• Article
  • June 1, 2017

Antibiotic-resistant Microbes Date Back 450 Million Years

Learning about evolutionary history could help researchers find solutions for antibiotic-resistant superbugs.

A new study sheds light on the evolutionary history of superbugs, some with ancestors dating back 450 million years—before the age of dinosaurs. Today's hospital superbugs, known as the enterococci, arose from an ancestor dating to about the time when animals were first crawling onto land, according to a study led by researchers from Massachusetts Eye and Ear, the Harvard-wide Program on Antibiotic Resistance and the Broad Institute of MIT and Harvard.

Published online in Cell, the study examined the evolutionary history of these pathogens, which evolved nearly indestructible properties and have become leading causes of modern antibiotic-resistant infections in hospitals.

Some superbugs are resistant to virtually all antibiotics. This is of concern in hospitals, where about 5 percent of hospitalized patients will fight infections that arise during their stay. As researchers around the world are seeking solutions for this problem, insight into the origin and evolution of antibiotic resistance could help inform their search.

The authors of the Cell study found that all species of enterococci, including those that have never been found in hospitals, were naturally resistant to dryness, starvation, disinfectants and many antibiotics. Because enterococci normally live in the intestines of most (if not all) land animals, it seemed likely that they were also in the intestines of land animals that are now extinct, including dinosaurs and the first millipede-like organisms to crawl onto land.

A comparison of the genomes of these bacteria provided evidence that this was the case, and researchers found whenever new types of animals appeared throughout evolutionary history, new species of enterococci appeared, too.

"We now know what genes were gained by enterococci hundreds of millions of years ago, when they became resistant to drying out, and resistant to disinfectants and antibiotics that attack their cell walls," says study leader Michael S. Gilmore, Ph.D.

The study's authors say these genes are now targets for research to design new types of antibiotics and disinfectants that specifically eliminate enterococci and remove them as threats to hospitalized patients.

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