Thermo Scientific™ Membrane Clostridium Perfringens (m-CP) Agar Base (Dehydrated)

Description

Rapidly isolate and presumptively identify Clostridium perfringens from water samples with selective and chromogenic Thermo Scientific™ Oxoid™ Membrane Clostridium Perfringens (m-CP) Agar Base (Dehydrated) when used with m-CP Selective Supplement. The medium was first described by Bisson and Cabelli¹ for the rapid quantitation of Clostridium perfringens from water samples.

The lack of b-D-glucosidase activity fermentation of sucrose and production of acid phosphatase differentiate presumptive Clostridium perfringens colonies from other Clostridium spp on the medium.

Use Membrane Clostridium Perfringens (m-CP) Agar Base for rapid isolation and presumptive identification of Clostridium perfringens from water samples.

• Selective: D-cycloserine, polymyxin B and recommended incubation at 44°C inhibit the growth of background flora such as Gram-negative organisms and staphylococci
• Chromogenic: Clostridium perfringens form characteristic yellow, opaque colonies while most other Clostridium appear as either purple colonies or blue/green colonies.
• Recommended in European Council Directive 98/83/EC for testing the quality of water intended for human consumption².
• Shown to give better recovery of Clostridium perfringens from water and sewage samples than the Bonde pour tube method¹.

In m-CP Medium lack of b-D-glucosidase activity (an enzyme involved in cellobiose fermentation), fermentation of sucrose and production of acid phosphatase are used to differentiate presumptive Clostridium perfringens colonies from other Clostridium spp.

Lack of b-D glucosidase activity means that Clostridium perfringens does not cleave the chromogen, indoxyl b-D glucoside, in the medium. Furthermore, as the organisms ferment the sucrose in the medium, reducing the pH, bromocresol purple changes from purple to yellow. This results in characteristic opaque yellow Clostridium perfringens colonies.

Most other Clostridium spp. will appear as either purple colonies, due to the lack of sucrose fermentation, or blue/green colonies where the organism is still cleaving Indoxyl b-D glucoside and also fermenting sucrose.

Presumptive positive Clostridium perfringens colonies can be further tested for acid phosphatase activity by exposure to ammonium hydroxide vapor for 20 to 30 seconds. Clostridium perfringens colonies turn pink or red as phenolphthalein diphosphate is cleaved by acid phosphatase. No color change will be seen with colonies of organisms that do not posses acid phosphatase. It is important this further test is carried out as there are a very small number of non-perfringens clostridia that produce yellow colonies. However, these colonies will remain yellow after exposure to ammonium hydroxide as they are acid phosphatase negative. 

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