Description
General description
Listeria agar acc. OTTAVIANI and AGOSTI contains the chromogenic compound 5-bromo-4-chloro-3-indolyl-β-D-glucopyranoside, which is a substrate for the detection of β-glucosidase. This enzyme is common in all Listeria that appears as blue-green colored colonies on the medium. Differentiation of Listeria monocytogenes from non-pathogenic Listeria sp. is achieved through the production of a phosphatidylinositol-specific phospholipase C (PI-PLC). Listeria monocytogenes hydrolyses the specific purified substrate added to the medium producing an opaque halo around the colonies. Most Listeria ivanovii also produce an opaque halo around the colonies after 48 h incubation. The inhibitors in the medium reduce the growth of the majority of concomitant gram-positive and gram-negative pathogens, as well as of yeasts and fungi. Agar is the solidifying agent, while lithium chloride, nalidixic acid, and cycloheximide provide selectivity.
Listeria Agar can be prepared by the addition of ChromoCult® Listeria Agar Selective-Supplement (1.00432) and ChromoCult® Listeria Agar Enrichment-Supplement (1.00439).
Application
ChromoCult® Listeria agar (base) is used for the isolation and differentiation of Listeria monocytogenes and other Listeria sp. from food and animal feed, environmental samples in the area of food production and food handling, and other materials.
Analysis Note
Appearance (colour): yellowish
Appearance (clearness): slightly opalescent to opalescent
pH-value (25 °C): 7.0 - 7.4
Growth promotion test in accordance with the current version of DIN EN ISO 11133.
Inoculum on reference medium (Listeria monocytogenes ATCC 13932 (WDCM 00021)):
Colony count (Listeria monocytogenes ATCC 13932 (WDCM 00021)):
Recovery on test medium (Listeria monocytogenes ATCC 13932 (WDCM 00021)): ≥ 50 %
Colonies (Listeria monocytogenes ATCC 13932 (WDCM 00021)): blue green colonies with opaque halo
Inoculum on reference medium (Listeria monocytogenes ATCC 35152 (WDCM 00109)):
Colony count (Listeria monocytogenes ATCC 35152 (WDCM 00109)):
Recovery on test medium (Listeria monocytogenes ATCC 35152 (WDCM 00109)): ≥ 50 %
Colonies(Listeria monocytogenes ATCC 35152 (WDCM 00109)): blue green colonies with opaque halo
Growth (Listeria innocua ATCC 33090 (WDCM 00017)): no limit
Colonies (Listeria innocua ATCC 33090 (WDCM 00017)): blue green colonies without opaque halo
Growth (Escherichia coli ATCC 8739 (WDCM 00012)): total inhibition
Growth (Escherichia coli ATCC 25922 (WDCM 00013)): total inhibition
Growth (Enterococcus faecalis ATCC 19433 (WDCM 00009)): total inhibition
Growth (Enterococcus faecalis ATCC 29212 (WDCM 00087)): total inhibition
Incubation: 44 ± 4 hours at 37 ± 1 °C
Reference media: Tryptic Soy Agar
A recovery rate of 50 % is equivalent to a productivity value of 0.5.
The indicated colony counts result from the sum of a triple determination.
Legal Information
CHROMOCULT is a registered trademark of Merck KGaA, Darmstadt, Germany
