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Modified Semisolid Rappaport Vassiliadis (MSRV) agar
The figure shows four MSRV agar plates. Bacteria have not been cultivated on the plate in image A. On the plate in image B has a bacterium, which is not a Salmonella sp. been applied to the right of the arrows, where you can see grey zones of bacteria. Salmonella enterica subsp. enterica has been applied onto the plates in images C and D. The plates in the images B and D have been incubated during 48 h at 41,5°C and the plate in image C has been incubated during 24 h at the same temperature. Note that the blue colour still can be discerned on plate C after 24 h, but has completely disappeared on plate D after 48 h, because Salmonella spp. has been swarming over the surface of the agar and forms a grey continuous layer.
Modified Semisolid Rappaport Vassiliadis (MSRV) agar is a selective enrichment medium for rapid detection of motile Salmonella spp. in feces and food products. When the MSRV agar plate is used, 100 µl of sample is distributed on three sites (see figure).
Content of the medium:
The difference between RVS medium and MSRV medium is that the MSRV medium contains a low koncentration of agar, which makes it possible for motile strains of Salmonella spp. to swarm in contrast to most other motile strains of bacteria. Most Salmonella strains are motile. Furthermore, the MRSV-medium also contains Novobiocin, which increases the selectivity.
No heavy greyish swarming zone is visible in a salmonella negative sample, whereas salmonella positive samples give a very heavy swarming, which covers the complete plate within 24-48 h.