A California policy limiting the use of antibiotics in animals raised for food is associated with a reduction in one type of antibiotic-resistant infection in people in the state, according to a new study published today in review Environmental Health Perspectives.
The results suggest that regulations limiting antibiotics in livestock can have a significant impact on human health.
The study was led by Joan Casey, an assistant professor in the Department of Environmental Sciences and Occupational Health (DEOHS) at UW, who conducted the research as an assistant professor at Columbia University. , with Kara Rudolph, assistant professor of epidemiology at Columbia.
In 2018, California Senate Bill 27 (SB27) banned, for the first time in the United States, the routine preventive use of antibiotics in food animal production and all use of antibiotics. antibiotics without a prescription from a veterinarian.
Casey and colleagues found that the policy was associated with a 7% reduction in resistance to a class of antibiotics used in livestock, extended-spectrum cephalosporins, among Escherichia coli bacteria isolated from urine in people with urinary tract infections.
“After climate change, antibiotic resistance is the second biggest public health issue we will face in the next 50 years, as few new antibiotics come online and resistance increases,” Casey said. “Anything we can do to reduce resistance is really exciting.”
The study includes co-authors Sara Tartof and Hung Fu Tseng of Kaiser Permanente, Meghan Davis and Keeve Nachman of Johns Hopkins University, and others from George Washington University, Becton Dickinson, the University of Arizona, Sutter Health and the University of California, San Francisco.
“Reducing antimicrobial resistance is a critical factor in improving community health,” said Tartof, an epidemiologist in the research and evaluation department at Kaiser Permanente in Southern California. “This study shows that changes in clinical practice alone will not be enough to reduce this threat. We need to strengthen our efforts with broader public policy initiatives to reduce antimicrobial use beyond the hospital setting as well.”
Researchers have previously demonstrated links between the widespread use of antibiotics on livestock and antimicrobial resistant infections in humans, which cause nearly 3 million infections and 35,000 deaths each year.
Antimicrobial resistant pathogens can spread from livestock to humans through contaminated meat, environmental routes such as water and air, and exposures of people working on or living near livestock operations.
To test the impact of new legislation on antibiotic-resistant infections in humans, the research team looked at data on antibiotic-resistant infections. E. coli in 7.1 million urine samples from people with urinary tract infections in 33 states from 2013 to 2021.
“In an ideal world, we’d have two Californias and we’d observe them both over time, but we don’t have either,” Casey explained. “We used statistical methods to create this dream, a synthetic California” in which the bill had not passed.
With this approach, called the synthetic control method, they first used a data set from states that had not changed their policy to match antimicrobial resistance patterns in California before the bill was passed. .
Then they compared the levels of four different antibiotic resistant E. coli in the California samples at the corresponding levels in their “synthetic California” data before and after the passage of the bill.
“We saw a reduction in actual California versus our synthetic California for one of the antibiotic classes that we believe may be related to on-farm antibiotic use,” Casey said.
This class, the extended-spectrum cephalosporins, is used in cattle and poultry farming. Although it accounts for less than 1% of US livestock antibiotic sales, 80% of those sales are to cattle, one of the most commonly raised meat animals in California.
Researchers found no bill-related changes in resistance patterns for three other classes of antibiotics: tetracycline, which is used in both livestock and humans, and aminoglycosides and fluoroquinolones , which are only used in humans.
Interpretation of the results is complicated by the fact that California has not made data on on-farm antibiotic use public, despite being required to do so by SB27.
“The California Department of Food and Agriculture has not made available data that allows the public to determine whether the implementation of SB27 resulted in a reduction in on-farm antibiotic use” , said Nachman, associate professor of environmental health engineering at Johns Hopkins University. “To circumvent the problem, we used a new statistical technique to begin to assess the law’s impact on an infection with a high public health burden,” Nachman said.
Researchers are engaged in further analyses, including whole genome sequencing of E. coli isolated from human urine and chicken meat at retail in California, to help complete the picture.
European Union regulations to restrict the use of antimicrobials in food animal production led to a 35% reduction in biomass-adjusted use from 2011 to 2018. In the United States, Maryland recently passed a law similar to California’s.
“Generally what we’re seeing is a growing trend of rising antimicrobial resistance,” Casey said. “Policies that lead to a plateau or lowering of this resistance are promising. A 7% cut – for a bill that we’re not sure how well it’s implemented – is pretty exciting. I hope this can stimulate other states to consider similar bills.”
La recherche a été financée par le National Institute of Environmental Health Sciences, le National Institute of Allergy and Infectious Diseases, le National Institutes of Health Office of the Director, Kaiser Permanente et le Johns Hopkins Berman Institute for Bioethics.