BISMUTH SULFITE AGAR - BS

Specifications

Ingredients Gms/Ltr :
Agar 20.00
Peptone 10.00
Bismuth sulphite 8.00
Beef extract 5.00
Dextrose 5.00
Disodium phosphate 4.00
Ferrous sulphate 0.30
Brilliant Green 0.025
* Dehydrated powder, hygroscopic in nature, store in a dry place, in tightly-sealed containers below 25°C
and protect from direct Sunlight.

Instructions for Use :
Dissolve 52.3gms in 1000ml of distilled water. Gently heat to boiling with gentle swirling and dissolve the
medium completely. DO NOT AUTOCLAVE. Cool to 45-50°C prior to dispense.
Appearance: Greenish yellow colour, solution opalescent with flocculent precipitate
pH (at 25°C): 7.7 ± 0.2

Principle :
BISMUTH SULPHITE AGAR is used for the selective isolation of Salmonella spp. Salmonella constitute
the most taxonomically complex group of bacteria among Enterobacteriaceae. Bismuth Sulphite Agar is a
modification of Wilson and Blair formula. Also this medium favors use of larger inoculum as compared
to other selective media, as it has unique inhibitory action towards gram-positive organisms and
coliforms. Peptone and Beef extract serve as sources as carbon, nitrogen, vitamins and essential growth
factors. Disodium phosphate acts as a buffereing agent. Dextrose is a fermentable carbohydrate source of
the growth of microorganisms. Bismuth Sulphite Indicator and Brilliant Green are complementary,
inhibiting to Gram-positive bacteria and coliforms, allowing Salmonella spp. to grow. Ferrous Sulphate is
used for H2S production. When H2S is present, the iron incorporated in medium is precipitated, and
positive cultures produce the characteristic brown to black color with metallic sheen. Agar is the
solidifying agent.