Liofilchem® Vogel Johnson Agar

Liofilchem® Vogel Johnson Agar is a selective and differential culture medium formulated for the isolation and identification of coagulase-positive, mannitol-fermenting strains of Staphylococcus aureus from food products and clinical samples.

The medium corresponds to the United States Pharmacopoeia (USP) specifications and enables early detection of S. aureus in heavily contaminated specimens through a combination of selective agents and differential indicators.

When supplemented with Liofilchem® Potassium Tellurite 1% Supplement (REF. 80022), S. aureus colonies appear black or gray with yellow zones, caused by tellurite reduction and mannitol fermentation.

Key Features

• Selective formulation: Lithium chloride, glycine, and tellurite inhibit non-target organisms.
• Differential system: Phenol Red indicator highlights mannitol fermentation.
• High sensitivity: Enables detection of S. aureus even in heavily contaminated foods.
• USP-compliant formulation: Based on the recognized Vogel and Johnson (1961) modification.
• Distinct morphology: S. aureus colonies appear black with yellow halos.
• Versatile use: Applicable to clinical, food, and environmental microbiology laboratories.

Principle

The selective agents lithium chloride, glycine, and potassium tellurite suppress most Gram-negative and other Gram-positive bacteria.

Mannitol fermentation by S. aureus lowers the pH, changing Phenol Red from red to yellow.

Reduction of tellurite results in black colony pigmentation, aiding in differentiation and presumptive identification.

Typical Formula (g/L)

Directions for Use

1. Suspend 60 g of powder in 1 L of distilled or deionized water.
2. Heat to dissolve completely.
3. Autoclave at 121°C for 15 minutes.
4. Cool to 45–50°C and aseptically add 20 mL of Potassium Tellurite 1% Supplement (REF. 80022).
5. Mix thoroughly and pour into sterile Petri dishes.

Quality Control

Incubation Conditions: 36 ± 1°C for 24–48 hours

Appearance (Dehydrated): Free-flowing, homogeneous, pink powder

Appearance (Prepared): Slightly opalescent, red-orange agar

Performance & Limitations

• Prolonged incubation may yield black coagulase-negative colonies that ferment mannitol; confirm identity with coagulase or biochemical tests.
• Intended for presumptive identification; further confirmatory tests may be required.

Product Specifications

Applications

• Food Microbiology: Detection of S. aureus in meat, dairy, baked goods, and processed foods.
• Clinical Microbiology: Isolation of coagulase-positive S. aureus from wound and respiratory specimens.
• Environmental Testing: Hygiene monitoring in production and packaging facilities.
• Pharmaceutical QC: Identification of Staphylococcus aureus contamination in production areas.

Unique Advantages

• High selectivity for Staphylococcus aureus detection.
• Distinct black/yellow colony differentiation for easy identification.
• USP-compliant formula ensures regulatory reliability.
• Compatible with Liofilchem® Potassium Tellurite Supplements.
• Accurate and reproducible results across multiple matrices.

Liofilchem® Vogel Johnson Agar is a selective and differential medium that simplifies the isolation and identification of Staphylococcus aureus from complex samples.

When supplemented with Potassium Tellurite 1% (REF. 80022), it provides distinct colony morphology and high selectivity, making it a trusted medium for clinical, food, and industrial laboratories worldwide.