Typically, to test the blood for the presence of harmful bacteria, a blood sample is placed into a growth medium in a petri dish. If bacteria do exist in the blood, they will begin to grow. However, it can take anywhere from 15 hours to a few days before the bacteria grow to detectable levels. A new technology involving melting bacterial DNA from blood samples could diagnose potentially fatal infections faster than ever before. Get results in hours, not days.
Scientists at the University of California, San Diego, led by Professor Stephanie Fraley, have been exploring this faster, more accurate alternative.
They developed a microfluidic chip on which a small blood sample is deposited and then heated to temperatures of 50 to 90ºC (122 to 194ºF). If bacteria are present in the liquid, the heat will cause their DNA molecules to melt. When these molecules disintegrate, their double-helical strands unfold in a manner unique to their nucleotide sequence.
To identify this pattern, a special dye is added to the sample. It can make the unwinding process produce fluorescence. By analyzing the properties of fluorescence, a characteristic called a melting curve can be obtained. This melting curve is then compared to other known melting curves for the specific bacteria.
Once a match is found, the bacteria in the blood sample can be identified. The entire process takes no more than six hours. This speed would not be possible without the use of custom machine learning algorithms. This algorithm can identify and eliminate the melting curve of the patient's own DNA and other "background noise."
In one test of the technology, blood samples taken from 17 children suspected of contracting the potentially fatal form of sepsis were analyzed. The new technology not only fully matched the results obtained by traditional methods, but also did not produce any false positive results. This is not always the case with other methods such as nucleic acid amplification, which simply enhance the signature of all DNA.
"This is the first time this approach has been tested in whole blood from patients with suspected sepsis," Fraley said. "So this study is a more realistic preview of how the technology will perform in a real clinical scenario." "
A paper on the research was recently published in the Journal of Molecular Diagnostics.
Compiled source: ScitechDaily