A Multiplex Quantitative Polymerase Chain Reaction Using Applied Biosystems 7500 Fast System for Simultaneous Identification of Three Species with Potential Applications to Food Analysis.

Consumption of -contaminated food is one of the most common causes of bacterial diarrhea. A previously developed quantitative polymerase chain reaction (qPCR) utilizing the SmartCycler instrument platform for identification of , , had to be modified to address the recent discontinuation of the SmartCycler system. In this study, a multiplex qPCR assay was optimized on the Applied Biosystems 7500 Fast (AB7500F) platform to continue using qPCR for the identification of three target spp. AB7500F qPCR efficiencies obtained by testing reference genomic DNA (gDNA) were 90.9%, 86.4%, and 94.6% for , , and , respectively, with all correlation coefficient values >0.99. The qPCR results exhibited 100% specificity by testing gDNA samples from 37 non-target reference strains and 86 target strains (50 , 27 , and 9 strains) in this study. The lowest detection level using gDNA was 4, 7, and 2 genome copies per reaction for , , and , respectively. With a 2-day enrichment procedure, the qPCR method correctly detected target species in a spiked food matrix (frog leg, an aquaculture product). The sensitivity in 25 g food matrix was 4 colony-forming units (CFUs) for , 3 CFUs for , and 2 CFUs for . The results suggest that this AB7500F-based qPCR has potential applications for the identification of , , and in contaminated food.