Genomic Epidemiology of Third-generation Cephalosporin-resistant from Argentinian Pig and Dairy Farms Reveals Animal-specific Patterns of Co-resistance and Resistance Mechanisms

Importance: Little is known about the ecology of critically important antibiotic resistance among bacteria with the potential to be opportunistic human pathogens (e.g., ) on South American farms. By studying 70 pig and dairy cattle farms in central-eastern Argentina, we identified that third-generation cephalosporin resistance (3GC-R) in was mediated by mechanisms seen more often in certain species and that 3GC-R pig were more likely to be co-resistant to florfenicol and amoxicillin/clavulanate. This suggests that on-farm antibiotic usage is key to selecting the types of present on these farms. 3GC-R and 3GC-R plasmids were diverse, suggestive of long-term circulation in this region. We identified the mobilization of the resistance gene from pig pathogens into on a novel mobile genetic element, which shows the importance of surveying poorly studied regions for antibiotic resistance that might impact human health.