Oxytetracycline-Glucose-Yeast Extract Agar Base

(O.G.Y.E.)

LAB 89

Description

A selective medium for the enumeration of yeasts and moulds in food, introduced by Mossel in 1970. Unlike many selective media for yeasts O.G.Y.E. has a neutral pH and it has been shown to give better recovery rates than those media with a low pH. Oxytetracycline is used to inhibit bacteria, certain high protein foods may reduce the effectiveness of this antibiotic as a selective agent. Rose Bengal Chloramphenicol LAB 36 is recommended in these instances.

Method for reconstitution

Weigh 37 grams of powder, disperse in 1 litre of deionised water. Allow to soak for 10 minutes, swirl to mix then sterilise by autoclaving at 115˚C for 10 minutes. Cool to 47˚C and aseptically add two vials of X089 Oxytetracycline selective supplement. Mix thoroughly and pour into Petri dishes.

Appearance: Pale yellow, clear.

pH: 7.0 ± 0.2

Minimum Q.C. organisms: Aspergillus sp. NCIMB 50097 Saccharomyces cerevisiae

Storage of Prepared Medium: Plates - up to 7 days at 2-8˚C in the dark. Capped containers - up to 1 month at 4˚C in the dark.

Inoculation: Surface spreading or pour plate.

Incubation: 25˚C aerobically for 5 days.

Growth Characteristics

Tetracycline resistant bacteria may grow, colonial morphology dependent upon species.

References

Mossel, D.A.A. et al. (1970). O.G.Y.E. for Selective Enumeration of Moulds and Yeast in Foods and Clinical Material. J. Appl. Bact. 35: 454-457.

Banks, J.G., Board, R.G. (1987). Some factors influencing the recovery of yeasts and moulds from chilled foods. Int. J. Food Microbiol. 4: 197-206.