Discovery prompts fear of pan-resistant bacteria
Bacteria carrying the MCR-1 gene, which makes bacteria resistant to the last-resort antibiotic colistin, has been found in a US patient for the first time. The discovery has fuelled fears that a pan-resistant bacteria could develop.
The 49-year-old woman from Pennsylvania had no recent history of travel. She presented at a health clinic in April with symptoms of a urinary tract infection, according to a report in the journal Antimicrobial Agents and Chemotherapy.
E. coli bacteria carrying the MCR-1 gene was found in a urine sample. Researchers wrote: 'To the best of our knowledge, this is the first report of MCR-1 in the USA'.
Colistin is one of the last defence antibiotics used to treat patients with multi-drug-resistant infections. The MCR-1 gene was first detected in China last year and has since been found in the EU.
Health officials are now working together to trace the patient's contacts and determine whether they are at risk.
While the bacteria identified was not pan-resistant, the presence of the gene is concerning as it raises the risk that pan-resistant bacteria could develop. The MCR-1 gene exists on a plasmid, or a small piece of DNA, that can move from one bacterium to another, spreading antibiotic resistance between bacterial species.
Moving forward, the researchers say further testing is critical to determine the gene's true prevalence in the US.
The Centers for Disease Control and Prevention (CDC) is part of a public health response to the discovery of MCR-1.
From autumn this year, its Antibiotic Resistance Lab Network will provide for seven to eight regional labs, as well as labs in all states and seven major cities and territories. These will detect and respond to resistant organisms found in human samples.
State labs will also detect new forms of resistance, including mutations allowing bacteria to survive last resort drugs.
Image © James Gathany/CDC
The BSAVA has opened submissions for the BSAVA Clinical Research Abstracts 2026.
