A bacterium found more than 300 meters underground (called Paenibacillus), shows resistance to the antibiotics used today, including "last resort" ones like daptomycin.
These microorganisms have been isolated from the outside world for more than four million years inside a cave in New Mexico. Scientists from McMaster and Akron Universities have examined them.
The results show that the bacterium is resistant to 18 different antibiotics and uses defense methods identical to those of similar species found on the surface.
This suggests that evolutionary pressure to conserve these resistance genes has existed for millions of years, not just since antibiotics were first used to treat disease.
Among the different ways that bacteria might be resistant to antibiotics, the scientists identified five new pathways that were of possible clinical concern. Finding these new pathways is particularly valuable as it gives researchers time to develop new drugs to combat this type of resistance, potentially decades before it will become a problem for physicians and their patients, according to a statement from Mc Master.
"The diversity of antibiotic resistance and its prevalence in microbes around the world should be sobering for all who use these life-saving medications," said Gerry Wright, author of the paper and scientific director of McMaster's Michael G. DeGroote Institute for Infectious Disease Research.
"This reflects the fact that we must understand that antibiotic use and resistance go hand in hand," he explained. Hazel Barton, Professor and Director of Integrative Bioscience at the University of Akron, said: "Exploring these challenging and remote environments offers a unique opportunity to test the genetic diversity of microbes unaffected by human activity."
The bacteria were found in the Lechuguilla cave, which is one of the longest in the world and the deepest in the United States. It is a UNESCO World Heritage Site. The restricted access makes it an ideal environment to study how microbes have evolved without the influence of human activity.
Although the use of antibiotics revolutionized the treatment of bacterial infections in the 20th century, the overuse of antibiotics has led to the emergence of antibiotic resistance in disease-causing bacteria.