The natural aquatic environment plays an important role in the emergence and spread of antibiotic resistance. Recent work has highlighted that water environments receive inputs of antibiotic compounds from wastewater treatment plants (WWTPs), livestock operations, aquaculture, and industry, which may contribute to selection pressure for elevation of resistance levels in native bacteria, and in turn, they could also serve as sinks, reservoirs, and sources of antibiotic resistant bacteria and resistance genes of clinical concern. In this context, this project is undertaken to investigate occurrences, concentrations, and geospatial distribution of antibiotics across surface water environment in Minnesota State (US). Water samples were collected during July-October 2020 at a total of 39 surface water sites from lakes and creeks in or near the Minneapolis/St. Paul (MSP) metropolitan area. They include 30 lakes in (sub)urban areas variably impacted by anthropogenic activities, and one lake with limited impact (acting as a reference to assess the background levels of antibiotics), and 4 creeks (for some, multiple samples were taken along the creek to evaluate small-scale geospatial distributions). Concentrations of 25 antibiotics in different classes (including sulfonamides, macrolides, tetracyclines, fluoroquinolones, beta-lactams, and other unclassified compounds) were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Preliminary results showed that 23 out of the 25 antibiotics were detected in the 39 lake/creek samples, with detection frequencies of the classified antibiotics declining in the order of sulfonamides (95%) &gt; macrolides (79%) &gt; beta-lactams (67%) &gt; tetracyclines (28%) &gt; fluoroquinolones (26%). In general, total antibiotic concentrations were found higher at sites in more urban regions, with several hotspots of certain antibiotics identified in the MSP area. Ongoing work is being undertaken to (1) investigate partitioning of the target antibiotics between the water columns and sediments in the selected lakes, and (2) explore relations of antibiotic concentrations with land use and hydrogeologic condition and identify primary sources of antibiotic input due to human activities. Outcomes of this work will be applied to develop an “antibiotic footprint” map that enables predictions of antibiotic geospatial distribution in a statewide scale and aid in mitigation of antibiotic resistance in the natural water environment.

Determination of antibiotic footprint in surface water environment of a metropolitan area

ACS Spring Meeting 2021

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