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United States Department of Agriculture

Agricultural Research Service

Research Project: ENVIRONMENTALLY SOUND MANURE MANAGEMENT FOR REDUCTION OF GAS EMISSIONS, NUTRIENTS, AND PATHOGENS

Location: Agroecosystem Management Research

Title: Assessment of antibiotic resistance in runoff from cattle feedlots

Authors
item Durso, Lisa
item Miller, Daniel

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: September 12, 2012
Publication Date: N/A

Interpretive Summary: Streams and ground water can be contaminated by manure when rain falls on feedlots and pastures, when grazing animals defecate directly in streams, and when manure is land applied. One concern is that antibiotic resistant bacteria in the manure can contaminate surface and ground water, and eventually impact human health via antibiotic resistant pathogens. One of the ways it is thought that this occurs is that the DNA or genes that code for antibiotic resistance can be exchanged between bacteria in the environment, even if the bacteria are not very closely related. For this reason, it is important to examine antibiotic resistance capabilities of all bacteria in a system, not just those that are known human pathogens. We examined the antibiotic resistance patters of bacteria isolated from beef cattle feedlot runoff, applied to vegetative strips of cool-season grasses. Samples included collection of rain water, and runoff from the cattle feedlots. Tetracycline resistant and Cefotaxime resistant bacteria were enumerated, and individual Escherichia coli isolates were screened for resistance to twelve antibiotics. Most of the runoff isolates contained resistance to at least one antibiotic, with some individual isolates demonstrated resistance to multiple antibiotics. These data support the importance of designing irrigation systems for land application of manures that minimize runoff for limiting transport of antibiotic resistance.

Technical Abstract: The use of antibiotics in veterinary medicine, especially at sub-therapeutic doses, is an important issue that has captured national attention, and there is considerable concern about the potential to transmit antibiotic resistance from animals to humans via fecal contamination of surface and ground water. Many of the genetic elements that confer antibiotic resistance have the potential to be transferred between bacteria, and the transfer of antibiotic resistance has been demonstrated to occur between some kinds of unrelated bacteria. For this reason, it is important to examine antibiotic resistance capabilities of all bacteria in a system, not just those that are known human pathogens. We examined the antibiotic resistance patters of bacteria isolated from beef cattle feedlot runoff, applied to vegetative strips of cool-season grasses. Samples included collection of rain water, and runoff from the cattle feedlots. Tetracycline resistant and Cefotaxime resistant bacteria were enumerated, and individual Escherichia coli isolates were screened for resistance to twelve antibiotics. Most of the runoff isolates contained resistance to at least one antibiotic, with some individual isolates demonstrated resistance to multiple antibiotics. These data support the importance of designing irrigation systems for land application of manures that minimize runoff for limiting transport of antibiotic resistance.

Last Modified: 8/22/2014