Detection of immunomagnetic bead captured Escherichia coli O157 : H7 by light addressable potentiometric sensor

A modified approach using a light addressable potentiometric sensor (LAPS) method to detect Escherichia coil O157:H7 in solutions is described, The ba cterial cells were captured by the specific antibody coated on magnetic bea ds. The immuno paramagnetic beads (IMB) were then concentrated by a magneti c separator. Fluorescein-labeled anti E. coli antibody and urease-conjugate d anti-fluorescein antibody were then used to label the cells captured by t he beads. After labeling, the mixtures were rapidly filtered through 0.45 o r 1.0 mu m nitrocellulose or polycarbonate filters. The production of NH3 f rom urea by the conjugated urease associated with the captured bacteria was then analyzed. The results indicate that IMB approach can be used to incre ase the specificity of the LAPS method for pathogenic bacteria detection. W ith this procedure, the presence of about one E. coil O157:H7 CFU per g of hamburger meat can be detected after a 6 h incubation.