A method combining immunomagnetic separation (IMS) and real-time (5V-nuclease) PCR was developed to detect
Escherichia coli O157:H7. Monoclonal antibody specific for the E. coli O157 antigen was added to protein A-coated magnetic
particles to create antibody-coated beads. The beads specifically captured E. coli O157:H7 from bacterial suspensions. The cells
were eluted from the beads and lysed by heating; the eluate was then assayed by real-time PCR, using primers and probe
specifically targeting the eaeA gene of E. coli O157:H7. Approximately 50% of the cells in suspension were captured by the
beads and detected by real-time PCR. No cross-reactivity was detected when other strains of E. coli were tested. This method
was applied to detect E. coli O157:H7 from ground beef. Both cell capture efficiency and real-time PCR efficiency were
reduced by meat-associated inhibitors. However, we were still able to detect up to 8% of E. coli O157:H7 from inoculated
ground beef samples. The detection sensitivity varied among ground beef samples. The minimum detection limit was b5102
cells ml1 for suspensions of E. coli O157:H7 in buffer and 1.3104 cells g1 for E. coli O157:H7 in ground beef. The
combination of IMS and real-time PCR results in rapid, specific and quantitative detection of E. coli O157:H7 without the need
for an enrichment culture step