Resistance to antimicrobial agents is increasing among human infections with Escherichia coli bacteria that produce the Shiga toxin, according to a study analyzing data from nearly 2,000 infections in the United States between 2010 and 2021. The findings were reported on June 8 by researchers at the University of Illinois Urbana-Champaign.
Csaba Varga, a professor of epidemiology at the university and leader of the study, said there is a need for antibiotic stewardship in both the food production chain and human health. Varga and graduate student Tarjani Bhatt used data collected by the U.S. Centers for Disease Control and Prevention through a national surveillance system, focusing on E. coli strain O157, which produces the Shiga toxin responsible for most severe illnesses.
The team analyzed 1,995 samples collected over an eleven-year period to assess changes in antimicrobial resistance rates over time as well as patterns related to age or geography. "Most of the previous studies have looked at snapshots in time, not how resistance changes year by year. We didn't have a clear picture of long-term trends, whether resistance was increasing, decreasing or staying the same," Varga said. "Resistance doesn't stay in one place; it moves through people, animals and the environment. Our study helps fill those gaps by looking at when, where and in whom resistance is emerging over time."
The research found that overall resistance remains low but has steadily increased—especially for common antibiotics such as tetracycline and sulfisoxazole. Resistance also varied by geographical region and age group; younger adults in their 20s and 30s were most likely to have infections resistant to some antibiotics.
Varga said it is puzzling that antibiotics are not typically recommended for treating Shiga-producing E. coli infections because treatment can trigger more toxin release, said. "Even though we don't usually treat this infection with antibiotics, we're still seeing resistance emerging and spreading, which tells us these bacteria are being exposed to antibiotics somewhere along the way." The results are published in Future Microbiology.
The researchers advocate for a 'One Health' approach addressing human health alongside animal agriculture practices and environmental controls due to foodborne transmission routes: "Better antibiotic stewardship in agriculture, along with food safety and environmental controls, will be key to slowing this trend. What happens on farms, in food production and in the environment can directly impact human health. Prevention has to happen from farm to fork," Varga said.
