Determination of the Antibiotic and Antibiotic Resistance Footprint in Surface Water Environments of a Metropolitan Area: Effects of Anthropogenic Activities

This study investigated geospatial distributions of antibiotics and antibiotic resistance genes (ARGs) in surface waters and their associations with anthropogenic activities. During July-October 2020, the concentrations of antibiotics (water and sediment) and ARGs (sediment) were measured at 39 sites in the Twin-Cities metropolitan area (Minnesota) that experience a gradient of impacts related to human activities. For water samples, the number of antibiotics detected and the concentrations of certain antibiotics (e.g., sulfonamides) positively correlated with urbanization indicators (e.g., urban percentage, population density, number of wastewater discharge points; rho = 0.32-0.46, p = 0.003-0.04) and negatively correlated with undeveloped land indicators (e.g., forest; rho = -0.34 to -0.62, p = <0.00001-0.04). Antibiotics in sediments exhibited geospatial distribution different from that in corresponding water samples and exhibited no associations with anthropogenic factors. Relative abundances of ARGs were not associated with anthropogenic factors, but several ARGs (e.g., bla(oxa), mexB, and sul2) were inversely related to the organic content of sediments (rho = -0.38 to -0.44, p = 0.01-0.04). Strong correlations were found among relative abundances of various ARGs and intI1 (rho >= 0.67, p < 0.05), highlighting their co-occurrence in (sub)urban surface waters. These results identified promising anthropogenic/environmental factors for predicting antibiotic geospatial distributions and useful gene markers to monitor ARGs in surface waters.