Groeth on VRB-G

Lynn kees.lyn at
Sun Apr 9 06:39:15 EST 2000

Tim Marsh wrote:
> Dear All,
> A colleague has been carrying out tests for Enterobacteriaceae using VRB-G
> (Violet Red Bile agar with Glucose, produced by Oxoid) agar.  The test is
> carried out as a pour plate using VRB-G, which is also overlaid with VRB-G.
> Approx. 60 of the plates have grown creamy white colonies on the surface of
> the overlay (not in the original test sample layer).  I thought this might
> have been environmental contamination, but all control plates used show no
> growth.
> The limited microscopy so far performed indicates that they are bacterial:
> small rods (slightly longer than Listeria sp.) and are also motile.
> Can anyone enlighten me?  Can you suggest what they might be or what the
> next stage of diagnosis might be?
> Thank you for any help!
> Tim
> ( Please reply to tmarsh at )

Colonies on the surfce of VRBA are quite usual and If your controls are
ok I doubt that they would be from contamination.
Sorry cant help with id. You could inoculate them into BGBB to confirm
coliforms. See also post from lamb.
ps let us know what you find.
Cheers Lynn

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