Shed Antimicrobial Exposures within High Plains Livestock Operations

Antibiotics have been in use within human medicine across the U.S. for over 70 years and have saved millions of lives. And, not surprisingly, antibiotic use within production agriculture settings has closely paralleled use within human medicine. Such use, particularly in hospitals and food animal production facilities, results in intense pressure upon targeted bacteria, some of which survive and embark upon a journey of resistance development.

The overall objective of this R21 project was to identify and quantify longitudinal antimicrobial resistance in livestock production where workers handle, manage and apply liquid manure slurry, given their persistent and pervasive use within livestock operations, whereupon specific management and policy recommendations for agricultural enterprises will be developed.  Specifically, this project sought to collect samples of fecal pats (fresh manure), stored dairy and swine manure slurry and soil cores from fecal-amended crop fields.

Data showed that the soil microbiome is quite rich in microbial density and species diversity with as many as ~60% of taxa not yet fully classified at the genus level. As expected, the manure harbored significant abundance of species reflecting the microbiome environment of the bovine gut. There was a change in microbiome composition from fresh manure to the manures stored in on-farm holding structures.

There was a high rate of tetracycline resistant genes present in both manure and soil samples although the latter group had comparatively lower rates. Based on DNA sequencing, these tet genes were found to be identical to those present in common human pathogens. And, the concentration of major chemical elements varied considerably in soil samples.

Funding: National Institute of Occupational Safety & Health (NIOSH) R21
Funding Period: 2013-2016