488 / 596
16
with 95% confidence intervals of (-0.03, 0.00) was obtained between presumptive and confirmed
1
results
indicating the difference between presumptive and confirmed methods was not
2
statistically significant at the 0.05 probability level.indicating no statistically significant
3
difference between the presumptive and confirmed results.
4
5
Detailed results of the POD statistical analysis are presented in Table 2016.2B and Figures 1C-
6
1D.
7
8
9
Discussion
10
11
No negative feedback was provided by the collaborating laboratories in regard to the
12
performance of the 3M MDA 2-
Listeria monocytogenes
method.For the raw chicken breast fillet,
13
Laboratory 10 reported isolating
Listeria monocytogenes
from two un-inoculated control samples.
14
The isolates were sent for further identification and it was determined that they were the same
15
strain as the inoculating organism, indicating that cross contamination of the sample occurred.
16
Due to the fact that cross contamination occurred, just cause for removal of the data was
17
established and the data generated by Laboratory 10 was therefore not included in the statistical
18
analysis.
19
Overall, the data generated during this evaluation demonstrates the reproducibility of this new
20
method. For the deli turkey analysis, the POD statistical analysis indicated
the difference
21
between the candidate method and reference method was not statistically significant at the 0.05
22
probability level. And thethatno statistically significant difference between the candidate method
23
and the reference methodor between the presumptive and confirmed results difference between
24
presumptive and confirmed candidate method was not statistically significant at the 0.05
25
probability
level.ofthe candidate method was obtained.
For raw chicken breast fillet, a
26
statistically significant difference was observed between the reference and the alternative
27
method.
The dLPOD data indicated The dLPOD being significantly greater than zero showed an
28
observed higher proportion of positive results by the candidate method than the reference
29
method.a positive correlation in data indicating more recovery of the target analyte by the
30
candidate method.
One possible contribution
for the higher observed proportion positive resultsto
31
the higher level of recovery
observed with the 3M MDA 2 –
Listeria monocytogenes
method was
32
the use of Demi-Fraser Broth for the candidate method. This enrichment media formulation is
33
less selective than the modified University of Vermont Medium used in the USDA reference
34
method and may have contributed to the higher
observed proportion positive results level of
35
recovery observed
during the evaluation.
36
A second possible contribution
to the higherfor the higher observed proportion positive
37
resultslevel of recovery was is
the length of the primary enrichment. Test portions evaluated by
38
the 3M MDA 2 –
Listeria monocytogenes
method were incubated for a minimum of 28 hours in
39
the primary enrichment, while the USDA reference method had a maximum primary enrichment
40
time of 26 hours. No statistically significant difference was observed between the candidate
41
method presumptive and confirmed results for this matrix.
42
43