552 / 596
Results were identical after 24 and 26 hours of sample enrichment. For the low inoculation level
1
of the MDA2 -
Listeria monocytogenes
assay, there were 12 presumptive positives and 12
2
confirmed positives following the USDA/FSIS MLG 8.09 reference method confirmation
3
procedure. There were 10 observed positives for the reference method. For the high inoculation
4
level, there were 5 presumptive positives and 5 confirmed positives following the USDA/FSIS
5
MLG 8.09 reference method confirmation procedure. There were 5 confirmed positives
6
following the reference method.Detailed results of the POD analyses are presented in Tables 11
7
and 15.
8
9
All five un
-
inoculated control test portions were negative by both the MDA2 -
Listeria
10
monocytogenes
assay and the corresponding reference method for each matrix above.
11
12
13
Product Consistency (Lot-to-Lot) and Stability Studies
14
15
Methodology
16
Three lots of MDA2 –
Listeria monocytogenes
test kits, 1 newly manufactured, 1 at the middle of
17
its expiration, and 1 at or slightly beyond expiration was analyzed to determine the stability of
18
the assay. For the MDA2 –
Listeria monocytogenes
test kit, one
Listeria monocytogenes
ATCC
19
7644 isolate was analyzed at a fractional positive level (2-8 positives), and testing 10 replicates.
20
One non-
Listeria monocytogenes
isolate,
Enterococcus faecalis
ATCC 29212, was analyzed at
21
the growth level achieved in a non-selective broth, testing 5 replicates.
22
23
Results
24
For the lot-to-lot/stability evaluation of the MDA2 -
Listeria monocytogenes
assay, there were 6
25
presumptive positives out of 10 replicates for all three lots at the low inoculation level. For the 5
26
un
-
inoculated control test portions, there were 0 presumptive positives out of 5 replicates for all
27
three lots.The five control test portions were negative. See Tables 16 for lot-to-lot/stability
28
results.
29
30
Robustness Study
31
32
Methodology
33
The robustness evaluated the ability of the method to remain unaffected by minor variations in
34
method parameters that might be expected to occur when the method is performed by an end
35
user. Three different parameters were evaluated, which are presented in Table 17.For each
36
parameter, one
Listeria monocytogenes
ATCC 7644isolate was analyzed at a fractional positive
37
level (2-8 positives), testing 10 replicates. One non-
Listeriamonocytogenes
isolate,
Enterococcus
38
faecalis
ATCC 29212, was analyzed at the growth level achieved in a non-selective broth, testing
39
5 replicates.
40
41
Results
42
43
For the robustness analysis of the MDA2 -
Listeria monocytogenes
assay, there were 6
44
presumptive positives out of 10 replicates for each variation evaluated. For the 5 control test
45