Scientific study reveals unexpected links between anti-cancer drugs and antibiotic effectiveness

Scientists from University of Galway have uncovered a surprising link between commonly used anti-cancer drugs and antibiotics that could offer a potential new approach to tackling notorious superbug infections.

The research team set out to find new ways to treat methicillin-resistant Staphylococcus aureus – better known as MRSA infections - using drugs that are currently ineffective due to antibiotic resistance – a growing challenge in healthcare.

The study investigated whether a range of anti-cancer drugs could help penicillin-type antibiotics, which are among the most widely used antibiotics, to become effective again.

The study was carried out by researchers Dr Aaron Nolan, Sarah Byrne, Dr Merve Zeden and Professor James O’Gara from the School of Biological and Chemical Sciences at University of Galway.

The team tested five anti-cancer drugs and revealed that four of them (5-fluorouracil; 5-fluororidine; gemcitabine; and mitomycin C) helped penicillin-type antibiotics to kill MRSA. These drugs interfere with the bacteria’s ability to make DNA, making the bacteria more vulnerable to the antibiotics.

A fifth anti-cancer drug which was tested (6-thioguanine) had the opposite effect and reduced the effectiveness of the antibiotics. Although this drug also affects DNA production in MRSA, it works in a different way, which may explain the different effects.

Dr Aaron Nolan, Postdoctoral Researcher and lecturer in Microbiology, explained: "We discovered several anti-cancer drugs that helped antibiotics to kill MRSA. But we also identified one anti-cancer drug that interfered with antibiotic effectiveness highlighting the importance of carefully prescribing the most appropriate antibiotic in patients undergoing chemotherapy." 

Sarah Byrne, PhD Researcher in Microbiology, said: “The antibiotic resistance crisis is one of the world's most urgent health challenges. These findings are particularly important for patients with cancer who may need treatment for bacterial infections while also taking chemotherapy drugs.”

MRSA is a type of S. aureus bacteria that has developed resistance to commonly used antibiotics, making infections more difficult to treat.

The findings also suggest that drugs already used to treat cancer could potentially be used alongside antibiotics to help them work against resistant bacteria.

Assistant Professor in Microbiology Dr Merve Zeden said: "Our findings suggest that certain drugs originally developed for cancer treatment may have the potential to be repurposed alongside antibiotics. This could offer a new strategy to re-sensitise bacteria that have become resistant to existing treatments."

The findings build on the team's ongoing research, which has identified the process of DNA production as a vulnerability in MRSA. By interfering with this process, some of the anti-cancer drugs tested in the study appear to make the bacteria more vulnerable to antibiotics.

The discovery opens new avenues for research into combination therapies that pair antibiotics with non-antibiotic drugs. Such approaches could help extend the lifespan of existing antibiotics and provide new options for infections caused by bacteria resistant to traditional antibiotic treatments.

Professor of Microbiology at University of Galway, James O'Gara, said: “We are excited by this discovery, which advances our long-term goal of finding new ways to boost the effectiveness of existing antibiotics against superbugs like MRSA. Because this approach relies on existing medications rather than developing completely new drugs, it could provide a faster route towards developing new strategies to improve patient care."

The paper is published in mBio, the flagship journal of the American Society for Microbiology, is available at https://journals.asm.org/doi/10.1128/mbio.01274-26.

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