Ten people in Denmark who had no contact with livestock contracted the potentially deadly infection, most likely through food.
A new study led by a GW researcher has found that people who have no contact with livestock can become infected by a dangerous superbug, most likely by eating contaminated food.
The study, “Evidence for Human Adaptation and Foodborne Transmission of Livestock-Associated Methicillin-Resistant Staphylococcus aureus,” was published Wednesday in Clinical Infectious Diseases.
Milken Institute School of Public Health researcher Lance Price along with a team of international researchers discovered that Methicillin-Resistant Staphylococcus aureus (MRSA), a serious infection often contracted by farm workers and veterinarians after contact with chickens, pigs and other animals, is spreading to humans in urban areas of Denmark even though those contracting the infection have not had contact with live animals. The infection likely comes from food, the study says.
“We’ve known for several years that people working directly with livestock are at increased risk for MRSA infections, but this is one of the first studies providing compelling evidence that everyday consumers are also potentially at risk,” Dr. Price said.
Dr. Price, Robert Skov at the Statens Serum Institute in Denmark and other researchers reviewed data from the institute and found 10 people living in urban areas who had been colonized or hospitalized with MRSA. The researchers used genetic analysis to study the MRSA in those cases and compared it to strains found in people, livestock and food products from other European countries.
None of those 10 people had worked on farms or had direct exposure to farm animals, researchers found. The strain of poultry-associated MRSA identified in the study was not found in Danish livestock but could be traced to poultry imported from other European countries.
The new strains found in the 10 urban Danes were nearly identical, suggesting they were exposed to a common source, most likely contaminated poultry, the study said.
“Our findings implicate poultry meat as a source for these infections,” Dr. Skov said. “At present, meat products represent only a minor transmission route for MRSA to humans, but our findings nevertheless underscore the importance of reducing the use of antibiotics in food-producing animals as well as continuing surveillance of the animal-food-human interface.”
Other research suggests modern farming practices, including giving low doses of antibiotics to farm animals to spur growth, and unsanitary living conditions have led to a surge of superbugs such as the new MRSA strain identified in this study. Food inspections also regularly don’t include testing for MRSA contamination. Instead, they focus on more common foodborne pathogens like salmonella.
The food industry needs to reduce the overuse of antibiotics on industrial farms and increase testing for MRSA, said Dr. Price, who also heads SPH’s Antibiotic Resistance Action Center. This MRSA problem is not unique to Denmark or the European Union and has the potential to become a larger issue.
“Superbugs don’t respect political or geographical boundaries, so we have to work together to address this public health threat,” he said. “I’m not sure that our international trade agreements are prepared to handle the specter of superbugs in meat.”
Dr. Skov said he fears that if there is not a reduction in the use of antibiotics in livestock, new and more dangerous strains that pose a greater threat to public health could emerge.
The study was an international collaboration involving 25 institutions and led by Dr. Price, Dr. Skov and the Translational Genomics Research Institute in Flagstaff, Ariz. Funding was provided by the National Institute of Allergy and Infectious Diseases, National Institutes of Health.