Egg yolk tellurite emulsion

Egg-yolk tellurite emulsion is a stabilized emulsion of egg yolk for microbiological use, which is added directly to nutrient media for the identification of strains of coagulase-positive Staphylococci by their lecithinase activity. Potassium tellurite has a selective activity and allows the growth of Staphylococcus as black colonies. Egg-yolk permits the detection of microbial lecithinase activity and tellurite reduction.

Egg-yolk tellurite emulsion is an additive consisting of an emulsion of egg-yolk used as a supplement to prepare Baird Parker agar base medium for the detection of Staphylococcus.

Appearance: pale yellow emulsion
Sterility test: sterile
Typical composition: Sterile egg-yolk 200 ml; NaCl 4.25 g; potassium tellurite 2.1 g; distilled water to give a final volume of 1000 ml.
Egg-yolk Tellurite Emulsion tested in BAIRD-PARKER-Agar Art. 1.05406.
Inoculum on reference medium
- Staphylococcus aureus ATCC 25923 (WDCM 00034):
10 - 100
- Staphylococcus aureus ATCC 6538 (WDCM 00032): 10 - 100
Inoculum
- Escherichia coli ATCC 25922 (WDCM 00013):
>10⁴
- Escherichia coli ATCC 8739 (WDCM 00012): >10⁴
- Staphylococcus saprophyticus ATCC 15305 (WDCM 00159): >10⁴
- Staphylococcus epidermidis ATCC 12228 (WDCM 00036): >10⁴
Recovery on test medium
- Staphylococcus aureus ATCC 25923 (WDCM 00034):
≥ 70%
- Staphylococcus aureus ATCC 6538 (WDCM 00032): ≥ 70%
Growth
- Escherichia coli ATCC 25922 (WDCM 00013):
no growth
- Escherichia coli ATCC 8739 (WDCM 00012): no growth
- Staphylococcus saprophyticus ATCC 15305 (WDCM 00159): poor to fair
- Staphylococcus epidermidis ATCC 12228 (WDCM 00036): poor to fair
Colony colour
- Staphylococcus aureus ATCC 25923 (WDCM 00034):
black
- Staphylococcus aureus ATCC 6538 (WDCM 00032): black
- Staphylococcus saprophyticus ATCC 15305 (WDCM 00159): black-grey
- Staphylococcus epidermidis ATCC 12228 (WDCM 00036): black-grey
Clear zones
- Staphylococcus aureus ATCC 25923 (WDCM 00034):
+
- Staphylococcus aureus ATCC 6538 (WDCM 00032): +
- Staphylococcus saprophyticus ATCC 15305 (WDCM 00159): -
- Staphylococcus epidermidis ATCC 12228 (WDCM 00036): -
Incubation: 24 - 48 hrs. at 37°C, E.coli: 48 hrs. Reference: Tryptic soy agar.

Replaces: 1.03785.0007

Strain origin: CECT^® 4972

Other cell culture collections:

DSM 17076

ATCC^® 700728

NCTC 12900

ATCC is a registered trademark of American Type Culture Collection

CECT is a registered trademark of Universitat de Valencia