Quantifying antimicrobial resistance at veal calf farms

Area of Science:

• Veterinary Microbiology
• Food Animal Health
• Antimicrobial Resistance Surveillance

Background:

• Antimicrobial resistance (AMR) in food animals poses a significant public health risk.
• Accurate quantification of AMR prevalence requires optimized sampling strategies.
• Veal calves are a potential reservoir for AMR transmission.

Purpose of the Study:

• To determine an optimal sampling strategy for quantifying AMR prevalence in veal calves.
• To evaluate the variation of AMR within and between calves on farms.
• To compare the efficacy of replica plating versus broth microdilution for AMR detection.

Main Methods:

• Faecal samples collected from 50 healthy veal calves across five farms.
• Escherichia coli isolates tested for resistance to five antimicrobials using replica plating and broth microdilution.
• Logistic regression and bootstrap analysis used to evaluate sampling strategies and test methods.

Main Results:

• Replica plating demonstrated comparable accuracy to broth microdilution for most antimicrobials, except ciprofloxacin.
• Pooled faecal samples generally yielded lower odds of detecting resistant isolates compared to individual samples, though not significantly.
• Bootstrap analysis confirmed consistent prevalence estimates from pooled samples, irrespective of composition.

Conclusions:

• An optimal sampling strategy involves pooled faecal samples from 20 animals, with 90 E. coli isolates tested via replica plating.
• Sampling strategies should account for within- and between-animal variation in AMR, which can differ by antimicrobial.
• This approach enhances precision and practicality for AMR surveillance in veal calf populations.