E.Coli & Coliforms Chromogenic Medium

Ingredients (g / L)

*Adjusted and/or supplemented as required to meet performance criteria.

Directions:

Suspend 52.2 g/L, boil in 1 minute, dispensing into flasks, at 121 ℃ autoclaving for 15 minutes, add 1mL prepared sample into a sterile in 9cm petri dish, transfer 15mL chromogenic medium when cooling down to 45-50 ℃, mix, inverted culture at 36 ± 1 ℃ for 18-24h after solidification

Or when cooling down to 45-50 ℃, pour into a sterile petri dish, after complete solidification, inverted culture at 37 ℃ in incubator for 1-2 hours, add 1mL uniform liquid sample with a suitable concentration, streak onto the medium , culture at 36 ± 1 ℃ for 18-24h.

Procedures:

1. Prepared sample solution according to national standards, SN standard, FDA standards or other methods.

2. Transfer 1mL sample onto chromogenic medium cooling down to 45-50 ℃, mix thoroughly or coating on plate;

3. Culture at 36 ± 1 ℃ for 18-24h, select the plate which have 200 to 300 typical colonies of E. coli and coliforms, total count of the colonies on the plate, typically E. coli colonies blue to purple, coliforms are pink, others yellow or colorless colonies.

4. For undermined colonies, streak them on nutrient agar plates, culture at 36 ± 1 ℃ for 12-16h, select single colony to do full set of E.Coli biochemical tests.

Quality Control:

1. Appearance:

The dehydrate powder medium is homogeneous, having good flowability, milky white, prepared medium is colorless solid.

2. Microbial sensitivity test:

Incubated at 36 ± 1 ℃ 18-24h:

Methods limitations:

The medium identification of E.Coli./Coliforms may occur false-positive in a few cases, but no false-negative, sometimes it needs to do other complementary tests

Typical features:

E.Coli typical colonies are blue to purple, coliforms colonies are pink, other bacteria are colorless or yellow colonies.

Storage:

The prepared plates must be used immediately, avoid direct exposure to light. The powder medium should be placed in a dark, dry place, storage temperature 2-8 ℃, avoid direct exposure to light.

Failure:

Dry powder media which are over the shelf life, caking and color variation cannot be used.

Note:

This medium is only for laboratory use.

Reference:

1. FRAMPTON, E.W., RESTAINO, L. a. BLASZKO, L.: Evaluation of ß-glucuronidase substrate  in a 24 hour direct plating method for Escherichia coli.  J. Food Protection, 51; 402-404 (1988).

2. KILIAN, M. a. BÜLOW, P.: Rapid diagnosis of Enterobacteriaceae. I. Detection of bacterial glycosidases.  Acta Pathol. Microbiol. Scand. Sect. B 84; 245-251 (1976).

3. LE MINOR, L. a. HAMIDA, F. BEN: Advantages de la recherche de la ßgalactosidase sur celle de la fermentation du lactose en milieu complexe dans le diagnostic bactériologique, en particulier des Enterobacteriaceae.  Ann. Inst. Pasteur (Paris), 102; 267-277 (1962).