A drug-resistant "superbug" that doctors have been dreading has shown up in the U.S. for the first time, researchers reported Thursday.
The bacteria has genetic changes that make it resistant to a last-ditch antibiotic called colistin and while it had been seen in Europe and China, no one in the U.S. had been seen with it before.
It doesn't spell doom just yet.
The mutant E. coli germ was found in a Pennsylvania woman with symptoms of a urinary tract infection, but it does not appear to be spreading at epidemic proportions.
What's worrying is the gene that made the E. coli drug-resistant. It's called mcr-1, and it is passed from one bacteria to another. It sits on a piece of material called a plasmid, which makes it easy for one species of bacteria to pass it along to another species of bacteria.
Scientist fear an E. coli bacteria with the mcr-1 gene could pass it to another superbug with other mutations-- creating a truly super-superbug that resists all known antibiotics.
If such a superbug spread, it would take the world back to a time when there were no antibiotics, says Dr. Tom Frieden, director of the Centers for Disease Control and Prevention.
"It is the end of the road for antibiotics unless we act urgently," he said.
This discovery suggests the drug-resistance gene has been here in the U.S., flying under the radar.
"This patient hadn't traveled," Frieden said.?
Patrick McGann and colleagues at the Walter Reed Army Institute of Research just outside Washington D.C. have been looking at samples from patients, keeping an eye out for bacteria with the mutation.
They reported Thursday they found one. The bacteria is E. coli bacteria with mcr-1. "I was extremely surprised when it came up positive," McGann told NBC News.
"To the best of our knowledge, this is the first report of mcr-1 in the USA," the Walter Reed researchers wrote in their report, published in the journal Antimicrobial Agents and Chemotherapy.
They've only been looking for this particular mutation for three weeks, so they said they're not sure just how widespread it is.
"We know now that the more we look, the more we are going to find," Frieden said in a speech at the National Press Club in Washington. "The more we look at drug resistance, the more concerned we become."
Later Thursday, the health and Human Services Department said scientists had also found the mcr-1 mutation in a sample from a pig. "Out of 949 animal samples screened so far, one strain of colistin-resistant E. coli was found in a pig intestinal sample," it said in a statement.
CDC has been warning for years about the threat of drug-resistant bacteria. It's been urging drug companies to develop new antibiotics, and asking people to make better use of the antibiotics now available so that more superbugs do not evolve. "The medicine cabinet is empty for some patients," Frieden said.