Development of Methodology for Rapid Bacterial Detection in Complex Matrices Using SERS

Fresh foods, including meats and produce are the fastest growing market in the supermarket and the class of foods most likely to cause a bacterial foodborne illness. As the rate of consumption of perishable products increases, rapid detection of pathogens within the food supply becomes a critical issue. Current methods used for the detection of bacteria that cause food-borne illnesses are time consuming, expensive and often require selective enrichment. In this study we adapted a separation technique originally developed for PCR to extract bacteria from ground beef using β-cyclodextrin (β-CD) and milk protein coated activated carbon (MP-CAC) as filtration agents. The recovered bacteria were bound to a gold slide via a 3-mercaptophenylboronic acid (3-MPBA) sandwich assay and detected with Surface Enhanced Raman Spectroscopy (SERS). The 3-MPBA sandwich assay used with the separation technique allowed detection of Salmonella enterica Enteritidis (BAA-1045), separated from a ground beef matrix, as low as 1x102 CFU/g. Detection at this level was accomplished in less than 8 hours, significantly faster than plate count or enrichment methods that require multiple days. Previously, SERS has been used to detect bacteria within simple matrices; this is the first study to have utilized SERS bacterial detection in a ground beef