Molecular beacons: a real-time polymerase chain reaction assay for detecting Salmonella

Molecular beacons are oligonucleotide probes that become fluorescent upon hybridization. We developed a real-time PCR assay to detect the presence of Salmonella species using these fluorogenic reporter molecules. A 122-base-pair section of the himA was used as the amplification target. Molecular beacons were designed to recognize a 16-base-pair region on the amplicon. As few as 2 colony-forming unit (CFU) per PCR reaction could be detected. We also demonstrated the ability of the molecular beacons to discriminate between amplicons obtained from similar species such as Escherichia coli and Citrobacter freundii in real-time PCR assays. These assays could be carried out entirely in sealed PCR tubes, enabling fast and direct detection of Salmonella in a semiautomated format.