April 4, 2013
Scientists' findings support the restriction of antibiotics in confirm livestock production
Following concerns that food animals are a significant methicillin-resistant Staphylococcus aureus (MRSA) reservoir for human infections, scientists have found conclusive evidence using whole genome sequencing that a type of MRSA that caused human infections in Denmark came from livestock.
While previous research has suggested that MRSA transfers from animals to humans, including a US study last year that looked at "pig-MRSA," the study by scientists from various research institutions in the UK and Denmark, including the University of Cambridge provides the strongest evidence to date that this phenomenon is occurring and provides fodder to those advocating for greater limits on antibiotics in agriculture.
"This study refutes the counterargument that's been out there -- that the animals and humans could have independently acquired MRSA," explained Johnson, who works on antimicrobial resistance issues for the Infectious Disease Society of America, an association of infectious disease physicians. Johnson said that with the level of detail provided by whole genomic sequencing in the latest study there is little doubt that the MRSA in these cases transferred animal to human.
The researchers argue that, considering the recent science on the matter, "surveillance of S. aureus and other animal pathogens from livestock and wildlife should be undertaken to monitor the emergence of new clones, and to further improve our understanding of bacterial pathogen evolution." Those advocating for limiting antibiotics in agriculture say the study is another sign that antibiotic-resistance is a growing health problem and the widespread use of antibiotics in food animal production is a major contributing factor.
"This study adds to the extensive scientific research supporting the connection between the overuse of antibiotics -- 80% of which are used on otherwise healthy animals in the US -- and the development of antibiotic resistant bacteria," said Louise Slaughter, US Congresswoman and a microbiologist, in the letter addressed to Food and Drug Administration Commissioner Margaret Hamburg. "This study ends any debate," said Slaughter in a statement Wednesday (Mar 27). "The extreme overuse of antibiotics in livestock is endangering human health."
Lance Price, a professor at George Washington University who has done extensive research on antimicrobial resistance at Translational Genomics Research Institute in Arizona, said the study presents "compelling evidence" that mecC-MRSA is jumping from livestock to humans. "It also shows that these host jumps are not limited to MRSA ST398 (the strain that we study)," Price said, adding that the new research also demonstrates how useful whole genomic sequencing is as a tool to "resolve transmission events like these."
On the other hand, Scott Hurd, a veterinarian and professor at Iowa State University criticised the study and called it inconclusive. Hurd, who served as Deputy Undersecretary for Food Safety at the USDA, said, in an email to Food Safety News that, "It is irresponsible science to make conclusions that one came from another in the absence of some other information."
