A news release from Northern Arizona University (NAU) last week outlines results of a study indicating a food-animal origin for antibiotic-resistance in pathogens, which then jumped to the human population. The study focused on methicillin-resistant Stapylococcus aureus (MRSA) using whole-genome sequencing to study 89 genomes from humans and animals, including turkeys, chickens and pigs, with samples from 19 countries on four continents.
Previous studies, such as from the Centers for Disease Control and Prevention, have shown that pigs can carry the resistant pathogen. The NAU researchers claim their genetic testing has tracked the series of events leading to human MRSA infections.
Their results indicate that humans initially passed the non-resistant Stapylococcus aureus pathogen to food animals. Then, use of tetracycline and methicillin in the animal populations led to the evolution of MRSA in animals. The MRSA pathogen then jumped back to humans, causing staph infections that are difficult to control with traditional antibiotics.
One of the researchers, Paul Keim, Regents’ professor and director of NAU’s Center for Microbial Genetics and Genomics, says the study describes evolution in action. "The most powerful force in evolution is selection. And in this case, humans have supplied a strong force through the excessive use of antibiotic drugs in farm animal production. It is that inappropriate use of antibiotics that is now coming back to haunt us.”
The NAU release received broad coverage in the consumer press last week, and undoubtedly will stoke the fires of the debate over antibiotic use in livestock. Antibiotic opponents will claim the study’s results represent the “smoking gun” showing antibiotic use in livestock created MRSA. Others will point out this is just one study, and that other research has failed to find such a link.
The fact is, antibiotic resistance is a complex subject, and debate likely will continue for years. To help unravel the issue’s complexity and build a dialog, the National Institute for Animal Agriculture (NIAA) held a symposium last fall titled "Antibiotic Use in Food Animals: A Dialogue for Common Purpose." Following the symposium, NIAA released a White Paper summarizing the science-based presentations from human health and animal health experts who presented information during the symposium.