Tryptic Soy Agar (TSA)
TSA is a general-purpose, non-selective culture medium suitable for the cultivation of a wide range of microorganisms including aerobic bacteria, yeasts, and moulds. It is one of the most widely used media in microbiology laboratories worldwide.
Composition
TSA is based on pancreatic digest of casein and soybean meal, supplemented with sodium chloride. The rich nutrient content supports the growth of fastidious organisms that may not grow on more selective media.
Applications
Violet Red Bile Glucose Agar (VRBG)
VRBG is a selective and differential medium designed for the detection and enumeration of Enterobacteriaceae in food, water, and environmental samples. The bile salts and crystal violet inhibit gram-positive organisms, while glucose fermentation with acid production is used to identify Enterobacteriaceae.
Composition
VRBG contains yeast extract, peptone, glucose, sodium chloride, bile salts, crystal violet, and neutral red as a pH indicator.
Applications
Key Differences
| Feature | TSA | VRBG |
|---|---|---|
| Selectivity | Non-selective | Selective (Enterobacteriaceae) |
| Organisms detected | All aerobic bacteria, yeasts, moulds | Enterobacteriaceae only |
| Incubation temperature | 30–35°C | 37°C |
| Incubation time | 48–72 h | 18–24 h |
| Colony appearance | Colourless/white | Pink to red with purple halo |
| Typical use | TVC, sterility, general | Food hygiene, water testing |
Which Medium Should You Choose?
Use TSA when you need a general count of all viable microorganisms — for example in cleanroom environmental monitoring or sterility testing.
Use VRBG when you specifically need to detect Enterobacteriaceae — for example in food hygiene testing or water quality monitoring.
Both media are available from CertaMedia in all formats: RODAC plates, petri dishes, flasks, and tubes.