A recent study led by Australian researchers has uncovered a surprising link between a common antibiotic and the emergence of antibiotic resistance in a different class, marking a significant milestone in the understanding of antibiotic interactions. This groundbreaking research, published in the journal Nature, reveals that rifaximin, primarily used to treat liver disease, can induce resistance to daptomycin, a key antibiotic effective against vancomycin-resistant enterococcus (VRE).

Dr. Adrianna Turner, the study’s lead author, shares her astonishment at this finding, which is the first documented case of one antibiotic causing resistance to another from a different class. “It was previously assumed that the risk of antibiotic resistance applied only to the antibiotic in use,” she explains.

The study challenges the long-held perception of rifaximin as a low-risk antibiotic. With leaders around the world recently pledging to tackle the growing issue of antimicrobial resistance—a phenomenon that leads to an estimated 4.95 million deaths globally each year—Turner emphasizes the importance of understanding these dynamics.

She likens the development of antibiotic resistance in bacteria to gaining new abilities in a video game: “When bacteria become resistant, it’s akin to gaining superpowers. For instance, when VRE is exposed to rifaximin, they don’t just gain one advantage; they acquire multiple capabilities that enable them to overcome even the most potent drugs like daptomycin.”

The researchers, affiliated with the Doherty Institute and Austin Health, found that rifaximin triggers changes in an enzyme within bacteria, leading to alterations in the VRE’s cell membrane and subsequent cross-resistance. Turner remains cautious, suggesting that other antibiotics may similarly provoke resistance across different antibiotic classes.

As researchers investigate the potential for daptomycin-resistant strains of VRE to spread among patients in hospitals, the eight-year study incorporated genomic analyses from patients in Australia and Germany, along with supporting evidence from animal models.

Turner stresses the necessity for enhanced surveillance and exploration of bacterial antibiotic resistance mechanisms, which will aid in developing diagnostic tests and genomic monitoring to better understand the prevalence of these resistant strains.

Prof. Jason Kwong from Austin Health reassured that rifaximin remains a valuable treatment option when prescribed appropriately for those with advanced liver disease. However, he highlights the need for greater awareness of the potential implications for both individual patients and public health at large. He advises clinicians to verify the effectiveness of daptomycin for patients who have received rifaximin through lab tests, as its efficacy may be compromised.

Prof. Martina Sanderson-Smith, a molecular bacteriologist at the University of Wollongong, describes the finding that resistance can affect different antibiotic classes as “both concerning and fascinating.” She calls for improved understanding of the implications of prescribing practices across various antibiotic classes, enabling clinicians to make more informed decisions regarding patient care.