Antibiotic resistance has become an environmental and public health issue of increasing concern. Natural aquatic environments play an important role in the emergence and spread of antibiotic resistance by receiving inputs of antibiotic compounds from wastewater treatment plants (WWTPs), livestock operations, aquaculture, and industry, and serving as sources and reservoirs of antibiotic resistant bacteria and resistance genes (ARB/ARGs). This project was undertaken to investigate occurrences, concentrations, and geospatial distributions of antibiotics and antibiotic resistance genes across surface waters in Minnesota, US. In 2020-2021, water and/or sediment samples were collected from ~90 sites, including lakes and creeks/rivers in urban, agriculture, and rural areas with variable impacts of human activities. Influent and effluent samples were also collected monthly from major WWTPs in the Twin Cities metropolitan area. Samples were processed with solid-phase extraction and analyzed using LC-MS/MS to quantify concentrations of 25 antibiotics (sulfonamides, macrolides, tetracyclines, fluoroquinolones, beta-lactams, and other uncategorized compounds). Lake/creek sediments samples were analyzed with qPCR to measure levels of selected ARGs and integrons associated with horizontal gene transfer. Total concentrations (from &lt; 5ng/L to 264 ng/L) and numbers (4-17 out of 25) of antibiotics detected in lake waters seemed to be positively related with the level of urbanization, and in general the total concentrations were dominated by sulfonamides, macrolides, or unclassified compounds (primarily trimethoprim). Antibiotics were detected in lake sediments with much lower concentrations and frequencies than that in water columns, exhibiting a considerably different spatial pattern, which was likely due to short hydraulic residence times of these (sub)urban lakes and absence of direct wastewater inputs. WWTPs effectively removed most antibiotics, while certain antibiotics remained in the final effluents with concentrations ranging from &lt;10 ng/L to µg/L-level. Ongoing work is focusing on applying statistical tools to evaluate the association of antibiotic occurrences and concentrations in surface water bodies with various anthropogenic factors (e.g., land use percentage, population, livestock density, and domestic and industrial wastewater discharge).

Determination of the antibiotic and antibiotic resistance footprint in surface waters: Effects of anthropogenic activities

ACS Spring 2022

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