What are the key ingedients in TSI media that produce the various reactions? Why is one sugar lower in % concentration than the other sugars?
- Ingredients: Dextrose, lactose, sucrose, sodium, thiosulfate, ferric ammonia citrate
- To detect bacteria that ferments only dextrose the concentration is 1/10 of the concentration of the sugars. Small acid produced in the slant oxidizes quickly through revert back to alkaline pH or red color.
- Low oxygen tension in the butt of the tube keeps an acid pH yellow color
- If hydrogensulfide from thiosulfate it reacts with ferrious citrate to form a black precipitant