Harlequin Salmonella ABC Medium

Salmonella spp. can be differentiated from other members of the Enterobacteriaceae family by their ability to produce a-galactosidase in the absence of β-galactosidase. Salmonella spp. is differentiated the substrate X-a-Gal is hydrolyzed producing green colonies. These are easily distinguished from the black or colorless colonies of other organisms. This medium is based on D.C.A Hynes and therefore contains the selective agents sodium deoxycholate and sodium citrate. Manufactured under exclusive license from Newcastle Upon Tyne Hospitals NHS Trust.


  1. Weigh 36.5 grams of powder, disperse in 1 liter of deionized water.
  2. Allow the mixture to soak for 10 minutes, swirl to mix.
  3. Sterilize the medium by bringing to the boil. DO NOT REMELT OR AUTOCLAVE THIS MEDIUM.
  4. Cool to 47°C, mix well and dispense into Petri dishes.
Typical Formulation g/Liter
Beef extract 5 g
Peptone 5 g
Sodium citrate 8.5 g
Sodium deoxycholate 5 g
Agar 12 g
X-α-Gal 0.08 g
CHE-β-Gal 0.3 g
Ferric ammonium citrate 0.5 g
IPTG 0.03 g
Grams per liter 36.5 g

Final pH: 7.2 ± 0.2