Differential Reinforced Clostridial Agar

Intended Use
Differential Reinforced Clostridial Agar is used for enumerating and cultivating sulfite-reducing clostridia.

Summary and Explanation
Differential Reinforced Clostridial Medium (broth) was developed by Gibbs and Freame in 1965.1 The medium could be used to enumerate clostridia in foods using the Most Probable Number (MPN) method. Differential Reinforced Clostridial Agar (DRCA) is based on Differential Reinforced Clostridial Medium, but with the addition of agar.
The assay is performed using unheated and heat-shocked tubes of DRCA containing replicate dilutions of the test sample.
Blackening of the medium is presumptive evidence for the presence of sulfite-reducing clostridia. In this method, heat-shocked tubes showing blackening are confirmatory for clostridia. Non-heat-shocked tubes showing blackening must be heat shocked to kill off vegetative cells and subcultured into DRCA to confirm the presence of sulfite-reducing clostridia.

Principles of the Procedure
Peptones, beef extract, yeast extract, starch and L-cysteine provide nutrients and co-factors required for good growth of clostridia. Dextrose is included in the medium as an Energy source. Partial selectivity of the medium is achieved through the addition of sodium acetate. Agar is the solidifying agent. Anaerobiosis in the medium is detected by the redox Indicator resazurin. The addition of ferric ammonium citrate to the medium is used to detect sulfite reduction. Blackening of the medium is due to the formation of iron sulfide.

Formula
Difco™ Differential Reinforced Clostridial Agar
=> Approximate Formula* Per Liter
  - Tryptone : 5.0 g
  - Peptone : 5.0 g
  - Beef Extract, Desiccated : 8.0 g
  - Yeast Extract : 1.0 g
  - L-Cysteine HCl : 0.5 g
  - Starch : 1.0 g
  - Dextrose : 1.0 g
  - Sodium Acetate : 5.0 g
  - Sodium Bisulfite : 0.5 g
  - Ferric Ammonium Citrate : 0.5 g
  - Resazurin : 2.0 mg
  - Agar : 15.0 g
*Adjusted and/or supplemented as required to meet performance criteria.

Poids	0,81 Kg   (810 g)
Volume	0,0075 m³   (7500 cm³)
Largeur	0,15 m   (15 cm)
Longueur	0,2 m   (20 cm)
Hauteur	0,25 m   (25 cm)

Les dimensions, le poids et le volume sont bruts (emballage inclus)