Combatting Antibiotic Resistance in Beef Cattle: Unraveling Respiratory Disease Pathogen Transmission for Precision Antibiotic Use

Project Title

Understanding the Molecular Epidemiology and Transmissions of Antimicrobial Resistance in Bovine Respiratory Disease Pathogens


Tim McAllister

Sheryl Gow (PHAC), Murray Jelinski, Antonio Ruzzini (WCVM), Trevor Alexander, Rahat Zaheer, Sara Andres-Lasheras (AAFC Lethbridge), Athanasios Zovoilis (University of Manitoba), Brian Warr (VAHS), Greg Dimmers (ABHS)

Status Project Code
In progress. Results expected in March, 2025 ANH.16.21C


Bacteria can trade genes (known as mobile genetic elements or MGE) among themselves. Some bacteria can assemble groups of genes together on the chromosome, then trade the entire sets of genes. This specific kind of MGE are called integrative conjugative elements (ICE). When ICE contain antibiotic resistance genes, their transfer across bacteria allows bacteria to immediately switch from being antibiotic susceptible to being muti-drug resistant (MDR), without having to be exposed to an antibiotic and evolve resistance. This project will study what triggers ICE formation and movement among different bovine respiratory disease (BRD) bacteria and identify those ICE that pose the greatest risk to the development of MDR.


  • Investigate the prevalence of antibiotic resistance (AMR) and multidrug resistance (MDR) in BRD pathogens isolated from sick and dead cattle compared to BRD pathogens isolated from low risk and healthy cattle,
  • Characterize the genomic nature of AMR and MDR in BRD pathogens, their association with ICE and other mobile genetic elements (MGE), and the potential for AMR co-selection,
  • Evaluate the origin, evolution and diversity of ICE associated with MDR in Mannheimia, Pasteurella and Histophilus BRD bacteria,
  • Investigate the risk of transferring AMR and virulence genes via ICE and other MGEs among different BRD bacteria and assess the role of ICE in the transmission of AMR in cattle production systems, and
  • Use high quality genomic data to predict and evaluate new vaccine targets for BRD pathogens.

 What They Will Do

This team will collect nasopharyngeal samples from 50 sick calves at two cow-calf operations, 75 low risk, 100 high risk and 300 sick or dead cattle from four commercial feedlots. Relevant production, management and antibiotic use data will also be collected. The BRD pathogens will be isolated and used for the lab analyses and experiments described above. They will also include 600 historical multi-drug resistant Mannheimia, Pasteurella and Histophilus and 666 M. bovis isolates collected from commercial feedlots between 2011 and 2019, as well as 286 newer BRD isolates collected through the CIPARS feedlot surveillance program.


Antibiotics will rapidly lose their effectiveness if ICE element mediated multidrug resistance becomes established in BRD pathogens. A better understanding of what triggers the development and transfer of CE elements will be key to identifying strategies to combat them.