Study Shows Antibiotic Resistance Risk in Commonly Used Drug

A recent roundtable brought together experts to discuss new research published this month in mSphere that raises fresh concerns about antibiotic resistance linked to the overuse of ionophores in animal agriculture. Dr. Alex Wong, Dr. Bruce Stewart-Brown, Dr. Gail Hansen, and Steven Roach examined the implications of the study and what it means for the future of antibiotic stewardship.

The misuse of antibiotics in industrial farming has long been a public health concern. When antibiotics are overused, bacteria can evolve resistance, rendering those drugs less effective, or sometimes entirely ineffective. In crowded, unsanitary farming conditions, producers have turned to antibiotics, including those critical to human medicine, as a preventive measure rather than a treatment for illness. This practice fuels antibiotic resistance, which already causes at least 35,000 deaths annually in the United States. It also increases the risks associated with treating infections, performing routine surgeries, and delivering chemotherapy.

In the 2010s, public pressure, including campaigns by PIRG and the Keep Antibiotics Working Coalition, led to major reductions in antibiotic use in the chicken industry. In response, many producers shifted toward ionophores, a class of antibiotics not used in human medicine, under the assumption that resistance to these drugs would pose no direct threat to people. By 2022, ionophores accounted for 37% of antibiotics used in animals.

But new research, including the recent mSphere study, reinforces a growing concern: even ionophores can contribute to antibiotic resistance through a process called “co-resistance,” a phenomenon where bacteria are simultaneously resistant to multiple antibiotics so exposure to one antibiotic increases the proportion of bacteria resistant to other antibiotics. For ionophores, co-resistance means that using these drugs in chickens or pigs leads not only to increased ionophore resistance which is not a risk for people but to increased resistance to other antibiotics that are needed to treat sick people.

This is why we cannot continue a piecemeal approach to antibiotic reduction in agriculture. The solution is not simply switching from one class of antibiotics to another, it is to dramatically reduce and ultimately end the routine, preventive use of antibiotics in animal farming altogether.

In 2018, under pressure from the Stop the Overuse of Antibiotics campaign, McDonald’s pledged to reduce antibiotic use in its global beef supply. As the largest buyer of beef in the United States, McDonald’s has enormous influence over industry practices. But since making that pledge, the company has backtracked, delaying action and narrowing its goals.

Now is the time to hold McDonald’s accountable. We are calling on the company to honor its 2018 commitment, establish an aggressive, transparent timeline for reaching its targets, and share antibiotic use data publicly.

Add your voice to the call. Sign our petition today and demand action from McDonald’s to protect public health and preserve the effectiveness of life-saving medicines.