Thermo Scientific™ Oxoid™ Rappaport-Vassiliadis Enrichment Broth (Dehydrated)

The Oxoid™ Rappaport-Vassiliadis (RV) Enrichment Broth is a selective medium designed to isolate Salmonella spp. from food, environmental samples, and human feces. Its formulation enhances the selective enrichment of Salmonella through optimal pH, osmotic pressure, and selective agents, making it superior to other enrichment broths for detecting Salmonella.

Key Features

1. Selective Enrichment for Salmonella:
   • Optimized for Salmonella spp., excluding Salmonella typhi.
   • Exploits unique characteristics of Salmonella:
     • Growth under high osmotic pressure.
     • Multiplication at low pH.
     • Resistance to malachite green.
     • Low nutritional requirements.
2. Enhanced Formulation:
   • Contains soya peptone, which supports improved growth of Salmonella spp. compared to other peptones.
3. Wide Applicability:
   • Effective for food safety testing, environmental monitoring, and clinical diagnostics.
4. High Performance:
   • Demonstrated superiority to Selenite and Tetrathionate broths for Salmonella enrichment.
   • Performs well even with small inocula from pre-enrichment cultures.
5. Convenient Preparation:
   • Dehydrated medium for easy reconstitution.
   • Stable storage and long shelf life.

Typical Formula (per litre)

Preparation Instructions

1. Reconstitution:
   • Suspend 30 g of dehydrated medium in 1 litre of distilled water.
   • Heat gently to dissolve completely.
2. Dispense:
   • Dispense into tubes or bottles (e.g., 10 mL per tube).
3. Sterilization:
   • Autoclave at 115°C for 15 minutes.
4. Storage:
   • Store prepared medium at 2–8°C.

Applications

1. Food Safety Testing:
   • Detects Salmonella spp. in various food products and environmental samples.
   • Effective in testing fluid whole milk and seawater samples.
2. Clinical Diagnostics:
   • Isolates Salmonella spp. from fecal specimens without pre-enrichment.
3. Environmental Monitoring:
   • Suitable for testing water and environmental samples for Salmonella spp.

Technique

1. Pre-Enrichment:
   • Incubate the test sample in Buffered Peptone Water (e.g., 25 g of sample in 225 mL) at 35°C for 16–20 hours.
2. Selective Enrichment:
   • Inoculate 0.1 mL of pre-enrichment culture into 10 mL of RV Broth.
   • Incubate at 42 ± 1°C for 24–48 hours (preferred: 42 ± 0.1°C for water baths).
3. Subculture:
   • Streak RV Broth culture onto XLD Agar or other selective media.
   • Incubate at 35°C for 18–24 hours.
4. Confirmation:
   • Identify colonies with typical Salmonella morphology using biochemical or serological methods.

Quality Control

Storage Conditions

• Dehydrated Medium: Store at 10–30°C.
• Prepared Medium: Store at 2–8°C.

Appearance

• Dehydrated Medium: Pale green, free-flowing powder.
• Prepared Medium: Blue-coloured solution.

Benefits

1. High Selectivity:
   • Favors Salmonella spp. while suppressing competing organisms.
2. Efficient Detection:
   • Effective even with small inoculum sizes (1:100 to 1:2000 inoculum/broth ratios).
3. Proven Superiority:
   • Outperforms other enrichment media for Salmonella spp. isolation.
4. Versatility:
   • Suitable for a wide range of sample types, including food, environmental, and clinical specimens.
5. Convenience:
   • Ready-to-prepare dehydrated format simplifies workflow.

Precautions

• Not recommended for detecting Salmonella typhi.
• Use small inoculum sizes to maintain the medium's selectivity.

References

1. van Schothorst, M., and Renaud, A.M. (1983). J. Appl. Bact. 54:209–215.
2. Rappaport, F., et al. (1956). J. Clin. Path. 9:261–266.
3. Vassiliadis, P., et al. (1976). Annales de Microbiologie (Institut Pasteur) 127B:195–200.
4. Moriñigo, M.A., et al. (1990). J. Microbiol. Methods 11:43–49.
5. Vassiliadis, P., et al. (1991). J. Food Prot. 54:421–423.

Summary

The Thermo Scientific™ Oxoid™ Rappaport-Vassiliadis Enrichment Broth is an advanced selective medium designed for reliable Salmonella spp. isolation. Its enhanced formulation and performance make it a trusted choice for food safety, clinical diagnostics, and environmental microbiology.