Brilliant Green Bile Agar

Intended Use

Brilliant Green Bile Agar is used for isolating, differentiating and enumerating coliform bacteria.

Summary and Explanation

Noble and Tonney¹ described Brilliant Green Bile Agar for determining the relative density of coliform bacteria in water and sewage. The medium is particularly useful in selectively isolating Salmonella spp. from other coliform bacteria.

Principles of the Procedure

Brilliant Green Bile Agar contains peptone as a source of carbon, nitrogen, vitamins and minerals. Lactose is a fermentable carbohydrate. Oxgall (bile) and brilliant green inhibit gram-positive bacteria and most gram-negative bacteria except coliforms. Basic fuchsin and erioglaucine are pH indicators. Monopotassium phosphate is a buffering agent. Agar is the solidifying agent.
Differentiation of the coliforms is based on fermentation of lactose. Bacteria that ferment lactose produce acid and, in the presence of basic fuchsin, form deep red colonies with a pink halo. Bacteria that do not ferment lactose form colorless to faint pink colonies. Coliform bacteria typically ferment lactose, producing deep red colonies, while Salmonella spp., which do not ferment lactose, produce colorless to faint pink colonies.

User Quality Control

Identity Specifications
Brilliant Green Bile Agar
Dehydrated Appearance: Light purple, free-flowing, homogeneous (may
                                     contain small dark particles).
Solution:                        2.06% solution, soluble in purified water upon
                                     boiling. Solution is bluish-purple, slightly opalescent.
Prepared Appearance:    Blue with or without a tint of purple, slightly opalescent.
Reaction of 2.06%
Solution at 25°C:            pH 6.9 ± 0.2
Cultural Response
Brilliant Green Bile Agar
Prepare the medium per label directions. Inoculate using the pour plate technique and incubate at 35 ± 2°C for 18-24 hours.

Formula

Brilliant Green Bile Agar
Approximate Formula* Per Liter
Peptone......................................................................... 8.25 g
Lactose............................................................................ 1.9 g
Oxgall......................................................................... 2.95 mg
Sodium Sulfite............................................................ 205.0 mg
Ferric Chloride.............................................................. 29.5 mg
Monopotassium Phosphate............................................. 15.3 mg
Agar............................................................................. 10.15 g
Erioglaucine................................................................. 64.9 mg
Basic Fuchsin................................................................ 77.6 mg
Brilliant Green............................................................ 29.5 μg
*Adjusted and/or supplemented as required to meet performance criteria.

Directions for Preparation from Dehydrated Product

1. Suspend 20.6 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. Test samples of the finished product for performance using stable, typical control cultures.

Procedure

See appropriate references for specific procedures.^2,3

Expected Results

Refer to appropriate references and procedures for results.^2,3

Limitations of the Procedure

The medium is sensitive to light, particularly direct sunlight, which produces a decrease in the productivity of the medium and a change in color from deep blue to purple or red. The medium should be prepared just prior to use and, when necessary to store the medium, it should be kept in the dark. 

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