Resistance to antimicrobials used at hatchery level among clinical Escherichia coli isolates from Ontario broilers

Area of Science:

• Veterinary Microbiology
• Antimicrobial Resistance Surveillance
• Poultry Health

Background:

• Chicks are vulnerable to bacterial infections at the hatchery stage, necessitating prophylactic antimicrobial use in some flocks.
• Understanding antimicrobial resistance trends is crucial for effective disease management in broiler production.

Purpose of the Study:

• To evaluate temporal changes in resistance to ceftiofur, gentamicin, and spectinomycin in *Escherichia coli* from Ontario broiler chickens (2008-2015).
• To identify production stage, year, and season as predictors of antimicrobial resistance.
• To correlate resistance patterns with published antimicrobial use data.

Main Methods:

• Analysis of *Escherichia coli* clinical isolates from broiler chickens in Ontario between 2008 and 2015.
• Logistic regression modeling to assess the influence of production stage, year, and season on antimicrobial resistance.
• Comparison of resistance trends with available hatchery-level antimicrobial use data.

Main Results:

• Stage of production, year, and season were significant predictors of resistance to ceftiofur, gentamicin, and spectinomycin.
• Ceftiofur resistance fluctuated, showing a decreasing trend from 2013-2015.
• Gentamicin and spectinomycin resistance increased over the study period, with high resistance clusters observed from 2013-2015, potentially linked to changes in antimicrobial use.

Conclusions:

• Antimicrobial resistance in *Escherichia coli* from Ontario broiler chickens is influenced by production stage, year, and season.
• Increasing resistance to gentamicin and spectinomycin highlights the need for monitoring and potential changes in antimicrobial stewardship.
• Observed resistance trends may correlate with shifts in the use of specific antimicrobials like ceftiofur and spectinomycin in hatcheries.