There have been calls to develop antibiotics that are just for use in animals, the idea being to have separate antibiotics for animals and people, so that antimicrobial resistance that develops as a result of antibiotic use in animals won’t impact people.

Makes sense, right?

It does, at least at first glance. However, “makes sense” and “will work” aren’t the same.  The concept is sound, but the reality is  different.

When an antibiotic is used in animals, there’s a chance of resistance developing in any of the bacteria carried by that animal, and that includes resistance in bacteria that cause disease in people. Transfer between different kinds of bacteria of genes that cause resistance is also a concern, and can also result in resistance in bacteria that infect people. Antibiotic residues can also contaminate the environment, selecting for more antibiotic resistance, and antimicrobial resistant bacteria themselves can can end up in the environment, potentially exposing animals and people. These are just a few examples of why antimicrobial resistance is such a complex ecological problem.

Let’s say a new antibiotic class is developed that it can kill a range of bacteria of concern in animals, and resistance to this antibiotic doesn’t also confer resistance to other antibiotics.

That would be great.  But, what would we want to do with a drug that kills clinically relevant bacteria and doesn’t create cross-resistance in bacteria that cause disease in people?

• We’d use it in people, not animals! We need new antibiotic drug classes in people, and since we’re typically targeting the same kinds of bugs in people and animals, any new drug class that works for animals is probably going to be of interest and use in people.

Ultimately, unless we have a drug class that can’t be used in humans (e.g. too toxic), I can’t see us ever having animal-only antibiotics.  That doesn’t mean we shouldn’t think about it, though. We need new drug classes, and maybe some would be used more in animals or in people, which would help reduce some of the issues around emergence of resistance. But animal-specific antibiotics aren’t likely, apart from a small number of drugs that target a really narrow range of bacteria that are only relevant in animals.

Where does this leave us?

Antimicrobial stewardship – by everyone – is the key.

• There’s still lots that we can do to reduce and improve antimicrobial use, in both animals and people. Importantly, we can do these things today, and for less than the hundreds of millions of dollars required to get a new human antimicrobial drug to market.

A key aspect of stewardship that gets overlooked frequently is improving health systems.

• Money invested in improving human and animal health systems will reduce the need for antibiotics and improve how we use them. It won’t fix the antimicrobial resistance problem (no one thing will), but it is among the most effective things we can do, and one that has many benefits beyond just antimicrobial resistance.