Hope is dying
Scientists: pneumonia has become invulnerable to the "antibiotic of last hope"
Some strains of pneumococcus present in US hospitals have become invulnerable to the action of colistin, one of the "antibiotics of last resort", which will make pneumonia a deadly disease in the near future, doctors say in an article published in the journal mBio.
"This is a very disturbing discovery, since pneumococci are much more likely to cause infections than other bacteria. It is important to understand that in this case they were also invulnerable to the action of carbapenem, another "last hope" antibiotic. With the development of a real disease, this would force doctors to use colistin to fight infection. We have never found pneumococci of this kind in the USA before," says David Weiss from Emory University in Atlanta (in a press release, Bacteria resistant to last–resort antibiotic missed by standard tests - VM).
In recent years, the problem of the appearance of so–called "superbugs" - 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). There is a real danger that all antibiotics will lose their effectiveness and medicine will return to the "dark ages".
The main "incubators" of such microbes, according to scientists today, are hospitals and livestock farms, where antibiotics are used to accelerate the growth of beef breeds of livestock. Both on farms and in hospitals, large numbers of potential carriers of infection, and bacteria themselves, and antibiotics are concentrated, forcing them to evolve and preventing "ordinary" bacteria from displacing less prolific super-microbes.
Most of these "superbugs" are not yet completely immune to the effects of drugs – almost all of them can be destroyed using so-called "last-resort antibiotics", relatively new drugs that are used only for medical purposes and only in the treatment of the most serious infections. Thus, scientists are trying to "prolong the life" of such drugs and delay the moment when microbes become resistant to their action.
Weiss and his colleagues discovered an extremely dangerous strain of pneumococcus, immune to the action of two "last-resort antibiotics" at once, studying samples of microbes collected in Atlanta hospitals in the treatment of particularly severe cases of pneumonia.
Observing the reaction of colonies of these bacteria to colistin, carbapenems and a number of other antibiotics, scientists initially believed that all these microbes were resistant to the action of the last two classes of drugs, but had no protection from the first drug.
Experiments on mice and small colonies of Klebsiella pneumoniae showed that this idea was erroneous – it turned out that a vanishingly small part of microbes, about 5% of their total number, was invulnerable to the action of colistin, despite the fact that they possessed the same sets of genes as their deceased "neighbors".
Why were there so few of these bacteria? The small size of their population, as Weiss and his colleagues explain, is due to the fact that the inclusion of genes that protect pneumococcus from an antibiotic reduces its viability in a "normal" environment. This contributes to the reproduction of those bacteria in which these DNA sections are disabled.
The presence of such a "hidden" invulnerability to colistin, according to doctors, can be an even more dangerous threat to the patient's health than the apparent resistance of microbes to antibiotics. When scientists infected mice with such microbes and tried to cure them with colistin, all the animals died 20-25 hours after infection, despite all attempts to save their lives.
The problem is compounded by the fact that today doctors do not have tools and techniques that would allow them to quickly find such "superbugs" inside the patient's body. For this reason, an attempt to cure their carriers with colistin is likely to end with the death of the patient, as in the case of mice, the researchers conclude.
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