Product number: NCM1004

Listeria Chromogenic Agar (according to the formulation of Ottaviani and Agosti) is a selective medium for the isolation and presumptive identification of Listeria monocytogenes from foodstuffs and related materials as described in ISO 11290-1:2017. This medium is not intended for use in the diagnosis of disease or other conditions in humans.

Lithium chloride in the base medium and supplementary antimicrobial compounds Ceftazidime, Polymyxin, Nalidixic acid and Cycloheximide provide the medium’s selectivity. Chromogenic activity is as a result of a chromogenic substrate for the detection of the β-glucosidase enzyme, common to all Listeria spp. and to a few strains of Enterococci and Bacilli.

The specific differential activity of this agar is obtained with a proprietary lecithin substrate for the detection of the phospholipase enzyme present in the L. monocytogenes colonies growing on this media. This enzyme activity will result in a halo of precipitation surrounding the target colonies.

With the combination of both the chromogenic and phospholipase enzyme reactions, it is possible to differentiate Listeria monocytogenes (blue colonies surrounded by an opaque halo) from other Listeria spp. (blue colonies without an opaque halo).


Formula Liter
Meat Peptone 18.0 g/L
Tryptone 6.0 g/L
Yeast Extract 10.0 g/L
Lithium Chloride 10.0 g/L
Sodium Chloride 5.0 g/L
Disodium Hydrogen Orthophosphate Anhydrous 2.5 g/L
Sodium Pyruvate 2.0 g/L
Glucose 2.0 g/L
Glycerophosphate 1.0 g/L
Magnesium Sulphate 0.5 g/L
5-Bromo-4-Chloro-3Indolyl-β-d-Glucopyranoside 0.05 g/L
Agar 13.5 g/L

Final pH: 7.2 ± 0.2 at 25°C
Formula may be adjusted and/or supplemented as required to meet performance specifications.


  1. Suspend 70.5 grams of the medium in 950mL of purified water.
  2. Heat with frequent agitation and boil for one minute to completely dissolve the medium.
  3. Autoclave at 121°C for 15 minutes.
  4. Cool to 45-50°C, and add 2 vials of reconstituted X072 supplement. Swirl to mix.
  5. Add 2 vials of X010 supplement (pre- heated to 48-50°C). Mix well with gentle end-over-end mixing.

Product was previously known as LabM Product: HAL010 Harlequin® Listeria Chromogenic Agar

Order Details

Product # Product Description
NCM1004A Harlequin Listeria Chromogenic Agar (Ottaviani & Agosti), 500 g
NCM1004B Harlequin Listeria Chromogenic Agar (Ottaviani & Agosti), 5 kg
NCM1004C Harlequin Listeria Chromogenic Agar (Ottaviani & Agosti), 10 kg
NCM1004D Harlequin Listeria Chromogenic Agar (Ottaviani & Agosti), 25 kg (European only size)
NCM1004E Harlequin Listeria Chromogenic Agar (Ottaviani & Agosti), 50 kg (US only size)

Reference Material

NCM1004 - Harlequin Listeria Chromogenic Agar (Ottaviani & Agosti), Safety Data Sheet [Danish] [Dutch] [English] [EU English] [Finnish] [French] [German] [Italian] [Spanish, Mexico] [Swedish]
NCM1004 - Harlequin Listeria Chromogenic Agar (Ottaviani & Agosti), Technical Specifications Sheet [English]

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