Triple Sugar Iron Agar – HX-MEDIA

Overview

Triple Sugar Iron Agar (TSI) is a differential culture medium used for the identification and differentiation of enteric Gram-negative bacteria based on their ability to ferment glucose, lactose, and sucrose, as well as produce gas and hydrogen sulfide (H₂S).

The medium contains three sugars (glucose in low concentration and lactose & sucrose in higher concentrations), phenol red as a pH indicator, and sodium thiosulfate with ferrous salts for H₂S detection. Fermentation of sugars leads to acid production, turning the medium yellow, while non-fermenters maintain a red (alkaline) reaction.

Characteristic reactions are observed in the slant and butt of the medium:

• A/A (yellow/yellow): glucose + lactose/sucrose fermentation

• K/A (red/yellow): glucose fermentation only

• K/K (red/red): no fermentation

• Black precipitate: H₂S production

• Cracks/lifting: gas production

Triple Sugar Iron Agar is widely used in clinical diagnostics, food safety testing, water analysis, and research laboratories for the identification of organisms such as Salmonella, Shigella, and Escherichia coli.

It provides clear visual differentiation, reliable biochemical results, and rapid preliminary identification, making it an essential medium in microbiological analysis.

🔬 Key Features

• Differentiates sugars, gas, and H₂S production

• Slant–butt format for clear reaction zones

• Useful for rapid Enterobacteriaceae identification

🎯 Applications

• Identification of Enterobacteriaceae

• Triple Sugar Iron Agar differentiation based on sugar fermentation, gas, and H₂S production

• Routine testing in clinical, food, and environmental microbiology

• Screening of Gram-negative rods in diagnostic workflows

🧪 Composition (Typical)

• Peptone: 20 g/L

• Yeast & Beef Extracts: 3 g/L each

• Lactose & Sucrose: 10 g/L each

• Glucose: 1 g/L

• NaCl: 5 g/L

• Ferrous Sulfate: 0.2 g/L

• Sodium Thiosulfate: 0.3 g/L

• Phenol Red: 0.024 g/L

• Agar: 12 g/L

🛠️ How to Use

• Inoculate by stab and streak.

• Incubate at 35–37°C.

• Read sugar, gas, and H₂S reactions.

⏳Storage and Shelf Life

• Store dry medium below 30°C, protected from light.

• Keep closed; use before expiry.

• Prepared slants: refrigerate and use soon.

👍 Ideal For

✔ Clinical and diagnostic labs

✔ Food and water testing

✔ Enterobacteriaceae identification workflows