Rapid Detection Of Escherichia Coli O157:H7

Escherichia coli O157:H7 is the most representative serotype of enterohem-orrhagic Escherichia coli, with very low infectious dose and strong pathogenicity. Numbers of outbreaks had been caused by E. coli O157:H7 in the past twenty years, which posed a tremendous challenge to public health. A rapid and sensitive diagnostic method for E. coli O157:H7 detection plays an important role in discovering infection sources and controlling the spread. In this study, a rapid and sensitive method was developed for the detection of E.coli O157:H7 without multiplication.The detection system was based on two functional nanoparticles. Monoclonal antibody of E.coli O157:H7 labeled dextran coated ferroso-ferric oxide nanoparticles were prepared. Then functional gold nanoparticles were prepared with polyclonal antibody of E. coli O157:H7 and considerable biotin labeled Oligonucleotide (beacon DNA), and the optimal ratio of those were groped.In this detection system, target bacteria were concentrated and separated by immunomagnetic iron-dextran nanoparticles, then hybridized with functional gold nanoparticles and HRP labeled streptavidin, and finally absorbance was detected at 450nm after TMB coloration.Immunomagnetic separation acted as a rapid process which could separate even toothful target bacteria (100cfu/mL) without multiplication. The biotin-streptavidin-enzyme system was utilized as a signal amplification system. The standard curve was drawn in optimization condition. The detection could be controlled within 1h with the sensitivity limits of 101cfu/mL.Specificity of the detection system was studied to assess the ability of system to respond only to target pathogens. The specificity was tested against 68 strains of bacteria include Salmonella, shigella, et al, and the result showed no cross-reaction. The detection system made an initial application in food samples, and was compared with routine detection method to assess the accuracy and sensitivity.A rapid and sensitive detection method for E. coli O157:H7 was built based on two functional nanoparticles in this research.