Factory farms could be helping to spread antibiotic-resistant bugs including MRSA into the community, new evidence suggests.
Scientists found drug-resistant bacteria being carried in the noses of industrial livestock workers in the US.
Compared with colleagues working on non-intensive farms, they were twice as likely to have multidrug-resistant strains of staphylococcus aureus bacteria.
Among the strains was methicillin-resistant S. aureus (MRSA), which causes potentially fatal infections.
The factory farms, which are common in the US, confined animals in large buildings and used antibiotics to promote their growth.
In contrast, the non-industrial farms reared animals without the use of antibiotics, typically outdoors on pasture.
Researchers carried out interviews with workers at both types of farm in North Carolina. Nose swabs were also collected and analysed for signs of bacteria.
Genetic markers showed that many of the bugs found originated in livestock. This study shows that these livestock-associated strains are present among workers at industrial livestock operations and that these strains are resistant not just to methicillin but to multiple antibiotics, including antibiotics that are used to treat human infections," said study leader Dr Christopher Heaney, from the Johns Hopkins Bloomberg School of Public Health in Baltimore.
At the time of the study, the bacteria were not making the workers ill. Many healthy people carry staphylococcus without coming to any harm. But when the drug-resistant bugs do cause an infection, they can be hard to treat. The research is in the online journal 'Public Library of Science ONE'.