Tracking antibiotic resistance genes in soil irrigated with dairy wastewater

Dungan, R.S. and McKinney, C.W. and Leytem, A.B. (2018) Tracking antibiotic resistance genes in soil irrigated with dairy wastewater. Science of the Total Environment. 635:1477-1483. 20 April 2018.

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Abstract

In southern Idaho, the application of dairy wastewater to agricultural soils is a widely used practice to irrigate crops and recycle nutrients. In this study, small-scale field plots were irrigated monthly (6 times) with dairy wastewater (100%), wastewater diluted to 50% with irrigation (canal) water, and diluted wastewater spiked with copper sulfate (50 mg Cu/L), while control plots were irrigated with canal water. In addition, half of all plots were either planted with wheat or were left as bare soil. Biweekly soil samples were collected during this period and processed to determine the occurrence and abundance of antibiotic resistance genes [blaCTX-M-1, erm(B), sul1, tet(B), tet(M), and tet(X)] and a class 1 integron-integrase gene (intI1) via quantitative real-time PCR (qPCR). Only sul1 and tet(X) were detected in soil (3 out of 32 samples) before the wastewater treatments were applied. However, the occurrence and relative abundance (normalized to 16S rRNA gene copies) of most genes [erm(B), intI1, sul1, and tet(M)] increased dramatically after wastewater irrigation and levels were maintained during the entire study period. blaCTX-M-1 was the only gene not detected in wastewater-treated soils, which is likely related to its absence in the dairy wastewater. Relative gene levels in soil were found to be statistically similar among the treatments in most cases, regardless of percentage of wastewater applied, presence or absence of plants, and level of copper in the wastewater. The key result from this study is that dairy wastewater irrigation significantly enlarges the reservoir of ARGs and intI1 in soils, while detection of these genes rarely occurred in soil irrigated only with canal water.

Item Type:	Article
NWISRL Publication Number:	1617
Subjects:	Irrigation > Furrow irrigation > Drainage water (see Percolation water) Manure Water
Depositing User:	Users 6 not found.
Date Deposited:	25 Apr 2018 18:52
Last Modified:	25 Apr 2018 18:52
Item ID:	1662
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/1662