• Deoxycholate citrate agar (DCA) is a selective and differential medium used to isolate Salmonella and Shigella species. It can also be used to isolate Yersinia species if extra bile salt added.
• DCA is the best and most economically prepared from the hydrated medium available commercially.

Composition of Deoxycholate citrate agar (DCA)

• Lab-lemco powder…………………………………5.0 gm/ltr
• Peptone…………………………………………….5.0 gm/ltr
• Lactose……………………………………………10.0 gm/ltr
• Sodium citrate……………………………………8.5 gm/ltr
• Sodium thiosulphate…………………………….5.4 gm/ltr
• Ferric citrate…………………………………….1.0 gm/ltr
• Sodium deoxycholate……………………………5.0 gm/ltr
• Neutral red………………………………………..0.02 gm/ltr
• Agar………………………………………………12.0 gm/ltr

Preparation of DCA:

• The medium is used at a concentration of 5.2 grams in every 100 ml of distilled water. For the isolation of Yersinia enterocolitica, an extra 2g of sodium deoxycholate should be added to every 100 ml of medium.
• Prepare the medium as instructed by the manufacturer.
• Heat with great care and do not boil or autoclave.
• As soon as the medium has cooled to 50-55°C, mix well and dispense aseptically in sterile petri dishes.
• Label the plates ‘DCA’
• Date the medium and give it a batch number.

Quality control

• pH of medium: this should be within the range of pH 7.1-7.5 at room temperature.
• Store the plates at 2-8°C, preferably in sealed plastic bags to prevent loss of moisture.

Use of DCA:

• Used as selective and differential medium for Salmonella and Shigella species from other enterobacteriaceae
• Also used to isolate Yersinia species

Deoxycholate citrate agar (DCA): composition, preparation and use

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