Background: Antimicrobial resistance (AMR) is a critical global health challenge, exacerbated by agricultural practices. This study investigates the impact of antimicrobial use in agriculture on the development and spread of AMR, comparing intensive and organic farming systems and assessing environmental dissemination through agricultural runoff.

Methods: Samples from farms in five regions were analyzed for antimicrobial residues, resistance genes, and multidrug-resistant bacteria using high-performance liquid chromatography (HPLC), polymerase chain reaction (PCR), and whole-genome sequencing (WGS). Water samples upstream and downstream of farms were tested for bacterial concentrations to evaluate environmental dissemination. Results were compared to findings from related academic studies.

Results: Antimicrobial residues were detected in 65% of samples from intensive farms, with resistance genes (blaCTX-M, tetA) prevalent in 72% of positive samples. Multidrug-resistant E. coli was found in 60% of isolates from intensive systems, compared to 10% from organic systems. Agricultural runoff increased bacterial concentrations in downstream water (3.4 × 10⁵ CFU/mL vs. 8.6 × 10³ CFU/mL upstream). Policy interventions limiting antimicrobial use reduced resistance rates by 40% within five years in regions implementing these measures.