Medium — Triple sugar iron (TSI) agar is used to differentiate enteric bacteria based on the ability to reduce sulfur and ferment carbohydrates.
1. It contains three carbohydrates — glucose, lactose, and sucrose.
2. It also contains the pH indicator phenol red
3. It also contains thiosulfate and ferrous sulfate.
Results
A. Uninoculated Medium
B. Positive Hydrogen Sulfide (H2S) Production – Black precipitate
C. Positive Glucose Fermentation — Red slant (alkaline) & Yellow butt (Acid); (+) CO2 *
D. Non Lactose Fermenter — Red slant (alkaline) & Red butt (alkaline)
E. Lactose or Sucrose Fermenter — Yellow slant (Acid) & Yellow butt (Acid); (+) CO2 *
* If portions of the medium are pushed up in the tube or if there are fissures or bubbles in the medium, then the organism is producing gas.
