Improved identification of Listeria spp.
The addition of lecithin to the medium permits the further differentiation of L. monocytogenes and pathogenic L. ivanovii, both of which have the ability to produce the phospholipase enzyme, lecithinase (PCPLC). The activity of this enzyme produces a clearly visible, opaque white halo around L. monocytogenes and pathogenic L. ivanovii colonies.
The presence of PCPLC and another phospholipase enzyme (PIPLC) are required for virulence, although detection of one is sufficient for the identification of pathogenicity. L. monocytogenes is the most common pathogenic Listeria spp. and has been found in humans and animals. Pathogenic strains of L. ivanovii (those that possess lecithinase activity) are primarily found in animals but have also been shown to cause infection in humans (ref 1).
Comparative studies have found OCLA to be superior to PALCAM or Oxford medium for the isolation of L. monocytogenes.
OCLA has been validated and approved for use by AFNOR (ref 2).
References: 1. Cummins, AJ., Fielding, A.K. and McLauchlin, J. (1994) J. Infection 28: 89-91.2. Oxoid Folio No. 1059.
For further information about OCLA and other Oxoid products for the isolation and identification of Listeria spp.:
Contact Oxoid Ltd on tel: 01256 841144 or visit www.oxoid.com
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|Publication:||Food Trade Review|
|Date:||Dec 1, 2005|
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