Development of a multiplex PCR assay for simultaneous detection of Escherichia coli O157:H7 and Salmonella from beef

This study aimed to develop a PCR protocol for routine use in the industrial food microbiology laboratory that simultaneously detects E. coli O157:H7 and Salmonella. Primers targeting the verotoxins, and uidA were multiplexed with the Salmonella invA gene. A pure culture detection limit of 5.96 × 102 E. coli O157:H7 pGFP_uv 380-94 and 1.70 × 102 CFU of S. Typhimurium DT104 SA 970081 per assay was achieved. Trials using experimentally contaminated ground beef detected an initial inoculum averaging 1.6 and 2.3 CFU/25g of E. coli O157:H7 pGFP_uv 380-94 and S. Typhimurium DT104 SA 970081 in under 19h. Similar levels of E. coli O157:H7 pGFP_uv 380-94 were recovered from experimentally contaminated ground beef frozen for 72h at −20°C. This assay enables next-day E. coli O157:H7 and Salmonella co-detection using a single protocol. The protocol is straightforward, inexpensive, and shows promise as a routine detection method.