Effects of Field Application of Sewage Sludge Aerobic Fermentation Products on Antibiotic Resistance Gene Prevalence in Pakchoi (Brassica chinensis L.)

• • Sludge fermentation product application increased total ARG abundance by 25.47% in rhizosphere soil and 73.08% in phyllosphere of pakchoi compared to unfertilized control, indicating significant resistance enrichment in edible plant parts. • • Soil antibiotic content rose by 12.70% in sludge-treated plots versus only ~3% with chemical fertilizer, demonstrating that sludge-derived exogenous antibiotics are a dominant contributor to resistance selection pressure. • • Chemical fertilizer application reduced ARG abundance by 53.40% in rhizosphere soil and 13.50% in phyllosphere, likely due to decreased microbial community abundance and diversity, which weakens ARG hosts and dissemination vectors. • • Specific microbial taxa, Sphaerobacter thermophilus and Aggregatilinea lenta, showed strong positive correlations (r≈0.95–1.00) with multiple ARGs, while Solirubrobacter sp. CPCC_204708 exhibited negative correlation (r≈−0.91), identifying potential microbial indicators for ARG monitoring.