TCBS Agar

🧫 TCBS Agar Interactive Microbiology Learning System

Intended Use

Selective and differential medium for isolation of Vibrio species from stool, seafood and environmental samples.

Principle

• High pH suppresses many intestinal bacteria.
• Bile salts, citrate and sodium thiosulfate increase selectivity.
• Sucrose differentiates fermenters.
• Bromothymol blue and thymol blue indicate pH changes.
• Ferric citrate detects H₂S (rare in Vibrio).

Composition

Component	Function
Peptones/Yeast extract	Nutrients
Sucrose	Differential carbohydrate
Sodium citrate	Selectivity
Ox bile	Inhibits Gram positives
Sodium thiosulfate	Sulfur source
Ferric citrate	H₂S indicator
Bromothymol blue & Thymol blue	pH indicators
Agar	Solidifying agent

Media Preparation

1. Suspend dehydrated medium in distilled water.
2. Heat gently until dissolved.
3. Do NOT autoclave.
4. Cool to 45–50°C and pour plates.
5. Store protected from light.

Interactive Colony Interpretation

Organism	Expected Result
Vibrio cholerae ATCC 14035	Large yellow colonies
Vibrio alginolyticus	Yellow colonies
Vibrio parahaemolyticus ATCC 17802	Blue-green colonies
Escherichia coli ATCC 25922	Inhibited/poor growth

• TCBS is not suitable for species confirmation.
• Biochemical or molecular identification is required.
• Old plates may reduce selectivity.
• Do not autoclave prepared medium.

1. MacFaddin.
2. Bailey & Scott's Diagnostic Microbiology.
3. Koneman's Color Atlas.
4. CLSI M22.