Image caption The birds are opportunistic feeders

Scientists fear migratory birds may be spreading hard-to-treat infections after discovering seagulls can carry antibiotic-resistant bacteria.

Portuguese researchers analysed 57 samples of droppings from the yellow-legged Caspian Gull Larus Cachinnans.

They found that one in 10 harboured bacteria resistant to a common antibiotic called vancomycin.

They told Proteome Science journal the birds probably pick up the infection from eating scraps in human garbage.

The white and grey gulls can often be seen flocking on rubbish tips, and are common in many southern parts of the UK.

The researchers have found similar antibiotic-resistant bacteria in other scavenger animals like wild foxes and wolves.

Fowl finding

For their study, the scientists collected and analysed bird dropping samples from an island off the Portuguese coast.

Lead scientist Gilberto Igrejas, of the University of Tras-os-Montes and Alto Douro, explained: "We used a novel technique called proteomics to detect the maximum number of bacterial proteins which are thought to be connected in some, as yet unknown, way to antibiotic resistance."

His team identified several strains of enterococcus bacteria in the samples - some of which were resistant to vancomycin.

Given that these are wild birds and not pets, they will not have encountered these antibiotics directly.

Instead, their exposure has come inadvertently from humans.

And the scientists believe wild migratory birds may be spreading antibiotic resistance from place to place, and to other animals and humans through their droppings.

Dr Igrejas said: "Migrating birds that fly and travel long distances can act as transporters, or as reservoirs, of antibiotic-resistant bacteria and may consequently have a significant epidemiological role in the dissemination of resistance."

Antibiotic-resistant bacteria are generally harmless to healthy people but can cause serious infections in the weak and vulnerable. There are usually other antibiotics that can be used to treat the infection.

The concern is that they could pass on their resistance to bacteria that can evade other antibiotics, ultimately leading to infections that would be incredibly difficult to treat.

The UK's Department for Environment, Food and Rural Affairs said it would study the findings "with interest".

An expert from the UK's Health Protection Agency said: "The study suggests that the wider environment has become contaminated with resistant bacteria, which is of concern as these bacteria may get recycled into the food chain. However there is no evidence that the seagulls were carrying the strain of resistant enterococci bacteria seen in hospital patients, which are also found in countries outside the distribution of this gull species."