Detection of Escherichia coli O157:H7 in raw meat by immunomagnetic separation and multiplex PCR

The aim of this research was to elaborate fast and sensitive method ofdetection of E. coli O157:H7 in food samples. Raw ground meat obtained from retail was artificially inoculated with low numbers of E. coli O157:H7. 18 h enrichment culture allowed pathogenic bacteria to multiply to the levels detectable in multiplex PCR. Immunomagnetic separation with magnetic beads coated with an antibody against E. coli O157:H7 were used to concentrate target bacteria and to separate PCR inhibitors. A portion of the bacterial suspension was used in a multiplex PCR to amplify eae (attaching and effacing) gene, stx (shiga toxin) genes and 90 kbp plasmid. The sensitivity of E. coli O157:H7 detection method was shown to be 1 cfu per 25 g of food sample. The total analysis can be completed within 24 h, whilst traditional methods involves enrichment, direct plating and confirmation tests with entire time at least 3 days.