Individual and Community-Level Drivers of Antimicrobial Resistance in Midwestern Beef and Dairy Cattle Communities

Having risen as a global concern, characterization of antimicrobial resistant (AMR) bacteria within different agricultural landscapes is essential to recognize and mitigate AMR-associated global health risks. Individual animal factors such as lactation stage, parity, and previous antimicrobial use and herd-level factors like size and production type may need to be supplemented with community-level factors such as landscape diversity, density of agricultural animals, soil composition, landscape fragmentation, and connectivity to describe AMR in across agricultural landscapes. Because cephalosporins are used extensively and commensal organisms often harbor resistance in cattle, we investigated herd and community level risk factors of broad-spectrum cephalosporin resistance (BSCR) in cattle across 54 cattle farms in two Ohio counties to explore the role of community-level factors in AMR. From the summer of 2019 through the summer of 2021, interview data, pooled manure samples from cattle, and deer manure samples were collected from farms (n=54) across two counties with different landscape types in Ohio. Proportions of BSCR Enterobacteriaceae were calculated using counts of bacterial colonies grown on non-selective and selective MacConkey agar plates. Herd level predictors included in analysis were outdoor access, other livestock species’ presence on the farm, cattle imports to the farm, and herd size. Community level predictors were calculated using a centroid buffer with a 3-kilometer radius around each farm and included cropland diversity, mean dairy kernel density, mean beef kernel density, distance to nearest hospital, distance to nearest wastewater treatment plant, and proportion of broad spectrum cephalosporin resistance in deer manure collected on the property. Beta regression was used to identify significant predictors across both counties combined and stratified by county. Of all models, those including only herd size outcompeted the others in the combined analysis and in County B. In the best fit model for County C, distance to wastewater treatment was the only significant predictor and showed positive relationship with BSCR. Based on our results, community factors did not consistently predict BSCR. However, wastewater treatment plants and beef kernel density had a near-significant effect on resistance that merits further exploration. Further exploration of community and landscape factors and expanding the One Health framework in AMR research in cattle may provide additional insights.