616 / 1195
For the plastic analysis there were 18 confirmed positives for the LPT method and 15
1
confirmed positives for the USDA reference method. All uninoculated samples were
2
negative with both methods. There were no false positives for the VIDAS method (dPOD
3
= 0, CI: -0.21 to 0.21). There was no significant difference between the LPT method and
4
the reference method using unpaired Chi-square test (
X
2
= 1.50) or the POD (dPOD =
5
0.15, CI: -0.09 to 0.38). See Tables 6, 8, 9 in the Appendix.
6
Concrete (sealed)
7
For the concrete analysis there were 14 confirmed positives for the LPT method and 15
8
confirmed positives for the USDA reference method. All uninoculated samples were
9
negative with both methods. There were no false positives for the VIDAS method (dPOD
10
= 0, CI: -0.27 to 0.27). There was no significant difference between the LPT method and
11
the reference method using unpaired Chi-square test (
X
2
= 0.12) or the POD (dPOD =
12
0.05, CI: -0.31 to 0.22). See Tables 6, 8, 9 in the Appendix.
13
Confirmation using Ottaviani Agosti agar
14
Confirmation using direct plating of LPT broth on ALOA showed exact agreement with
15
the traditional reference plating media.
16
Overall Results
17
The inclusivity and exclusivity evaluation showed no unexpected results. The VIDAS
18
LPT method detected all of the
Listeria
strains tested and none of the non-
Listeria
strains
19
tested. For the method comparison study, there were no significant differences between
20
the LPT method and the reference method for detection of
Listeria
for the majority of the
21
foods and surfaces tested using the unpaired chi-square test at 5% level and the POD
22
analysis. There were three matrices where there was a significant difference (hot dogs,
23
mixed salad and stainless steel) with the LPT method showing significantly better
24
recovery. There was one false positive result out of the 420 low level samples tested by
25
the LPT method.
26
Overall Conclusions
27
The results of this study demonstrate that the VIDAS
®
LPT method was equivalent or
28
better than the reference methods for the detection of
Listeria
in a variety of foods and
29
select environmental surfaces. The VIDAS
®
LPT method offers a significant savings in
30
time and improved convenience when compared to the traditional reference methods by
31
using a simple one step enrichment, giving presumptive results in less than 28 hours for
32
25g food samples and less than 24h for environmental surfaces. The LPT test method
33
was determined to be equivalent to the reference methods for the detection of Listeria
34
species in 125g test portions of ground beef, deli ham and turkey and Mexican style soft-
35
cheese (queso fresco). In addition, confirmation using direct plating of LPT broth on
36
ALOA showed exact agreement with the traditional plating media
37
References
38
55