A new approach to surface plasmon resonance (SPR) biosensors for rapid and highly sensitive detection of bacterial pathogens is reported. It is based on the spectroscopy of grating-coupled long-range surface plasmons (LRSPs) combined with magnetic nanoparticle (MNP) assay. The interrogation of LRSPs allows increasing the biosensor figure of merit (FOM), and the employment of MNPs further enhances the sensor response by a fast delivery of the analyte to the sensor surface and through the amplified refractive index changes associated with the capture of target analyte. This amplification strategy is particularly attractive for detection of large analytes that diffuse slowly from the analyzed sample to the sensor surface. The potential of the presented approach is demonstrated in a model experiment in which Escherichia coli O157:H7 was detected at concentrations as low as 50 cfu mL(-1), 4 orders of magnitude better than the limit of detection achieved by regular grating-coupled SPR with direct detection format.