Potential Use of DNA Aptamer-Magnetic Bead Separation-PCR Assay for Salmonella Detection in Food

Salmonella is one of the most common food-borne pathogens that can cause illness. In this study, the sensitivity and the specificity of Aptamer-Magnetic bead Separation-Polymerase Chain Reaction (AMS-PCR) method were determined for Salmonella spp. detection.
Different concentrations of Salmonella enterica were mixed with streptavidin-magnetic beads coated with biotinylated DNA aptamer. The bound bacteria were eluted and tested with PCR targeting the invA gene of Salmonella. Ten different serovars of Salmonella enterica and four non-Salmonella were tested to determine the specificity of the DNA aptamer. For field application, 14 different food samples were tested and compared with the culture method.
The limit of detection of AMS-PCR method was 102 CFU/ml which was 10 times more sensitive than conventional PCR without AMS (103 CFU/ml). The AMS-PCR assay showed high specificity as it detected ten different serovars of Salmonella enterica with no cross-reactivity with other food-borne pathogens. AMS-PCR reduced the analytical duration from 6 to 7 h instead of 4 days by the culture method.
In comparison with the culture method, AMS helped to improve the upstream sample preparation in reducing the pre-enrichment and enrichment times. So, it seems that combining AMS with PCR is cost-effective and time-saving. In addition, it is highly specific for monitoring of Salmonella spp. in food chain.