Co-occurrence of antimicrobials and metals as potential drivers of antimicrobial resistance in swine farms

The application of animal manures to cropland is an important nutrient recycling strategy in many parts the world. Commonly, aggregated manure wastes contain chemical stressors including veterinary antimicrobials, heavy metals, and antimicrobial resistance genes (ARGs) that can stimulate development proliferation (AMR). While presence antimicrobials well-documented, co-occurrence other potentially impactful swine remains underreported. This study quantifies analyzes correlations between certain ARGs present samples from farms Iowa, United States. Relationships different stages production or feed composition are also investigated. Results revealed substantial levels tetracyclines [up 1,260 µg g −1 dry weight (d.w.) for oxytetracycline] detected all samples. Tiamulin, two ionophores (monensin lasalocid), one macrolide (tilmicosin) were at maximum class concentrations 9.4, 0.547, 0.472 d.w., respectively. median relative abundances ermB tetM 0.13 0.17 copies wet (w.w.) (normalized 16S gene), Additionally, high copper (Cu), iron (Fe), zinc (Zn) samples, with 887, 1,900, 2,100 Notably, uranium (U) was 11 up 0.77 . A global analysis AMR-stressor relationships using Spearman’s rank correlation indicates Cu, Ba most positively significantly correlated cytotoxic anhydrotetracycline (ATC) and/or anhydrochlortetracycline (ACTC) tested facilities (Cu-ATC: ρ = 0.67, p 0.0093; Cu-ACTC: 0.75, 0.0022; Ba-ATC: 0.84, 0.0002). Interestingly, strongly, each ( 0.92, < 0.0001), suggesting possible co-selection, despite absence tetracycline concentrations. demonstrates complexity interactions multiple storage pits prior application.