The Non-Enteric Rods: TSI test
The sugar components of TSI (triple sugar iron agar) can be useful in
differentiating Chart 5 organisms. Some of the Chart 5 bacteria can utilize
glucose or sucrose and will produce acid. Others utilize peptones in the media,
producing alkaline by-products. Gas and hydrogen sulfide production are not
observed with Chart 5 organisms. Interpret the color in both the slant and the
butt of the tubes as follows:
1. Slant (Acid = yellow | Alkaline = red)
2. Butt (Acid = yellow | Alkaline = red)
This slide shows typical TSI reactions. (These
results are read as slant color/butt color.) From left to right they are:
a. uninoculated
b. acid/acid
c. alkaline/little change
d. acid/little change
