VetBact logo


Swedish University of Agricultural Sciences

Veterinary bacteriology: information about important bacteria
Veterinary bacteriology

Show all growth media

Brilliant Green (BG) agar

Brilliant Green (BG) Agar

The figure shows three BG agar plates. Bacteria were not cultivated on the plate in image A. On the plate in image B, Escherichia coli has been cultivated. Note that the colour of this plate has changed from yellowish-red to yellow where colonies appear and, therfore, the colonies appear as yellowish. Salmonella sp. has been cultivated on plate C. Note that the colour of this plate has changed from yellowish-red to dark red and that the colonies are pink. E. coli does only grow poorly on BG agar. - Click on the image to enlarge it.

Image: Karl-Erik Johansson (BVF, SLU) and Lise-Lotte Fernström (BVF, SLU).




Brilliant Green (BG) Agar is used for selective isolation of Salmonella spp.

Content of the medium:

  • Yeast extract
  • Enzymatic digest of casein
  • Enzymatic digest of animal tissue
  • NaCl
  • Lactose
  • Sucrose
  • Brilliant green
  • Phenol red
  • Agar

The enzymatic digests provide sources of nitrogen, amino acids and carbon. The yeast extract supplies vitamins required for growth of bacteria. NaCl maintains the osmotic balance of the medium. Lactose and sucrose are the carbohydrates in the medium. Brilliant green (BG) inhibits gram-positive bacteria and most gram-negative rods other than Salmonella spp. The pH is 6.9. Phenol red is the pH indicator, which turns the yellow upon acidification due to fermentation of lactose and/or sucrose. Agar is the solidifying agent.

Other comments:

  • Salmonella colonies appear as red to pink-white, because the agar around the colonies is red. However, the reddish tint can vary depending upon incubation time and strain.
  • Lactose- or sucrose fermenters, which are not inhibited by BG, form colonies, which appear to be yellowish and surrounded by a yellow-green zone, because of the pH change.
  • Colonies of other non-lactose and non-sucrose fermenters than salmonella, may be similar to salmonella colonies.
  • Salmonella enterica subsp. enterica, serovars Typhi and Paratyphi do not grew well on BG agar.

Updated: 2024-03-17.

Recently Updated

Recent blog posts

Swedish University of Agricultural Sciences