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Procedure for the Isolation of Salmonella species by the Modified Semi-solid Rappaport Vassiliadis (MSRV) Method
Laboratory Procedure MFLP-75
June 15, 2004
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(PDF Version - 118.28 K)HEALTH PRODUCTS AND FOOD BRANCH
OTTAWA
C. Poppe1, E.D. Mann2, S. Shaw3, D.
Warburton4, and A. Sewell4
OIÉ Reference Laboratory for Salmonellosis1,2
Laboratory for Foodborne Zoonoses, Health Canada, Guelph, N1G 3W4
Lab Services3, [Agriculture] Canadian Food Inspection Agency, Ottawa, K1A 0C6,
Evaluation Division4, Bureau of Microbial Hazards,
Health Canada, Ottawa, K1A 0L2
1. APPLICATION
The method is applicable to the detection of viable, motile Salmonella spp. from feeds, raw foods, feces, litter, fluff, dust and other environmental samples. It is also a suitable screening test for processed foods and environmental samples. The method should not be used for culture of samples when Pullorum Disease or Fowl Typhoid, caused by S. Pullorum and S. Gallinarum, respectively, is suspected. This revised method replaces MFLP-75, dated September 1998 and the supplement, dated September 1999.
2. DESCRIPTION
This method was developed by Chau and Huang (8.2) and DeSmedt et al. (8.4, 8.5) and has been compared with the HPB method (MFHPB-20) by Poppe et al. (8.9, 8.10) and Oggel et al. (8.8) for the isolation of Salmonella. This method is based on the ability of Salmonella spp. to grow and exhibit motility on Modified Semi-Solid Rappaport Vassiliadis (MSRV) medium after incubation at 42°C under adequate moisture conditions. Most strains of Salmonella spp. are able to migrate more than 20 mm from the inoculation site within 24-48 h (a minimum of 48 h is recommended for processed foods and other stressed samples). Use of this media can reduce the time required for identification of a positive sample by 24 h compared to the conventional culture method.
3. PRINCIPLE
MSRV medium is a very soft semi-solid agar medium. The plates are fragile and must be handled with care. Apart from these limitations, it is very simple to use, usually providing strong presumptive evidence for the presence of Salmonella within 48 h of initiating pre-enrichment broths. Following pre-enrichment the MSRV agar is inoculated. Motile Salmonella migrate across the surface of the semi-solid agar.
Note:This method does not detect non-motile salmonellae. Pathogenic, non-motile strains have not been implicated in foodborne disease(s) since 1964 (8.11; E.C.D. Todd, pers. com.). Non-motile strains represent <1% of isolates from clinical samples and animal feeds (J. Oggel, AAFC and H. Lior, HPB; pers. com.). Confirmatory biochemical and serological tests are performed on isolated colonies.
4. DEFINITION OF TERMS
See Appendix A of Volume 3.
