Test checks simultaneously for the production of hydrogen sulfide, acid fermentation of lactose, sacharose, glucose
and gas production from glucose. Medium, together with MIU and Simmons agar, is most used for
Enterobacteriaceae identification, especially Escherichia and Salmonella. A demonstration of TSI, MIU and Simmons
utilization is available in video section.
Peptic peptone 10g, Casein peptone 10g, Meat extract 3g, Yeast extract
3g, Lactose 10g, Sacharose 10g, Dextrose 1g, NaCl 5g, Fe2SO4 0.2g,
Na-thyosulphate 0.3g, Phenol red 0.024g, Agar 12g, H2O ad 1000 ml.
Pour the medium filling the bottom half of the tube and creating a slant in
the upper half.
Harvest a well isolated colony and inoculate a TSI tube by stabbing the
medium then zigzag streaking on the surface of the slant. Incubate at 37
°C, 24 hours.
H2S production: positive if a black precipitate of iron sulfide forms.
Lactose / sacharose fermentation: positive for yellow color of slant and
negative for red.
Glucose fermentation: positive if medium changes to yellow, negative if no
Gas production: gas bubbles captured in the bottom part of the medium
are observed. Sometimes gas production is so high that medium is
pushed up to the cap.
Do not incubate more than 24 hours. False positive or negative results
1. Helgomar Raducanescu, Valeria.Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. Margaret Barnett, 1992. Microbiology Laboratory Exercises. Wm. C. Brown Publishers.
|TSI (left), MIU and Simmons agar
(c) Costin Stoica