622-623 / 1195
Table 3.
Comparison of LPT and USDA/FSIS MLG Methods for Detection of
Listeria
in Food – 25g
a
American Type Culture Collection
b
Silliker Microtech
c
X
2
is defined by Mantel-Haenszel as (n-1)(AF-(B+C+D)E)
2
/(A+B+C+D)(A+E)B+C+D+F)(E+F) where n+A+B+C+D+E+F. A X
2
value greater than 3.84 indicates
significance at
p
>0.05.
Matrix
Test
Portion
Size
APC
Results,
Cfu/g
Contaminatio
n Level
MPN/25g
Total
Sample
s
VIDAS LPT
Reference
Method
Chi
Sq.
e
Positive Confirmed
Chicken
nuggets
L. welshimeri
ATCC
a
35897
25g
<100
Uninoculated
NA
5
0
0
0
-
Low
0.277
20
5
5
5
0
Deli ham
L. Seeligeri
SM
b
293
IMVS1150
25g
<10,000
Uninoculated
NA
5
0
0
0
-
Low
0.465
20
9
9
6
0.94
Pepperoni
L. Innocua
SM294
ATCC33090
25g
70,000
Uninoculated
NA
5
0
0
0
-
Low
0.944
20
15
15
10
2.6
Hot dogs (beef)
L.
monocytogenes
Serotype 4b
SM ScottA
25g
380,000
Uninoculated
NA
5
0
0
0
-
Low
0.10
20
6
6
1
4.22
Chicken liver
paté
L.
monocytogenes
Serotype 1
SM 20V ex beef
25g
30,000
Uninoculated
NA
5
0
0
0
-
Low
0.544
20
11
11
8
0.88