Triple Sugar Iron Agar
Triple Sugar Iron-Agar (English for Dreizucker-Eisen-Agar), TSI-Agar for short, describes a test tube nutrient medium which is used to detect hydrogen sulfide- producing and / or sugar- fermenting bacteria. The test consists of agar mixed with a pH indicator ( phenol red ) and the three sugars lactose (1%), sucrose (1%) and glucose (0.1%). In medical microbiology, it is mainly used to detect pathogenic enteric bacteria such as salmonella and shigella .
During the fermentation of the sugars mentioned, acidic metabolites are formed , which turn the indicator from red (pH> 7.3) to yellow (1> pH> 7.3). Some bacteria are able to reduce thiosulfates to sulfides , which further reacts to hydrogen sulfide. The hydrogen sulfide in turn leads to a reaction with iron , which finally precipitates as black iron sulfide .
Individual evidence
- ↑ Tankeshwar Acharya: Triple Sugar Iron Agar (TSI): Principle, Procedure and Interpretation. In: microbeonline.com. 2013, accessed June 17, 2017 .