Desoxycholate Citrate Agar (Hynes) 500g, Oxoid

An improved medium, based on the Hynes modification of Leifsons medium for the isolation of Salmonellae and Shigellae. The improvement gives larger and more numerous colonies of Shigella species which can easily be picked off and emulsified in saline for slide agglutination tests.

Desoxycholate Citrate Agar (Hynes), Oxoid Composition

Desoxycholate Citrate Agar (Hynes), Oxoid Preparation:
Suspend 52g in 1 litre of distilled water. Bring to the boil over gauze and flame, to dissolve completely. Agitate to prevent charring. Cool to approximately 50°C and pour into sterile Petri dishes. Dry the agar surface before use.
THIS MEDIUM IS HEAT SENSITIVE: AVOID EXCESSIVE OR PROLONGED HEATING DURING RECONSTITUTION. DO NOT AUTOCLAVE OR REMELT.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared agar plates at 2-8°C.

Precautions
The medium is best used freshly prepared.
Stock cultures of Shigella species may become predominantly in the R-phase when subcultured away from DCA media. Such cultures are difficult to use for control purposes without first heavily streaking the cultures on DCA plates and picking off the few S-phase colonies i.e. the macro-colonies on the agar surface, for further subculture.
When making biochemical tests on colonies picked from the surface of DCA plates, purity subcultures should be carried out because the colony may be contaminated with Escherichia coli present as micro-colonies.