Effective pre-treatment technique based on immune-magnetic separation for rapid detection of trace levels of Salmonella in milk

A rapid and effective pre-treatment method based on immune-magnetic separation (IMS) with enrichment culture was developed to rapidly detect trace levels of Salmonella. Immune-magnetic beads were prepared and their capture efficiency exceeded 90% with less than 106 CFU/mL of Salmonella. IMS was performed on 25-mL samples without pre-enrichment; instead, the trapped target pathogens were cultured in buffered peptone water for a short time. This pre-treatment was significantly shorter and simpler: the 5 h processing time included IMS for 1 h and enrichment for 4 h. Enzyme-linked immunosorbent assay, loop-mediated isothermal amplification test, and fluorescence quantitative real-time PCR in combination with the pre-treatment method allowed detection of 10−1 CFU/mL of Salmonella (12.3 CFU in 25 mL of milk) in approximately 6.5-8 h. The pre-treatment method developed in this study was effective and can be applied to rapid screening of trace pathogens in liquid food samples.