Concentration and Detection of Low Levels of <em>Escherichia coli</em> 0157:H7, <em>Listeria monocytogenes</em> 4b, and <em>Salmonella enteric</em> Typhimurium in High Organic Load Lettuce Wash

Foodborne illness traced to fruits and vegetables coupled with new draft guidelines for produce issued in the Food Modernization and Safety Act (FMSA) have increased attention and research on methods for ensuring end-product safety. For large volume samples, such as produce wash, many current food testing protocols utilize random sampling of small volumes. An alternative and novel method has been developed to increase the probability of finding low numbers of cells via collection and concentration of representative sub-samples of larger volumes for indirect testing of food-borne pathogens. Demonstrated here is a user friendly, low-cost semi-automated method used to detect Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica Typhimurium from 5% organic load lettuce wash. This method could be useful for measuring microbial load reduction levels after flume washing of fresh produce, such as demonstrated here on samples from a pilot-scale leafy greens processing line.