Modification of Rappaport-Vassiliadis enrichment broth into a semisolid motility medium (MSRV) provided a sensitive means for detecting Salmonella in contaminated foods. The type of peptone, the concentration of magnesium chloride, the presence of novobiocin and the temperature of incubation were determinants in medium performance. The analytical procedure consists of preenrichment for 20 h, followed by motility enrichment on MSRV for 24 h and, if there is migration, serological tests with the motile culture. The test result is obtained within 48 h from the start of preenrichment. This approach gave 39% more Salmonella-positive samples than enrichment in tetrathionate brilliant green broth with subsequent plating.

The effect of low Salmonella cell concentrations in combination with high numbers of competitive flora after pre-enrichment on subsequent isolation with motility enrichment in modified semisolid Rappaport-Vassiliadis (MSRV) was studied. Salmonella was always detected on MSRV if the cell concentration in the preenrichment culture was at least 60 per ml, even if they were outnumbered by competitive bacteria by a factor of 107. In a total of 52 experiments, Salmonella detection on MSRV directly after preenrichment was successful in 46 tests. Combination of direct motility enrichment with additional motility enrichment after 8 h in tetrathionate brilliant green (TBG) broth resulted in 49 positive tests, compared to only 33 positive results after enrichment in TBG for 24 h with subsequent plating on selective agars.

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A comparative collaborative study was performed in 15 laboratories to validate the use of motility enrichment on Modified Semisolid Rappaport-Vassiliadis (MSRV) medium for Salmonella detection in cocoa and chocolate products. The use of MSRV was compared with a cultural procedure using Rappaport-Vassiliadis broth and selenite cystine broth as selective enrichments. Artificially contaminated milk chocolate samples as well as Salmonella reference capsules added to Salmonella-free cocoa and milk chocolate were used as test samples. Motility enrichment produced 347 positive test results compared to 320 for the cultural procedure. For samples containing a lactose positive Salmonella strain, motility enrichment was far more productive than the cultural procedure, while for the other samples no significant statistical difference in the productivity of both procedures was observed at the 5% level.