Coliform Chromogenic Medium

Usages:
For the rapid detection and enumeration of coliform bacteria.
 
Principle:
Peptone and yeast extract powder provides carbon and nitrogen sources and traces elements; sodium chloride maintains osmotic equilibrium; agar as medium coagulant; dodecyl sulfate inhibits Gram-positive bacteria; chromogenic substrate and large intestine flora β- galactosidase-glucosidase specific reaction, hydrolysis of the substrate, the release of the colour groups produce green colonies on the light yellow plate.
 
Formulation (per litre):
Peptone:10g
Yeast extract powder: 3g
sodium chloride:5g
sodium lauryl sulfate:0.1g
Agar:12g
Chromogenic substrate 2.7g
Final pH 7.0 ± 0.2
 
How to use:

1. Suspend 32.8g of this product, adding 1L of distilled or deionized water, heated to boiling stirring until completely dissolved, dispensing into flask without autoclaving.
2. Take 25g or 25mL of the sample with aseptic procedures, added to the flask containing 225mL of sterile phosphate-buffered saline (or saline) which is shaken thoroughly homogenized with a homogenizer for 1min into a 1:10 dilution, then continue to make for 1:10 dilution. select 3 of appropriate serial dilutions, each dilution was inoculated for 2 plates.
3. Pouring method: Cooled in a water bath to about 50^oC, sterilized petri dish having a diameter of 90mm, 1ml samples were inoculated per dish, then poured into about 15ml of the above dissolution medium, and mix to solidify, cultivating at 37^oC for 24 hours.
4. Using surface inoculation: cooled to about 50^oC, shake devoted to the medium in a sterile petri dish. stored in the refrigerator for a day or stored at room temperature for several days (dark, 4^oC). The sample was collected via streaked method or filter method, cultivating 37^oC for 24 hours.
5. Observe the results.

 
Quality control:
This product appears light yellow after pouring into the plate, these strains were inoculated after 36 ± 1 ? 18 ~ 24h culture growth in the following table.

Strains codes	Growth of bacteria	Features
Escherichia coli (ATCC25922)	Good	Green colonies
Citrobacter (ATCC8090)	Good	Green colonies
Salmonella Typhimurium (CMCC50115)	Good	Colourless colonies
Enterococcus faecalis (ATCC29212)	Suppressed	-

Storage: Keep container tightly closed, store in a cool, dry place, away from bright light.