(AB) Oxford Listeria Agar, 500 grams

Curtis et al. formulated Oxford Medium Base for the selective isolation of Listeria from mixed cultures. The USDA has recently recommended this medium for the isolation of Listeria monocytogenes from processed meats and poultry products. Listeria hydrolyze esculin to 6,7-dihydro-coumarin which in turn reacts with ferric ions in the medium to give black colonies. Lithium chloride and added antibiotics are incorporated in the medium to suppress the growth of Gram positive cocci as well as Gram negative rods. Oxford Listeria Agar, with addition of antibiotics, is used for the selective isolation of Listeria monocytogenes from food. (Alpha Biosciences # O15-102-500gm)

Use: Oxford Listeria Agar, with addition of antibiotics, is used for the selective isolation of Listeria monocytogenes from food.

Description: Curtis et al. formulated Oxford Medium Base for the selective isolation of Listeria from mixed cultures. The USDA has recently recommended this medium for the isolation of Listeria monocytogenes from processed meats and poultry products. Listeria hydrolyze esculin to 6,7-dihydro-coumarin which in turn reacts with ferric ions in the medium to give black colonies. Lithium chloride and added antibiotics are incorporated in the medium to suppress the growth of Gram positive cocci as well as Gram negative rods.

Formula* per Liter:

• Casein Digest Peptone .......... 3.0g
• Pancreatic Digest of Animal Tissue..... 5.0g
• Beef Extract .............................. 3.0g
• Sodium Chloride .................................... 5.0g
• Glycine ..................................... 10.0g
• Lithium Chloride ..................................... 0.5g
• Agar ..........................................15.0g
• Phenylethyl Alcohol ................................ 2.5g

Final pH: 7.3 ± 0.2 at 25.0°C

* Grams per liter may be adj. or formula supplemented to obtain desired performance

Preparation: Mix 46 grams of medium in a Liter of purified water. Heat with repeated stirring and boil for one minute to dissolve completely. Sterilize by autoclaving for 15 minutes at 121.0°C. Cool to 45.0°C and pour into sterile Petri dishes.

Quality Control Specifications:

1. The powder is homogeneous, free flowing and light beige.
2. Visually the prepared medium is light to medium beige and slightly hazy.
3. Expected cultural response after 24-48 hours at 35.0°C.

Organism                                                                             Result

Escherichia coli ATCC 25922                                              Inhibited

Listeria monocytogenes ATCC 7644                                    Growth

Staphylococcus aurous ATCC 25923                                  Inhibited

Storage: Store the sealed bottle containing the dehydrated medium at 2 to 8.0°C. Once opened and recapped, place the container in a low humidity environment at the same storage temperature. Protect it from moisture and light. The dehydrated medium should be discarded if it is not free flowing or if the color has changed from the original light beige color.