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Triple Sugar Iron Agar, TSI
Used for differentiation of gram-negative enteric bacilli based on fermentation of dextrose, lactose and sucrose and hydrogen sulfide production.
Catalog Number: AS-1365
Based on their ability to produce hydrogen sulfide and ferment carbohydrates, Gram-negative Enterobacteriaceae are biochemically characterized using Triple Sugar Iron (TSI) agar, a differential culture medium. The medium is composed of three types of carbohydrates: dextrose, sucrose, and lactose; yeast extract, which serves as a source of vitamins; and a mixture of peptone, which supplies necessary nutrients. Phenol red is used as a pH indicator; colorimetric changes indicate the presence of acidic (yellow) or alkaline (red) circumstances. To identify the creation of hydrogen sulfide, which is seen as black iron sulfide precipitates, iron salts and sodium thiosulfate are added. Osmotic balance is sustained by sodium chloride.
Similar to Kligler Iron Agar, TSI agar contains sucrose, which allows Proteus and Salmonella species to be distinguished from one another. Proteus fermentation of sucrose causes general acidification, whereas Salmonella usually ferments dextrose and then, because of peptone catabolism, returns the slant to an alkaline state.
Storage
Keep the container at 15-30 °C and prepared medium at 2-8 °C.
| Composition | gr/L |
| Enzymatic Digest of Casein | 15 |
| Enzymatic Digest of Animal Tissues | 8 |
| Yeast Enriched Peptone | 3 |
| Dextrose | 1 |
| Lactose | 10 |
| Sucrose | 10 |
| Ferric Ammonium Citrate | 0.5 |
| Sodium Chloride | 5 |
| Sodium Thiosulfate | 0.5 |
| Phenol Red | 0.024 |
| Agar | 12 |
| Final pH at 25°C | 7.4 ± 0.2 |
| Dehydrated Appearance | Pink, free-flowing, homogeneous. |
| Prepared Appearance | Red, slightly opalescent. |
| Reaction of 6.5% Solution at 25°C | pH 7.4 ± 0.2 |
| Incubate at 35 ± 2 °C for 18 to 24 hours with loosened caps. Use fresh cultures for inoculation and use stab and streak method. | |||||
| Organism (ATCC) | Recovery | Slant | Butt | Gas | H2S |
| Escherichia coli (25922) | Good | A** | A | + | – |
| Pseudomonas aeruginosa (9027) | Good | K*** | K | – | – |
| Salmonella enterica (14028) | Good | K | A | + | + |
| Shigella flexneri (12022) | Good | K | A | – | – |
| Proteus vulgaris (13315) | Good | A | A | + | + |
