Coliforms Chromogenic Medium is used for fast, accurate detection of coliforms in food, water, milk, ice cream and meat, culture for 24 hours, the colonies of coliforms are blue-green, other bacteria are yellow or colorless, gram-positive bacteria are inhibited.

Ingredients (g/L):

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

Directions:

Suspend 47.9g of the medium in 1L of distilled water, 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 30 to 200 typical colonies of E. coli, total count of the colonies on the plate, typically E. coli colonies blue-green, 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 BGLB Fermentation 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 Coliforms may occur false-positive in a few cases, but no false-negative, sometimes it needs to do other complementary tests

Typical features:

Coliforms typical colonies are blue-green, coliforms colonies are colorless, 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.: evalsuation 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).