Antibiotics and bacterial biofilm formation may lead to chronic lung, sinus and ear infections, according to a recent study.

New research from scientists at the University of South California and the Oak Crest Institute of Science illustrates how bacterial biofilms -- highly structured communities of microorganisms that attach to one another and to surfaces to form a slimy, polysaccharide cover -- can actually thrive, rather than decrease, when given low doses of antibiotics.

"This research addresses the long standing issues surrounding chronic ear infections and why some children experience repeated ear infections even after antibiotic treatment," Paul Webster, lead author of the study, said in a statement. "Once the biofilm forms, it becomes stronger with each treatment of antibiotics."

During the study, non-typeable Haemophilus influenzae(NTHi) bacteria a common pathogen of humans was exposed to non-lethal doses of ampicillin, a class of antibiotics commonly used to treat respiratory, sinus and ear infections, or other beta-lactam antibiotics. The dose of the antibiotic was not enough to kill the bacteria which allowed the bacteria to react to the antibiotic by producing glycogen, a complex sugar often used by bacteria as a food source, to produce stronger biofilms when grown in the laboratory.

Researchers said that with the introduction of antibiotic-produced glycogen, the biofilms have an almost endless food source that can be used once antibiotic exposure has ended.

Webster said modern medicine needs to find ways of detecting and treating biofilm infections before the bacteria are able to form these protective structures. The difficulties of treating biofilm infections, which can be up to 1,000 times more resistant to antibiotics, have prompted some physicians to propose a gradual move away from traditional antibiotic treatments and toward non-antibiotic therapies.

"If antibiotics are to continue to be relevant for treating bacterial infections it is important that their effects on biofilms be explored," Webster said. "One step in this direction would be to develop routine screening methods to test the effects of antibiotics on in vitro formed biofilms."

The findings were recently published in the current issue of PLOS ONE.