Land Use and Environmental Variables Influence Tetracycline-Resistant Bacteria Occurrence in Southeastern Coastal Plain Streams

The global presence of antimicrobial resistance (AMR) in aquatic systems has the potential to influence public health by reducing antibiotic efficacy, and the environment by altering the structure and activity of microbial communities. Wastewater treatment plant (WWTP) discharge, agricultural runoff, and variables such as precipitation, warm temperatures, and nutrient availability are thought to increase AMR occurrence in the environment. In this study, we examined relationships between tetracycline-resistant Escherichia coli counts and land use, precipitation, temperature, and nutrient availability within the Ogeechee River basin in Georgia. Due to its widespread use in agriculture and medicine, tetracycline was selected as a pathway for AMR occurrence in the study area. Tetracycline-resistant E. coli levels were compared across WWTP effluent, agricultural runoff, and reference sites over 13 wk. Discharge from WWTPs had tetracycline-resistant E. coli counts 2 to 50 times greater than reference sites. Tetracyclineresistant E. coli counts were positively correlated with temperature and precipitation, indicating that environmental factors and runoff were significant contributors to the presence of AMR in this study. Furthermore, increased precipitation appeared to enhance the spatial scale of AMR in the Ogeechee River system; elevated levels of tetracycline-resistant E. coli occurred at reference sites after a major precipitation event, but not during drier months. Results from this study suggest that considering both environmental conditions and land use could be useful for managing AMR in surface waters.