Rapid detection of Salmonella in food by immunomagnetic separation-real-time PCR assay

The aim of this study was to develop a rapid and specific method for detection of Salmonella in food using immunomagnetic separation combined with real-time PCR (IMS-real-time PCR) . The immunomagnetic beads used in the study were prepared by coating goat anti- Salmonella antibody to Dynabeads M- 280 tosylactivated, and the separation conditions were further optimized. Specifically designed primers and a probe target the ttr locus were employed in real- time PCR. A preenrichment step, an IMS, DNA extraction, and hybridization probe-based real-time PCR analysis were performed in the order for the IMS-real-time PCR assay. The results showed that primers and probe could specifically detect Salmonella in our experiments. A result within 8h could be achieved with IMS- real- time PCR assay, and the detection limit was as low as6. 5CFU / 25 g. Compared with the reference method on 150 collected samples, 27 positive samples were detected with the IMS- real- time PCR assay, whereas only 18 for IMS / culture and 14 for the conventional standard methods.