From Antarctic lakes to forest soil in Puerto Rico to the guts of mice, scientists are finding antibiotic-resistant genes almost everywhere they look.
The findings in the journal Current Biology revealed how widespread antibiotic-resistant genes are in nature. They also raised questions about how the prevalence of resistant genes might relate to a major health problem: bacterial infections in humans that increasingly don't respond to antibiotics.
"We did not really know the extent of their abundance," said Joseph Nesme, a researcher at the University of Lyon in France.
To try to determine the prevalence of antibiotic-resistant genes, scientists tapped into a reservoir of public data to compare DNA samples found in nature with those of "superbugs" that have infected patients in hospitals. Ultimately, researchers discovered antibiotic-resistant genes in 71 environments, from human feces to English prairies.
Scientists have long known that antibiotic-resistant genes are present in nature. Such organisms existed long before human beings began using bacteria in the environment to help produce the-saving antibiotics. Most of the genes are benign, with little potential for making the leap to animals and humans. But sometimes that transfer does happen.
"What we're seeing more and more of, that's unquestionably true, is that these resistant genes are becoming more and more abundant in pathogens" that can then carry antibiotic resistance to new organisms, said Lance Price, an epidemiologist at George Washington University. "They are getting incorporated into organisms that they never were in before."
Once that happens, resistant genes tend to thrive and multiply, given their ability to adapt and to stand up to certain antibiotics. Scientists are working to decipher precisely how resistant genes in nature find their way into pathogens such as E. coli that can carry them on to humans and animals, with grave health consequences. Price said that the growing threats in medicine are largely rooted in misuse of antibiotics, and that the solutions lie in human hands.