Brilliant Green Agar with Sulfadiazine

Peptic digest of animal tissue provides nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is a source of vitamins, particularly the B-group. Sucrose and lactose are fermentable carbohydrates providing carbon and energy. Phenol red is the pH indicator, turning the medium a yellow color with the formation of acid as a result of lactose/sucrose fermentation. Brilliant green inhibits Gram-positive bacteria and most Gram-negative bacilli other than Salmonella spp. Lactose/sucrose fermenters are usually inhibited. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Sulfadiazine makes the medium more selective. Bacteriological agar is the solidifying agent.

When there is a suspicion that the material under study contains low concentrations of salmonellae, it is necessary to initially inoculate the sample in Brilliant Green Tetrathionate Broth (LC-1253) or Selenite Cystine Broth (LC-1220) as a pre-enrichment step.

As this medium is very inhibitory it allows for moderately heavy inocula, which should be evenly distributed on the surface of the medium.

Typical formula in g/L, adjusted and/or supplemented as required to meet performance criteria.

Preparation

Suspend 58.2 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Sterilize in autoclave at 121 °C for 15 minutes. Cool to 45-50 °C, mix well and dispense into plates.

Instructions for use

1. Inoculate and incubate at 35 ± 2 °C for 18-24 hours.
2. At the same time, inoculate other selective media that are less inhibitory, such as Desoxycholate Agar (LC-1020), Salmonella Shigella Agar (LC-1064), XLD Agar (LC-1274), MacConkey Agar (LC-1052), EMB Agar (LC-1050) or Hektoen Enteric Agar (LC-1030).
3. The medium changes to red during incubation at 35-37 °C.
4. Confirm by transferring a few of the suspect colonies to TSI (LC-1046).

• American Public Health Association. Standard Methods for the Examination of Water and Wastewater, 11th Edition APHA, New York, 1960.
• American Public Health Association. Recommended Methods for the Microbiological Examination of Foods, APHA, Inc. New York, 1958.