Research Of Rapid Detection Method Of Two Foodborne Pathogens Based On Immunomagnetic Nanobeads And Quantum Dots

Food safety is a public health problem that the every countrie focus on. Foodbornediseases caused by pathogenic microorganisms in food pose a serious threat to human health.Staphylococcus aureus, Shigella flexneri as the most common food poisoning pathogenicbacteria can easily pollute our food, which widely exist in nature. Therefore, it isindispensable to establish a simple, feasible, fast and effective method to detect the two kindsof bacteria.It is possible to monitor in real time the pollution episodes in food processing,storage, marketing and other aspects, in order to ensure food safety and health.A quantitative detection model was established to detect Staphylococcus aureus andShigella flexneri using magnetic nanobeads to concentrate the target bateria and quantumdots as fluorescent markers, basing on antigen-antibody reaction and biotin-streptavidinconjugation with a laptop-controlled portable device.The main research results are as follows(1) The results showed that the optimal separation condition for103CFU/mL of mixedbacteriathe were the response time45min, the magnetic separation time1.5min, the PBSconcentration0.01mol/L respectively by comparing the capture efficiency throughpreparation of immuno-magnetic nanobeads which coated with anti-Staphylococcus aureusand anti-Shigella flexneri, combing with the traditional surface plating method.(2) The optimal conditions for capture were feasible, and the capture efficiency wasstable relatively of Staphylococcus aureus33.29%~40.86%, Shigella flexneri83.41%~91.06%in the range of concentration from102to105CFU/mL. This method had ahigh sensitivity and specificity. It could capture the concentration of101CFU/mLStaphylococcus aureus and Shigella flexneri. The simultaneous capture efficiency wasslightly lower than that for the individual seperations because of the interference among theIMBs with different antibodies for separating103CFU/mL of mixed bacteriathe.(3)Liner relationships between target bacteria cell numbers (lgN) and the fluorescenceintensity (FI) were found for the cell numbers ranging from102~105CFU/mL. The regressionmodel can be expressed as FI=9.2744lgN+50.14, with R2=0.9626(Staphylococcus aureus),FI=18.616lgN+53.784, with R2=0.9778(Shigella flexneri).(4) Predicted value and the actual value of the target bacteria concentrations is Similar. Specific test results show that the model has a good specificity. The relative standarddeviation was2.9%, and the detection time was within2h.(5) The lamb wash water sample with105CFU/mL Staphylococcus aureus and Shigellaflexneri were detected by the method, the results showed that the fluorescent emission peakwere not obvious, fluorescent intensity were low, so it needs to decrease the interference ofsample matrix, to let it use for food sample detection.This study establish a rapid, quantitative detection method of Staphylococcus aureus andShigella flexneri by immunomagnetic separation technology and quantum dot fluorescentlabeling techniques combined within2h which meet real-time detection needs. It provide abasis method for the the detection in food samples. This method was simple, fast and can be abetter way to detect two foodborne pathogens Specifically and Simultaneously.