Rapid quantification of Salmonella typhimurium inoculated to meat products by real-time PCR.

The objective of this study was to use a 5'-nuclease (TaqMan) real-time PCR method with primers and probe specific to the spaQ gene as a rapid approach to quantitatively determine Salmonella Typhimurium. The result showed that the correlation coefficient between real-time PCR estimates and bovine serum albumin (BSA) plate counts of S. Typhimurium was 0.99, independently of 10(5)-fold numbers of bystander Escherichia coli O157:H7 or total viable counts. The sensitivity of the real-time quantitative PCR assay was 10 CFU/mL for pure S. Typhimurium culture without enrichment. A known number of S. Typhimurium target cells were inoculated to dumpling fillings and chicken nuggets and DNA was extracted for real-time PCR analysis. The sensitivity was 60 CFU/g for S. Typhimurium inoculated to the food samples without any preceding procedure of enrichment. The duration of the entire experiment from DNA isolation and purification to PCR amplification was less than 12 h. This study demonstrated that real-time PCR is a rapid and reliable technique for quantifying S. Typhimurium possessing the spaQ gene in pure culture and in meat products.