Oxoid - Product Detail

Brilliance™ E. coli/coliform Agar (formerly Chromogenic E. coli/coliform Agar) is a chromogenic medium to aid differentiation between Escherichia coli and other coliforms in cultures produced from food and environmental samples.

Typical Formula*	gm/litre
Chromogenic mix	20.3
Yeast extract	3.0
Peptone	5.0
Lactose	2.5
Sodium chloride	5.0
Di-sodium hydrogen phosphate	3.5
Potassium di-hydrogen phosphate	1.5
Neutral red	0.03
Agar	15.0
pH 7.0 ± 0.2 @ 25°C

* Adjusted as required to meet performance standards

Directions
Suspend 55.8g of Brilliance E.coli/coliform agar in 1 litre of distilled water. Sterilise by autoclaving at 121°C for 15 minutes. Cool to approximately 50°C. Mix well and pour and into sterile Petri dishes.

Description
Brilliance E.coli/coliform agar is a differential agar used for the presumptive identification of Escherichia coli and coliforms from food and environmental samples. The agar base uses two enzyme substrates to differentiate between Escherichia coli and other coliforms. One chromogenic substrate is cleaved by the enzyme glucuronidase, which is specific for Escherichia coli and produced by approximately 97% of strains^1,2,3. The second chromogenic substrate is cleaved by galactosidase, an enzyme produced by the majority of coliforms. This results in purple Escherichia coli colonies, as they are able to cleave both chromogenic substrates, and pink coliform colonies, as they are only able to cleave the galactosidase chromogen.

Technique
Dry the surface of the medium. Prepare the food sample by diluting as appropriate with 0.1% sterile peptone water (CM0009) and homogenise in a stomacher or laboratory blender. Pipette 0.5ml or 1.0ml of the homogenate, as appropriate, on to the plate, and spread over the surface with a glass spreader. Incubate the plates for 18-24 hours at 37°C.

Calculate the total number of coliforms per gram by multiplying purple and pink colonies by the dilution factor. The number of presumptive Escherichia coli is obtained by multiplying the number of purple colonies by the dilution factor.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C, and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Appearance
Dehydrated medium; Straw to straw/pink free flowing powder
Prepared medium; Opaque pink coloured gel.

Positive controls:	Expected results
Escherichia coli ATCC®25922*	Good growth; purple colonies
Klebsiella pneumoniae ATCC®13883*	Good growth; pink colonies
Negative control:
Pseudomonas aeruginosa ATCC®27853*	Good growth; straw colonies

* This organism is available as a Culti-Loop®.

Precautions
Refer to the material safety data sheet before handling this product.
Some pathogenic strains, typically Escherichia coli O157:H7 are usually glucuronidase negative and therefore will not give purple colonies on this medium.

References
1. Kilian M. and Bulow P. (1976). Acta. Pathol. Microbiol. Scand. Sect. B 84: 245-251.
2. Kilian M. and Bulow P. (1979). Acta. Pathol. Microbiol. Scand. Sect. B 87: 271-276.
3. Frampton E.W., Restaino L. and Blaszko N. (1988). J. Food Prot. 51(5): 402-404.