Key to new antibiotics could be deep within isolated cave

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 April 11 in the Journal PLoS ONE.