Harlequin® Listeria Chromogenic Agar (Ottaviani & Agosti) (LCA), 500g

Harlequin® 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 to diagnose diseases 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 a result of a chromogenic substrate for the detection of the β-glucosidase enzyme, common to all Listeria spp. and 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.

Combining both the chromogenic and phospholipase enzyme reactions makes it possible to differentiate Listeria monocytogenes (blue colonies surrounded by an opaque halo) from other Listeria spp. (blue colonies without an opaque halo).

LCA Agar forms part of Neogen’s innovative One Broth One Plate Listeria (OBOP-L) workflow that has been validated according to ISO 16140-2 and certified by AFNOR.

Typical Formulation

Formula Litre
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

Preparation

Suspend 70.5 g of the medium in 950 mL of purified water.
Heat with frequent agitation and boil for 1 minute to completely dissolve the medium.
Autoclave at 121°C for 15 minutes.
Cool to 45–50°C and add 2 vials of reconstituted NCM4002-0.5* supplement, each reconstituted using 5 mL of sterile deionized/RO water. Swirl to mix.
Add 2 vials of NCM4001-0.5* supplement (preheated to 48–50°C). Mix well with gentle end-overend mixing.

*Larger vials may be available. Please see the appropriate supplement data sheet for availability and preparation instructions.

Previous Item Number: This product was previously known as LabM Product: HAL010 Harlequin® Listeria Chromogenic Agar