OXOID Triple Sugar Iron (TSI) Agar

OXOID Triple Sugar Iron (TSI) Agar – Differential Medium for Enteric Bacteria

OXOID Triple Sugar Iron (TSI) Agar is a high-quality differential medium used for the identification and characterization of Gram-negative enteric bacteria based on their ability to ferment sugars (glucose, lactose, sucrose) and produce hydrogen sulfide (H₂S) and gas. Manufactured by Oxoid, TSI Agar is widely used in clinical, food, and water microbiology laboratories.

 What is TSI Agar?

Triple Sugar Iron Agar is designed to differentiate Enterobacteriaceae by their sugar fermentation patterns and H₂S production. The medium contains glucose, lactose, sucrose, phenol red (pH indicator), and ferric ions for H₂S detection.

 Key Features

• Differential Medium – Distinguishes bacteria based on sugar fermentation, gas, and H₂S production
• Multiple Sugar Analysis – Glucose, lactose, and sucrose included
• H₂S Detection – Black precipitate indicates hydrogen sulfide production
• Reliable and Standardized – Suitable for routine identification of enteric pathogens

 Composition (Typical per Liter)

• Peptone: 20.0 g
• Beef extract: 3.0 g
• Yeast extract: 3.0 g
• Lactose: 10.0 g
• Sucrose: 10.0 g
• Glucose: 1.0 g
• Sodium chloride: 5.0 g
• Ferric ammonium citrate: 0.3 g
• Sodium thiosulfate: 0.3 g
• Agar: 15.0 g
• Phenol red: 0.024 g
• Final pH: 7.4 ± 0.2 at 25°C

 Principle of the Medium

• Glucose Fermentation Only → yellow butt, red slant
• Glucose + Lactose/Sucrose Fermentation → yellow butt and slant
• Non-Fermenters → red slant and butt
• H₂S Production → black precipitate in butt
• Gas Production → cracks or bubbles in agar

 Applications

• Clinical Microbiology – Differentiation of enteric pathogens like Salmonella and Shigella
• Food and Water Testing – Detection of coliforms and enteric bacteria
• Research Laboratories – Characterization of Gram-negative bacilli
• Pharmaceutical QC – Identification of microbial contaminants

 Directions for Use

1. Suspend TSI Agar powder in distilled water.
2. Heat to dissolve completely.
3. Sterilize by autoclaving at 121°C for 15 minutes.
4. Cool to ~50°C if pouring slants; pour into test tubes and allow to solidify at an angle to create slants.
5. Inoculate by stabbing the butt and streaking the slant with the test organism.

 Storage & Shelf Life

• Store in a cool, dry place (10–30°C)
• Protect from moisture and light
• Keep tightly sealed

 Precautions

• For laboratory use only
• Maintain aseptic technique
• Avoid prolonged heating to prevent caramelization of sugars

 Why Choose OXOID TSI Agar?

With Oxoid quality assurance, TSI Agar provides accurate differentiation, reproducible results, and reliable identification of enteric bacteria, making it a laboratory staple worldwide.