Antibiotic resistance

Antibiotic resistance ‘hardwired’ into bacteria

Researchers with McMaster University in Ontario and the University of Akron in Ohio are leading the way in understanding the origins of antibiotic resistance – a global challenge that is creating a serious threat to the treatment of infectious diseases.

Gerry Wright, scientific director of McMaster’s Michael G DeGroote Institute for Infectious Disease Research, and Hazel Barton, associate professor of biology at the University of Akron, discovered a remarkable prevalence of antibiotic-resistant bacteria isolated from the Lechuguilla Cave in New Mexico, one of the deepest and largest caves in the world and a place isolated from human contact for more than 4 million years.

The research was published April 11 in the journal PLoS ONE.

“Our study shows that antibiotic resistance is hardwired into bacteria. It could be billions of years old, but we have only been trying to understand it for the last 70 years,” Wright said. “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.”

Researchers collected strains of bacteria from the deep and isolated recesses of the Lechuguilla Cave in Carlsbad Cavern National Park. They then examined these bacteria for antibiotic resistance.

They found that while none of the bacteria are capable of causing human disease or have ever been exposed to human sources of antibiotics, almost all were resistant to at least one antibiotic, and some were resistant to as many as 14 different antibiotics, the announcement said. In all, resistance was found to virtually every antibiotic doctors currently use to treat patients.

For instance, the researchers were able to identify a type of resistance that has yet to emerge in the clinic in a group of bacteria distantly related to the bacterium that causes anthrax.

Barton said, “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.'”

The development of antibiotic-resistant bacteria is becoming an increasing health concern. 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 important questions, Wright said.

“Most practitioners believe that bacteria acquire antibiotic resistance in the clinic,” he said. “As doctors prescribe antibiotics, they select for members of the community that are resistant to these drugs. Over time, these organisms spread, and eventually, the bacteria that commonly cause these infections are all resistant. 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. 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, Barton added, noting that this is why the Lechuguilla Cave was the perfect environment for looking at the pre-existing reservoir of antibiotic resistance in nature.

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

Their findings support recent studies at McMaster that suggest that antibiotic resistance has a long evolutionary past, the announcement said.

The paper is available at