There are a host of ‘known unknowns’ when it comes to AMR, amongst which is the contribution of antibiotic use in the farming industry to AMR in human health. By volume, the amount of antibiotics used in farming for growth promotion and disease prophylaxis dwarfs the amount used in human medicine in many contexts, so it is important that we learn more about its potential impact. 

A new study conducted by the US Department of Agriculture published in the Journal of Food Protection is welcome for addressing this topic, but care must be taken in understanding and communicating the data. The title of the article is ‘Similar Levels of Antimicrobial Resistance in U.S. Food Service Ground Beef Products with and without a "Raised without Antibiotics’ Claim”. This could easily be taken to mean that the use of antibiotics in the beef industry is not a driver for AMR in the food chain. In fact, the study finds that tetracycline resistant E.coli was found significantly more frequently in antibiotic-raised than antibiotic-free beef (54.2% v 35.2%, respectively, p<0.01).  

Interestingly, this phenotypic data contrasts with the authors’ genotypic evaluation of Tet^Rgene carriage. The authors suggest there may be an influence of contamination of meat by drug-resistant bacteria at some stage in the supply chain. If that could be demonstrated in a follow-up study, it would be of huge importance because it would reveal a clear target for intervention. It means that poor hygiene in the supply chain is potentially introducing AMR-bacteria that could be undermining worthy efforts to restrict antibiotic use in animal husbandry. While the authors state that their findings should not be used to argue against regulation of antibiotic use in farm animals, this is a good example of how important it is that research findings are communicated clearly to a wider audience. In this instance the impact, or otherwise, of antibiotic use in farm animals on AMR cannot be commented on due to the influence of everything that happens to the product after it leaves the farm.

We urgently need to address our known unknowns; but this requires unbiased, good-quality science, subjected to high standards of peer review, which must then be communicated responsibly to a wider audience.