A new study using gene sequencing finds the superbug MRSA can be transmitted from animals to humans.

Researchers in England and Denmark used whole genome sequencing to establish the animal-to-human transmission of methicillin-resistant Staphylococcus aureus, the MRSA bacteria.

“Our findings demonstrate that the MRSA strains we studied are capable of transmission between animals and humans, which highlights the role of livestock as a potential reservoir of antibiotic-resistant bacteria,” says Ewan Harrison, lead author of the study and a scientist at the University of Cambridge. The study was published in the journal EMBO Molecular Medicine.

The New York Times reports that Louise M. Slaughter, (D-N.Y.) sent a letter to the U.S. Food and Drug Agency Commission Margaret Hamburg calling for immediate action to reduce the use of antibiotics in livestock.

Slaughter says the study, conducted on two small farms in Denmark, “ends any debate” about whether giving antibiotics to livestock is a risk to humans. “The extreme overuse of antibiotics in livestock is endangering human health,” Slaughter says.

Keeve Nachman, a scientist at the Johns Hopkins Center for a Livable Future, says scientists had shown a connection between animals and people before, but never in as much detail.