Key to new antibiotics could be deep within isolated cave

By Chantall Van Raay, April 12, 2012

    New Mexico's Lechuguilla Cave, a place isolated from human contact until very recently, is home to a remarkable prevalence of antibiotic-resistant bacteria. The discovery that bacteria have developed defenses against antibiotics could indicate the presence of previously unknown, naturally occurring antibiotics that doctors could use to treat infections. Photo by Max Wisshak.
Antibiotic-resistant bacteria found in one of the deepest, most isolated caves in the
world could mean good news in the battle against superbugs.

Researchers from McMaster and the University of Akron have discovered a remarkable
prevalence of such bacteria in New Mexico's Lechuguilla Cave, a place isolated from
human contact until very recently.

The discovery that bacteria have developed defenses against antibiotics could indicate
the presence of previously unknown, naturally occurring antibiotics that doctors could
use to treat infections.

McMaster's Gerry Wright, scientific director of the Michael G. DeGroote Institute for
Infectious Disease Research, and Hazel Barton, associate professor of biology at the
University of Akron, collected strains of bacteria from the cave's deepest recesses.

None of the bacteria are capable of causing human disease, nor have they ever been
exposed to human sources of antibiotics but they pair found that almost all were
resistant to at least one antibiotic. Some were resistant to as many as 14 different
antibiotics.

In all, resistance was found to virtually every antibiotic that doctors currently use to
treat patients.

"Our study shows that antibiotic resistance is hard-wired into bacteria. It could be
billions of years old, but we have only been trying to understand it for the last 70
years," said Wright. "This has important clinical implications. It suggests that there are
far more antibiotics in the environment that could be found and used to treat currently
untreatable infections."

The researchers also identified resistance in bacteria related to the bacterium that
causes anthrax. This resistance has yet to emerge in the clinic.

"We can say to doctors, 'While this isn't a problem right now, it could be in the future, so
you need be aware of this pre-existing resistance and be prepared if it emerges in the
clinic, or you are going to have a problem,'" said Barton.

Resistance to antibiotics among bacteria is a growing concern for human health. With
the emergence of bacteria such as multi-drug resistant Staphylococcus and the global
spread of resistance to all clinically used drugs, where and how these organisms acquire
resistance are becoming important questions, said Wright.

"In extreme cases these organisms are resistant to seven or more drugs and are
untreatable using traditional treatment, and doctors must resort to surgery to remove
infected tissue," said Wright. "The actual source of much of this resistance is harmless
bacteria that live in the environment."

Because antibiotics are heavily prescribed and used in agriculture, it is difficult to find
an environment where antibiotics do not exert some kind of influence. That made
Lechuguilla Cave the perfect environment to look at the pre-existing reservoir of
antibiotic resistance in nature.

Since it was discovered in 1986, access to the cave has been limited to a few expert
cavers and researchers each year. It is surrounded by an impermeable layer of rock,
meaning it can take water up to 10,000 years to reach its deepest recesses, an age well
beyond the discovery of antibiotics.

The research was published Wednesday in the Journal PLoS ONE.