Several different serovars of Salmonella enterica, corresponding to those commonly found in meat products based on the USDA-FSIS quarterly reports on Salmonella serotyping, will be enumerated at different populations using digital droplet PCR, and compared to conventional surface plate enumeration methods. The experiments will be repeated using a mixed microflora, using purge from vacuum-packaged beef as a source of the non-pathogenic bacteria.
Ground beef with different fat contents will be inoculated with individual strains of Salmonella. The target populations of Salmonella will range from 2 cells/10 grams to 1000 cells per gram. The samples will be enumerated by both DDPCR and standard methods, and a comparison will be made between the two methods to establish the sensitivity of the DDPCR method.