The dangerous bacteria found in modern hospitals may have descended from ancestors who lived in the digestive system of the first animals to roam the earth.
Modern superbugs
Enterococci are one of the so-called superbugs. This means they cannot be killed with antibiotics and cleaning agents. It should be noted that today the problem of superbugs has become extremely serious, since they show resistance to almost all types of antibiotics known to mankind.
In a new study, scientists have found that some of the traits that allow modern superbugs to resist antibiotics may have helped them survive in ancient animals that made their way onto land about 450 million years ago.
By analyzing the genome and growing models of enterococci, the researchers were able to "look into the past" and partially imagine their early ancestors and evolution to modern superbugs.
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Features of enterococci
Enterococci are most commonly found in the human intestine, but they can also cause infections of the urinary tract, blood and other organs. Researchers have tried to find an answer to the question of why enterococci are so well adapted to survive in modern hospitals and are able to resist many types of antibiotics. It is these bacteria that most often lead to nosocomial infections.
When this kind appeared
Researchers analyzed the genetic data of enterococci to determine when their genus originated. To do this, they used a method that takes into account the expected rate at which the bacteria's DNA changes, allowing scientists to estimate the approximate time of occurrence of this genus.
Scientists' calculations show that the ancestors of enterococci appeared presumably 425-500 million years ago. Around the same time, animals first came out of the ocean onto land. In addition, the researchers found that when enterococci were evolutionarily separated from their closely related genus Vagococcus, they acquired genes that allowed them to survive under environmental stress.
Laboratory experiment
The researchers also conducted a separate experiment: in the laboratory, they raised some types of enterococci, acting on them with different conditions. They found that, compared to other bacteria, enterococci grow better in harsh conditions such as fasting, dryness and exposure to disinfectants. All of the species used in the study were also naturally resistant to a range of antibiotics, even though some species had never been seen in the hospital before.
What is the difference between the life of enterococci on land and in the ocean
Taken together, all of these data indicate that enterococci descended from ancestors that lived in the intestines of animals when they came out on land. In the aquatic environment, bacteria that live in the intestines of animals are released into the ocean, then sink to the seabed, where they are consumed by plankton, which are then eaten by other fish. However, the bacteria that live in the body of terrestrial animals are excreted in the feces and can remain dormant for long periods of time, as a result of which they dry out and die. But enterococci turned out to be specially adapted to survive in these dry, harsh conditions. The same traits that enabled their ancestors to survive in dry environments, during times of famine and other harsh conditions on earth appear to help modern bacteria survive in hospitals.
Having developed the ability to survive in the unfavorable conditions of the land, the ancestors of enterococci passed it on to their descendants, who can now survive drying out, starvation and disinfection in a modern hospital.
Additional research
Scientists plan to further investigate genes that allow enterococci to adapt to challenging conditions, hoping that this will help develop new types of antibiotics and disinfectants aimed exclusively at this type of bacteria.
Scientists note that this study is a hypothesis that is consistent with the data available to date, but it is difficult to prove it, given that hundreds of millions of years have passed since the first animals came to land.
Anna Pismenna