Rappaport Soy Broth (Vassiliadis) ISO
Rappaport Soy Broth (Vassiliadis) is recommended by ISO 6579 and ISO 19250, after the pre-enrichment step, for the selective isolation of Salmonella spp.
Rappaport medium was modified by Vassiliadis by reducing Malachite green concentration and increasing incubation temperature, thus offering a better stability of the pH of the prepared medium and optimizing the concentration of Magnesium chloride, resulting in an improved recovery of Salmonellae.
Soy peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Potassium phosphates balance the low pH of the medium, combined with the presence of Magnesium chloride to raise the osmotic pressure, and Malachite green to inhibit other organisms. Sodium chloride supplies essential electrolytes for transport and osmotic balance.
Preparation
Suspend 26,6 grams of the medium in 1 liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Dispense into appropriate containers and sterilize in autoclave at 115 °C for 15 minutes. DO NOT OVERHEAT.
Instructions for use
* For detection of Salmonella spp. in food, animal feed, animal faeces, and environmental samples according to ISO 6579:
– Preenrichment in non-selective liquid medium:
Inoculate the Buffered Peptone Water with the sample or dilutions, and incubate at 34-38 ºC for 18±2 h.
– Enrichment in/on selective media:
Inoculate, with the culture obtained in the pre-enrichment stage, the Rappaport Soy Broth (Vassiliadis) or the Modified Semisolid Rappaport Vassiliadis medium (MSRV), and the MKKTN Broth. The Rappaport Soy Broth and the Modified Semisolid Rappaport medium are incubated at 41,5 ºC for 24±3 h, and the MKKTN Broth at 34-38 ºC for 24±3 h.
– Plating out on selective solid media:
From the selective enriched cultures, inoculate two selective isolation agar; XLD agar and any other selective medium complementary to XLD agar, Salmonella Chromogenic Agar , Brilliant Green Agar, Bismuth Sulfite Agar, DCLS Agar, Desoxycholate Citrate Agar , Hektoen Enteric Agar, Salmonella Shigella Agar and XLT4 Agar.
Incubate the XLD plates inverted at 34-38 ºC for 24±3 h.
Incubate the second selective medium in accordance with the manufacturer’s instructions.
– Confirmation:
Subculture colonies of presumptive Salmonella and confirm their identity by biochemicals and serological tests.