Environmental monitoring for antimicrobial resistance in a metropolitan watershed

Abstract

Monitoring antimicrobial resistance (AR) in surface water has been proposed to identify sources, drivers, and transmission of AR in the environment and signal emerging AR threats. We conducted a year-long surface water AR assessment to inform the design of environmental AR monitoring approaches for an urbanized watershed in Atlanta, Georgia, USA. Escherichia coli with extended-spectrum β-lactamase (ESBL-Ec) production, colistin resistance (CST-Ec), or meropenem nonsusceptibility (MEM-Ec) were quantified by culture from 11 sites (6 river mainstem, 5 tributary) and characterized by whole-genome sequencing. ESBL-Ec was detected across all sites in 77% (109/142) of samples tested, while CST-Ec was detected in 35% (48/138) of samples, primarily from two sites near combined sewer overflows and a large hospital. We detected MEM-Ec at 5 sites (5/85 samples; 6%), including an ST167 E. coli isolate carrying the blaNDM-5 gene in January 2019; statewide, Georgia reported only 10 clinical, blaNDM-harboring E. coli isolates in 2019. Spatial stream network models showed strong clustering of resistant E. coli in time, but not space, and weak associations with environmental factors like land cover and wastewater infrastructure. This suggests that public health data can be gleaned from monitoring AR in this watershed at sentinel sites representing the major population center.