A new study indicates that antibiotic resistant superbugs may have existed even before the dinosaur age. According to researchers, enterococci bacteria strains have been developing their immunity for the last 450 million years.

Genetic studies have shown scientists how these antibiotic-resistant strains developed their defense against the drugs and also how they developed into what they are today.

Bacterial Evolution

Bacteria species have been adapting to life with and inside multi-cellular animals since they first emerged around 3.5 billion years ago.

"Understanding how the environment in which microbes live leads to new properties could help us to predict how microbes will adapt to the use of antibiotics, antimicrobial hand soaps, disinfectants and other products intended to control their spread," Ashlee M. Earl, researcher and leader of the Bacterial Genomics Group at the Broad Institute, said.

Animals first entered the sea nearly 542 million years ago in a period known as the Cambrian Explosion. Since then, bacteria species developed various types of relationships with animals. For instance, some developed a symbiotic partnership with the multi-cellular creatures.

Symbiosis is the process where the bacterium lives off an animal and it also provides some beneficial effects to the creature. This way, both profit off each other. Healthy bacteria species are present in the intestines of humans and animals even today. They protect and serves the host by helping in proper digestion of food.

Other not-so-helpful bacteria species evolved to cause harm to animals and gave rise to various bacterial infections and diseases.

What Researchers Revealed

Genomic research indicated that the enterococci bacteria living inside the intestines of animals today were also present in the stomachs of ancient land creatures that walked the Earth millions of years ago. Researchers claim that normal bacteria die once excreted or removed from the host's body. However, millions of years of evolution have led to the modern enterococci to develop immunity, which keeps it alive even when it is ejected from the animal's body.

The new evolved strain instead survives dry conditions and lack of nourishment. Such antibiotic-resistant superbugs re-enter the food chain when they sink into the sea and a marine creature subsequently ingests them.

Michael Gilmore, director of Harvard Infectious Disease Institute, says that thanks to the recent genomic study, scientists know exactly which genes caused the enterococci to evolve into the modern-day version, which is resistant to dryness, antibiotics, and disinfectants. Using the results, researchers will try to formulate better antibiotics to counter these genetic developments.

The results of the study have been published in the journal Cell.

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