Are Ionophores in Animal Feed Fueling Antibiotic Resistance? Expert Insights on the Risks to Human Health

Since ionophores are a type of antibiotic mainly used in animals, many people believe they don’t affect human health. However, recent research indicates that these antibiotics could play a role in developing antimicrobial resistance (AMR) that impacts humans.

Ionophores are frequently used in poultry and livestock to prevent diseases and boost growth. In the U.S., they accounted for 37% of antibiotics used in food animals by 2022. Despite their widespread use, they are considered less critical for human medicine, leading to more relaxed regulations.

The new study raises questions about these assumptions. It suggests that ionophores might contribute to AMR indirectly. This could happen through mechanisms like cross-resistance, where a gene for ionophore resistance might also enable resistance to important antibiotics. Alternatively, co-selection could occur, with ionophore resistance genes linked to those causing resistance to medically significant antibiotics. The exact risks to human health remain uncertain.

Researchers examined public data to explore fears about ionophores co-selecting for AMR. They found over 2,400 strains carrying two specific resistance genes, narA and narB, across 51 countries, sourced from various species, including poultry, cattle, and humans. The study noted the presence of narAB sequences in ten bacterial species, particularly in Enterococcus faecalis and Enterococcus faecium.

On average, each of the 2,400 isolates contained 8.26 resistance genes. Most of these genes are linked to resistance against critical antibiotics like erythromycin, tetracycline, and aminoglycosides. The researchers also found mutations associated with resistance to drugs like daptomycin and ampicillin.

Interestingly, they noted strong connections between resistance traits in Enterococcus faecalis and several important resistance genes, including those linked to vancomycin resistance. In Enterococcus faecium, similar positive associations were found.

Overall, the findings indicate that ionophore use might not be as safe as previously thought. While it’s still unclear how resistance genes transfer between animals and humans, the study suggests that such a transfer is likely.

For a deeper understanding of the issue, you can read more in the Antimicrobial Chemotherapy journal, where this study was published. The research was conducted by scientists at Carleton University and backed by Perdue Farms and the Natural Sciences and Engineering Research Council (NSERC).

Recent discussions on social media reveal growing public concern about antibiotic use in food production. Many people are calling for stricter regulations and more transparency about how these substances may impact health. As awareness of AMR increases, further research and open conversations about its implications will become even more crucial.

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