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13
Results of Collaborative Study
1
2
For this collaborative study, the 3M Molecular Detection Assay (MDA) 2 -
Listeria
method was
3
compared to the USDA FSIS MLG 8.09 reference method for deli turkey and raw chicken breast
4
fillet. A total of 13 laboratories throughout the United Statesand Canada participated in this
5
study, with 11 laboratories submitting data for the deli turkey and 12 laboratories submitting data
6
for the raw chicken breast fillet. See Table 1 for a summary of laboratory participation for each
7
matrix. Each laboratory analyzed 36 test portions for each method per matrix: 12 inoculated
8
with a high level of
Listeria
, 12 inoculated with a low level of
Listeria
, and 12 un-inoculated
9
controls.
10
A background screen of the matrix indicated an absence of indigenous
Listeria
species in both
11
matrices.Ten (10) replicate test portions (randomly sampled from 50% of the total packages used
12
in the analysis) were screened for the presence of
Listeria
species. All test portions produced
13
negative results for the target analyte.
14
Results for the heat stress analysis of the inoculum for the deli turkey are presented in Table 2.
15
Table 2016.1A and 2016.1B summarize the inter-laboratory results for all foods tested, including
16
POD statistical analysis. As per criteria outlined in Appendix J of the AOAC Validation
17
Guidelines, fractional positive results were obtained.Detailed results for each laboratory are
18
presented in Tables 2016.2A and 2016.2B. For each matrix, the level of
Listeria
was determined
19
by MPN on the day of initiation of analysis by the coordinating laboratory. MPN results are
20
presented in Tables 2016.2A and 2016.2B.The individual laboratory and sample results are
21
presented in Tables 1-2 of the Supplementary Materials. The APCresults for each collaborating
22
are presented in Table3 of the Supplementary Materials.
23
24
Deli Turkey (125 g Test Portions)
25
26
Deli turkeytest portions were inoculated at a low and high level and were analyzed for the
27
detection of
Listeria
spp. Un-inoculated controls were included in each analysis. Laboratories 8
28
and 10 received test portions but were unable to conduct the analysis and therefore no data was
29
submitted. All other laboratories submitted data for both methods evaluated. The MPN levels
30
obtained for this matrix, with 95% confidence intervals, were 0.63 CFU/test portion (0.49,0.80)
31
for the low inoculum level and 4.52 CFU/test portion (3.19, 6.42) for the high inoculum level.
32
For the low inoculum level, 68 out of 132 test portions (POD
CP
of 0.52) were reported as
33
presumptive positive by the 3M MDA 2 –
Listeria
method with 66out of 132 test portions
34
(POD
CC
of 0.50) confirming positive. For samples that produced presumptive positive results on
35
the 3M MDA 2 –
Listeria
method, 66out of 132 samples confirmed positive (POD
C
of 0.50). For
36
test portions evaluated by the USDA/FSIS MLG reference method, 60 out of 132 test portions
37
produced positive results. A dLPOD
C
value of 0.04 with 95% confidence intervals of
38
(-0.08, 0.17) was obtained between the candidate and reference method, indicating no statistical
39
significant difference between the two methods. A dLPOD
CP
value of 0.02 with 95% confidence
40
intervals of (-0.11, 0.14) was obtained between presumptive and confirmed results indicating no
41
statistically significant difference between the presumptive and confirmed results.
42
AOAC Rese rch Institute
Expert Review Panel Use Only
OMAMAN-29 A/ Collaboartive Study Manuscript
OMA ERP June 2016
ERP Use Only