# Antimicrobial Resistance in Bovine Respiratory Disease Pathogens: A Systematic Review and Analysis of the Published Literature

## TL;DR

This paper reviews antimicrobial resistance in bacteria causing cattle pneumonia in North America and finds that resistance varies by antibiotic and sample timing.

## Contribution

The study provides a systematic analysis of antimicrobial resistance trends in bovine respiratory disease pathogens from 2015 to 2024.

## Key findings

- Resistance to tulathromycin and tildipirosin varies among common BRD pathogens.
- Sample collection timing is associated with the prevalence of antimicrobial resistance.
- Limited studies prevent evaluating long-term trends in resistance.

## Abstract

Bovine respiratory disease, or cattle pneumonia, is the most common disease affecting cattle in North American feedlots. Antibiotics are commonly used to treat the underlying bacterial infections that cause cattle pneumonia; however, antimicrobial resistance in these bacteria may threaten the usefulness of antibiotics labeled to treat this disease. A review of scientific articles published between 2015 and 2024 was conducted to determine (1) if changes in antimicrobial resistance over time have occurred and (2) if antimicrobial resistance is common in the bacteria causing cattle pneumonia. Trends over time could not be evaluated due to the limited number of published studies. This review and analysis does suggest that antimicrobial resistance for three approved antibiotics varies considerably among the most common bacteria that cause cattle pneumonia and timing of sample collection is associated with the prevalence of resistance. These results provide veterinarians with valuable information regarding the current state of antimicrobial resistance in bacteria that cause cattle pneumonia and enable them to make science-based antimicrobial stewardship decisions in cases of cattle pneumonia.

Bovine respiratory disease (BRD) is the most significant disease challenge in the feeder cattle industry in North America. Antimicrobials are commonly administered in BRD cases due to the role of bacterial pathogens. However, reports of antimicrobial resistance (AMR) in these pathogens raise concerns regarding their long-term effectiveness to treat BRD cases. A systematic literature review was conducted to summarize AMR in North American BRD pathogens and determine if changes in AMR prevalence over time could be identified for antimicrobials routinely used for treatment and control of BRD. Generalized linear models were used to test associations between the proportion of resistant isolates for each of the three bacterial agents and antimicrobial agent, isolation year, and timing of sample collection. The antimicrobial agent and timing of sample collection were significantly associated with the proportion of antimicrobial resistant isolates, with increased probability of resistance to tulathromycin seen in Mannheimia haemolytica (24.08%) and Histophilus somni (8.19%) and increased resistance to tildipirosin in Pasteurella multocida (21.48%), while samples collected at arrival demonstrated a lower proportions of resistant bacteria. Trends over time could not be evaluated due to the limited number of published studies. These findings highlight the differences in AMR seen between antimicrobials, BRD pathogens, and sample types and emphasize the need for continued AMR surveillance.