Vogel Johnson Agar 20mL Plate, 10/Pk

This product provides 20mL of Vogel Johnson (VJ) Agar in a pre-poured, sterile petri dish. This highly specialized medium is designed for the selective isolation and early detection of coagulase-positive Staphylococcus aureus, particularly from heavily contaminated food or clinical samples.

The "Double Identification" System: VJ Agar is unique because it filters out background noise while simultaneously performing two diagnostic tests on the growing colonies:

1. Selective Barrier:

   • The medium contains Tellurite (Potassium Tellurite), Lithium Chloride, and a high concentration of Glycine. This potent combination inhibits the growth of most background bacteria (like E. coli and Proteus), allowing Staphylococcus to thrive without competition.

2. Differentiation 1 (The Black Colony):

   • S. aureus has the ability to reduce Potassium Tellurite into metallic tellurium.

   • Visual Result: Colonies appear jet black.

3. Differentiation 2 (The Yellow Zone):

   • The medium contains Mannitol and the pH indicator Phenol Red. Pathogenic S. aureus typically ferments mannitol, producing acid.

   • Visual Result: The red agar turns distinctively yellow around the black colonies.

Diagnostic Significance:

• Black Colonies surrounded by Yellow Zones: Strong presumptive evidence of Staphylococcus aureus (coagulase-positive).

• Black Colonies with No Yellow: Likely non-pathogenic staphylococci (coagulase-negative) or other tellurite-reducing organisms.

Common Applications:

• Food Safety: Detecting S. aureus in foods prone to mishandling (meats, potato salads, pastries).

• Clinical Screening: Identifying S. aureus carriers via nasal or skin swabs.

• Pharmaceutical QC: Microbial limits testing (USP <61>) for non-sterile products.

Key Features:

• High Selectivity: Effectively inhibits Gram-negative competitors.

• Double Differential: Tests for Tellurite reduction and Mannitol fermentation simultaneously.

• Rapid ID: Provides presumptive identification within 24-48 hours.

• Visual Clarity: Black colonies on yellow backgrounds are easy to spot.

• Format: Sterile pre-poured agar plates (10-pack).

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