BRILLANT GREEN BILE AGAR

Specifications

Ingredients Gms/Ltr :
Agar 10.15
Peptic digest of animal tissue 8.25
Lactose 1.90
Sodium sulphite 0.205
Ferric chloride 0.0295
Monopotassium phosphate 0.0153
Erioglaucine 0.0649
Basic fuchsin 0.0776
Brilliant green 0.0295
Oxbile 0.00295
* 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 20.70gms in 1000ml distilled water. Gently heat to boiling with gentle swirling and dissolve the
medium completely. Allow to stand for 5-10 minutes so that the agar hydrates correctly. Sterilize by
autoclaving at 15 psi (121°C) for 10 minutes. Cool to 45 - 50°C and pour into sterile Petri plates.
Appearance: Blue to purple colour, clear slightly opalescent gel
pH at 25°C: 6.9 ± 0.2

Principle
BRILLIANT GREEN BILE AGAR is used for enumeration of coliform bacteria in water and foods. It
uses Basic fuchsin to differentiate between positive lactose-fermenting and lactose-non-fermenting
bacteria. The Peptic digest of animal tissue provides the essential nutrients for growth: nitrogen,
vitamins, minerals and amino acids. Lactose is the fermentable carbohydrate providing carbon and
energy. Ox bile and Brilliant green inhibit Gram-positive bacteria and most Gram-negative bacteria
except Coliforms. Acetaldehyde production by lactose-fermenting organisms, such as E.coli, produce
characteristic red colonies with a pink surrounding area, marked by its reaction with Sodium sulphite in
the presence of Basic fuchsin, a pH indicator. Lactose non-fermenters form colorless, transparent colonies.
For the enumeration of coliform bacteria employ sample dilutions, which yield between 10 - 50 colonies
per plate using the pour plate method. Therefore, several dilutions should be made in the melted
medium, poured and once gelled, incubated at 35 ± 2°C for 18 - 24 hours. The coliform colonies have an
intensely red center zone surrounded by a pink halo sharply outlined against the uniformly blue
background of the medium. Salmonella spp. which do not ferment Lactose, produce colorless to pale pink
colonies. The medium is sensitive to light, which reduces its effectiveness and changes its color from
strong blue to purple or pink. The medium should be prepared immediately before use and, if necessary,
stored in the dark for as little time as possible.