Appearance (Colour)
Cream
Appearance (Form)
Free flowing, homogeneous powder
Solubility
55.83 gm/liter
Solubility before autoclaving (Clarity)
Clear to slightly opalescent
Gel strength
Firm, comparable with 1.5% agar gel
pH (25°C)
6.8 ± 0.2
Prepared Medium Appearance after autoclaving (Clarity)
Clear to very slightly opalescent
Prepared Medium Appearance after autoclaving (Colour)
Light to medium amber
Cultural Response
Inoculate and incubate at 37 ± 2°C for 18 - 24 hours
Organism
Escherichia coli ATCC 25922
Inoculum (cfu) 10-100
Growth : Good
Recovery Rate : >=70.0%
Colony characteristics : Blue-dark violet colonies
Organism
Escherichia coli ATCC 8739
Inoculum (cfu) 10-100
Growth : Good
Recovery Rate : >=70.0%
Colony characteristics : Blue-dark violet colonies
Organism
Salmonella enteritidis ATCC 13076
Inoculum (cfu) 10-100
Growth : Good
Recovery Rate : >=70.0%
Colony characteristics : Colourless colonies
Organism
Enterococcus faecalis ATCC 29212
Inoculum
Growth : Inhibited
Applications
Differential medium recommended for presumptive identification of Escherichia coli and other coliforms in food and environmental samples.
Principle
Peptone and Yeast extract provides the nitrogenous sources of nutrition and other essential growth nutrients. Disodium phosphate and Potassium dihydrogen phosphate serves as buffering agents. Lactose is the fermentable carbohydrate source and Sodium chloride
maintains the osmotic equilibrium. Glucuronidase present in E coli, cleaves one of the chromogenic substrates to yield blue to violet colonies. The other chromogenic substrate is cleaved by majority of coliforms (due to activity of enzyme galactosidase) resulting in formation of rose-pink coloured colonies.
Composition
Ingredients
gm/lt.
Peptone
5.00
Yeast extract
3.00
Lactose
2.50
Disodium hydrogen phosphate
3.50
Potassium dihydrogen phosphate
1.50
Sodium chloride
5.00
Chromogenic mixture
14.50
Agar
15.00
Directions
1. Add 55.83 gm powder to 1.0 liter distilled/purified water.
2. Gently heat and bring to boiling.
3. Autoclave at 15 psi pressure at 121°C for 15 minutes.
