Membrane filter-assisted surface enhanced Raman spectroscopy for the rapid detection of E. coli O157:H7 in ground beef.

Consumption of food contaminated with Escherichia coli O157:H7 is one of the major concerns in ensuring food safety. Techniques that are simple and suitable for fast screening to detect and identify pathogens in the food chain is vital to ensure food safety. In this work, we propose a simple and rapid technique to detect low levels of E. coli O157:H7 using membrane filtration and silver intensification steps in combination with surface enhanced Raman spectroscopy (SERS) analysis. The target bacteria can be captured and separated efficiently by two different antibody bearing nanoparticle complexes (magnetic nanoparticles and gold nanoparticles with a Raman reporter). After centrifugal filtration, the bacteria-nanoparticle complexes left on the filter membrane were localized by silver intensification process before probing by SERS. Extremely low concentration of E. coli O157:H7 (~10 CFU/mL) could be detected within 1h and 3h from both pure culture and ground beef samples, respectively. This method can potentially be used as an effective pathogen screening tool for routine monitoring.