Prevalence and pattern of antimicrobial susceptibility in Escherichia coli isolated from pigs reared under antimicrobial-free and conventional production methods.

Objective: To determine and compare levels and patterns of antimicrobial resistance among Escherichia coli isolated from pigs on farms that did not use antimicrobial agents versus pigs produced under conventional methods.

Design: Cross-sectional study. Sample Population-35 antimicrobial-free and 60 conventional swine farms.