Listeria Identification Agar Base 500g

About Listeria Identification Agar Base 500g

HiMedia's Listeria Identification Agar Base (PALCAM) is a selective culture medium used to isolate and identify Listeria species, particularly Listeria monocytogenes, from clinical and food samples. It contains lithium chloride and polymyxin for selective inhibition of other bacteria, an egg yolk emulsion to aid in the repair of damaged cells, and a dual-indicator system of esculin/ferric citrate and mannitol/phenol red to differentiate Listeria species. Listeria colonies appear grey-green with a black precipitate after incubation, and an overlay with blood can be used to detect hemolysis.
 Purpose:

• Selective Isolation:The agar base is designed to selectively grow Listeria species while inhibiting most other bacteria. 
• Identification:The dual indicator system helps differentiate between Listeria species and allows for the identification of L. monocytogenes. 
• Food Safety:It's particularly useful for isolating L. monocytogenes from food products and animal feeds, with performance standards in accordance with ISO 11290-2. 

Key Components and Mechanisms:

• Selective Agents (e.g., Polymyxin, Acriflavine, Lithium Chloride):These components suppress the growth of other microorganisms, creating a selective environment for Listeria. 
• Egg Yolk Emulsion:The addition of egg yolk is beneficial for the repair of damaged Listeria cells, which can occur in food samples. 
• Esculin & Ammonium Ferric Citrate:These react when esculin is hydrolyzed by Listeria, resulting in a black precipitate around the colonies, indicating a positive reaction. 
• Mannitol & Phenol Red:Listeria species fermenting mannitol produce acidic byproducts, causing a color change of the indicator from red to yellow around the colonies. 
• Blood Overlay (Optional):Overlaying the inoculated plates with sheep blood helps to identify haemolytic Listeria species by showing a zone of clearing around the colonies. 

Growth Characteristics:

• Upon incubation at 35-37C for 24-48 hours, Listeria colonies appear grey-green with a black precipitate, indicating esculin hydrolysis. 
• When a blood overlay is added, haemolytic Listeria species will show a zone of clearing around the colonies.