Deoxycholate Agar (DOC)

Deoxycholate Agar (DOC):

  • To isolate and differentiate between various members of the family Enterobacteriaceae.
  • DOC contains sodium deoxycholate and citrate which work to inhibit the growth of Gram-positive organisms.
  • The medium also contains the sugar lactose, which serves to differentiate among enterics that ferment and do not ferment lactose.
  • Fermentation of lactose appears as a red color due to the pH indicator neutral red, which is included in the medium.
  • Neutral red is colorless above pH 6.8 and red below 6.8.


The plate here shows common reactions observed on a DOC plate. The reactions are as follows:

A. Heavy lactose fermentation

B. Reduced growth of a Gram-positive organism

C. No lactose fermentation

D. Light lactose fermentation




Deoxycholate Agar

Deoxycholate Agar


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