PCR diagnostics: Nobel and many advantages
Millions of microorganisms live in our body. And not all of them are peace-loving. How to recognize enemies invisible to the eyes, especially when it comes to pathogens of dangerous diseases? DNA level diagnostics come to the rescue. The results of the analysis can be found already 3-4 hours after treatment. For the invention of the polymerase chain reaction (PCR), which is based on the identification of the species of any living organism, the American scientist Carrie Mullys was awarded the Nobel Prize.
In the 70s of the twentieth century, enzymes were discovered that break down DNA at specific points. Researchers have the opportunity to “cut” DNA into shorter and more stable fragments.
After this, a new discovery followed: scientists “taught” DNA to copy itself and build to such sizes that it is easy to identify. In fact, this made it possible to identify any object of interest by the selected DNA fragment: here is the DNA of the common cold pathogen, this is staphylococcus, this is the herpes virus.
Read on: Molecular medicine: why delve into our DNA
As a material for analysis, you can use a sample of the patient’s tissue, a single human hair, a drop of dried blood found at the crime scene, and the brain of a mummy. Even the body of a mammoth, lying 40 rear. years in permafrost, will be able to tell what the prehistoric giant was sick with.
More and more specialists are recommending PCR diagnostics instead of conventional bacteriological tests. First of all, these are urologists and gynecologists – in their sphere the advantages of the method are especially highly valued. All harmful pathogens of urogenital infections – chlamydia, ureaplasmosis, gonorrhea, herpes, gardnerellosis, mycoplasma infection, etc. are quickly and with guarantee detected.
Pulmonologists (doctors who deal with lung diseases) have also adopted a new method, because it allows you to distinguish between viral and bacterial pneumonia, tuberculosis. In hematology, DNA diagnostics detect cytomegaloviruses, oncoviruses. Well, and, of course, infectious disease doctors did not stand aside: PCR is used as an express method for the diagnosis of salmonellosis, diphtheria, viral hepatitis B, C and G.
Advantages of the method:
– The causative agent is detected directly by a specific DNA site, unlike enzyme-linked immunosorbent assay, in which a harmful microbe is detected indirectly (by special proteins – products of its vital activity).
– A clear identification of the DNA of one particular pathogen is possible. The method allows you not to confuse it with any other, as happens in the same enzyme-linked immunosorbent assay, where the antigens of several microorganisms often react cross-react.
– The method can detect even one single pathogenic bacterium among billions of others and in a few hours provide 50 billion copies of it! That is, it works where other methods (microscopic, bacteriological, enzyme immunoassay) fail.
– The method is universal. Indeed, everything in the world of DNA consists of the same four nucleotides – adenine (A), guanine (G), cytosine (C) and thymine (T). Therefore, the method is applicable absolutely to any bacteria and viruses. Moreover, you can find not only anyone, but anywhere – in blood, urine, sputum, biopsy (a small piece of tissue), soil.
– The results of the analysis can be obtained extremely quickly, because the pathogen does not need to be grown artificially (this is the procedure that takes a lot of time during laboratory research). The answer, as a rule, is ready after 3-4 hours after treatment.
One drawback is hypersensitivity
As often happens, the advantages of a method sometimes become its disadvantages. We are talking about the phenomenal sensitivity of PCR, which can result in “false positive” results if there is at least a tiny amount of “foreign” DNA in the dishes, pipettes, and other equipment for analysis. PCR will propagate this DNA and produce the wrong result.
But this problem is solved – dishes and materials should be disposable, and DNA amplification (multiple copying) must be carried out in a separate room from sample preparation. That is why you can trust the results of PCR diagnostics if you contacted a reputable laboratory equipped with the latest technology.