Vogel-Johnson Agar (VJ Agar) is a selective and differential medium used for the detection and enumeration of coagulase-positive, mannitol-fermenting Staphylococcus aureus from clinical and industrial samples. It is particularly valued in the pharmaceutical and cosmetic industries for testing raw materials and finished products for S. aureus contamination.
Vogel-Johnson Agar is based on the Tellurite-Glycine formulation but with the addition of a pH indicator to enhance differentiation. The Pancreatic Digest of Casein provides essential nitrogen and amino acids. Yeast Extract supplies vitamins and growth factors. Mannitol is the fermentable carbohydrate, and Phenol Red acts as the pH indicator. The medium’s selectivity is provided by Lithium Chloride and Glycine, which inhibit most other bacteria. Furthermore, the addition of Potassium Tellurite inhibits most Gram-positive and Gram-negative bacteria while allowing Staphylococcus aureus to reduce tellurite to metallic tellurium. This results in the formation of black colonies. If the organism also ferments mannitol, the surrounding medium turns from red to yellow due to acid production.
Advantages
- Dual Differentiation: Simultaneously identifies organisms based on tellurite reduction (black colonies) and mannitol fermentation (yellow halo).
- High Selectivity: Effectively suppresses the growth of most non-staphylococcal flora, including Gram-negative bacteria and many other Gram-positive cocci.
- Rapid Detection: Allows for the presumptive identification of pathogenic S. aureus within 24 to 48 hours.
- Optimized for Industrial Safety: Widely used in USP and pharmaceutical quality control protocols for microbial limit testing.
- Clear Results: The high contrast between black colonies and a yellow medium simplifies the screening of complex samples.
Instructions for use
Suspend 61.0 g of the powder in 1 liter of distilled or deionized water. Mix thoroughly and heat with frequent agitation; boil for one minute to ensure complete dissolution. Preparation: Sterilize by autoclaving at 121 °C for 15 minutes. Note: Cool the medium to 45–50 °C and aseptically add 20 mL of a sterile 1% Potassium Tellurite Solution (Cat. 6011). Mix well and pour into sterile Petri dishes. Inoculate the sample and incubate at 35 ± 2 °C for 24–48 hours. Typical S. aureus colonies appear black and are surrounded by a yellow zone.
Technical specifications
| Catalogue number | 1079 |
| Brand | Condalab |
| Application | Detection and enumeration of Staphylococcus aureus |
| Typical Composition (g/L) | Pancreatic Digest of Casein (10.0); Yeast Extract (5.0); Mannitol (10.0); Dipotassium Phosphate (5.0); Lithium Chloride (5.0); Glycine (10.0); Phenol Red (0.025); Bacteriological Agar (16.0) |
| Final pH (at 25 °C) | 7.2 ± 0.2 |
| Preparation | 61.0 g/L (plus Tellurite Supplement) |
| Storage Temperature | 2 – 25 °C |
Available packaging options
| 1079 | 500 g plastic bottle |
| Brand | Condalab |
| Pack size | 500 g |
