A common perception of human urine as a "sterile" environment, free of bacteria or germs may not be correct, a study suggests.

Bacteria are present even in the urine of healthy people, so it's not as sterile as has been previously believed, U.S. researchers say.

"Doctors have been trained to believe that urine is germ-free," says study co-investigator and dean Linda Brubaker of Loyola University Chicago Stritch School of Medicine. "These findings challenge this notion, so this research opens the door to exciting new possibilities for patient treatment."

In urine samples taken from 90 women in the study, the researchers found bacteria in the urine from both healthy women and those suffering from overactive bladders.

However, they said, the type of bacteria detected was different in each group and may be a factor in their overall health.

"The presence of certain bacteria in women with overactive bladder may contribute to overactive bladder symptoms," lead investigator and Loyola graduate student Evann Hilt says.

Determining whether such bacterial differences may be "clinically relevant for the millions of women with overactive bladder" will require further study, she says.

Of the approximately 15 percent of all women who suffer from an overactive bladder, around 40 to 50 percent are not responsive to currently available treatments, the researchers noted.

In presenting the study at this year's meeting of the American Society for Microbiology in Boston, the researchers suggested that different bacteria found in women with an overactive bladder might suggest why some don't respond to treatment.

The study could open up new options, they said, since it used a technique able to identify bacteria that don't show up in standard urine culture techniques normally employed to spot urinary tract problems.

"If we can determine that certain bacteria cause overactive bladder symptoms, we may be able to better identify those at risk for this condition and more effectively treat them," Loyola professor of immunology and microbiology Alan Wolfe said.

The next goal in the research would attempt to determine the difference between helpful and harmful bladder bacteria as well as how they might be interacting with each other in the body.

Such knowledge can be a help to both doctors treating bladder complaints and the women who suffer from them.