Thermo ScientificTM OxoidTM Egg Yolk Emulsion

A stabilised emulsion of egg yolk for use in culture media. It may be added directly to nutrient media for the identification of Clostridium, Bacillus and Staphylococcus species by their lipase activity.

Egg Yolk Emulsion, Oxoid Directions:
Suspend 21.5g of MYP Agar (CM0929) in 450ml of distilled water and bring gently to the boil to
dissolve. Sterilize by autoclaving at 121°C for 15 minutes. Cool to approximately 50°C and
aseptically add 50ml of Egg Yolk Emulsion (SR0047C) and the contents of one vial of Polymyxin B
Supplement (SR0099E) reconstituted as directed. Mix well and pour into sterile Petri dishes.
Alternatively, suspend 8g of Blood Agar Base (CM0055) in 200ml of distilled water and add 2g of
sodium chloride. Sterilize by autoclaving at 121°C for 15 minutes. Cool to approximately 50°C and
aseptically add 20ml Egg Yolk Emulsion (SR0047C). Mix well and pour into sterile Petri dishes.

Storage conditions and Shelf life
Keep at temperatures between 2° and 8 °C. Use before expiry date on the label.

Precautions
On this medium Bacillus cereus is indistinguishable from Bacillus thuringiensis.
Identify Bacillus cereus by colony form, colour, egg yolk hydrolysis and confirm with cell and spore morphology.
Occasional strains of Bacillus cereus show weak or negative egg yolk reactions.