This is a selective medium for the isolation of Salmonella spp. and Shigella spp. from clinical specimens and environmental samples. This formulation was developed by Hynes through a modification of Leifson’s DCA medium.
The peptone provides the required carbon, nitrogen and vitamins. Lactose is a fermentable carbohydrate and neutral red is a pH indicator. Sodium thiosulphate and ferric citrate are used to detect hydrogen sulphide production indicated by the black centred colonies of hydrogen sulphite positive organisms. Sodium desoxycholate and sodium citrate inhibit most Gram-positive organisms.
Deoxycholate Citrate Agar (DCA) Hynes
Additional Information
| Shelf Life (days) | |
|---|---|
| Storage Temp (°C) | |
| Dehydrated Medium Appearance | |
| Prepared Medium Appearance | |
| Dehydrated Medium Colour | |
| Prepared Medium Colour | |
| Dehydrated PH | |
| Prepared PH |
Product Description
| Organisms | Ref. No | Result |
| Salmonella typhimurium | NCTC 12023 | Growth, translucent colonies with black centre |
| Shigella sonnei | NCTC 8574 | Growth, colourless/pale pink colonies |
| Enterococcus faecalis | NCTC 12697 | Inhibited |
Formula*
| g/L | |
| Peptone | 10.0 |
| Lactose | 10.0 |
| Sodium desoxycholate | 5.0 |
| Sodium citrate | 8.5 |
| Sodium thiosulphate | 5.4 |
| Ferric citrate | 1.0 |
| Neutral red | 0.02 |
| Agar | 12.0 |
| Total | 52.0 |
| *Adjusted/supplemented as required to meet performance requirements |
Preparation
Suspend 52g of the medium in one litre of deionised / purified water. Allow the medium to soak whilst mixing for 10 minutes. Heat with frequent agitation and boil for one minute to completely dissolve the medium. DO NOT AUTOCLAVE this medium. Cool to 45-50°C and aseptically dispense into appropriate sterile containers.