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Scientists are
studying an ancient pathogen for clues as to how to fight a drug-resistant
"superbug" in hospitals and other healthcare settings. They've found
that resistance to modern antibiotics dates back millions of years.
Enterococci are
one of a group of six bacteria known as "superbugs," microbes that
infect patients and are resistant to antibiotics, making them potentially
lethal. Scientists studying the enterococcus family found they developed
resistance to harsh conditions some 450 million years ago, well before
dinosaurs came on the scene.
They say lesser
animals deposited feces on land that contained bacteria that learned to survive
harsh environmental conditions, such as drying by the sun.
Found in 30,000
year-old ice
The ancient
“grandfather” of the bacterium, found frozen in 30,000-year-old ice, can be
extracted and revived by modern scientists. That's how hardy enterococci are,
according to Michael Gilmore, an ophthalmologist and microbiologist who heads
Harvard University's extensive program on antibiotic resistance.
“The enterococci
are sort of like the cockroach of bacteria. They're very, very difficult to
kill. And so we think it's the traits that developed in enterococcus in order
to survive on the land that are exactly what make them so rugged and able to
survive now in hospitals,” said Gilmore.
Gilmore oversaw
a team of researchers that sequenced the genomes of 24 members of the
enterococci family, finding 45 different properties that make them resistant to
antibiotics and disinfectants in modern hospitals.
Traced to
Cambrian Explosion
By peering back
into the bacteria's genetic material, investigators were able to trace
enterococci's lineage to the Cambrian Explosion 542 million years ago when
animals first emerged from the sea.
It was bacteria
nestled in the intestines of crawling animals a million years later that developed
resistance to their environment. Gilmore said scientists are studying the
pathogen's genes to identify targets for the development of new weapons to
fight the superbug.
Gilmore added by
characterizing the ancient DNA of enterococcus, "We can start looking at
these different resistances and trying to identify for example new compounds
that undermine those. So, those become the target set for the next generation
of disinfectants or antibiotics."
Defenses are
developed
Gilmore said
enterococci live harmlessly in the digestive tracts of all animals along with
thousands of other bacteria. In a hospital setting, people are often treated
with antibiotics to prevent infections, but the drugs also kill helpful
microorganisms that keep enterococci under control.
Without that
check, the superbug, which is not killed off, develops resistance to the
antibiotics. Overtime, Gilmore said it and other superbugs have developed
defenses, including a tough outer layer, that make it difficult for antibiotics
to penetrate.
Unhindered, the
drug-resistant bacteria can find their way into the bloodstream or organs
through wounds or the use of catheters. Once infected, patients, whose bodies
are now overrun by superbugs, do not respond to antibiotics and can die of
septic shock and organ failure. Gilmore said the aim of research that traces
enterococcus to its prehistoric origins is to take out this superbug that
threatens hospitalized patients.