BiGGY Agar

Intended Use

BiGGY (Bismuth Sulfite Glucose Glycine Yeast) is a selective and differential medium used in the detection, isolation and presumptive identification of Candida species.

Summary and Explanation

BiGGY Agar is based on the formulation of Nickerson.1 Nickerson developed the medium in 1953 following a study of sulfite reduction by Candida species.
Differentiation of Candida is based on growth patterns and pigmentation of isolated colonies. The bismuth sulfite acts as an inhibitory agent to suppress bacterial growth, which enables the recovery of isolated colonies of Candida. Candida species reduce the bismuth sulfite, resulting in pigmentation of colonies and, with some species, pigmentation in the surrounding medium.

Principles of the Procedure

Candida species, through a process of substrate reduction, produce sulfide and bismuth which combine to produce brown to black pigmented colonies and zones of dark precipitate in the medium surrounding colonies of some species. Dextrose and yeast extract provide the nutrients in the formulation. NOTE: A decrease in pH is normal and does not affect performance.

User Quality Control

Identity Specifications
BiGGY Agar
Dehydrated Appearance: Medium fine, homogeneous, free of extraneous
                                     material.
Solution:                        4.5% solution, soluble in purified water upon
                                     boiling. Solution is light to medium, cream yellow,
                                     hazy to cloudy.
Prepared Appearance:    Light to medium, cream yellow, hazy to cloudy.
Reaction of 4.5%
Solution at 25°C:           pH 6.8 ± 0.2
Cultural Response
BiGGY Agar
Prepare the medium per label directions. Inoculate with fresh cultures and incubate at 25 ± 2°C for 18-24 hours (3-5 days if necessary).

Formula

BiGGY Agar
Approximate Formula* Per Liter
Bismuth Ammonium Citrate........................................... 5.0 g
Sodium Sulfite.............................................................. 3.0 g
Dextrose.................................................................... 10.0 g
Glycine....................................................................... 10.0 g
Yeast Extract................................................................ 1.0 g
Agar.......................................................................... 16.0 g
*Adjusted and/or supplemented as required to meet performance criteria.

Directions for Preparation from Dehydrated Product

1. Suspend 45 g of the powder in 1 L of purified water. Mix thoroughly.
2. Heat with frequent agitation and boil for not more than 1 minute to completely dissolve the powder. DO NOT AUTOCLAVE.
3. Cool to approximately 45-50°C. Swirl to disperse the insoluble material and pour into plates.
4. Test samples of the finished product for performance using stable, typical control cultures.

Procedure

Consult appropriate references for information about the processing and inoculation of specimens such as tissues, skin scrapings, hair, nail clippings, etc.^2-5 The streak plate technique is used primarily to obtain isolated colonies from specimens containing mixed flora. When using slants, streak the surface of the slant with a sterile inoculating loop needle using two to three isolated colonies.
Incubate plates in an inverted position (agar side up) for up to 5 days at 25 ± 2°C.

Expected Results

Within 5 days of incubation, the plates should show isolated colonies in streaked areas and confluent growth in areas of heavy inoculation. Slants should show evidence of growth.
Examine plates and slants for colonies showing characteristic growth patterns and morphology. The following table summarizes typical Candida colonial morphology.⁶

Limitations of the Procedure

1. The test organism used for inoculating an assay medium must be cultured and maintained on media recommended for this purpose.
2. For successful results of these procedures, all conditions of the assay must be followed precisely.
3. Aseptic technique should be used throughout the assay procedure.
4. The use of altered or deficient media may cause mutants having different nutritional requirements that will not give a satisfactory response.

*Store at 2-8° C.

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