The research was published on Thursday in the journal Chemistry and Biology.

Researchers were developing antibacterial agents to target a critical protein in DNA replication and repair - the DNA clamp - when they made the "chance discovery", said the paper's lead author, Associate Professor Aaron Oakley.

"While testing specific compounds that would bind to the clamp and prevent it from interacting with its binding partners, we noticed that one compound had a similar molecular structure to carprofen, an anti-inflammatory widely used in veterinary medicine."

Researchers tested carprofen and two other anti-inflammatory drugs and found they had an antibiotic effect on bacteria such as E. coli.

"In effect, they prevented the bacteria from copying their DNA," Prof Oakley said.

He believes the research could lead to a class of chemicals that could be used to treat so-called superbugs, which develop resistance to traditional antibiotics.

"It's going to be very difficult for the bacteria to evolve resistance against this particular class of chemicals that we're developing because you would need a lot of different mutations to happen, all at the same time, in different proteins ... in order to overcome that resistance," he said.

The research has attracted international attention from countries including the United States.

Prof Oakley cautioned that the findings were preliminary and, because of the relatively weak antibacterial effect recorded from drugs used in veterinary medicine, people should be discouraged from trying to use existing anti-inflammatories as antibiotics.

"These drugs themselves are not going to be antibiotics," he said. "The really exciting thing is that this effect exists. It helps confirm that we are doing the right thing by targeting this protein.

"Hopefully the future generation of compounds that we can generate from our research, hopefully some of those will be really good antibiotics. I hope we can save lives from this."