Several strains of pneumococcus present in US hospitals have become immune to colistin, one of the "antibiotics of last resort" that will make pneumonia a deadly disease in the near future, doctors said in an article published in the journal mBio.
“This is a very disturbing finding, as 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 antibiotic "last resort". If a real illness developed, this would force doctors to use colistin to fight infection. We've never found this kind of pneumococcus in the US before,”says David Weiss of Emory University in Atlanta, USA.
In recent years, the problem of the emergence of the so-called "superbugs" - microbes that are resistant to the action of one or more antibiotics, has become more and more acute for physicians. Among them there are both rare infectious agents and very common and dangerous pathogens, such as Staphylococcus aureus (Staphilococcus 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 cattle. Both on farms and in hospitals, there are large numbers of potential carriers of the infection, both bacteria themselves and antibiotics, forcing them to evolve and preventing "ordinary" bacteria from crowding out the less prolific super microbes.
Most of these "superbugs" are not yet completely immune to the action of drugs - almost all of them can be destroyed using the so-called "antibiotics of last resort", relatively new drugs that are used only for medical purposes and only to treat the most serious infections. Thus, scientists are trying to "extend the life" of such drugs and delay the moment when the microbes become resistant to their action.
Weiss and his colleagues discovered an extremely dangerous strain of pneumococcus that is immune to the action of two "antibiotics of last resort" at once, studying microbial samples collected in Atlanta hospitals in the treatment of severe cases of pneumonia.
Observing the reaction of colonies of these bacteria to colistin, carbapenems and a number of other antibiotics, scientists initially thought that all these microbes were resistant to the action of the last two classes of drugs, but did not have protection against 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, were immune to the action of colistin, despite the fact that they possessed the same set of genes. as their dead "neighbors".
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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 the antibiotic reduces its viability in a "normal" setting. This promotes the multiplication of those bacteria in which these sections of DNA are turned off.
The presence of such a "hidden" immunity 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 these microbes and tried to cure them with colistin, all animals died within 20-25 hours after infection, despite all attempts to save their lives.
The problem is aggravated by the fact that today doctors do not have the 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 in the death of the patient, as in the case of mice, the researchers conclude.
