OGYE Agar Base

Intended Use

OGYE Agar Base is for use with the antimicrobial agent, oxytetracycline, in isolating and enumerating yeasts and molds in foods.

Summary and Explanation

Acidified agar may be used for enumerating yeasts and molds in foods and dairy products. However, in some cases, antimicrobics better suppress bacterial growth and improve recovery
of yeasts and molds.1,2
Mossel et al.3,4 described Oxytetracycline-Glucose Yeast Extract (OGYE or OGY) Agar for selectively isolating and enumerating yeasts and molds in foods. Mossel et al. demonstrated
improved recovery compared to acidified agar media.
OGYE Agar is specified as a standard methods medium for use with dairy products.1

Principles of the Procedure

OGYE Agar Base contains yeast extract to supply B-complex vitamins which stimulate growth. Dextrose is the carbon energy source. Agar is the solidifying agent. The addition of oxytetracycline inhibits the growth of bacteria.

User Quality Control

Identity Specifications
OGYE Agar Base
Dehydrated Appearance: Tan, free-flowing, homogeneous.
Solution:                       3.7% solution, soluble in purified water upon
                                    boiling. Solution is medium amber, very slightly
                                    opalescent.
Prepared Appearance:      Medium amber, slightly opalescent.
Reaction of 3.7%
Solution at 25°C:             pH 7.0 ± 0.2
Cultural Response
OGYE Agar Base
Prepare the medium per label directions (with the addition of oxytetracycline). Inoculate using the pour plate technique and incubate at 22 ± 3°C for 48-72 hours (up to 5 days if necessary).

Formula

OGYE Agar Base
Approximate Formula* Per Liter
Yeast Extract................................................................ 5.0 g
Dextrose.................................................................... 20.0 g
Agar.......................................................................... 12.0 g
*Adjusted and/or supplemented as required to meet performance criteria.

Directions for Preparation from Dehydrated Product

1. Suspend 37 g of the powder in 1 L of purified water. Mix thoroughly.
2. Heat with frequent agitation and boil for 1 minute to completely dissolve the powder.
3. Autoclave at 121°C for 15 minutes.
4. Aseptically add 100 mg of the antimicrobial agent, oxytetracycline, to the medium at 50°C. Mix well.
5. Test samples of the finished product for performance using stable, typical control cultures.

Procedure

See appropriate references for specific procedures.

Expected Results

Refer to appropriate references and procedures for results.

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