FILTRATION CAPTURE AND IMMUNOELECTROCHEMICAL DETECTION FOR RAPID ASSAY OF ESCHERICHIA-COLI O157-H7

A new approach for rapid assay of bacteria in liquid samples is descri bed. Cells were labeled by incubation with an enzyme-antibody conjugat e and captured by filtration of the sample/conjugate mixture through a 0.2 mu m filter. The enzyme-labeled cells were detected by placing th e filter on the surface of an electrode, incubating with enzyme substr ate, and measuring the current produced by oxidation of the electroact ive enzyme product. Assay time was 25 min and a detection limit of sim ilar to 5000 cells/ml was obtained for E. coli O157:H7. Background cur rent due to non-specific binding of conjugate to the filter was the pr imary factor controlling the detection limit, and fewer than 50 cells could be detected when very small sample volumes (10 mu l) were used t o minimize background current. (C) 1998 Elsevier Science B.V.