Triple Sugar Iron Agar (TSI 2)
The purpose of this test is to determine whether organisms can ferment glucose, sucrose and/or lactose with or without production of gas. The ability of the organism to produce hydrogen sulphide from thiosulphate in an acid environment is also tested. Typically used to help differentiate between groups, genera and species among Enterobacteriaceae. Fermentation of glucose alone will show as a yellow colour in the butt of the medium, fermentation of sucrose and/or lactose will cause both butt and slant to be yellow. Production of hydrogen sulphide leads to blackening. Results are given as slant/butt/gas production/hydrogen sulphide production. 1. Uninoculated medium. 2. Alkaline/acid/gas/hydrogen sulphide: Salmonella (18 hours). The gas can be seen at the bottom of the tube. 3. Alkaline/acid/gas/hydrogen sulphide: Salmonella (48 hours). The yellow colour in the butt of the medium is obscured by the blackening caused by the production of hydrogen sulphide. 4. Alkaline/acid/gas/hydrogen sulphide: Proteus (18 hours). The gas produced is not visible in this picture. 5. Alkaline/acid/gas/hydrogen sulphide: Proteus (48 hours).
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