Understanding RVSEB (Rappaport-Vassiliadis Soya Peptone Broth): Principle, Preparation, and Uses
Rappaport-Vassiliadis Soya Peptone Broth (RVSEB) is a selective enrichment medium designed for the isolation and detection of Salmonella species from food, water, and clinical samples. It plays a crucial role in microbiological quality testing, especially in pharmaceutical, food, and environmental laboratories.
📘 Introduction
The detection of Salmonella requires selective enrichment because of its lower numbers compared to competing microorganisms in a sample. RVSEB provides a favorable environment for Salmonella growth while suppressing non-target bacteria through selective agents and optimal incubation conditions.
🧪 Composition of RVSEB (per liter)
- Soya Peptone – 4.5 g
- Sodium Chloride – 8.0 g
- Potassium Dihydrogen Phosphate – 1.6 g
- Magnesium Chloride (anhydrous) – 13.6 g
- Malachite Green – 0.04 g
- Distilled Water – 1000 ml
- pH after sterilization – 5.2 ± 0.2 at 25°C
⚗️ Principle of RVSEB
The medium is based on the principle that Salmonella species can survive and multiply under conditions that inhibit the growth of competing bacteria. Magnesium chloride and malachite green act as selective agents that inhibit Gram-positive organisms and many Gram-negative bacteria, allowing Salmonella to flourish.
The low pH (5.2) and high osmotic pressure also favor the selective enrichment of Salmonella by creating stress conditions that these bacteria can tolerate better than most others.
⚙️ Preparation of RVSEB Medium
- Weigh all components as per the formula and dissolve them in 1000 ml of distilled water.
- Heat gently with continuous stirring until all components are completely dissolved.
- Adjust the pH to 5.2 ± 0.2 if necessary.
- Dispense into screw-capped bottles or tubes.
- Sterilize by autoclaving at 115°C for 15 minutes.
- Cool the medium to room temperature before inoculation.
🧫 Inoculation and Incubation
- Transfer 0.1 ml of the pre-enriched sample (from Buffered Peptone Water) into 10 ml of RVSEB.
- Incubate at 42°C ± 0.5°C for 18–24 hours.
- After incubation, streak a loopful of culture onto selective agar plates such as XLD agar or Bismuth Sulphite Agar for isolation.
🔬 Result Interpretation
The RVSEB broth becomes slightly turbid after incubation. Subculturing on selective agar reveals typical Salmonella colonies such as:
- On XLD Agar – Red colonies with black centers.
- On Bismuth Sulphite Agar – Black or brown colonies with a metallic sheen.
🧍♂️ Quality Control
Recommended test organisms for QC of RVSEB:
| Organism | Growth Response |
|---|---|
| Salmonella Typhimurium ATCC 14028 | Good growth |
| Escherichia coli ATCC 25922 | Inhibited |
| Enterococcus faecalis ATCC 29212 | Inhibited |
💡 Applications
- Detection and isolation of Salmonella from food, water, and environmental samples.
- Used in pharmaceutical microbiology for raw material and finished product testing.
- Applicable in public health laboratories for routine surveillance.
- Part of ISO and pharmacopoeial microbiological test methods for Salmonella.
⚖️ Advantages
- Highly selective and effective for Salmonella enrichment.
- Suppresses competing microbial flora efficiently.
- Provides consistent results with reproducible growth patterns.
⚠️ Precautions
- Do not overheat the medium during preparation, as malachite green may decompose.
- Ensure accurate pH for selective performance.
- Use freshly prepared medium for best results.
📚 References
- ISO 6579: Microbiology of Food and Animal Feeding Stuffs — Detection of Salmonella.
- Pharmaceutical Microbiology Guidelines, USP & IP.
- Oxoid and HiMedia Product Manuals for RVSEB.
💬 About the Author
Siva Sankar is a Pharmaceutical Microbiology Consultant and Auditor with extensive experience in sterility testing, validation, and GMP compliance. He provides consultancy, training, and documentation services for pharmaceutical microbiology and cleanroom practices.
📧 Contact: siva17092@gmail.com
Mobile: 09505626106
