BILE CHRYSOIDINE GLYCEROL AGAR BASE (GCG AGAR)
CAT Nº: 2041
For the isolation and differentiation of Enterobacteria
and several gram negative aerobic bacteria
FORMULA IN g/l
Meat Peptone
10.00
Ferric Ammonium Citrate
2.00
Ox Bile
8.00
Sodium Thiosulfate
0.65
Yeast Extract
5.00
Bromothymol Blue
0.12
Sodium Chloride
5.00
Chrysoidine
0.025
Casein Peptone
2.00
Bacteriological Agar
10.00
Final pH 7.5 ± 0.2 at 25ºC
PREPARATION
Suspend 42.8 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. DO NOT AUTOCLAVE. Dissolve 1 gram of urea in 20 ml of
glycerol and add it aseptically. The prepared medium should be stored at 8-15°C. The color is green.
The dehydrated medium should be homogeneous, free-flowing and beige in color. If there are any physical changes,
discard the medium.
USES
BILE CHRYSOIDINE GLYCEROL AGAR BASE (GCG AGAR) is used for the isolation and differentiation of Enterobacteria
and several gram negative aerobic bacteria due to different biochemical reactions that allows the differentiation of a
larger variety of colonies.
Meat peptone and Casein peptone provide nitrogen, vitamins, minerals and amino acids essential for growth. Sodium
chloride supplies essential electrolytes for transport and osmotic balance. Yeast extract is source of vitamins, particularly
the B-group. Sodium thiosulfate provides Sulphur and Ferric ammonium citrate is the indicator for H2S production. H2S
positive colonies are black-centered. Urea is a source of nitrogen for those organisms producing urease. When urea is
degraded to urease, alkaline products will occur (green to blue green coloration). When glycerol is used, acid will be
formed (yellow coloration).
Inoculate and incubate at 36 ± 1°C for 18-24 hours.
MICROBIOLOGICAL TEST
The following results were obtained in the performance of the medium, with glycerol and egg added, after incubation at
a temperature of 36 ± 1°C and observed after 18-24 hours.
CFU/Plate
Recovery
%
Escherichia coli ATCC 8739
10 - 100
≥ 50
Pseudomonas aeruginosa ATCC 9027
10 – 100
≥ 50
Citrobacter freundii ATCC 8090
10 - 100
≥ 50
Salmonella typhimurium ATCC 13311
10 - 100
≥ 50
Microorganisms
Colony Appareance
Large greenish-yellow. Culture medium
unchanged
Dark green to bluish green. Surrounding culture
medium dark green
Yellow with a black center. Surrounding culture
medium light yellow
Greenish- yellow with light black center.
Surrounding culture medium greenish yellow
1
LABORATORIOS CONDA, S.A.
www.condalab.com
Enterobacter faecalis ATCC 29212
10 - 100
≥ 50
Enterococcus durans ATCC 10541
10 -100
≥ 50
Proteus mirabilis ATCC 25933
10 - 100
≥ 50
Shigella flexnerii ATCC 29929
10 -100
≥ 50
Acinetobacter amitrans ATCC 19606
10 - 100
≥ 50
Staphylococcus aureus ATCC 25923
100 -1000
Inhibited
Whitish – yellow. Surrounding culture medium
light yellow
Whitish – yellow. Surrounding culture medium
may turn to light yellow
Greenish – yellow with black center. Swarming
inhibited. Surrounding culture medium green
Greenish – yellow. Surrounding culture medium
green
Green. Surrounding culture medium green
Small, whitish –grey, opaque. Surrounding culture
medium unchanged
BIBLIOGRAPHY
Ziesché, K. et al. (1985) Der Galle-Chrysoidin-Glycerol (GCG)-Nährboden in seiner Anwendung zur Diagnostik gramnegativer aerober
Bakterien, besonders der Enterobacteriaceae. Zeitschr. Gesamte Hygiene 31: 516-
STORAGE
25ºC
Once opened keep powdered medium closed to avoid hydration.
2ºC
2
LABORATORIOS CONDA, S.A.
www.condalab.com