If your young child has an ear infection that will not go away, it may be caused by a slime-like substance in the middle ear that experts call bacterial "biofilm," says a report in the Journal of the American Medical Association.

This biofilm makes it harder for antibiotics to do their jobs, leading to long-lasting ailments.

Bacteria appear to be hiding in this usually protective slimy film in kids with chronic middle ear infections, the study found.

The discovery is not going to lead to any new treatments right away, but it may eventually help physicians get a better handle on one of the plagues of childhood.

Ear infections, in fact, are the most common illnesses that bring children to pediatricians.

"It's a particularly big disadvantage to working moms," says study co-author Dr. J. Christopher Post, at Allegheny General Hospital. "It really compromises a woman's ability to participate in the workforce."

Evidence Clearly Links to the Film

Ear infections are so common in children - affecting eight or nine of every 10 children - because the developing middle ear sometimes cannot fully drain fluid, says Dr. Craig Derkay, at Eastern Virginia Medical School.

Also, the immune system in a child is not fully developed and cannot tackle infections, he explains.

Over-prescribing of antibiotics, meanwhile, has made matters worse by helping ear-infection germs develop immunity to existing drugs, says Dr. Derkay.

Dr. Post studied mucosal tissue from the middle ears of 50 children with chronic ear infections. Some of the children got ear infections repeatedly, while others continually suffered from fluid in their ears.

All the children were scheduled to undergo operations to insert drainage tubes in their ears.

The researchers found evidence of mucosal biofilms in 46 of the 50 children. They did not find any biofilms in another group of eight healthy children and adults whose ears were studied as they underwent cochlear implant operations for hearing loss.

Biofilms are very common in nature, says Dr. Post. For example, the slime you might find on rocks next to a pond is a type of biofilm.

"It's like a little city of bacteria," he says, in which germs communicate with each other and are well-protected against the outside world.

New Approach May Help Clear Infections

The new research suggests that treating chronic ear infections with antibiotics is "not helpful," says Dr. Post. "Biofilms by their nature are very resistant to antibiotics."

Instead, researchers must find another approach that either gets rid of biofilms or stunts their growth, perhaps by flooding the ear with "good bacteria," says Dr. Post. That approach is known as probiotics.

For now, the research is "just sort of an explanation as to why not all children are responding to these antibiotics" and need to have drainage tubes put in, says Dr. Derkay.

Always consult your physician for more information.