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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Environmentally Integrated Dairy Management Research » Research » Publications at this Location » Publication #421739
Research Project: Managing Nutrients and Assessing Pathogen Emission Risks for Sustainable Dairy Production Systems

Location: Environmentally Integrated Dairy Management Research

Title: Quantitative microbial risk assessment for ingestion of antibiotic resistance genes from private wells contaminated by human and livestock fecal sources

Author
item Burch, Tucker

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/11/2024
Publication Date: 12/11/2024
Citation: Burch, T.R. 2024. Quantitative microbial risk assessment for ingestion of antibiotic resistance genes from private wells contaminated by human and livestock fecal sources. Meeting Abstract. December 11, 2024.

Interpretive Summary:

Technical Abstract: Antibiotic resistance (AR) is a public health problem with human, agricultural, and environmental dimensions. Water is recognized as a potential route of AR infection, but risks associated with drinking water are largely unknown. This study used quantitative microbial risk assessment to estimate the risk of ingesting class 1 integron genes (intI1) and five antibiotic resistance genes (ARGs) from private wells contaminated by human and/or livestock fecal sources. ARGs included erm(B), sul1, tet(A), tet(W), and tet(X), and all gene targets were quantified in 138 private well-water samples from a rural county in northeast Wisconsin along with 5 human-specific and 6 bovine-specific microbial source-tracking (MST) markers. Daily probabilities of ingestion varied from 0 to 8.8×10-1 by gene target and fecal source (i.e., human or bovine). Daily probabilities of ingestion for tet(A) were significantly greater for wells with MST markers present compared to wells with no MST markers detected. These included tet(A) associated with bovine MST markers in wells with = 20 feet depth-to-bedrock (4.5×10-1 [95% CI: 2.7 – 6.1×10-1]), tet(A) associated with bovine MST markers in wells with > 20 feet depth-to-bedrock (3.8×10-1 [2.5 – 5.3×10-1]), and tet(A) associated with bovine and human MST markers in wells with = 20 feet depth-to-bedrock (6.6×10-1 [4.3×10-1 – 8.7×10-1]). Of 12,000 private well users in the county, median estimates for the number of residents ingesting target ARGs per day in their drinking water varied from 910 (tet(A)) to 1,500 (intI1 and tet(X)), but only 190 [47 – 360] cases of tet(A) ingestion could be identified as occurring in excess of background exposure levels associated with uncontaminated wells. While ingestion of ARGs is not directly associated with infection, results illustrate the relative contribution of human and livestock fecal sources on ARG exposure via drinking water and highlight rural groundwater as a potential point of exposure.