The chronic usage of antibiotics over time has led to an increase in antimicrobial resistance, which is classified by the World Health Organization as one of the greatest threats to public health in the 21st century. Antibiotics can enter the environment in a variety of ways, including wastewater discharge and runoff from animal manure that is applied to agricultural fields. In this project, we used a microgeographical analysis to study potential “hotspots” of antibiotics in Minnesota surface waters. The work presented here is part of a broader project that aims to both quantify point sources of antibiotics within Minnesota waterways and analyze antibiotic fate of five antibiotic classes:  sulfonamides, macrolides, tetracyclines, fluoroquinolones, and beta-lactams. Water samples were collected from six different sampling sites within central and southern Minnesota, all impacted by wastewater treatment plant (WWTP) discharge. Water samples collected at each site included an upstream sample, a sample from near the wastewater discharge, and three samples taken at different distances downstream from the WWTP. Samples were filtered and acidified, then split and spiked with isotopically labelled antibiotic surrogates prior to solid phase extraction with Oasis HLB cartridges. Extracts were eluted with methanol and reconstituted in ultrapure water. Antibiotics were quantified using liquid-chromatography mass spectrometry. Additionally, other water chemistry parameters were measured alongside such as dissolved organic carbon , anions, total suspended solids, and pH. Here, we present selected antibiotic concentrations determined during the first sampling season.

Antibiotic concentrations within Minnesota surface waters

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