New York, Feb 24 (IANS): Besides treating bacterial infections, some antibiotics may also give rise to harmful new bacteria, research suggests.

"For a long time we have thought that bacteria make antibiotics for the same reasons that we love them - because they kill other bacteria," said Elizabeth Shank, assistant professor of biology at University of North Carolina at Chapel Hill.

"However, we have also known that antibiotics can sometimes have pesky side-effects, like stimulating biofilm formation," Shank added.

The researchers have now shown that this side-effect - the production of biofilms - is not a side-effect after all, suggesting that bacteria may have evolved to produce antibiotics in order to produce biofilms and not only for their killing abilities.

Biofilms are communities of bacteria that form on surfaces, a phenomenon dentists usually refer to as plaque. Biofilms are everywhere. In many cases, biofilms can be beneficial, such as when they protect plant roots from pathogens. But they can also harm, for instance when they form on medical catheters or feeding tubes in patients, causing disease.

"That suggests that antibiotics can independently and simultaneously induce potentially dangerous biofilm formation in other bacteria and that these activities may be acting through specific signalling pathways," Shank noted.

"It has generated further discussion about the evolution of antibiotic activity, and the fact that some antibiotics being used therapeutically may induce biofilm formation in a strong and specific way, which has broad implications for human health," Shank added.

The study appeared in the journal Proceedings of the National Academy of Sciences.