Australian researchers led by Henrietta Venter at the University of South Australia, Adelaide, conducted laboratory experiments to determine whether commonly used NAMs, at concentrations similar to those found in the intestinal environment of nursing home residents, could enhance ciprofloxacin-induced mutagenesis in Escherichia coli.

The drugs tested included ibuprofen, diclofenac, acetaminophen (paracetamol), furosemide, metformin, atorvastatin, tramadol, temazepam, and pseudoephedrine. The findings were published in npj Antimicrobials and Resistance, part of the Nature portfolio.

Because NAMs are often prescribed alongside antibiotics, the team measured mutation frequencies in the presence of ciprofloxacin, a fluoroquinolone antibiotic known to induce genetic mutations and widely used to treat urinary tract infections, among the most common bacterial infections in older adults. The frequent use of ciprofloxacin has already led to the emergence of ciprofloxacin-resistant E coli, posing a growing threat in nursing home settings.

Overall, the results showed that two commonly used painkillers, ibuprofen and acetaminophen, can significantly exacerbate antibiotic resistance through mutation at concentrations relevant to the gut. This was reflected in an increased number of bacterial mutants and higher maximum cell density.