Wastewater surveillance reveals patterns of antibiotic resistance across the United States

Antibiotic resistance is a growing public health threat, with over 2.8 million antibiotic-resistant infections and 35,000 attributable deaths annually in the U.S. Clinical surveillance can miss asymptomatic carriage of antibiotic resistance. Here, we sought to use wastewater monitoring to assess community-level burden of antibiotic resistance. We quantify concentrations of antibiotic resistance genes (ARGs) by digital droplet PCR in wastewater solids obtained from 163 wastewater treatment plants in 40 states in the United States. We measure 11 ARGs that confer resistance to beta-lactams (blaCMY, blaCTX-M, blaKPC, blaNDM, blaOXA-48, blaTEM, blaVIM, mecA), colistin (mcr-1), tetracycline (tetW), and vancomycin (vanA). The South has higher overall ARG concentrations compared to the Midwest. We pair these data with national data sets including antibiotic use, social vulnerability, size of animal agriculture operations, location of healthcare facilities, and presence of airports to investigate potential drivers of resistance. We also generate predictive maps of ARG concentrations for counties with data within the range of our training set in the United States. We show social vulnerability indicators (housing burden and access to health insurance) and indicators of international travel are associated with increased ARG concentrations in wastewater, while antibiotic usage is only weakly positively associated. Our results provide a national baseline of ARG concentrations and highlight the complexity of factors driving spread of antibiotic resistance.