Agricultural pollution associated with antibiotic resistance in bacteria

Pharmaceuticals and other emerging contaminants in the environment are a growing cause for concern. One particular issue is the increase in antibiotic-resistant bacteria.  Agriculture is often noted as a source of excessive antibiotic use.  Over 70% of all antibiotics produced in the U.S. are used in animal agriculture. Overuse can encourage the selection of antibiotic-resistant genes (ARG).

To better understand the relationship between agricultural contamination and ARG abundance over a year-long period, ISTC researchers Wei Zheng and Laurel Dodgen contributed to a project led by Marquette University Professor Krassimira R. Hristova. The study was designed to characterize the emerging chemical contaminants and ARG profiles of 20 surface water locations in an area of Kewaunee County, WI which has an abundance of large-scale farms and where cattle outnumber humans 5 to 1. The team focused primarily on pharmaceuticals and personal care products (PPCPs) and hormones. ISTC’s role was to analyze the PPCPs and hormones in the collected river water and sediment samples to help establish the relationship with ARG.

The results of the study were published in FEMS Microbiology Ecology in 2018. They suggest that Kewaunee County river sediments accumulate contaminants from non-point sources at a higher rate when manure is applied to farmland than when it is not. If these contaminants contain antibiotics, they can either directly increase or co-select for the increase of ARGs in the environment. The study provides a better understanding of how confined animal feeding operations and manure- fertilized farmland impact environmental and human health.

Zheng continues to collaborate with Marquette researchers to determine the chlortetracycline residues in river sediments and water samples and investigate its environmental fate and potential effects. The goal is to evaluate the relationship between the development of chlortetracycline-derived ARG and contaminant residues in the environment.