Research

Background

Bovine respiratory disease (BRD) is the most costly and significant disease in North American
feedlot cattle. Antimicrobials are the mainstay for preventing, treating, and controlling BRD, but their administration can select for antimicrobial resistance (AMR) in bacteria. BRD is a
multifactorial disease complex in which bacteria, viruses, host, management practices, and
environment play an important role.

The main bacterial species associated with BRD are Pasturella multocida (PM), Mannheimia haemolytica (MH), Histophilus somni (HS), and Mycoplasma bovis (MB). It is well documented that PM, MH, and HS can contain mobile elements that carry AMR genes that can be transferred to other bacteria.

Trueperella pyogenes (TP) and Bibersteinia trehalosi (BT) are two bacterial species less
frequently described in clinical BRD cases. However, these mobile elements that share AMR genes have been found in these bacteria as well. MB is often excluded from AMR surveillance programs as it is challenging to work with in the laboratory.

This project aims to determine whether these bacteria and their potential AMR genes are contributing to AMR in feedlot cattle, potentially compromising treatment success.

Objectives

The objectives of this project are to:

1. Isolate TP, BT, and/or MB from beef cattle respiratory samples at different feedlot production stages.
2. Carry out antimicrobial susceptibility testing to determine AMR in these bacteria.
3. Study the possible risk factors associated with higher AMR in MB at feedlot entry.
4. Characterize the genome of TP and BT and AMR genes associated with mobile elements.
5. Evaluate the ability of TP and BT to transfer AMR genes to other bacteria associated with BRD.

Implications of the Research

This project will provide information on the contribution of lesser known BRD-associated bacteria to AMR in feedlot cattle, and whether these bacteria play a significant role in transferring AMR to other pathogens that play a role in causing BRD.