Antibiotic Resistance Found In Ancient DNA
September 5, 2011

Antibiotic Resistance Found In Ancient DNA


A team comprised primarily of Canadian researchers has discovered antibiotic resistance in the DNA of 30,000-year-old bacteria found in the Yukon permafrost, various media outlets reported last week.

The scientists, who published their findings in the journal Nature, note that resistant microbes are commonly thought to have developed after the development of synthetic antibiotics over 70 years ago. However, they discovered that it is not a "modern phenomenon," but is in fact "a natural phenomenon that predates the modern selective pressure of clinical antibiotic use."

According to Nicholas Wade of the New York Times, "The new finding is the first direct evidence that antibiotic resistance is a widespread natural phenomenon that preceded the modern medical use of antibiotics“¦ Experts had long predicted this on theoretical grounds, but they say the new finding underlines the need to use antibiotics sparingly, given that the genes for antibiotic resistance are ubiquitous and can easily be promoted by antibiotics."

The DNA from the ancient bacteria, which according to Wade had been retrieved from a layer of mud approximately 20 feet below the surface, was studied by biochemist Gerard Wright of McMaster University in Hamilton, Ontario.

"When the researchers analyzed DNA from the drill cores back in the lab, they found fragments of genes conferring resistance against various antibiotics, such as penicillin, tetracycline, and vancomycin. (As further proof that they were indeed looking at ancient DNA, the scientists identified sequences in the samples from animals and plants common in the area 30,000 years ago, such as mammoths, bison, and certain grasses; they did not find any DNA from modern animal or plant life.)," Science news reporter Kai Kupferschmidt said in an August 31 article.

Kupferschmidt added that, in order to rule out the possibility of the sample getting contaminated by modern DNA, they sprayed the outside of the drilling equipment with fluorescent E. coli cells. In doing so, they ensured that any material that leaked into the core would be immediately visible under ultraviolent light.

The bad news about the study's findings, according to what New York University microbiologist Martin J. Blaser told Wade, is "the fact that the genes for resistance are so ancient and widespread means there is no easy solution to the problem of resistance--we will never invent a super-antibiotic that clears everything up."

Joining Wright on the study were Vanessa M. D´Costa, Lindsay Kalan, Mariya Morar, and Hendrik N. Poinar, all of McMaster University; Duane Froese and Fabrice Calmels of the University of Alberta; Yukon government official Grant Zazula; and Regis Debruyne of the Muséum National d´Histoire Naturelle in Paris, France.


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