A sterile emulsion of egg yolks for use in bacteriological culture
edia. It may be added directly to nutrient media for the
their lipase and/or lecithinase activity.
Presented in 100ml bottles, add 100ml to
900ml of Bacillus cereusmedium, or 50ml to Blo
od Agar Base LAB 28 containing Fildes
extract and serum.
For detection of lecithinase activity (especially in the investigation of
`bitty cream’ conditions) add 0.5 or 1.0ml of the emulsion to 10ml of
sterile Blood Agar Base (LAB 28) or Nutrient
Broth No.2 (LAB 14).
In order to clear the medium, raise the final salt concentration by the
addition of 1% of sodium chloride. After incubation for up to 5 days
at 35ºC, lecithinase
producers render the broth opalescent, whilst, on
the solid medium, the c
olonies are surrounded by opaque zones.
Egg Yolk Tellurite Emulsion
A sterile egg yolk emulsion containing potassium tellurite for use in
Parker Medium (LAB 85). Baird
Parker Medium is widely
in the food industry for the detect
ion of pathogenic
Parker plates containing Egg Yolk Tellurite
Emulsion should be
protected from dehydration by storing in vapour
Add 50ml to 1 litre of Baird
Parker Medium LAB 85.
(50ml Egg Yolk Tellurite Em
ulsion contains the equivalent of 3ml of
potassium tellurite. This is the amount recommended for 1 litre
Parker Medium, i.e. concentration in X085 is 0.21% w/v.
concentration in Baird
Parker Medium is 0.01% w/v.)
Lactic Acid 10%
A sterile solution of 10% lactic acid added to culture media to reduce
the pH, in order to suppress bacterial growth.
Add 1 vial (5ml) to 1 litre of Malt Extract Agar LAB 37.
Add 2 vials (10ml) to 1 litre of Potato Dextrose Agar LAB 9
Addition of X037 should be carried out after sterilisation and cooling
the medium to 47ºC.
Potassium Tellurite Solution 3.5%
A sterile solution of 3.5% potassium tellurite. A selective agent for
addition to Hoyles’s Medium (LAB 27), fo
r the selective isolation
Add 1 vial (2ml) to 200ml of Hoyle’s Medium (LAB 27).