Liofilchem® Listeria Oxford Agar Base (ISO 11290), 500g

Listeria Oxford Agar Base (ISO 11290) from Liofilchem® is a dehydrated basal culture medium formulated for the isolation and presumptive identification of Listeria monocytogenes in food, dairy, environmental, and animal feeding stuff samples, in compliance with ISO 11290 standards.

The medium is supplied without antibiotics and acriflavine, allowing laboratories to customize selectivity through the addition of the appropriate Listeria Oxford selective supplement.

Principle of the Medium

Listeria Oxford Agar Base supports the growth of Listeria species while enabling differentiation based on esculin hydrolysis:

• Tryptone, peptone, meat extract, and yeast extract provide essential nutrients, amino acids, vitamins, and growth factors.
• Sodium chloride maintains osmotic balance.
• Starch acts as a protective agent against toxic substances and provides a minor energy source after hydrolysis.
• Lithium chloride contributes to selectivity by inhibiting competing flora.
• Esculin and ammonium ferric citrate allow presumptive identification:
  Listeria species hydrolyze esculin to esculetin, which reacts with ferric ions to produce black or brown halos around colonies.
• Agar serves as the solidifying agent.

The addition of Listeria Oxford Supplement introduces selective agents (cefotetan, phosphomycin, colistin, cycloheximide, acriflavine) that suppress contaminating bacteria and fungi.

Typical Colony Appearance

• Listeria monocytogenes: Grey-brown colonies with a distinct brown to black halo, typically convex in shape.

Preparation

1. Suspend 60.0 g of powder in 1 liter of distilled or deionized water.
2. Heat to boiling with agitation until completely dissolved.
3. Autoclave at 121 °C for 15 minutes.
4. Cool to 45–50 °C.
5. Aseptically add Listeria Oxford Supplement as specified.
6. Mix well and pour into sterile Petri dishes.

Applications

• Detection of Listeria monocytogenes in food products
• Dairy, meat, and ready-to-eat food testing
• Environmental monitoring in food processing facilities
• Public health and regulatory microbiology
• Quality control laboratories

Quality Control Performance

Product Specifications

• Final pH: 7.3 ± 0.1
• Appearance: Clear medium, dark amber in color
• Shelf Life: 4 years
• Storage: 10–30 °C, protected from light

Packaging Options

Standards & Compliance

• ISO 11290-1: Detection of Listeria monocytogenes
• TIL-IDF (1988): Milk and milk products – Listeria detection

Liofilchem® Listeria Oxford Agar Base (ISO 11290) is a reliable, standardized basal medium for the isolation of Listeria monocytogenes. When combined with the appropriate selective supplement, it provides high selectivity, clear differentiation, and compliance with international food safety standards, making it an essential medium for food, environmental, and public health microbiology laboratories.