Triple Sugar iron Agar (TSI Agar)
The medium contains three sugars namely:
glucose, sucrose, and lactose as well as amino acid. Gas
production is also detectable on this medium, likewise
the production of hydrogen-sulphide (H2S). Some
enterobacteria and other urinary tract pathogens ferment
all the three sugar present and produce sufficient acid
which change the colour of the indicator to yellow.
Other microorganisms ferment only one of
these sugars, producing little amount of acid indicated
by yellow colour at the bottom. The sugars and protein
were attached oxidatively to release ammonia, which
turn the indicator to pink-red in the medium and the
production of media along the stabbed line. Gas
production can also be detected by the production of
bubbles cracks or by separation of the medium.