Simultaneous detection of Staphylococcus aureus and Salmonella typhimurium using multicolor time-resolved...

Foodborne illnesses caused by Staphylococcus aureus and Salmonella typhimurium are common public health issues worldwide, affecting both developing and developed countries. In this study, aptamers labeled with multicolor lanthanide-doped time-resolved fluorescence (TRFL) nanoparticles were used as signal probes, and immobilized by Fe₃O₄ magnetic nanoparticles were used as the capture probes. The signal probes were bonded onto the captured bacteria by the recognition of aptamer to form the sandwich-type complex. Under the optimal conditions, TRFL intensity at 544nm was used to quantify S. typhimurium (y=10,213×-12,208.92, R²=0.9922) and TRFL intensity at 615nm for S. aureus (y=4803.20×-1933.87, R²=0.9982) in the range of 10²-10⁵CFU/ml. Due to the magnetic separation and concentration of Fe₃O₄ nanoparticles, detection limits of the developed method were found to be 15, 20CFU/ml for S. typhimurium and S. aureus, respectively. The application of this bioassay in milk was also investigated, and results were consistent with those of plate-counting method. Therefore, this simple and rapid method owns a great potential in the application for the multiplex analysis in food safety.