Schematic real-time PCR results for the first step reaction. Representative real-time PCR results as established by the first step multiplex reaction (described in Materials and Methods). The plots show average normalised linear amplification of representative samples shown for demonstration of typical results obtained from Salmonella and non-Salmonella bacteria. With DNA from non-Salmonella bacterial samples, only the IAC-specific, ROX-labelled molecular beacons hybridise to the IAC amplicons, generating violet fluorescence, whereas the invA-specific, FAM-labelled molecular beacons retain their stem-and-loop structure and cannot produce a green fluorescent signal. With DNA from Salmonella samples, both molecular beacons hybridise to their respective target amplicons and generate both green and violet fluorescence. The dashed line on the plots represents the normalised threshold for detection of fluorescence, the baseline above which fluorescence increases significantly on amplification and detection of the target sequence.