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Results were identical after 24 and 26 hours of sample enrichment. For the low inoculation level
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of the MDA 2 -
Listeria
assay, there were 15 presumptive positives and 15 confirmed positives
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following the USDA/FSIS MLG 8.09 reference method confirmation procedure. There were 11
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observed positives for the reference method. For the high inoculation level, there were 5
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presumptive positives and 5 confirmed positives following the USDA/FSIS MLG 8.09 reference
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method confirmation procedure. There were 5 confirmed positives following the reference
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method. Detailed results of the POD analyses are presented in Tables 9 and 13.
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9
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Product Consistency (Lot-to-Lot) and Stability Studies
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Methodology
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Three lots of MDA 2 -
Listeria
test kits, 1 newly manufactured, 1 at the middle of its expiration,
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and 1 at or slightly beyond expiration were analyzed to determine the stability of the assay. For
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the MDA 2 -
Listeria
test kit, one
Listeria monocytogenes
ATCC 7644 isolate was analyzed at a
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fractional positive level (2-8 positives), and testing 10 replicates. One non-
Listeria
isolate,
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Enterococcus faecalis
ATCC 29212, was analyzed at the growth level achieved in a non-
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selective broth, testing 5 replicates.
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Results
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For the lot-to-lot/stability evaluation of the MDA 2 -
Listeria
assay, there were 6 presumptive
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positives out of 10 replicates for all three lots at the low inoculation level. For the 5 uninoculated
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control test portions, there were 0 presumptive positives out of 5 replicates for all three lots. The
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five control test portions were negative. See Table 16 for lot-to-lot/stability results.
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Robustness Study
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Methodology
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The robustness evaluated the ability of the method to remain unaffected by minor variations in
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method parameters that might be expected to occur when the method is performed by an end
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user. Three different parameters were evaluated, which are presented in Table 18. For each
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parameter, one
Listeria monocytogenes
ATCC 7644
isolate was analyzed at a fractional positive
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level (2-8 positives), testing 10 replicates. One non-
Listeria
isolate,
Enterococcus faecalis
ATCC
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29212, was analyzed at the growth level achieved in a non-selective broth, testing 5 replicates.
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Table B: Robustness Parameters
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Parameter
Low Value
Nominal Value
High Value
Lysis Time
13 minutes
15 minutes
17 minutes
Enrichment Volume
18 µL
20 µL
22 µL
Lysate Volume
18 µL
20 µL
22 µL
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Table C: Robustness Parameter Variations
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Treatment
Lysis Time
Volume
Volume
# of Replicates
AOAC Research Institute
Expert Review Panel Use Only
OMAMAN-29 D/ PTM Validation Report 111501
OMA ERP - June 2016
ERP Use Only