Sunday, March 1, 2009

Triple Sugar Iron (TSI) Test

MediumTriple 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


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.