Nearly half of Mediterranean gulls in southern France have some form of resistance to antibiotics, a new study finds.

Bacteria are known to evolve rapidly, and they can develop resistance to antibiotics that are the front line for fighting many human diseases. In recent decades, the evolution of antibiotic-resistant superbugs — fueled in part by the overprescription of antibiotics — has become more and more worrisome, many experts have said.

The spread of resistance is no longer a local problem in hospitals, the new study's researchers note. Antibiotic-resistant bacteria are also spreading to and throughout the environment.

"Gulls have developed behaviors that entail closer and closer contact with us, and opportunities arise for the exchange of bacteria. This is why they are extremely interesting to study," said study leader Mirva Drobni at Uppsala University in Sweden.

Nearly half of the birds carry some form of resistance to antibiotics, and a tenth pack ESBL-producing bacteria, which have the capacity to break down some of our most powerful and important antibiotics and furthermore have an ability to spread extremely rapidly.

The resistance pattern was the same among gulls and humans, which indicates that human- and bird-borne bacteria and their resistance mechanisms are being mutually exchanged.

"These findings are worrisome as they also indicate a higher degree of resistance in bacteria from gulls than we see in humans in the same region. At present we don't know whether they constitute merely a reservoir for antibiotics resistance or whether they are moreover a source of further dissemination to humans," Drobni said.

The study is being published today in the journal PLoS One.