R & F® Bacillus cereus/Bacillus thuringiensis (BCBT) Chromogenic Plating Medium

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Colony Appearance

Bacillus cereus and Bacillus thuringiensis appear as turquoise flat dull colonies, 2.0-7.0 mm in diameter with a precipitate (halos) after 24 h at 35°C. Many other Bacillus species will not grow; however, Bacillus circulans and Bacillus anthracis will appear as white colonies 1.0-2.0 mm in diameter. Listeria monocytogenes and L. ivanovii grew as turquoise domed glossy colonies, pinpoint to ≤ 1 mm in diameter. All other Listeria species will grow as white domed colonies, pinpoint to ≤ 1 mm in diameter. Enterococcus sp., Staphylococcus sp. and Streptococcus sp. will either not grow or produce white pinpoint colonies. Gram (-)s are inhibited

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Mechanism

Our plating medium contains the chromgen X-inositol phosphate (X-IP) that detects the enzyme phosphatidylinositol phospholipase C (PI-PLC), virulence factor, which is found in Bacillus cereus/B. thuringiensis. Bovine albumin is added for the enzyme to recognize the chromogenic substrate. The color of the Bacillus cereus/B. thuringiensis colonies are turquoise. Other Bacillus strains either do not grow or do not produce PIPLC.

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Industry Types

Processing and refrigerating of rice dishes, dry cereals, desserts, pasta dishes, dairy products, soups and sauces

See Product Brochure, Use Protocol, SDS, Certificate of Analysis and Medium Preparation for more information about our medium.
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Advantages/Benefits

1. Our chromogenic medium is the only chromogenic agar that uses the virulence factor, PIPLC enzyme for detection.

2. Highly selective/differential detection system identifies only the pathogenic Bacillus species (B.c. & B.t.). Sensitivity for B. cereus/B. thuringiensis is 100% – no false negatives. Only a small percent of Enterococcussp., Staphylococcus sp. and Streptococcus grew on our medium (pinpoint white colonies).

3. Competitors’ chromogenic media use the β-glucosidase reaction in which other non-B. cereus/B. thuringiensis species will grow on the agar and produce false positives.

4. MYP (Mannitol Egg Yolk Polymyxin) agar is commonly used plating medium and is dependent on lecithinase activity on the egg yolk in the agar. There is a tendency of zones from individual colonies to coalesce which often causes difficulty in colony enumeration – a major drawback of the medium. Also, other Bacillus sp. that grow on MYP besides B. cereus/B. thuringiensis will give positive egg yolk reactions – creamy white with egg yolk precipitate.

5. Unlike our medium, MYP will require supplemental tests to confirm B. cereus/B. thuringiensis making it very costly.

6. In contrast to the lecithinase reaction in MYP where colony coalescing can adversely affect enumeration of B. cereus/B. thuringiensis, the water insoluble chromogen in our medium colors only the colonies and positively identifies B. cereus/B. thuringiensis.

7. The shelf life of prepared plates remains stable for at least 60 days, stored in the dark at 2-8°C. One bottle of plating medium powder and two boxes of supplements will make approximately 230 plates.
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Publications

* Peng, H., V. Ford, E.W. Frampton, L. Restaino, L.A. Shelef, and H. Spitz. 2001. Isolation and enumeration of Bacillus cereus from foods on a novel chromogenic plating medium. Food Microbiol. 18: 231-238.

* BCM B. cereus/B. thuringiensis is R & F® B. cereus/B. thuringiensis
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Ordering Information

M-0450

R & F® Bacillus cereus/Bacillus thuringiensis Chromogenic Detection System (220 g Bottle of Powder & two Supplement Boxes – Makes 220-240 Plates)

M-0400

R & F® Bacillus cereus/Bacillus thuringiensis Chromogenic Plating Medium (220 g Bottle)

M-0410

R & F® Bacillus cereus/Bacillus thuringiensis Supplement for Plating Medium (1 Box)

M-0460

R & F® Bacillus cereus/Bacillus thuringiensis Chromogenic Prepared Plate (Minimum Order of 20 Plates – Shelf life is 60 Days)