Children who experience a nasty and persistent wet cough may be affected by an antibiotic-resistant slime, new research suggests.

Some kids with stubborn coughs had a newly-discovered "bacterial slime - called a biofilm - in their lungs," Menzies School of Health Research said on Wednesday.

Researchers made the discovery using a powerful microscope, in a collaborative study from MSHR, The Telethon Kids Institute and the University of Western Australia.

A study on the findings, published in the Lancet Microbe on Wednesday, is the first in the world to demonstrate the biofilm in children.

Researchers used a procedure that involved flushing patients' airways with a sterile solution to capture fluid samples, and using those samples to test for germs.

"When bacteria live in these slimes they can be more than a thousand times more resistant to antibiotics than the bacteria that cause the acute infections that you take your child to the doctor for," Dr Ruth Thornton, who co-authored the study said.

She said it could explain why when your child finishes their antibiotics, they get another infection.

Kids suffering from prolonged infections and extended coughs can go on to develop a condition called protracted bacterial bronchitis, or PBB.

Children who have recurrent PBB are at increased risk of getting severe lung disease, called bronchiectasis, Dr Robyn Marsh, lead author of the findings said.

She said most children can have a two week course of antibiotics and recover from PBB.

"But we also know that some kids will have repeated episodes of bronchitis that never seem to get better."

The reason some children do not respond to antibiotics is not yet clear, she said.

The discovery is an "exciting" path forward for children who have been suffering with persistent coughs, Professor Anne Chang, Menzies Head of Child Health said.

"We've suspected these children have biofilm-associated infections for a while but until now, no one has proven it," Prof Chang said.

"Now that we've seen it, we can start investigating new ways to treat these children so that fewer of them will progress to having severe lung disease."