Chapman Stone Agar is formulated with a high concentration of Sodium Chloride (5.5%), which acts as a selective agent by inhibiting the growth of most other bacteria while allowing Staphylococci to thrive. The medium contains Gelatin as a substrate for gelatinase activity and Mannitol for fermentation studies. Yeast Extract and Tryptone provide the nitrogenous compounds, vitamins, and minerals required for bacterial growth. A unique feature of this medium is that it does not contain a pH indicator in the base; instead, after incubation, the plate is flooded with a reagent (Stone's method) to observe gelatin hydrolysis. Staphylococcus aureus typically produces pigmented colonies and exhibits positive gelatinase activity, making this medium ideal for the "Stone reaction" used in food microbiology to screen for enterotoxigenic strains.
Advantages
- Selective Isolation: The salt content effectively suppresses background flora, simplifying the recovery of Staphylococci.
- Clear Differentiation: Allows for the simultaneous observation of pigmentation, mannitol fermentation, and gelatin liquefaction.
- Standardized for Food Testing: Frequently used in the analysis of food products for the presence of coagulase-positive Staphylococci.
- Optimized Formulation: Ammonium Sulfate and Potassium Phosphate ensure stable osmotic and pH conditions during incubation.
- Reliable Stone Reaction: Specifically designed to produce distinct zones of gelatin clearing when testing for pathogenicity.
Technical specifications
| Catalogue number |
1017 |
| Brand |
Condalab |
| Application |
Isolation and differentiation of Staphylococci |
| Typical Composition (g/L) |
Yeast Extract (2.0); Tryptone (10.0); Sodium Chloride (55.0); D-Mannitol (10.0); Gelatin (30.0); Dipotassium Phosphate (5.0); Bacteriological Agar (15.0); Ammonium Sulfate (75.0) |
| Final pH (at 25 °C) |
7.0 ± 0.2 |
| Preparation |
202.5 g/L |
| Storage Temperature |
2 – 25 °C |
Available packaging options
| 1017-500G |
500 g plastic bottle |
