Label-free screening of foodborne Salmonella using surface plasmon resonance imaging
It is estimated that 95% of the foodborne infections are caused by 15 major pathogens. Therefore, rapid and effective multiplex screening techniques for these pathogens with improved efficiencies could benefit public health at lower costs. Surface plasmon resonance imaging (SPRi) provides a label-free, multiplex analytical platform for pathogen screening. In this study, we have developed a singleplex immunoassay for Salmonella to evaluate the potential of SPRi in pathogen detection. Anti-Salmonella and control ligands were arrayed onto the SPRi sensor chip in a microarray format. The influences of ligand immobilization pH and concentration were optimized, and a pause flow protocol was adopted to improve assay rapidity and sensitivity. The method shows good specificity against 6 non-Salmonella species and was able to detect 5 of 6 Salmonella serotypes, including 3 serotypes most frequently associated with outbreaks. Limits of detection were found to be 2.1 × 106 CFU/mL in phosphate-buffered saline and 7.6 × 106 CFU/mL in the presence of chicken rinse matrix with 8.9 × 107 CFU/mL of indigenous microflora. The condition of antibody array regeneration was optimized for sequential sample injections. Finally, the SPRi immunoassay was used to detect Salmonella directly from artificially spiked chicken carcass rinse samples. As low as 6.8 CFU/mL of Salmonella could be detected after overnight enrichment in buffered peptone water, demonstrating the potential in streamlined pathogen screening with minimal sample preparation and without detection labels.
KeywordsSurface plasmon resonance imaging Salmonella Foodborne pathogen Label-free detection Chicken rinsate Food safety
The authors thank Dr. Marinella Sandros, Dr. Fatima Hibti, and Dr. Chiraz Frydman for their helpful discussions and Dr. Nasreen Bano for the maintenance and preparation of bacterial culture.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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