Researchers have reported the first U.S. documented case of a bacterial superstrain genetically hardwired to defeat attempts to kill it. The resistance gene, called mcr-1, was found in an E. coli culture from a 49-year-old Pennsylvania patient with a urinary tract infection (UTI). The gene causes the bacteria to resist colistin, a drug often reserved as a last resort antibacterial treatment for resistant infections, including Klebsiella pneumoniae and Acinetobacter.
“The recent discovery of a plasmid-borne colistin resistance gene, mcr-1, heralds the emergence of truly pan-drug resistant bacteria. The gene has been found primarily in Escherichia coli, but has also been identified in other members of the Enterobacteriaceae from human, animal, food and environmental samples on every continent,” notes the article published in Antimicrobial Agents and Chemotherapy journal.
Of even greater concern is the involvement of resistance genes in the plasmids, a cell’s genetic replication engine. If multiple-drug resistant genes take hold across the whole Enterobacteriacea family of bacteria, many of our current antibacterial treatments could fail in a hurry.
“It remains unclear what the true prevalence of mcr-1 is in the population,” the research authors write. “The association between mcr-1 and IncF plasmids is concerning as these plasmids are vehicles for the dissemination of antibiotic resistance and virulence genes among the Enterobacteriaceae. Continued surveillance to determine the true frequency for this gene in the USA is critical.”
Additionally, the Pennsylvania patient’s sample contained at least 15 other antibiotic-resistant genes in addition to mcr-1, some of which have been documented in Europe. Yet the patient reported no travel within five months prior to the infection, the researchers said.
In May 2016, the Walter Reed National Military Medical Center in Silver Spring, Md., began testing every sample of extended-spectrum β-lactamase (ESBL)-producing E.coli for the mcr-1 gene and colistin resistance.