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VIDAS LPT - Summary 2012
EUROFINS IPL Nord SAS
–
1 rue du Professeur Calmette
–
59046 LILLE cedex
p 4/14
o
Dairy products (including raw milk cheeses),
o
Seafood (including smoked fishes),
o
Vegetables,
-
Environmental samples (including raw water).
The protocol
consists of an enrichment in LPT broth, incubated for 26 to 30 hours at 30°C ± 1°C (1:10 product
dilution 1/10).
A VIDAS
®
LPT test
is then performed using a 2-3 mL LPT broth, boiled for 5 1 minutes at 95-100°C. A 0.5 mL
test sample of heated broth is used to perform the VIDAS test.
1.2.3 Specific protocol for surface samples
This protocol applies for:
surface samples prepared with a swab: knife blade, slicer
, …
surface samples prepared with a sponge or a wipe : table, work surface, storage tank
…
This specific protocol consists of an enrichment in LPT broth, incubated for 22 to 30 hours at 30°C ± 1°C.
En fonction du
type de prélèvement, l’échantillon aura été préparé de la manière suivante
:
-
with swab: enrichment in 10 mL LPT broth,
-
with sponge : enrichment in 100 mL LPT broth.
A VIDAS
®
LPT test
is then performed using a 2-3 mL LPT broth, boiled for 5 1 minutes at 95-100°C. A 0.5 mL
test sample of heated broth is used to perform the VIDAS test.
1.2.4 Confirmation of positive results
The positive results following the VIDAS
®
LPT test are confirmed by isolating 10
μ
l of the unheated LPT enrichment
broth on two selective
Listeria
agars (selective
Listeria
agar according to Ottaviani and Agosti (ChromID OAA) and
Palcam agar) and performing the conventional tests described in the CEN or ISO standardized methods (including
the purification step), or performing an identification strip test without purification (API).
The characteristic aspect of
Listeria
spp. on Palcam agar and / or selective agar according to Ottaviani and Agosti
(ChromID OAA) is sufficient to confirm the VIDAS® LPT results positive. This point has been verified during the
certification study.
The positive enrichment broths (LPT 26h or LPT 22h) were also stored for 72 hours at 2
–
8°C and a second series
of VIDAS
®
LPT tests and confirmation tests was performed for all the positive samples from the accuracy study in
order to validate the possibility of deferring the VIDAS
®
LPT test and the confirmations.
Comments about the confirmations:
In the event of a positive VIDAS
®
LPT test and the absence of characteristic colonies on selective agar, the
following supplementary confirmation option may be used:
-
transfer 1 mL unheated LPT broth into a 6 mL LX broth tube or into a 10 mL LPT broth tube,
-
incubate for 22 to 26 hours at 30°C ± 1°C,
-
isolation on selective two agars, and completion of the tests described above.
1.3 Scope
The scope is as follows:
-
Human food products (general protocol):
o
Meat products,
o
Dairy products (including raw milk cheeses),
o
Seafood (including smoked fishes),
o
Vegetables,
-
Environmental samples (general and specific protocols).