Modified Rappaport Vassiliadis Medium

Composition**

Final pH (at 25°C): 5.2±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 30.07 grams of dehydrated medium in 1000 ml distilled water. Heat gently if necessary to dissolve the medium completely. Dispense as desired into tubes and sterilize by autoclaving at 10 lbs pressure (115°C) for 15 minutes.

Principle And Interpretation

The original formulation described by Rappaport et al (1) with magnesium chloride hexahydrate was modified by Vassiliadis et al (2) by lowering the concentration of malachite green and raising the incubation temperature to 43°C. This medium is recommended as the selective enrichment medium for isolation of Salmonella from food and environmental specimens. Recently ISO committee has recommended the medium with casein enzymic hydrolysate for the detection of Salmonellae (3).

The casein enzymic hydrolysate used is reported to enhance the growth of Salmonella

The test specimen is added to Buffered Peptone Water (M614) and incubated at 35°C for 16 - 20 hours. This pre-enriched peptone water culture is inoculated into Modified Rappaport Vassiliadis Medium and incubated at 42±1°C for 24-48 hours and further subcultured on Brilliant Green Agar (M016).

Quality Control

Appearance: Light yellow to light blue coloured homogeneous free flowing powder

Colour and Clarity of prepared medium: Blue coloured clear solution without any precipitate.

Reaction: Reaction of 3% w/v aqueous solution at 25°C. pH : 5.2±0.2

pH: 5.00-5.40

Cultural Response

M11371: Cultural characteristics observed after an incubation at specified temperature for 24-48 hours.

Storage and Shelf Life

Store below 30°C in tightly closed container and use freshly prepared medium. Use before expiry date on the label.

Reference

1. Rappaport F., Konforti N. and Navon B., 1956, J. Clin. Path., 9:261.
2. Vassiliadis P. et al, 1976a, Annales de Microbiologie (Institut Pasteur), 127B : 195.
3. International Organization for Standardization (ISO), 1993, Draft ISO/DIS 6579.