Oxford Listeria Selective Agar, Base

Listeria Selective Agar Base (OXFORD Formulation)

EMD Cat. No. 1.07004.0500

500 g

Selective agar for the isolation and detection of Listeria monocytogenes. This culture medium is in accordance with the standard 143:1990 of the IDF-FIL for milk and milk products for the detection of Listeria monocytogenes.

Additives

EMD Cat. No.	Product	Pack Size
1.07006.0001	Oxford Listeria Selective Supplement	1 x 13 vials

Mode of Action	Preparation
Experimental Procedure and Evaluation	Quality Control
Typical Composition (g/liter)	Literature
Picture/Image

Mode of Action
The Oxford Agar formulation is based on Columbia Agar with the addition of lithium chloride, acriflavin, colistin sulfate, cefotetan, cycloheximide and fosfomycin. These ingredients suppress the growth of the common bacteria (e.g. Gram-negative bacteria and a greater part of Gram-positive bacteria).
Lithium chloride is one of the ingredients of Oxford Agar base, whereas the other substances derive from the Oxford Listeria Selective Supplement (Cat. No. 7006).
Listeria monocytogenes hydrolyses esculin to esculetin and forms a black complex with iron(III)ions. Therefore Listeria monocytogenes produces brown-green colored colonies with a black halo.

Preparation
Suspend 29.25 g in 500 ml of purified water, autoclave (15 min at 121 °C). Dissolve the lyophilisate of 1 vial Oxford Listeria Selective Supplement (Cat. No. 1.07006.) by adding 5 ml of a 1:1 mixture of ethanol and sterile distilled water. Mix gently and add the contents to the culture medium cooled to 50 °C. Pour the medium into plates and leave to solidify.
pH: 7.0 ± 0.2 at 25 °C.
The prepared agar (incl. supplement) is clear and bluish-brown.

Experimental Procedure and Evaluation
Inoculate by spreading the sample on the surface of the medium and incubate at 35 °C up to 48 h aerobically. Listeria monocytogenes grows as brown-green colored colonies with a black halo (esculin splitting). Further biochemical tests should be carried out.

Quality control

Test strains	Growth	Black zone
Listeria monocytogenes ATCC 19118	good / very good	+
Listeria monocytogenes IRH 7	good / very good	+
Listeria monocytogenes RIUM 3	good / very good	+
Listeria innocua ATCC 33090	good / very good	+
Staphylococcus aureus ATCC 25923	none
Enterococcus faecalis ATCC 19433	none
Erysipelothrix rhusiopathiae ATCC 19414	none
Escherichia coli ATCC 25922	none

Typical Composition (g/liter)
Peptone 23.0; starch 1.0; sodium chloride 5.0; agar-agar 13.0 (= Columbia agar); esculin 1.0; ammonium iron(III) citrate 0.5; lithium chloride 15.0.

Literature

CURTIS, G.D.W., MITCHELL, R.G., KING, A.F., GRIFFIN, E.J.: A selective differential medium for the isolation of Listeria monocytogenes. Letters in Appl. Microbiol., 8; 95-98 (1989).

Listeria monocytogenes