884-885 / 1195
Table 2. Comparison of presumptive positives using the LMX method and confirmed positive
Listeria monocytogenes
inoculated
232
samples in various food matrices at low level of inoculation (0.2-2 CFU/test portion). No false-positives were detected.
233
Matrix
Strain
MPN
a
/ 25 g
N
b
Presumptive
Confirmed
dPOD
C
f
95% CI
g
X
c
POD
C
d
95% CI
x
POD
C
e
95% CI
Ground Beef
L. monocyto
-genes
ATCC 13932
0.945
25
7
0.28
0.14-0.48
7
0.28
0.14-0.48
0
-0.24--0.24
95% CI 0.43-1.54
Queso Fresco
L. monocyto
-genes
ATCC 19114
0.794
95% CI 0.47-1.31
25
11
0.44
0.27-0.63
11
0.44
0.27-0.63
0
-0.26-0.26
Deli Ham
L. monocyto
-genes
ATCC 7644
1.31
95% CI 0.79-2.55
25
16
0.64
0.45-0.80
16
0.64
0.45-0.80
0
-0.25-0.25
Deli Turkey
L. monocyto
-genes
ATCC 7644
1.31
95% CI 0.79-2.55
25
16
0.64
0.45-0.80
16
0.64
0.45-0.80
0
-0.25-0.25
a
MPN = Most Probable Number is based on the POD of reference method test portions across labs using the AOAC MPN calculator, with 95% confidence interval
234
b
N = Number of test potions
235
c
x = Number of positive test portions
236
d
POD
C
=
Confirmed candidate method positive outcomes divided by the total number of trials
237
e
POD
R
= Confirmed reference method positive outcomes divided by the total number of trials
238
f
dPOD
C
= Difference between the presumptive positives and confirmed positive POD values
239
g
95% CI = If the confidence interval of a dPOD does not contain zero, then the difference is statistically significant at the 5% level
240
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