Ibuprofen or paracetamol can encourage antibiotic resistance when used in combination with ciprofloxacin, Australian researchers say.

The University of SA researchers tested the effect of ciprofloxacin on Escherichia coli when used in combination with nine different non-antimicrobial agents: ibuprofen, diclofenac, paracetamol, furosemide, metformin, atorvastatin, tramadol, temazepam and pseudoephedrine.

They used Petri dishes to investigate the effect on E. coli strains BW25113 and 6146 under conditions similar to those found in the gut, they wrote in Nature last month.

While none of the non-antimicrobials used alone affected E. coli cell growth, the use of ibuprofen or paracetamol with ciprofloxacin was associated with more mutations than ciprofloxacin use alone.