Rappaport-Vassiliadis (MSRV) Medium Semi-Solid

Rappaport-Vassiliadis (MSRV) Medium Semi-Solid is a modification of Rappaport-Vassiliadis Soy Broth for detecting motile Salmonella spp. in faeces and food products.[1]
The original research on MSRV Medium revealed a semi-solid could be used as a rapid and sensitive test for isolating motile Salmonella spp. from food products following pre-enrichment or selective enrichment.[2]

The semi-solid medium allows motility to be detected as halos of turbid growth around the original point of inoculation.
The peptones are to provide vitamins, nutrients and nitrogen to encourage growth of Salmonella spp.
The salt maintains the osmotic balance and potassium dihydrogen phosphate is a buffer for stabilising the pH of the medium.
Malachite green is included as a selective agent that inhibits Gram-positive organisms and some Gram-negative organisms.

References
(1) ISO 6579-1:2017. Microbiology of the food chain – Horizontal method for the detection, enumeration and serotyping of Salmonella – Part 1: Detection of Salmonella spp.
(2) De Smedt J.M., Bolderdikj R., Rappold H. and Lautenschlaeger D. 1986. Rapid Salmonella Detection in Foods by Motility Enrichment on a Modified Semi-Solid Rappaport-Vassiliadis Medium. J. Food Prot. 49:510-514

Shelf Life (days)	1095 days
Dehydrated Medium Appearance	Fine Powder
Dehydrated Medium Colour	Beige – light blue
Dehydrated PH	5.25±0.15
Prepared Medium Appearance	Semi-solid gel
Prepared Medium Colour	Turquoise blue
Prepared PH	5.25±0.15
Container	500G, 5KG, 10KG

Shelf Life (days)

1095 days

Dehydrated Medium Appearance

Fine Powder

Dehydrated Medium Colour

Beige – light blue

Dehydrated PH

5.25±0.15

Prepared Medium Appearance

Semi-solid gel

Prepared Medium Colour

Turquoise blue

Prepared PH

5.25±0.15

Container

500G, 5KG, 10KG

Formula*

g/L

Enzymatic digest of animal and plant tissue

4.6

Acid hydrolysate of casein

4.6

Sodium chloride

7.3

Potassium dihydrogen phosphate

1.5

Magnesium chloride anhydrous

10.9

Malachite green oxalate

0.04

Agar

2.7

Total

31.64

*Adjusted/supplemented as required to meet performance requirements

Preparation

Suspend 14.238g of the medium in 450ml of deionised / purified water.
Allow the medium to soak whilst mixing for 10 minutes.
Heat with frequent agitation and boil for one minute to completely dissolve the medium.
DO NOT AUTOCLAVE this medium.
Cool to 45-50°C and aseptically add 1 vial of LS0160 MSRV Novobiocin Selective Supplement (or 2ml of BM4032 MSRV Novobiocin Solution) per 450ml of product. Allow to mix thoroughly then aseptically dispense into appropriate sterile containers.

Organisms	Ref. No	Result
Salmonella typhimurium	NCTC 12023	Growth, turbid zone extending from inoculation point
Salmonella enteritidis	NCTC 12694	Growth, turbid zone extending from inoculation point
Escherichia coli	NCTC 12241	Inhibited, possible growth without turbid zone
Enterococcus faecalis	NCTC 12697	Inhibited