777 / 1195
0.01 (-0.10, 0.13) was obtained between presumptive and confirmed VIDAS LMX results for
1
both confirmation procedures. The confidence intervals obtained for dLPOD
CP
indicated no
2
significant difference between the presumptive and confirmed results.
3
For the high level inoculum, a dLPOD
C
value of 0.02 (-0.01, 0.06) was obtained between the
4
AOAC 993.12 method and the VIDAS LMX method. The confidence intervals obtained for
5
dLPOD
C
indicated no significant difference between the two methods. A dLPOD
CP
of
6
0.00 (-0.02, 0.02) was obtained between presumptive and confirmed VIDAS LMX results. The
7
confidence intervals obtained for dLPOD
CP
indicated no significant difference between the
8
presumptive and confirmed results. Results of the POD statistical analysis are presented in Table
9
2013.1A below, and Table 2013.2A-2Band Figures 1A-1B of the Appendix.
10
11
12
Queso Fresco (125 gram Test Portions)
13
14
Queso fresco test portions were inoculated at a low and high level and analyzed (Table 4) for the
15
detection of
Listeriamonocytogenes
. Un-inoculated controls were included in each sample set.
16
Fourteen laboratories participated in the analysis of this matrix and the results of 12 laboratories
17
were included in the statistical analysis. Laboratory 2 did not report any data for this matrix.
18
Laboratory 11 reported 10reference method test portions (including
19
5 un-inoculated control replicates) that produced non-
Listeria monocytogenes
profiles, with 5 of
20
the test portions producing questionable API profiles of
L. grayi
. Colonies on these plates
21
contained one or more of the following biochemical reactions not typically associated with
L.
22
monocytogenes
: Gram-negative,non-beta-hemolytic and catalase negative.Based on the
23
preliminary biochemical tests conducted the test portions should not have been carried through
24
for final biochemical identification on API
Listeria
strips which resulted in the misidentification
25
of the test portion as
Listeria
spp. The selective agar plates for these test portions were sent to the
26
coordinating laboratory for further examination. The coordinating laboratory verified the
27
supplementary results (Gram stain, hemolysis and catalase reaction) reported by the participating
28
laboratory and were not able to identify any
Listeria
species. The results from this laboratory
29
were excluded from statistical analysis. The MPN levels obtained for this test portion, with 95%
30
confidence intervals, were 0.59 CFU/test portion (0.46, 0.74) for the low level and 5.41 CFU/test
31
portion (3.53, 8.30) for the high level. For VIDAS LMX test portions, no differences were
32
observed between confirmation of samples using the proprietary chromogenic ALOA and the
33
reference method agar.
34
For the high level, 144 out of 144 test portions were reported as positive by the VIDAS LMX
35
method with all test portions confirming positive. For the low level, 70 out of 144 test portions
36
were reported as positive by the VIDAS LMX method with all 70 test portions confirming
37
positive. For the un-inoculated controls, 0 out of 144 samples produced a presumptive positive
38
result by the VIDAS LMX method and nosamples confirmed positive. For test portions
39
analyzed by the AOAC OMA 993.12 method, 144 out of 144 high inoculum and 69 out of 144
40
low inoculum test portions confirmed positive. For the un-inoculated controls, 0 out of 144 test
41
portions confirmed positive.
42
For the low level inoculum, dLPOD
C
values of 0.01 (-0.10, 0.13) were obtained between the
43
AOAC OMA 993.12 method and the VIDAS LMX method. The confidence intervals obtained
44
for dLPOD
C
indicated no significant difference between the two methods. dLPOD
CP
values of
45
0.00 (-0.12, 0.12) were obtained between presumptive and confirmed VIDAS LMX results. The
46
confidence intervals obtained for dLPOD
CP
indicated no significant difference between the
47
presumptive and confirmed results using either confirmation process.
48
11