Detection of Salmonella spp. Using a Generic and Differential FRET-PCR

To facilitate the detection of Salmonella and to be able to rapidly and conveniently determine the species/subspecies present, we developed and tested a generic and differential FRET-PCR targeting their tetrathionate reductase response regulator gene. The differential pan-Salmonella FRET-PCR we developed successfully detected seven plasmids that contained partial sequences of S. bongori and the six S. enterica subspecies. The detection limit varied from ∼5 copies of target gene/per PCR reaction for S. enterica enterica to ∼200 for S. bongori. Melting curve analysis demonstrated a Tm of ∼68°C for S. enterica enterica, ∼62.5°C for S. enterica houtenae and S. enterica diarizonae, ∼57°C for S. enterica indica, and ∼54°C for S. bongori, S. enterica salamae and S. enterica arizonae. The differential pan-Salmonella FRET-PCR also detected and determined the subspecies of 4 reference strains and 47 Salmonella isolated from clinically ill birds or pigs. Finally, we found it could directly detect and differentiate Salmonella in feline (5/50 positive; 10%; one S. enterica salamae and 4 S. enterica enterica) and canine feces (15/114 positive; 13.2%; all S. enterica enterica). The differential pan-Salmonella FRET-PCR failed to react with 96 non-Salmonella bacterial strains. Our experiments show the differential pan-Salmonella FRET-PCR we developed is a rapid, sensitive and specific method to detect and differentiate Salmonella.