pre-
15
validation target analyte background screen results and APC results are presented in Table 5. The
16
heat stress data for selected matrixes are presented in Table 6. The inoculum levels for each
17
environmental surface are presented in Table 7. A summary of POD analyses [14] are presented
18
in Tables 8-15. As per criteria outlined in Appendix J of the Official Methods of Analysis
19
Manual [15], fractional positive results were obtained for all matrixes.
20
21
Internal Study
22
23
Raw chicken leg pieces (25 g)
24
25
For the low inoculation level of the MDA 2 -
Listeria
assay, there were 4 presumptive positives
26
and 9 confirmed positives following the USDA/FSIS MLG 8.09 reference method confirmation
27
procedure resulting in 5 false negative samples. There were 5 observed positives for the
28
reference method. For the high inoculation level, there were 3 presumptive positives and 3
29
confirmed positives following the USDA/FSIS MLG 8.09 reference method confirmation
30
procedure. There was 1 confirmed positive following the reference method. Even though 5 false
31
negatives were confirmed, analysis show there to be no statistical difference when compared to
32
the reference method. Detailed results of the POD analyses are presented in Tables 8 and 12.
33
This matrix analysis was conducted using Demi Fraser with FAC brand X.
34
35
Raw chicken fillet (25 g)
36
37
For the low inoculation level of the MDA 2 -
Listeria
assay, there were 4 presumptive positives
38
and 4 confirmed positives following the USDA/FSIS MLG 8.09 reference method confirmation
39
procedure. There were 5 observed positives for the reference method. For the high inoculation
40
level, there were 2 presumptive positives and 2 confirmed positives following the USDA/FSIS
41
MLG 8.09 reference method confirmation procedure. There were 5 confirmed positives
42
following the reference method. Detailed results of the POD analyses are presented in Tables 8
43
and 12. This matrix analysis was conducted using Demi Fraser with FAC brand Z.
44
45
46