Medium 9. Rappaport Vassiliadis Salmonella Enrichment Broth

Principle And Interpretation

Rappaport Vassiliadis Salmonella Enrichment Medium is designed according to the revised formulation by Van Schothorst et al (1) and is recommended for the selective enrichment of Salmonellae from pharmaceutical products. This medium can also be used in direct enrichment of samples containing low inoculum. Present medium is a modification of the Rappaport Vassiliadis Enrichment Broth described by Van Schothorst and Renauld (2). It is prepared as per the formulation in Indian Pharmacopoeia (9) and is in accordance with the harmonized methodology of USP/EP/BP/JP/IP(3,4,5,6,9) has been found to be superior to other Salmonella selective medias. Addition of magnesium chloride to the medium was reported by Peterz et al (7). Salmonella species can be isolated from human faeces without pre-enrichment by using this medium.

Salmonella generally survive at little high osmotic pressure, grow at slightly low pH and are resistant to malachite green compared to other bacteria. These characteristics are exploited in this medium for selective enrichment of Salmonella. Magnesium chloride present in the medium raises the osmotic pressure. Natural sugars of soya peptone provide essential growth nutrients and enhance the growth of Salmonella (8). Phosphate buffers the medium to maintain constant pH. Sodium chloride maintains the osmotic balance. Malachite green inhibits many gram-positive bacteria, while selectively enriches Salmonella. The relatively lower concentration of nutrition, also aids selective enrichment of Salmonella. This medium was reported to be superior to Salmonella selective medium like Tetrathionate Broth and Selenite enrichment broth and to Tetrathionate- Brilliant Green Broth for the detection of Salmonellae in milk samples. The enriched culture of Rappaport Vasiliadis Salmonella Enrichment Broth (MM1491) can be further subcultured and isolated on Brilliant Green Agar (MM016) or Xylose Lysine Deoxycholate Agar (MM031).