Product number: NCM0183

Differential Reinforced Clostridial Medium ISO (DRCM) is a medium for the detection and enumeration of the spores of sulfite-reducing anaerobes as described in ISO 26461-1, and is not intended for use in the diagnosis of disease or other conditions in humans.

Sulfite reducing anaerobes, in particular Clostridia, can be indicators of remote and intermittent pollution. Widespread in the environment, being found in human and animal feces, soil and waste water, the spores are more resistant to physical and chemical factors than vegetative cells and able to survive for long periods in water. The spores may also be resistant to chlorination at the levels commonly used in water treatment.

DRCM has been developed for use with the Most Probable Number (MPN) method to determine the MPN of anaerobes (Clostridia) per volume of sample. The formulation includes peptone, yeast extract, meat extract, starch & L-Cysteine for nutrition with glucose providing the energy source. Sodium acetate provides partial selectivity.

Clostridia are able to reduce sulfite to sulfide – forming iron sulfide. Iron (III) citrate is included in the formulation as an indicator of sulfite reduction. Blackening in the medium indicates that iron sulfide has been formed and therefore that sulfite reduction has occurred. Other bacteria are able to form sulfide, so vegetative cells must be first be removed from the test sample by an appropriate process e.g. heat treatment.


Formula Liter
Peptone Tryptic Digest of meat 10.0 g/L
Meat Extract 10.0 g/L
Yeast Extract 1.5 g/L
Starch 1.0 g/L
Hydrated Sodium Acetate 5.0 g/L
Glucose 1.0 g/L
L-Cysteine Hydrochloride 0.5 g/L
Sodium Sulfite 0.4 g/L
Iron (III) Citrate 0.07 g/L

Final pH: 7.1 ± 0.2 at 25°C
Formula may be adjusted and/or supplemented as required to meet performance specifications.

Preparation (Single strength medium)

  1. Dissolve 30.1 grams of the medium in one liter of purified water.
  2. Heat with frequent agitation to completely dissolve the medium, if necessary.
  3. Dispense 25 mL aliquots of the medium into screw-capped bottles of capacity 25 mL.
  4. Autoclave at 121°C for 15 minutes.
  5. Medium should be used on day of preparation. If medium is stored, tubes should be reheated to deoxygenate the medium.
  6. Tubes should not be reheated more than once.

For Double strength medium prepare as per single strength but reduce the volume of water by half.

Product was previously known as LabM Product: LAB220 DRCM (ISO) - Differential Reinforced Clostridial Medium

Order Details

Product # Product Description
NCM0183A DRCM Differential Reinforced Clostridial Medium (ISO), 500 g
NCM0183B DRCM Differential Reinforced Clostridial Medium (ISO), 5 kg
NCM0183C DRCM Differential Reinforced Clostridial Medium (ISO), 10 kg
NCM0183D DRCM Differential Reinforced Clostridial Medium (ISO), 25 kg (European only size)
NCM0183E DRCM Differential Reinforced Clostridial Medium (ISO), 50 kg (US only size)

Reference Material

NCM0183 - DRCM Differential Reinforced Clostridial Medium (ISO), Safety Data Sheet [Danish] [Dutch] [English] [EU English] [Finnish] [French] [German] [Italian] [Spanish, Mexico] [Swedish]
NCM0183 - DRCM Differential Reinforced Clostridial Medium (ISO), Technical Specifications Sheet [English]

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