Project Number: 6022-63000-006-008-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2017
End Date: Aug 31, 2022
Our primary objective in the proposed study will be to identify, enumerate, and determine movement and fate of Antimicrobial resistant bacteria (AMR) (e.g. Escherichia (E.) coli) through the life cycle of broiler chickens (antibiotic induction—to excreta via poultry litter—through soil—to water runoff) over a 13-yr period based on pasture management [hayed (H), continuously grazed (CG), rotationally grazed (R), rotationally grazed with a buffer strip (RB), and rotationally grazed with a fenced riparian buffer (RBR)]. Secondly, we will assess potential functional shifts in soil microbiological structure and community richness based on AMR bacterial presence and management.
Targeted feed additives (e.g., bacitracin, chlortetracycline, monensin, penicillin, and salinomycin) from stored and frozen (-20°F) manure, soil, and runoff samples (since 2004) will be analyzed using liquid chromatography-mass spectrometry techniques. Using Illumina high-throughput sequencing of 16S Ribosomal RNA (rRNA) genes, soil bacterial community composition will be determined. Antibiotic resistance of Escherichia (E.) coli (via API 20E) isolated from manure, runoff, and soil, as well as uptake potential in plant tissue will be determined using Avian plates and the Sensititer automated system. Soil microbial functional shifts, species richness, and opportunist pathogen presence over time will be assessed and linked to Antimicrobial resistant bacteria (AMR) counts and previously collected runoff data (pH, electrical conductivity, total suspended solids, total organic carbon, and total metals). We hypothesize that conservation pasture management practices (i.e., rotationally grazed (R), rotationally grazed with a buffer strip (RB), and rotationally grazed with a fenced riparian buffer (RBR)) will have a more diverse soil ecology, which will promote xenobiotic degradation and reduce AMR movement in soil and water systems. However, we suspect hayed pasture will have less AMR in runoff, owing to the absence of cattle manure. In addition, we hypothesize lower persistence of antibiotics in soil over time, albeit increased incidence of multiple antibiotic resistance. We also anticipate some antibiotics will have greater movement in both water and soil environments, which will interact with soil microbiological communities.