The threat of a “post-antibiotic era” has moved closer to reality, after the first case of resistance to the “last-resort” antibiotic colistin has been identified in the United States. Researchers identified the colistin-resistant gene mcr-1 in a woman with a urinary tract infection.

Carbapenem-resistant Enterobacteriaceae (CRE) bacteria have become one of the biggest threats for antibiotic-resistant infections in the US, responsible for around 9,000 drug-resistant infections each year and 600 deaths. Colistin is one of the only antibiotics that has still shown some effectiveness against CRE, but a new report suggests this might be about to change.

In the journal Antimicrobial Agents and Chemotherapy, investigators from the Walter Reed Army Institute of Research (WRAIR) and the Multidrug Resistant Organism Repository and Surveillance Network (MRSN) reveal the first case of colistin resistance in the US.

The report reveals that last month, a 49-year-old female presented at a military treatment center in Pennsylvania with a urinary tract infection (UTI).

On testing a urine sample from the women, researchers found that it contained a strain of Escherichia coli — a species of Enterobacteriaceae — that possessed a colistin-resistant gene called mcr-1.