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A new study published in Nature Communications reveals a hidden source of antibiotic resistance, providing an early warning sign for researchers and public health officials.
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The novel gene, found in contaminated freshwater sediment in New South Wales by researchers at Macquarie University and the University of Sydney, provides bacteria with resistance to polymyxin, a critical last-line antibiotic used when others stop working.
The mcr-12 gene is the first of its kind to be discovered outside a clinical, food or livestock setting. It's also the first to be found outside a Gammaproteobacterial host (such as E. coli) and the first in the Southern Hemisphere. Scientists discovered mcr genes only a decade ago and have since believed they were found only in bacteria from hospitals, patients or livestock.
"Polymyxin resistance genes are typically associated with settings where there has been direct antibiotic exposure, so this discovery challenges our previous assumptions," says Dr. Brodie Gillieatt, the lead researcher from Macquarie University.
Concerningly, the gene still worked when it moved from its original host to several different pathogenic bacteria—a problem if the gene spreads to a clinical setting.
Amy K. Cain, a professor of microbiology at Macquarie University, says the discovery is timely. "The gene has not yet spread to major human pathogens. Detecting it now gives researchers and public health officials a chance to monitor its spread before it becomes a widespread clinical problem."
The gene was also found to be associated with heavy metal resistance genes in freshwater contaminated by heavy metals, raising the possibility that metal pollution could help maintain antibiotic resistance genes.
"It highlights the role of environmental pollution in antibiotic resistance, meaning environmental management may also play a role in slowing the spread," says Gillieatt. "These types of resistance genes are likely circulating in wider environmental reservoirs, and we simply have not invested in their detection until now. We need broader surveillance."
Research priorities are now focused on mapping where the gene occurs and testing whether and how mcr-12 could mobilize.
More information: Brodie F. Gillieatt et al, Novel polymyxin resistance gene family mcr-12 from environmental Pigmentiphaga litoralis, Nature Communications (2026). DOI: 10.1038/s41467-026-75587-4
Provided by Macquarie University
This story was originally published on Phys.org.
