Stealthy “superbugs” that cause dangerous infections are one of the world’s biggest public health concerns. Yet these antibiotic-resistant microbes, which are spreading fast in hospitals, aren’t a new phenomenon.
Today’s “enterococci” superbugs likely arose from ancestors dating back 450 million years ago, according to a new study in the journal Cell. That’s around the time animals first emerged from the ocean and began crawling on land, and it’s well before the age of dinosaurs.
Scientists said that studying the evolutionary history of these virulent microbes could lead to better tools for fighting antibiotic resistance in the modern era.
“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 Earl, an author of the study and a group leader for the Bacterial Genomics Group at the Broad Institute of MIT and Harvard, said in a statement.
Drug-resistant bacteria infect millions of people around the world, the World Health Organization said. But it’s difficult to know precisely how many people are affected each year, or how many infections result in death.
The most dangerous bugs are resistant to multiple types of antibiotics and can pass on genetic material to other bacteria, allowing those to develop drug resistance as well. These microbes can easily contaminate medical equipment, such as blood catheters and ventilators, raising the risk that patients in hospitals and nursing homes will catch infections during their stay.
Researchers from Harvard Medical School and MIT said they wanted to understand why, among a vast number of bacteria, enterococci are so well adapted to the modern hospital environment.
To answer that question, they decided to “rewind the clock” to the earliest existence of enterococci by analyzing fossil records and studying their environmental distribution and genetic and biochemical differences.
They already knew that bacteria appeared on Earth some 4 billion years ago. As animals evolved in the sea, the bacteria learned to live in and on them. Some bacteria protected and served the animals — akin to the healthy microbes in our intestines — while others remained in the environment or caused diseases.
When animals began crawling onto land around 450 million years ago, the bacteria moved with them. Many microbes weren’t suited for the dry life. When animals excreted their intestinal microbes — as in, they pooped — most bacteria dried out and died over time.
Not the enterococci, however. These hardy microbes genetically evolved to resist dryness and starvation, meaning they could thrive outside of an animal’s gut, the scientists found.
Hundreds of millions of years later, the descendants of those early enterococci can resist dryness, starvation, and now disinfectants and antibiotics that try to attack their cell walls. This resilience allows them to thrive in otherwise sterile hospital settings.
Researchers said they are now taking a closer look at the genes that helped transform ancient enterococci into modern-day hazards.
“These are now targets for our research to design new types of antibiotics and disinfectants that specifically eliminate enterococci, to remove them as threats to hospitalized patients,” Francois Lebreton, the study’s first author a Harvard researcher, said in a press release.