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In this paper, we propose a novel detection method for Escherichia coli O 157∶H7 using a quartz crystal microbalance (QCM) immunosensor based on beacon immunomagnetic nanoparticles (BIMPs), streptavidin-gold, and a growth solution.The magnetic nanoparticles were loaded with polyclonal anti-E.coli O157∶H7 antibody (target antibody, T-Ab) and biotin-IgG (beacon antibody, B-Ab) at an optimized ratio of 1∶60 (T-Ab/B-Ab).First, using the BIMPs, the target bacteria in a sample were captured and separated.Second, multi-fold streptavidin-gold was conjugated to the BIMPs based on the biotim-avidin system.Third, the gold particles on the BIMPs were enlarged in growth solution and collected using a magnetic plate.aur}us andanti-E.coli 0157:H7complexes containing target bacteria, BIMPs, and enlarged gold particlesTbewereimmobilized on the gold electrodes, result吨in changes in the~and frequency ofthe immunosensors. BIIVIP-conjugated enlarged gold particles were used as "mass enhancers" to amplify the frequency change. The frequency shift was correlated withthe bacterial concentration.