630-631 / 1195
Table 7.
Comparison of LPT and USDA Method for Detection of
Listeria
on Environmental Surfaces
a
American Type Culture Collection
b
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.
c
surfaces were inoculated with a competitor,
Enterococcus faecalis
SM244 at a target:competitor ratio of 1:10.
Matrix
Contaminatio
n Level
Inoculation
Level Added
per 100 cm
2
Samplin
g
Device
Total
Samples
VIDAS LPT
Reference
Method
Chi
Sq.
b
Positiv
e
Confirme
d
Ceramic
L .innocua
ATCC
a
33090
Plus competitor
c
Uninoculated
NA
Sponge
5
0
0
0
-
Low
1.8 x 10
4
20
6
6
3
1.26
Stainless steel
L.monocytogenes
Plus competitor
c
Uninoculated
NA
Sponge
5
0
0
0
-
Low
1.3 x 10
2
20
11
10
1
11.61
Plastic
L.welshimeri
ATCC 35897
Uninoculated
NA
Swab
5
0
0
0
-
Low
1.6 x 10
5
20
18
18
15
1.50
Concrete
L.monocytogenes
NCTC 11994
Plus competitor
c
Uninoculated
NA
Swab
5
0
0
0
-
Low
8.7 x 10
2
20
14
14
15
0.12