TSI AGAR (ISO 6579-1) - IDENTIFICATION OF ENTEROBACTERIACEAE - 1 INTENDED USE

Sep 27, 2026

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TSI (Triple Sugar Iron) Agar is used for rapid identification of enterobacteria by assessing fermentation patterns of lactose, glucose (with or without gas) and sucrose, including hydrogen sulfide production. The formulation matches standards NF EN ISO 6579-1 and NF EN ISO 19250 for detecting Salmonella spp. Sugar fermentation causes phenol red acidification to yellow, while lactose or sucrose fermentation turns the tube slant yellow; non-fermenters show no color change. H2S appears as black iron sulfide and gas as bubbles or agar fragmentation.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages5

Reading Time13 min

AccessFree to download

1 Intended use

2 History

3 Principles

4 Typical composition

5 Preparation

6 Instructions for use

7 Results

TSI AGAR (ISO 6579-1) IDENTIFICATION OF ENTEROBACTERIACEAE 1 INTENDED USE | TSI (Triple Sugar Iron) Agar is used for the identification of enterobacteria by the rapid detection of the fermentation of lactose, glucose (with or without gas production) and of sucrose, as well as the production of hydrogen sulfide.
The typical composition corresponds to that defined in the standards NF EN ISO 6579-1 and NF EN ISO 19250 for the detection of Salmonella spp..
2 HISTORY | | --- | | Hajna developed the formulation of this agar containing three sugars by adding sucrose to a two-sugar (lactose and glucose) medium of Kligler. The addition of sucrose increases the sensitivity of the medium by leading to the early detection of coliform bacteria which ferment lactose slowly and degrade sucrose more rapidly. The medium also favors the differentiation of certain Proteus strains (lactose-negative) which ferment sucrose within 24 hours of incubation.
3 PRINCIPLES | | Sugar fermentation results in an acidification which makes phenol red (pH indicator) turn yellow) .
The detection of bacteria fermenting only glucose is facilitated by decreasing the concentration of the sugar to 1/10 of that of lactose or sucrose, so that the small quantity of acid produced on the slant during fermentation is rapidly oxidized. This causes a rapid return to the red color or else a more pronounced re-alkalinization. The acid reaction (yellow color), on the contrary, is maintained in the depth of the agar, in the butt of the tube.
Bacteria fermenting lactose or sucrose will make the slant of the tube turn yellow.
Bacteria fermenting none of these sugars will not change the color of the medium .
The production of H2S is revealed in the butt by the appearance of black iron sulfide, due to the reduction ofthiosulfate in the presence of ferric citrate.
The production of gas (H2 , CO2), resulting from sugar fermentation, is revealed by the appearance of bubbles or by the fragmentation of the agar.
4 TYPICAL COMPOSITION | The composition can be adjusted in order to obtain optimal performance. For 1 liter of media : -Yeast extract ................................ ................................ ................................ ............... 3,0 g -Meat extract................................ ................................ ................................ ................. 3,0 g -Peptone ................................ ................................ ................................ ..................... 20,0 g -Sodium chloride ................................ ................................ ................................ .......... 5,0 g -Lactose ................................ ................................ ................................ ...................... 10,0 g -Sucrose ................................ ................................ ................................ ..................... 10,0 g -Glucose ................................ ................................ ................................ ....................... 1,0 g -Sodium thiosulfate ................................ ................................ ................................ ....... 0,3 g - Iron (III) citrate ................................ ................................ ................................ ............. 0,3 g -Phenol red ................................ ................................ ................................ .............. 24,0 mg -Bacteriological agar................................ ................................ ................................ 9,0 g pH of the ready-to-use media at 25 °C : 7,4 ± 0,2 . 5 PREPARATION • Dissolve 61,6 g of dehydrated media ( BK221) in 1 liter of distilled ordemineralized water. • Slowly bring to boiling, stirring with constant agitation until complete dissolution. • Dispense in tubes. • Sterilize in an autoclave at 121°C for 15 minutes. • Incline

FAQs

What does TSI Agar (Triple Sugar Iron) test for during enterobacteria identification?

It evaluates fermentation of lactose, glucose (with or without gas) and sucrose, and also checks hydrogen sulfide production.

How do fermentation results change the color of phenol red on TSI Agar?

Sugar fermentation acidifies the medium and turns phenol red yellow; alkalinization is shown by a dark red color. Bacteria fermenting lactose and/or sucrose make the slant yellow.

How are gas and hydrogen sulfide detected in TSI Agar?

Gas production appears as bubbles in the butt or fragmentation of the agar. Hydrogen sulfide appears as black iron sulfide due to reduction of thiosulfate in the presence of ferric citrate.

Sep 27, 2026

Uploaded by lugxt