Selective isolation of coagulase positive Staphylococci in food.
Description:
Baird-Parker modified the Tellurite Glycine Medium of Zebovitz, Evans and Niven. It is recommended for microbial limit tests by the USP. Potassium Tellurite and Lithium Chloride selectively suppresses the growth of most bacteria but allows the growth of Staphylococcus aureus. The addition of pyruvate and glycine enhances the growth of Staphylococci. The differentiation of coagulase-positive staphylococci is noted by the reduction of Potassium Tellurite which results in a black colony. Staphylococcus that contain lecithinase break down the egg yolk and cause a clear zone. An opaque zone may be formed due to lipase activity.
Components:
Shown as g/liter
Casein Digest Peptone 10.0
Lithium Chloride 5.0
Beef Extract 5.0
Agar 17.0
Yeast Extract 1.0
Glycine 12.0
Sodium Pyruvate 10.0
Total: 60g/liter
Directions:
Dissolve 60g. in 800ml of ddH2O, heating to boiling with stirring until completely solubilized. Dispense into appropriate containers, loosen caps and autoclave for 15-30 minutes at 121C (15 psi). After cooling to 45-50 degrees C add 10ml of a sterile I% Potassium Tellurite solution and 50ml of sterile egg yolk emulsion.
Storage and Stability:
Store powdered media at RT. Opened bottles should be capped tightly and kept in a dark, low humidity environment. Prepared media should be kept refrigerated and used within a short period of time.