TSI slant

Triple Sugar Iron Agar (English for triple sugar iron agar ), in short TSI agar test tube called a nutrient medium used for the detection of hydrogen sulfide production and / or sugar -fermenting bacteria. The test consists of agar, mixed with a pH indicator ( phenol red), and the three sugars of lactose (1%), sucrose (1%) and glucose ( 0.1%). In medical microbiology it is mainly used for the detection of pathogenic enteric bacteria such as Salmonella and Shigella.

In the fermentation of these sugars are preferentially formed acidic metabolites which swing round the indicator from red ( pH> 7.3 ) to yellow ( 1> pH> 7.3 ). Some bacteria are able to reduce thiosulfate to sulfide which further reacts to form hydrogen sulfide. The hydrogen sulphide in turn leads to a reaction with iron, which finally precipitated as black iron sulphide.

• Nutrient