A 49-year-old Pennsylvania woman has become the first American to become infected with bacteria resistant to colistin, the antibiotic of last resort in treating such pathogens, researchers from the US Department of Defense revealed this week in a published report.
The discovery, which was detailed in a paper published Thursday in the journal Antimicrobial Agents and Chemotherapy, involved a bacterial urinary tract infection which was found to have 15 genes for resistance to various antibiotics. Unlike previous forms of antibiotics, however, the superbug was not vulnerable to treatment with the potent polymyxin antibiotic colistin.
Colistin-resistance has been detected in bacteria in the past, according to Scientific American, but in those cases the resistance genes were located on a type of DNA that was not easily shared with other kinds of bacteria, and it made the pathogen weaker. In the case of this new strain, however, experts report that the bacteria itself has been infected by a tiny piece of genetic material called a plasmid, which conveyed a gene known as mcr-1 that confers resistance to colistin.
Bacteria carrying this plasmid can share copies of it with other microbes they come into contact with, enabling colistin resistance to easily and rapidly spread from pathogen to pathogen. As the study warns, the discovery “heralds the emergence of truly pan-drug resistant bacteria.” There is no indication as to how the pathogen entered the woman’s system, noted CNN.
So how did this happen, and what do we do now?
As James Johnson, an infectious disease specialist at the University of Minnesota, told Scientific American, the emergence of the mcr-1 gene likely occurred due to the overuse of colistin in food animal production. His theory is supported by a Thursday blog post from the Department of Health and Human Service and the USDA announcing that they had found colistin-resistant bacteria in a sample obtained from the intestine of a pig in the US.
The patient reportedly had not traveled outside of the US for a period of at least five months, and was treated and released as doctors found no other medical issues, Dr. Alex Kallen, a doctor with the US Centers for Disease Control and Prevention, told CNN. The CDC added that it was on the lookout for other potential cases at the medical facility where the woman was treated, and USDA officials said that they were investing to see if any additional animals had been infected.
Kallen called the two reported incidents a “warning sign, more than a catastrophe,” and doctors emphasized to the Washington Post that the woman’s UTI is treatable using other antibiotics, but the concern that the mcr-1 gene could spread to microbes that are already resistant to other forms of treatment remains high.
“It basically shows us that the end of the road isn’t very far away for antibiotics – that we may be in a situation where we have patients in our intensive care units, or patients getting urinary-tract infections for which we do not have antibiotics,” CDC Director Tom Frieden told the newspaper in an interview Thursday. “I’ve cared for patients for whom there are no drugs left. It is a feeling of such horror and helplessness. This is not where we need to be.”
“It’s hard to imagine worse for public health in the United States,” added George Washington University professor Dr. Lance Price, who is also the director of the Antibiotic Resistance Action Center (ARAC) in Washington, DC. “We may soon be facing a world where CRE [carbapenem-resistant enterobacteriaceae] infections are untreatable.”
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