Antibiotic-resistant bacteria might be the lurking terror of modern medicine, but these unkillable superbugs existed long, long before the 20th century discovery of penicillin and other drugs. In fact, the oldest superbugs could be nearly half a billion years old, arising alongside the very first animals and amassing their indestructible qualities over the eons.
That's the finding from researchers at Harvard University and MIT's Bacterial Genomics Group. They examined the genomes of multiple species of the bacteria enterococcus, which is one of the most naturally antibiotic-resistant microbes. If enterococci as a group really evolved 450 million years old, then they must have adapted to living inside every conceivable animal, from the first one that crawled into land to the dinosaurs to humans. The bacteria would also have survived multiple mass extinction events that killed off a huge percentage of their hosts.
These particular bacteria are able to deal with extreme temperature swings and shifts in the acidity of their environment, as well as being largely unbothered by dry conditions and a prolonged lack of food. Disinfectants and antibiotics alike have little effect on them, making them a challenge to contain and treat whenever they do show up in hospitals.
Enterococci are found in the intestines of just about every land animal, which suggests these creatures have a deep history in the evolution of life on Earth. The group's genomic research suggests that, as the first marine animals emerged nearly half a billion years ago, the ancestors of today's enterococci strains were among the microbes to take up residence inside their primordial intestines.
It's when animals started moving onto land that the true hardiness of enterococci became apparent. Animals routinely poop out some of their microbes. When all animals lived in oceans, bacteria were adapted to their returns to a watery environment, surviving on the sea floor until they were gobbled up again by small scavengers and then in turn by fish, which restarts the cycle. By contrast, microbes excreted onto land often find themselves unable to survive the relatively hot, arid conditions that greet them.
Not so enterococci, which evolved the genes necessary to survive this cataclysmic change in conditions, resist drying out, and live long enough to be consumed once again by another animal. Those same adaptations now make it so difficult for disinfectants and antibiotics to get rid of them in hospitals. And that, as much as anything, speaks to what makes these bacteria so impossible to get rid of. If nearly half a billion years of animal evolution, mass movement from sea to land, and multiple mass extinction couldn't kill off these microbes — indeed, if they have now taken up residence in the guts of just about every species on the planet — what chance do some trifling antibiotics have?
Superbugs: Victims and outbreaks
Superbugs: Victims and outbreaks
Kelly and Ryan Breaux stand holding a portrait of their deceased daughter Emma Breaux, at their home in Breaux Bridge, Louisiana, on June 16, 2016. The husband and wife lost twins, Emma and Talon, to different superbugs that they contracted while in the neonatal unit at Lafayette General Hospital. U.S. Picture taken June 16, 2016. TO MATCH SPECIAL REPORT USA-UNCOUNTED/SURVEILLANCE REUTERS/Edmund Fountain
Kelly and Ryan Breaux sit holding a portrait of their deceased daughter Emma Breaux in their home in Breaux Bridge, Louisiana, on June 16, 2016. The husband and wife lost twins, Emma and Talon, to different superbugs that they contracted while in the neonatal unit at Lafayette General Hospital. U.S. Picture taken June 16, 2016. TO MATCH SPECIAL REPORT USA-UNCOUNTED/SURVEILLANCE REUTERS/Edmund Fountain
Four-year-old Luke Reimer, of Batavia, Illinois, holds a photograph, June 18, 2009, of his twin sister Madeline who died after being born with MRSA (Methicillin resistant Staphylococcus aureus), a bacterium that is resistant to many antibiotics. (Photo by Chuck Berman/Chicago Tribune/MCT via Getty Images)
Stephanie Hall (L), sits on the couch with her sister, Crystal Silva (R), and their ten year old niece Destini and nephew Kane in El Paso, Texas, U.S. on July 2, 2016. The children's mother, Natalie Silva, contracted Methicillin-resistant Staphylococcus aureus, more commonly known as MRSA, a skin infection that can turn fatal once it enters the bloodstream, when she went to the hospital to deliver Kane. After a 10 month battle with MRSA, Silva died, leaving Hall and the family to raise the two children. TO MATCH SPECIAL REPORT USA-UNCOUNTED/SURVEILLANCE REUTERS/Dan Dalstra
Monica Berckes, poses with the funeral program of her late mother Marianne Rumsey, who died at 61, several months after contracting MRSA during heart surgery, at her home in Secaucus, New Jersey, June 2, 2016. Picture taken June 2, 2016. TO MATCH SPECIAL REPORT USA-UNCOUNTED/SURVEILLANCE REUTERS/Mike Segar
Zachary Rubin (C), medical director of clinical epidemiology and infection prevention, and Robert Cherry (R), chief medical and quality officer for UCLA Health System, attend a news conference by UCLA Health System and county officials at the Ronald Reagan UCLA Medical Center in Los Angeles, California February 19, 2015. The large Los Angeles teaching hospital has told scores of patients they were possibly exposed to a drug-resistant bacterial "superbug" during endoscopy procedures that infected seven patients and may have contributed to two deaths. REUTERS/Jonathan Alcorn (UNITED STATES - Tags: HEALTH DISASTER)
A sample bottle containing E. coli bacteria is seen at the Health Protection Agency in north London March 9, 2011. For decades scientists have managed to develop new medicines to stay at least one step ahead of the ever-mutating enemy, bacteria. Now, though, we may be running out of road. Methicillin-resistant Staphylococcus aureus, commonly known as MRSA, alone is estimated to kill around 19,000 people every year in the United States -- far more than HIV and AIDS -- and a similar number in Europe, and other drug-resistant superbugs are spreading. Picture taken March 9, 2011. To match Special Report ANTIBIOTICS/ REUTERS/Suzanne Plunkett (BRITAIN - Tags: HEALTH SCI TECH)
An employee displays MRSA (Methicillin-resistant Staphylococcus aureus) bacteria strain inside a petri dish containing agar jelly for bacterial culture in a microbiological laboratory in Berlin March 1, 2008. MRSA is a drug-resistant "superbug", which can cause deadly infections. REUTERS/Fabrizio Bensch (GERMANY)
A view of the UCLA Medical Center in Los Angeles, California March 19, 2015. UCLA, the hospital at the center of the "superbug" outbreak that killed two people and infected seven last month has received poor patient safety scores and had its payments cut by Medicare for high rates of hospital-acquired infections. REUTERS/Lucy Nicholson
This digitally-colorized scanning electron micrograph depicts four magenta-colored, spherical methicillin-resistant Staphylococcus aureus (MRSA) bacteria in the process of being phagocytized by a blue-colored human white blood cells in this undated handout photo. TO MATCH SPECIAL REPORT USA-UNCOUNTED/SURVEILLANCE National Institute of Allergy and Infectious Diseases (NIAID)/Handout via REUTERS ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. EDITORIAL USE ONLYONLY
MIAMI - OCTOBER 17: Miami VA Medical Center hospital registered nurse, Rafael Sepulveda, pulls on rubber gloves while attending to patients in the Emergency room October 17, 2007 in Miami, Florida. The hospital has strict policies in place to ensure that the staff uses procedures in the fight against methicillin-resistant Staphylococcus aureus bacteria, commonly referred to as MRSA. The staph bacterium is resistant to most common antibiotics and has been responsible for more than nearly 19,000 deaths each year, according to the Centers for Disease Control and Prevention (Photo by Joe Raedle/Getty Images)