Using sequencing, researchers at the Walter Reed Army Institute of Research are searching for bacteria that harbor the mcr-1 gene, which bestows resistance to colistin, an antibiotic of last-resort, NBC News reports. And in mid-May, they uncovered a strain of E. coli obtained from a Pennsylvania woman with a urinary tract infection that had the mcr-1 gene.
This, NBC News adds, was the first time this antibiotic resistance gene has been seen in the US. Since it had been uncovered in livestock and people outside the US for decades, Erik Snesrud at the Multidrug Resistant Organism Repository and Surveillance Network lab wasn't surprised to see it.
Once he and his colleagues uncovered mcr-1 gene in the E. coli sample, they set out to determine where it was located using a PacBio sequencing approach. It was, NBC News says, on a plasmid, meaning that the antibiotic resistance gene could be passed to other microorganisms via horizontal transfer.
"We are very concerned to see it in there with this particular plasmid," Patrick McGann, also from MRSN, tells NBC News. Further, NBC News adds, this E. coli strain already had seven resistance genes within its chromosomes and seven on its plasmids.
Luckily, the strain was still susceptible to carbapenems, and the woman from whom it was isolated has been treated and is doing fine.
Still, finding a microbe that is resistant to colistin is concerning. "The medicine cabinet is empty for some patients. It is the end of the road for antibiotics unless we act urgently," Center for Disease Control and Prevention Director Thomas Frieden said in a recent speech.