Bacillus Cereus Chromogenic Medium (Generation Ⅲ) is used for the rapid detection of Bacillus cereus in food, water, dairy products and meat products. Improved chromogenic reagents and additives have enhanced specificity and sensitivity significantly. The colonies of Bacillus cereus are blue-green and have an opaque ring around, other bacteria are blue-green, yellow or colorless, Gram-negative bacteria are inhibited.

Ingredients (g/L):

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

Directions:

Suspend basal medium 7.95g in 180mL of distilled water; add Bacillus cereus additive 0.6g and 20ml of sterile water, put into some glass balls, constant vibrating for 5-10min to emulsify uniformly, autoclave the above two at 121 ℃ for 15min. When cooling to about 45-50 ℃,add the Bacillus cereus additive into basic medium, and mix thoroughly, pour into sterile petri dishes. Make the medium thickness is about 1-2mm, so advantageous to observe opaque ring.

Procedures:

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

2. Enrichment culture for the samples solution at 30 ± 1 ℃ for 18- 24 hours.

 Transfer 25g sample solution into 225mL GN Broth or Shigiella Broth, enrichment culture for 18- 24hours at 36 ± 1 ℃;

3. Take enrichment broth streak to inoculate Bacillus Cereus Chromogenic Medium (Generation Ⅲ), culture at 36 ± 1 ℃ for 18- 24 hours, the typical colonies of Bacillus cereus are blue-green and have an opaque ring around, if not so in 24 hours, culture for 48 hours.

4.  For undetermined colonies, streak on nutrient agar plate, culture for 18- 24hours at 36 ± 1 ℃, select single colony to do full set of 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 identification of Bacillus cereus medium, sometimes there may be a false positive, it needs be done other complementary tests. The color of Bacillus thuringiensis on chromogenic medium is the same as Bacillus cereus, but rarely inspect in food

Typical features:

The typical colonies of Bacillus cereus are blue-green and have an opaque ring around

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. P.R. Mortimer, G. McCann, Lancet, 1043 (1974)

2. E. Bouza, S. Grant, C. Jordan, et. al, Arch. Ophthamol., 97, 488 (1979)

3. K. Wohlgemuth, C.A. Kirkbride, E.J. Bicknell, R.P. Ellis, Am. Vet. Met, Ass., 161, 1691 (1972)