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Eurofins IPL Nord SAS – 1 rue du professeur Calmette – 59046 LILLE cedex
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VIDAS LMX – Summary 2012 v01
Study realized by :
EUROFINS IPL Nord SAS
(formerly IPL Santé Environnement Durables Nord
)
1 rue du Professeur Calmette
59046 LILLE cedex
FRANCE
for :
BIOMERIEUX
Chemin de l'Orme
69280 MARCY L'ETOILE
FRANCE
1 Introduction
1.1 Validation references
The VIDAS LMX method has been validated in February 2010 according to the reference method EN ISO
16140:2003, with respect to the reference EN ISO 11290-1/A1:2005, for all human food products and for
environmental samples.
1.2 Protocol and principle of the alternative method
1.2.1 Protocol
The diagram summarising the method is shown in appendix A.
General protocol
for human food products (meat products, dairy products (except raw milk cheeses), vegetables)
and environment samples is composed :
-
an enrichment of 25 g sample in 225 ml
LMX broth
(dilution 1/10
)
, supplemented with 500 µl a selective mix,
incubated for
26 h to 30 h at 37°C ± 1°C
,
-
followed by a VIDAS LMX test, from a 250 µl part, after heating for 5 minutes at 95-100°C.
Positive results with VIDAS LMX tests have to be confirmed:
-
with the tests described in the ISO 11290-1 method, after isolation of LMX broth on selective agar for
Listeria
monocytogenes
( eg :Chrom’ID Ottaviani Agosti…)
or
-
after isolation of LMX broth on
Listeria monocytogenes
chromogenic agar (Chrom’ID Ottaviani Agosti or
RapidL’mono…). The typical aspect of
Listeria monocytogenes
on chromogenic plates will be sufficient to
validate a positive VIDAS LMX test. Any selective medium part of a AFNOR VALIDATION certification will have
to be able to be used.
Note: In absence of characteristic colony on chromogenic plate with positive VIDAS LMX test, another voice of
confirmation can be followed : transfer 0.1 ml of non heated LMX broth in a 6 ml LX broth and incubate for 22-26h
at 37°C, and then isolate on chromogenic plate.
Specific protocol
for raw milk cheeses is composed:
-
an enrichment of 25 g sample portion in 450 ml
LMX broth
, supplemented with 500 µl a selective mix,
incubated for
20 h to 24 h at 37°C ± 1°C
,
-
then an inoculation of 3 ml of LMX broth in a 6 ml
LX broth
, incubated for
6 h to 8 h at 37°C ± 1°C,
-
followed by a VIDAS LMX test, from a 250 µl part, after heating for 5 minutes at 95-100°C.
Notes:
-
Each flask containing 225 ml of supplemented LMX broth will be pre-heated at 37°C +/- 1°C (it’s possib le to put
them the day before the tests in an incubator).
-
The freeze-dried selective factors must be reconstituted with 6 ml of distilled water and can be kept during 7
days between 2-8°C.
-
It’s important to well shake the freeze-dried selective factors in the flask before sampling.
-
Protocol reference: 14226 C