**[SYBR Green I PCR assay using ABI 7500]**

#### **[Detection studies with diversity food samples]**

Before inoculating into food, five bacterial strains were incubated in 5 ml LB broth for overnight. 100 l of each culture broth was inoculated in 25 g of each food material. These food samples were then mixed with 225 ml of LB broth and incubated for overnight. Food segments in sample solution must be removed before assay because PCR can be inhibited by them. Among the 10 samples, water contaminated with *Salmonella* spp. were analyzed without any pre-treatment, other samples were filtered through gauze before assay. 1 ml of each prepared sample solution was transferred to 1.5 ml e-tube and centrifuged at 12,000 rpm for 10 min. The supernatant was removed and the pellet was re-suspended in 500 ml deionized water. Centrifugation and re-suspension in deionized water was performed one more time for exact assay. 150 l of Deionized water and 50 l of 10% chelex resin was added to the pellet and mixed throughly. The solution was heated at 100°C for 10 min, and centrifuged at 12,000 rpm for 10 min. 5 l aliquot of this solution was taken for SYBR Green I assay. PCR using ABI 7500 (Perkin-elmer, USA) was cycled 35 times as follows: 30 sec denaturation at 94°C, 30 seconds annealing at 60°C, and 30 seconds polymerization at 72°C. The products of real-time PCR were run on 2% agarose gel electrophoresis and melting curves were acquired on the SYBR channel using a ramping rate of 1°C / 30 seconds for 60 ~ 94°C.
