Feedlot sampling uncovers neglected gene involved in antimicrobial resistance

Researchers at the University of Saskatchewan have discovered how a previously overlooked gene is involved in antimicrobial resistance. The antimicrobial resistance gene (ARG) encodes for an α/β-hydrolase, named EstT, capable of inactivating macrolide antibiotics commonly used to treat livestock diseases. The findings are published in Proceedings of the National Academy of Sciences (PNAS).

The research team, led by Tony Ruzzini, made the discovery after analysing bacteria collected from watering bowls at a western Canadian beef cattle feedlot.

Ruzzini said scientists have previously identified the existence of this gene that’s commonly found in many animal pathogens and their microbiomes, but its purpose remained unknown. The researchers discovered that EstT can break the ring structure of the antibiotic through hydrolysis.

The gene was found in a cluster with three other ARGs — a clue that it could be involved in antimicrobial resistance. Once the gene was identified, the team worked to clone it and test it against a panel of many antibiotic drugs from different classes.

“This gene, even though we found it in an environmental organism, it is also present in pathogens that are responsible for causing bovine respiratory disease,” said Ruzzini.

Ruzzini added that his research team is continuing to learn more about how EstT works.

“As AMR surveillance systems rely more on molecular tools for detection, our knowledge of this specific gene and its integration into those systems will help to better inform antimicrobial use,” said Ruzzini.

The research was supported by the Saskatchewan Health Research Fund, Saskatchewan’s Agriculture Development Fund, the Beef Cattle Research Council, and the Mitacs Globalink Internship program.

Article: Dhindwal, P., Thompson, C., Kos, D., Planedin, K., Jain, R., Jelinski, M., Ruzzini, A., 2023. A neglected and emerging antimicrobial resistance gene encodes for a serine-dependent macrolide esterase. Proceedings of the National Academy of Sciences of the United States of America, 120(8), e2219827120, doi: 10.1073/pnas.2219827120

[SOURCE: University of Saskatchewan]