Emergence of an almost untreatable superbug linked to a commonly used antibiotic

The emergence of a virtually untreatable superbug has been linked to a common antibiotic, an Australian-led study has found.

The study – published in Nature – discovered that rifaximin, an antibiotic used to treat liver diseases, causes resistance to another antibiotic, daptomycin.

Daptomycin is one of the few drugs effective against vancomycin-resistant enterococci (VRE), a contagious bacterial infection that can cause serious reactions in hospital patients.

Dr. Adrianna Turner, lead author of the study, said the “truly surprising” finding was the first recorded case of an antibiotic causing resistance to an antibiotic from a different class. It used to be thought that the risk of antibiotic resistance only applied to that one antibiotic.

The findings also overturned the widely held idea that rifaximin was a low-risk antibiotic.

Last month, international leaders committed to decisive action on antimicrobial resistance – the development of bacteria that resist treatment. This included the goal of reducing the estimated 4.95 million global deaths due to antimicrobial resistance annually by 10 percentage points by 2030.

Turner said that when bacteria become resistant to an antibiotic, “it’s a bit like acquiring a new skill in a video game.”

“But when exposed to rifaximin, the VRE bacteria don’t just get one boost – they gain multiple abilities, such as super speed and super strength, allowing them to easily defeat even the final boss, in this case the antibiotic daptomycin. .”

Using rifaximin causes changes in an enzyme in the bacteria, which then leads to changes in the cell membrane of the VRE, causing cross-resistance, researchers from the Doherty Institute and Austin Health discovered.

Turner did not rule out the possibility that other antibiotics could cause resistance to antibiotics in different classes.

Researchers are now investigating whether daptomycin-resistant strains of VRE can be transmitted to other patients in the hospital.

The eight-year study involved genomic analyzes of patient isolates from Australia and Germany, and used animal models to support the hypotheses.

Turner said the findings highlight the need for surveillance and research into how bacteria become antibiotic resistant, allowing researchers to create diagnostic tests and genomic surveillance to understand the prevalence of such bacteria.

Professor Jason Kwong of Austin Health emphasized that rifaximin is still effective when used properly and that those using it to treat advanced liver disease should continue to do so.

“But we need to understand the implications for the future, both in the treatment of individual patients and from a public health perspective,” he said.

He advised doctors treating patients with VRE who have taken rifaximin to confirm that daptomycin is working through a laboratory test, as its effectiveness may be affected.

Kwong emphasized the importance of drug regulators asking whether the use of one drug makes another less effective when approving new drugs.

Prof. Martina Sanderson-Smith, a molecular bacteriologist at the University of Wollongong, said the finding that antibiotic resistance could affect different types of antibiotics was “really worrying and interesting”.

She said the findings highlight the difficulties in responsible use and prescribing of antibiotics, and the need to balance safety with clinical need.

“We need to better understand the potential consequences of prescribing all classes of antibiotics based on this idea of ​​shared resistance between antibiotic classes, so that doctors can make more informed decisions,” she said.