Rapid Conventional PCR and Real-Time-qPCR Detection of Low Numbers of Salmonella enterica from Ground Beef without Enrichment

Abstract

Detection of low numbers of Salmonella in complex food matrices such as ground beef by polymerase chain reaction (PCR) without enrichment is particularly difficult because of the presence of PCR inhibitors and fat. This study used soluble starch for the removal of fat in ground beef followed by the use of activated carbon coated with milk proteins for the removal of PCR inhibitors prior to conventional PCR and RealTime qPCR. This methodology without pre-enrichment allowed detection with conventional PCR of 5 CFU/g and 1 CFU/g with the real-time qPCR in ground beef containing 7%, 15%, and 27% fat. The total assay time was 5 h from the seeding of a 25 g sample of ground beef to agarose gel detection of amplicons of a 284 bp invA gene fragment specific for Salmonella and 4.5 h for real-time qPCR detection.