Ocean in a drop
Doctors have learned to identify all known infections by a drop of blood
Geneticists from the USA have created a "universal" infection test that finds traces of all 307 known bacterial pathogens and all their particularly dangerous varieties in a drop of blood or saliva. Its description and the first test results were presented in the journal mBio (Allicock et al., BacCapSeq: a Platform for Diagnosis and Characterization of Bacterial Infections).
"When our development is approved, it will allow doctors to quickly and very accurately search for traces of all known pathogenic microbes, including the "culprits" of blood poisoning, one of the three leading causes of death in the United States. Our technology is a thousand times more sensitive than traditional methods of "blind" testing," said Orchid Allicock from Columbia University in New York (USA).
In recent years, the problem of the appearance of so-called "super–bacteria" - microbes resistant to the action of one or more antibiotics - has become more and more acute for doctors. Among them there are both rare pathogens of infections and very common and dangerous pathogens, such as Staphylococcus aureus or Pneumococcus (Klebsiella pneumoniae).
The problem is compounded by the fact that microbes often develop immunity to antibiotics not individually, but "collectively", exchanging selected secrets. For example, in July last year, doctors discovered that bacteria found in sewage in New Delhi, the capital of India, had developed protection against so-called carbapenems, "antibiotics of last resort", and began exchanging genes for the production of an "antidote" to them.
For this reason, doctors today need to create a system that can very quickly determine the type of infection and select an antibiotic for it, to which it has not yet managed to develop immunity. As a rule, today such tests are available only in large medical centers, and most of them have extremely low accuracy.
Allikok and her colleagues solved this problem by creating a "universal" infection test. It is a set of four million magnetic nanoparticles capable of recognizing and catching unique fragments of the genome of all pathogenic bacteria thanks to small fragments of DNA attached to them.
If such particles are immersed in a sample of blood or saliva, then they will "stick" to fragments of the genome of these microbes, which will allow them to be caught and separated using a powerful magnet. After that, scientists can multiply these fragments of DNA using special enzymes and "read" them using a DNA sequencer.
Even if there are hundreds or thousands of different strains of microbes in the sample, such a procedure allows them to be recognized almost instantly, which significantly saves time for doctors and accelerates the start of treatment of the patient. This is especially important in cases where doctors cannot even imagine which bacteria can cause a particular disease.
The scientists tested the operation of this system on blood samples with "artificial" forms of infection, as well as in the field, studying which microbes infect residents of Uganda and a number of other African countries suffering from blood poisoning, HIV and their combinations.
In the blood of one of the carriers of the virus, as Allikok notes, her team managed to find an extremely unexpected causative agent of sepsis – the bacterium Gardnerella vaginalis. This microbe used to be considered a relatively harmless inhabitant of the microflora of the genitals, sometimes causing vaginosis.
In the past, this case would have remained unexplained, but the brainchild of Allikok and her colleagues helped African doctors find the "culprit" of blood poisoning and choose the right treatment. Scientists hope that in the near future they will be able to create a similar set of labels for pathogenic fungi and viruses.
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