Objective: The aim of this study was to compare three formulations of Rappaport-Vassiliadis enrichment media-the original formulation (RV), a modification (RVJ) by Chaiwat Jatisatienr with change of the basic ingredients, reduction of the amount of malachite green oxalate and increase of the pH up to 7, a commercially prepared dried medium (RVO) and to search the food samples collected from supermarkets and butcher shops in Berlin/Germany.

Materials and Methods: For the comparative study, 300 food samples (such as organs from pigs and poultry), very often known to be contaminated with Salmonella-spp, were obtained from supermarkets and butcher shops in Berlin/Germany. After pre-enrichment of each 25 g-sample in 225 ml buffered peptone water overnight at 37°C, 0,1 ml of the preparation was transferred to 10 ml of the three RV formulations. These were then incubated for 48hrs at 43°C, thereafter the following ingredients were incubated on solid selective plating-out media: brilliant green phenol red lactose sucrose agar (BPLSA), malachite green phenol red lactose sucrose agar (MPLSA), and mannitol lysine crystal violet brilliant green agar (MLCBA). The solid media were incubated at 37°C overnight and then from suspect colonies-of salmonella spp. polyvalent salmonella antiserum were prepared, by slide agglutination tests to identify isolates.

Results: From more than 34% of the totally 300 samples 18 different Salmonella serotypes were isolated.. The isolation rates of the three different formulations of Rappaport-Vassiliadis media were 29% for RV, 30% for RVJ and 28% for RVO. There was no relevant statistically significant difference between the three RVs. Comparing the isolation rates on the selective solid plating-out media, the highest relative incidence of positive findings appeared when using the combinations RVO and RVJ with MLCBA, and RVO with BPLSA.

Conclusion: Therefore, it was concluded that three formulations of Rappaport-Vassiliadis are not different from each other, and selective MLKBA agar has characteristics comparable with internationally recommended BPLSA culture media.