(Freeman Formulation)

HAL1

Description

The first substrate, CHE-ß-Gal, is enzymatically cleaved by ß- galactosidase producing organisms giving black colonies in the presence of iron. Most Enterobacteriaceae are ß-galactosidase positive and these produce black colonies on Salmonella ABC. The second substrate, X-a-Gal, is hydrolysed by Salmonella spp. producing green colonies that are easily distinguished from the black or colourless colonies of other organisms. The medium is based on D.C.A Hynes and hence utilises sodium desoxycholate and sodium citrate as inhibitors. Isolation of Salmonella  spp. by culture remains the most reliable method of detection. However, most media are highly non-specific and consequently place a heavy burden on the laboratory in terms of biochemical and serological confirmation of suspect colonies. With improved specificity, the ABC medium dramatically reduces the need for ‘false positive’ screening, saving labour and reducing consumable costs.