Drug-Resistant Bacteria Found in Wild Arctic Birds

Ker Than
for National Geographic News
January 24, 2008
Microbes that are immune to commonly used drugs have been found inside birds living in some of Earth's most remote regions, scientists say.

The research suggests that antibiotic resistance has spread deep into nature—and humans are likely to blame.

"This is an indication how far we have pushed antibiotic resistance," said study leader Björn Olsen, a professor in the department of infectious diseases at Uppsala University Hospital in Sweden.

The researchers sampled waste from 97 birds belonging to a dozen different species from the Arctic tundra of northeastern Siberia, northern Alaska, and northern Greenland.

Eight birds—including sandpipers, geese, and gulls—carried Escherichia coli bacteria that was resistant to one or more commonly prescribed antibiotics.

"Many of these antibiotics are used at hospitals against severe infections such as pneumonia, urinary tract infections, or septicemia [blood poisoning]," Olsen said.

He and his team report their findings in the January issue of the journal Emerging Infectious Diseases.

Spreading Immunity

Olsen believes there are good reasons to suspect humans are to blame for the birds' resistant bacteria.

"We collected penguin samples [in Antarctica] and never found this kind of resistance down there. If it was a naturally circulating resistance, then we should have found it."

Also, only a fraction of the Arctic birds sampled carried drug-resistant bacteria. If the immunity had developed naturally, the researchers noted, more birds should have carried the resistant strain.

"This is not a natural resistance," Olsen said. "I believe what we found on the tundra is a reflection of pickup from human activity."

The researchers speculate that the birds contracted drug-resistant E. coli from contact with human sewage or waste in lower latitudes before migrating north.

Infected birds could spread resistant bacteria to other animals or—in rare cases—even back to humans as the birds migrate around the world, Olsen said.

(Related news: "New Bird Flu Strain Spreads Fast, Is Resistant to Vaccine" [November 1, 2006].)

Natural Resistance?

Although they think it is unlikely, the researchers say it's possible that the bacteria developed immunity on their own or acquired it from their fellow microbes.

"In nature you have a lot of circulating natural resistance," Olsen said.

"This resistance has been circulating for billions of years as a means for fungi and bacteria and other microorganisms to control each other."

Michael Yeaman is a microbial pathologist at the University of California, Los Angeles, who was not involved in the study.

The idea that the birds caught the bacteria from humans is interesting, he said, but he would have been more surprised if no resistant microbes were found at all.

"There are microbes in existence today that are resistant to antibiotics that have yet to be discovered or developed," Yeaman said.

And Terry Hazen, a senior scientist at Lawrence Berkeley National Laboratory in California, notes that some bacteria are known to be resistant to substances they have never come into contact with.

"There's a lot of compounds in the environment that are actually quite similar in structure to antibiotics," Hazen said.

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