Detection of immunomagnetically captured Escherichia coli O157 : H7 by antibody-conjugated alkaline phosphatase

A rapid and sensitive detection process for Escherichia coli O157:H7 was de veloped using alkaline phosphatase (APase)-labeled anti-E. coli O157 antibo dies to tag the targeted bacteria. Immunomagnetic beads or antibody-labeled streptavidin-coated magnetic beads were then used to capture the APase-tag ged E. coli. Immunomagnetically captured bacteria were washed and distribut ed into microplates or optical cuvettes. The enzyme-catalyzed hydrolysis of p-nitro-phenol phosphate in alkaline solutions was then followed. Less tha n 1000 cfu/ml of E. coli O157:H7 could be detected. This approach was appli ed to detect the bacteria artificially spiked in beef hamburgers. Less than 1 cfu/g of E. coli O157:H7 produced a significant response after cultural enrichment for 4-6 h at 37 degreesC.