Listeria enrichment broth??

Roy Markussen roy at miclis.no
Tue Oct 29 16:01:52 EST 1996

richard wrote:
> If you have experience using Listeria Enrichment Broth or
> modified Listeria Enrichment Broth I would like to talk to you.
> Specifically, how critical is incubation temperature?
> Does L monocytogenes grow well in these at 37 rather than
> the recommended 30 C?
> What in your experience is the limit of detection?
> Please respond either here or by private email.
> Thanks.

The Listeria Enrichment Broth from Oxoid has worked out quite good here.
We use it for the detection of L. monocytogenes in foodstuffs.

The problem is that L. innocua, that we have quite a lot of in Norway,
tends to outgrow L. monocytogenes in a range of approx. 1:20.

That makes the verification-job a bit more complicated. It is recomended
to use GenProbe for final verification.

The method I would recommend is to use the two step method, where then
enrichment broth is less selective the fist 24 hour incubation, an then
proceed to a more selective step the second incubation step.

Half the amount of antibiotics in the first incubation step does the

This is for recommended for samples with little copmetative growth.

Roy Markussen
Tonsberg public food control, Norway
nmt-tonsberg at miclis.no

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