Russell Double Sugar Agar (Powder)

Russell Double Sugar Agar is a differential agar medium used for the identification of enteric bacteria based on the fermentation of dextrose and lactose with or without gas production. The original formula of Russell Double Sugar Agar developed by Russell was modified by Nicols by replacing litmus indicator with phenol red. Selected colonies are transferred from the primary plating medium to tubes of Russell Double Sugar Agar using a straight bacteriological wire, stabbing the butt of the tube and streaking the slanted portion of the medium. Inoculated tubes after incubation are observed for pH reactions and gas formation. Phenol red indicates fermentation of the carbohydrates by the production of a yellow color (acid reaction); lack of fermentation is indicated by a red color (alkaline reaction). Gas formation is indicated by the presence of bubbles or cracks in the medium. After 24-48 hours incubation under aerobic conditions, a tube with a red slant and yellow butt indicates dextrose fermentation. Lactose fermentation is indicated by a yellow slant and butt. A red slant and butt indicates no fermentation. Other biochemical or serological tests are performed as required to confirm identification. Quality Control Specifications: 1. The powder is homogeneous, free flowing and light beige to pink. 2. Visually the prepared medium is red and clear to trace hazy. Expected cultural response after 24-48 hours at 35 degrees C: Organism ATCC Result (Slant/Butt/Gas/H2S) Escherichia coli ATCC 25922 A/A/+ Proteus mirabilis ATCC 12453 K/A/- Pseudomonas aeruginosa ATCC 27853 K/K/- Salmonella typhimurium ATCC 14028 K/A/+ Shigella flexneri ATCC 12022 K/A/- Key: K = Alkaline, A = Acid Storage: Store the sealed bottle containing the dehydrated medium at 2 to 30 degrees C. Once opened and recapped, place the container in a low humidity environment at the same storage temperature. Protect it from moisture and light. The dehydrated medium should be discarded if it is not free flowing or if the color has changed from the original light beige color to pink color.