Comparison of E. coli O157:H7 preparation methods used for detection with surface plasmon resonance sensor

This paper reports the detection of Escherichia coli (E. coli) O157:H7 with a surface plasmon resonance (SPR) sensor using three sample preparation methods: untreated (viable), heat-killed then soaked in 70% ethanol, and detergent-lysed. The SPR sensing surface consists of a monoclonal antibody immobilized onto a mixed -COOH and -OH terminated self-assembled monolayer (SAM) of alkanethiols on a gold surface. The limit of detection (LOD) for each method is determined by the minimum measurable shift in resonant wavelength corresponding to the specific binding of E. coli O157:H7 and the subsequent binding of an antibody for amplification. Detergent-lysed samples produce the lowest LOD at 104 cfu/ml, while the LOD is 105 cfu/ml for heat-killed samples and 106 cfu/ml for untreated samples, respectively. Possible reasons for different limits of detection are discussed.