The detection of Salmonella in skimmed milk powder enrichments using conventional methods and immunomagnetic separation

Skimmed milk powders were spiked with one of three Salmonella serovars and incubated in buffered peptone water for 24 h. No false-negative results were obtained by immunomagnetic separation (IMS), compared to seven for selenite cysteine, one for Müller-Kauffmann tetrathionate and two for Rappaport-Vassiliadis enrichment broths. Salmonella virchow was detected and enumerated during the pre-enrichment incubation by IMS and indirect conductance techniques. The Salm. virchow cell number did not increase after 12 h incubation and remained at 3 times 10⁶ cfu ml^-1. IMS was able to capture Salm. virchow cells at cell numbers ca 50 ml^-1 in the presence of a 1000 greater number of non-salmonella cells.