Livestock waste is a major reservoir for antibiotic resistance genes, some of which can potentially transfer to bacteria that infect humans, according to a new study.
This transfer could make common infections much harder to treat, the researchers said.
The study by Michigan State University (MSU) and partner researchers spanned 14 years and the team said it represents the most comprehensive survey of livestock antibiotic resistant genes to date. The research team examined over 4,000 manure samples from pigs, chickens and cattle across 26 countries.
“This research shows that what happens on farms doesn’t stay on farms,” said James Tiedje, University Distinguished Professor at MSU and one of the authors of the study published in Science Advances. “Genes from manure can make their way into the water we drink, the food we eat and the bacteria that make us sick.”
The team built a global map highlighting regions where antibiotic resistance genes are most common, plus a system to rank which genes pose the greatest threat to human health. Livestock manure may act as an important environment for detecting the early signs of antibiotic resistance gene proliferation, which create a chance for intervention.
The researchers noted that, as the world’s leading beef producer, the US shows significantly higher abundance and diversity of antibiotic resistance genes in cattle manure compared to other countries. China, as the world’s largest pig producer, likewise showed elevated levels of bacterial abundance, diversity and overall resistance risk in swine manure.
Antimicrobial resistance (AMR) occurs when antibiotics are overused, making genes resistant and treating infections more difficult. AMR is one of the top global public health and development threats according to the World Health Organization.
“Antibiotic resistance isn’t just a medical issue, it’s an environmental one, too,” Tiedje said. “And it may pose an even greater risk than other pollutants because if these genes end up in harmful bacterium, they can directly cause deadly infections.”
Antibiotics play a vital role in protecting animal health, but part of the problem is that antibiotics are regularly used to promote faster growth in animals in addition to treating disease – this increases the risk that AMR will develop as a result of overuse.
“We need antibiotics to control disease,” Tiedje added. “That’s why it’s so important to protect their effectiveness. If resistance spreads too far, these life-saving drugs won’t work when we really need them.” However, the study also found signs that efforts to reduce farm antibiotic use are paying off.
Denmark and other European countries led the way by banning growth-promotion antibiotics and they’ve seen lower resistance levels as a result said Tiedje. The US and China have introduced restrictions on the use of antibiotics in animals and there has been a decline in resistance genes in livestock manure over time, showing that such policies work - although there is still much to be done, he said.
More on AMR
- What is AMR? Here’s what you need to know about antimicrobial resistance
- Microplastics ratchet up antibiotic resistance [Premium]
- Antibiotic resistance meets AI [Premium]
- How AI could fuel a mammoth antibiotic discovery
For over 100 years Chemistry & Industry (C&I) magazine has reported on the scientific advances being harnessed to tackle society's biggest challenges. C&I covers advances in agrifood, energy, health and wellbeing, materials, sustainability and environment, as well as science careers, policy and broader innovation issues. C&I’s readers are scientific researchers, business leaders, policy makers and entrepreneurs who harness science to spark innovation.
Get the latest science and innovation news every month with a subscription to Chemistry & Industry magazine. You can subscribe to C&I here.
Visit Blog