Thermo Scientific™ Remel™ HE Agar

Description

• Selectively isolate and differentiate gram-negative enteric pathogens using Thermo Scientific™ Remel™ Hektoen Enteric (HE) Agar (Dehydrated)
• The HE Agar slightly modified from the original formulation and has lower bile salt concentrations and the absence of sodium desoxycholate
• King and Metzger developed HE Agar to simultaneously grow Salmonella and Shigella as well as inhibit normal intestinal flora 1
• HE Agar is a selective and differential agar primarily used to recover Salmonella and Shigella from patient specimens
• In the medium the amount of carbohydrate and peptone was increased to counteract the inhibitory effects of bile salts and indicators
• Selective medium - Growth of gram-positive organisms is inhibited by bile salts Differential medium - Addition of sucrose, lactose and salicin helps in differentiating pathogens based on the color of colonies and the medium surrounding them
• Easy to interpret – Shigella: green colonies Salmonella: green colonies with a black precipitate in the center Meat peptone supplies essential nutrients for bacterial growth
• Sucrose, lactose and salicin are added to help differentiate pathogens
• If hydrogen sulphide is produced from sodium thiosulphate it reacts with ferric ammonium citrate to form a black precipitate in the center of the colony
• Acid fuchsin and bromthymol blue are indicators with low toxicity and bile salts inhibit the growth of gram-positive organisms.