Part of Thermo Fisher Scientific
Organisms this product works with:
Other products used in the isolation of Listeria monocytogenes :
CHROMOGENIC LISTERIA AGAR (ISO)
a medium for isolation, enumeration and presumptive identification of Listeria species and Listeria monocytogenes from food samples
|Enzymatic digest of animal tissues|
|Enzymatic digest of casein|
|Magnesium sulphate (anhydrous)|
|Disodium hydrogen phosphate (anhydrous)|
|X-glucoside chromogenic mix|
Final pH 7.2 ± 0.2 @ 25°C
OCLA (ISO) SELECTIVE SUPPLEMENT
OCLA (ISO) DIFFERENTIAL SUPPLEMENT†
BRILLIANCE LISTERIA DIFFERENTIAL SUPPLEMENT†
Modified ISO Formulation
Suspend 34.5g of Chromogenic Listeria Agar (ISO) in 480ml of distilled water. Mix well and sterilize by autoclaving at 121°C for 15 minutes. Cool the medium to 46°C and add one vial of Chromogenic Listeria Selective Supplement (ISO), reconstituted as directed and one vial of Brilliance Listeria Differential Supplement. Mix well and pour into sterile Petri dishes.
Suspend 34.5g of Chromogenic Listeria Agar (ISO) Base in 480ml of distilled water. Mix well and sterilise by autoclaving at 121ºC for 15 minutes. Cool the medium to around 50ºC, and add one vial of Chromogenic Listeria Selective Supplement (ISO), re-suspended as directed, and one vial of OCLA (ISO) Differential Supplement. Mix well and pour into sterile Petri dishes.
Listeria monocytogenes is the most common pathogenic Listeria spp. and has been shown to be pathogenic to both man and animals. Some Listeria ivanovii strains also possess these enzymes and, although Listeria ivanovii are primarily pathogenic to animals, there are strains which have been shown to cause infection in humans2. Studies have shown this medium to be superior to PALCAM and Oxford medium for the isolation of Listeria monocytogenes3.
OCLA (ISO) uses the chromogen X-glucoside for presumptive identification of Listeria spp. This chromogen is cleaved by ß-glucosidase, which is common to all Listeria species. Other organisms that possess this enzyme, such as enterococci, are inhibited by the selective agents within the medium: lithium chloride, polymyxin B and nalidixic acid, whilst amphotericin inhibits the growth of yeasts and moulds that may be present in the sample. Listeria monocytogenes and pathogenic Listeria ivanovii are then further differentiated by their ability to produce the phospholipase enzymes PIPLC and PCPLC which hydrolyse phosphotidyliositol or lethicin in the medium, producing an opaque white halo around the colony.
This medium is designed to identify Listeria spp. based on their utilisation of a chromogenic substrate. OCLA Base (ISO), when used with OCLA (ISO) Selective Supplement (SR0226) and OCLA (ISO) Differential Supplement (SR0244) following the manufacturer’s instructions, conform to the formulation described by Ottaviani and Agosti (ALOA) in ISO 11290-1:1997 (Incorporating Amendment No.1)1. This ALOA formulation incorporates phosphatidylinositol so that phosphatidylinositol phospholipase C (PIPLC), produced by Listeria monocytogenes, is detected. Alternatively, adding lecithin (Brilliance Listeria Differential Supplement (SR0228)) instead of phosphatidylinositol means that phosphatidylcholine phospholipase C (PCPLC) activity can be detected. Both PIPLC and PCPLC are associated with the virulence of Listeria and, therefore, detection of either enzyme is a useful indicator of pathogenicity.
Chromogenic Listeria Agar (ISO) can be used following a variety of enrichment procedures i.e. ISO, NMKL, FDA, AFNOR (UNI 03/04 - 04/054), etc.
The following method is a summary of ISO 11290-1:1997 (Incorporating Amendment No. 1):
Storage conditions and Shelf life
The dehydrated medium should be stored at 10-30°C and used before the expiry date on the label.
Prepared medium may be stored for up to 2 weeks at 2-8°C.
Dehydrated medium: Straw coloured, free-flowing powder
Prepared medium: Translucent cream gel
|Listeria monocytogenes ATCC®7644 *||Good growth: blue/green plus halo|
|Listeria innocua ATCC®33090 *||Good growth: blue/green no halo|
|Enterococcus feacalis ATCC®29212 *||Inhibited|
1. ISO 11290-1:1997 (Microbiology of food and animal feeding stuffs - Horizontal method for the enumeration of Listeria monocytogenes - part 1, Incorporating Amendment 1.)
2. Cummins, A.J., Fielding, A.K. and McLauchlin, J. (1994) Listeria ivanovii infection in a patient with AIDS. Journal of Infection 28, p89-91
3. Data on file at Oxoid.