Davies 1997). Two-stage enrichment using RVS followed by MRSV has proved to be an effective technique for enhanced isolation in samples from certain premises but not others. The advantage of this technique is the provision of Salmonella in virtually pure culture. Cold enrichment is a standard technique for the isolation of Yersinia enterocolitica (De Boer 1992) which works by suppression of cold-sensitive contaminants. Other studies have shown either no reduction or an increase in Salmonella isolation following the storage of incubated enrichment media for 72 hours (D'Aoust and others 1994, 1995, Eriksson and others 1999). This means that the efficiency of diagnostic laboratories can be increased, as pre-enrichment and enrichment media can be refrigerated to reduce the need for weekend working and to allow samples to be received and processed for a greater proportion of the working week. References BERNER, I., KONETSCHNY-RAPP, S., JUNG, G. & WINKELMANN, G. (1988) Characterisation of ferrioxamine E as the principle siderophore of Erwinia herbicola (Enterobacter agglomerans). Biological Metals 1, 51-56 D'AOUST, J. Y., SEWELL, A. M. & GRECO, P. (1994) Detection of Salmonella in dry foods using refridgerated pre-enrichment and enrichment broth cultures: summary of collaborative study. Joturnal of the Association of Official Analytical Chemists International (United States) 77, 1490-1491 D'AOUST, J. Y., SEWELL, A. M. & MCDONALD, C. (1995) Recovery of Salmonella spp. from refridgerated pre-enrichment cultures of dry food composites. Journal oftheAssociation of OfficialAnalytical Chemists International (United States) 78, 1322-1327 DAVIES, R. H. (1997) Principles and practice of Salmonella isolation. Proceedings of the EU Concerted Action Workshop CT94-1456. Factors affecting the microbial quality of meat. 4. Microbial methods for the meat industry. Gent, Belgium, October 14 to 16, 1996. Bristol, University of Bristol Press. pp15-26 DE BOER, E. (1992) Isolation of Yersinia enterocolitica from foods. International Journal of Food Microbiology 17, 75-84 ERIKSSON, E., ENGVALL, A. & GUNNARSSON, A. (1999) Effects of pooling samples and cold storage of pre-enrichment broth on sensitivity for detecting E coli 0157 in cattle faeces. Proceedings of the EU Concerted Action Workshop CT98-3935 (Verotoxigenic E coli in Europe). 1. Methods for Verotoxigenic E coli. November 24 to 26, 1998. Edinburgh. pp 36-40 HEINONENTANSKI, H., PHILLIP, W. & BOHM, R. (2000) The role of ferrioxamine E in pre-enrichment medium for determining Salmonella in environmental samples according to ISO method. Microbiological Research 155, 65-68