OXOID Eosin Methylene Blue (EMB) Agar – Reliable Medium for Gram-Negative Bacteria Isolation

 Overview

OXOID Eosin Methylene Blue (EMB) Agar is a high-quality selective and differential culture medium designed for the isolation and differentiation of Gram-negative enteric bacteria. It is widely used in clinical laboratories, food safety testing, and water quality analysis to detect lactose-fermenting organisms, particularly coliforms.

This premium-grade microbiological medium is manufactured by Oxoid Ltd., part of Thermo Fisher Scientific, ensuring consistent performance and international quality standards.

 Principle of EMB Agar

EMB Agar works based on selective inhibition and lactose fermentation differentiation:

• Eosin Y and Methylene Blue dyes inhibit Gram-positive bacteria
• Lactose acts as a fermentable carbohydrate
• Acid production from lactose fermentation causes color changes

Colony Appearance:

• Strong lactose fermenters (e.g., E. coli) → Metallic green sheen
• Moderate fermenters (e.g., Klebsiella, Enterobacter) → Pink to purple colonies
• Non-lactose fermenters (e.g., Salmonella, Shigella) → Colorless colonies

 Key Features & Benefits

• Selective for Gram-negative bacteria
• Differential identification of lactose fermenters
• Clear colony morphology for easy interpretation
• High reproducibility and batch consistency
• Trusted brand for laboratory diagnostics
• Suitable for routine and research applications

 Applications

• Clinical microbiology laboratories
• Detection of coliform bacteria in water
• Food and beverage safety testing
• Pharmaceutical microbiology
• Environmental monitoring and research

Composition (Typical Formula per Liter)

• Peptone – Nutrient source
• Lactose – Fermentable sugar
• Dipotassium phosphate – Buffering agent
• Eosin Y – Selective dye
• Methylene blue – Indicator dye
• Agar – Solidifying agent

 Preparation & Usage Instructions

1. Suspend the required amount of powder in distilled water
2. Heat to dissolve completely
3. Sterilize by autoclaving at 121°C for 15 minutes
4. Cool to 45–50°C and pour into sterile Petri dishes
5. Allow to solidify
6. Inoculate the sample and incubate at 35–37°C for 18–24 hours

 Storage & Shelf Life

• Store in a cool, dry place (10–30°C)
• Keep container tightly closed
• Protect from moisture and direct sunlight

 Why Choose OXOID EMB Agar?

Choosing OXOID EMB Agar ensures:

• Accurate microbial detection
• Consistent laboratory results
• Compliance with international standards
• Reliable performance across applications