Deoxycholate Agar was first described by Leifson for the isolation of intestinal pathogens and for the enumeration of colon bacilli in milk and water. The medium conforms to that given by the APHA for performing the direct count of conforms in dairy products. In the microbiological analysis of dairy products and water, Deoxycholate Agar is normally used for enumeration of conforms in pour plates. It may also be used for isolation of enteric pathogens by surface inoculation from rectal swabs, feces or other specimens. Deoxycholate Agar should be used in parallel with other plating media when used for this purpose. Sodium deoxycholate and sodium citrate are incorporated in the medium to inhibit the growth of Gram positive organisms. Fermentation of lactose causes an acid reaction in the medium resulting in the formation of deep red colonies. Deoxycholate Agar is used for the isolation of enteric organisms and differentiation of the lactose fermenters. (Alpha Biosciences # D04-104-500gm)
Use: Deoxycholate Agar is used for the isolation of enteric organisms and differentiation of the lactose fermenters.
Description: Deoxycholate Agar was first described by Leifson for the isolation of intestinal pathogens and for the enumeration of colon bacilli in milk and water. The medium conforms to that given by the APHA for performing the direct count of conforms in dairy products. In the microbiological analysis of dairy products and water, Deoxycholate Agar is normally used for enumeration of conforms in pour plates. It may also be used for isolation of enteric pathogens by surface inoculation from rectal swabs, feces or other specimens. Deoxycholate Agar should be used in parallel with other plating media when used for this purpose. Sodium deoxycholate and sodium citrate are incorporated in the medium to inhibit the growth of Gram positive organisms. Fermentation of lactose causes an acid reaction in the medium resulting in the formation of deep red colonies.
Formula* per Liter:
- Peptic Digest of Animal Tissue ...... 5.0g
- Lactose ......................................... 10.0g
- Casein Digest Peptone................... 5.0g
- Sodium Chloride ............................ 5.0g
- Dipotassium Phosphate ................. 2.0g
- Ferric Citrate .................................. 1.0g
- Neutral Red .................................... 0.03g
- Sodium Deoxycholate ................... 1.0g
- Agar .................................................16.0g
- Sodium Citrate ............................... 1.0g
Final pH: 7.3 ± 0.2 at 25.0°C
* Grams per liter may be adj. or formula supplemented to obtain desired performance
Preparation: Mix 46 grams of the medium in a Liter of purified water until evenly dispersed. Heat with repeated stirring and boil for one minute. Pour plates can be prepared after the medium has been cooled to 45-50°C. Do not autoclave.
Quality Control Specifications:
1. The powder is homogeneous, free flowing and light pinkish-beige.
2. Visually the prepared medium is clear to trace hazy and brownish-red.
3. Expected cultural response after 40-48 hours at 35.0°C.
Organism                                                                 Result
Escherichia coli ATCC 25922Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Growth, Pink to red colonies
Salmonella typhimurium ATCC 14028Â Â Â Â Â Â Â Â Â Growth, Colorless colonies
Staphylococcus aureus ATCC 25923Â Â Â Â Â Â Â Â Â Â Â Â Growth Inhibited
Storage: Store the sealed bottle containing the dehydrated medium at 2 to 30.0°C. Once opened and recapped, place the container in a low humidity environment at the same storage temperature. Protect it from moisture and light. The dehydrated medium should be discarded if it is not free flowing or if the color has changed from the original light pinkish-beige color.
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