Step 11: Load the qPCR machine
The 96-well plate with samples is loaded into the qPCR machine. The plate is repeatedly heated and cooled over 45 minutes to amplify, or increase, the DNA in the sample.
Heating the plate breaks apart the two strands of any DNA present in the samples, and cooling allows for newly assembled DNA strands to anneal – in other words, be brought back together.
During this process, if the target DNA sequence of the bacteria of interest is present, the probe attached to the target DNA sequence will cause a fluorescent signal on the qPCR machine.
As the DNA of interest is amplified, the probe’s fluorescence is also increased, and this is shown in an S-shaped, curved line. The sooner the curved line pops up on the screen, the more concentrated the DNA of the bacteria of interest is within the sample. In the tens of thousands of samples that Rm3 Labs has tested, the laboratory has detected salmonella in only one sample. The curved lines on the screen show the results for positive quality control samples.
All other lines are flat, which is what an operator hopes to see in client samples because it indicates no bacteria of interest is present.