| TSI, MIU and Simmons agar |
| TSI Medium blackening due to H2S production (left tube) |
False-positive H2S production on TSI medium (left).
| Triple Sugar Iron (TSI) |
DESCRIPTION
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.
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.
MEDIUM PREPARATION
Composition:
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.
PROCEDURE
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.
RESULTS
H₂S production: positive if a black precipitate of iron sulfide forms and negative if no
black precipitate is observed.
Lactose/sucrose fermentation: positive if the slant turns yellow; negative if it remains
unchanged.
Glucose fermentation: positive if the medium turns yellow; negative if no color change
occurs.
Gas production: positive if gas bubbles are observed, usually trapped in the lower
part of the medium. In cases of strong gas production, the medium may be pushed
upward toward the cap.
Composition:
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.
PROCEDURE
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.
RESULTS
H₂S production: positive if a black precipitate of iron sulfide forms and negative if no
black precipitate is observed.
Lactose/sucrose fermentation: positive if the slant turns yellow; negative if it remains
unchanged.
Glucose fermentation: positive if the medium turns yellow; negative if no color change
occurs.
Gas production: positive if gas bubbles are observed, usually trapped in the lower
part of the medium. In cases of strong gas production, the medium may be pushed
upward toward the cap.
NOTES
Do not incubate more than 24 hours. False-positive or false-negative results may
appear.
Klebsiella oxytoca strains can produce a dark brown pigment when growth on media
containing gluconate and ferric citrate. The TSI slant is darkened by pigment, not by
hydrogen sulfide production.
Do not incubate more than 24 hours. False-positive or false-negative results may
appear.
Klebsiella oxytoca strains can produce a dark brown pigment when growth on media
containing gluconate and ferric citrate. The TSI slant is darkened by pigment, not by
hydrogen sulfide production.
REFERENCES:
1. Helgomar Raducanescu, Valeria.Bica-Popii,1986. Bacteriologie veterinara, Ed.
Ceres, Bucuresti.
2. Margaret Barnett, 1992. Microbiology Laboratory Exercises. Wm. C. Brown
Publishers.
1. Helgomar Raducanescu, Valeria.Bica-Popii,1986. Bacteriologie veterinara, Ed.
Ceres, Bucuresti.
2. Margaret Barnett, 1992. Microbiology Laboratory Exercises. Wm. C. Brown
Publishers.
(c) Costin Stoica
A demonstration of TSI, MIU and Simmons utilization is available in video section.
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