Combining Surveillance and Treatment of Antimicrobial Resistance Genes in Wastewater and Sludge to Reduce Barriers to Sustainable Development in the Environmental Dimension

Abstract:

Antimicrobial resistance (AMR) surveillance and treatment in wastewater and sludge plays an important role in achieving the United Nations Sustainable Development Goals (SDGs), enabling early detection of emerging threats to directly reduce health risks (SDG 3, SDG6) and indirectly supporting other goals. Combining surveillance and treatment efforts could allow a nearer systems-level AMR risk reduction in the environmental dimension. In this research, we 1) quantified antimicrobial resistance genes (ARG) and microbial populations in a suburban-rural wastewater treatment plant weekly from 2021 – 2023 via qPCR and 16S rRNA sequencing, 2) evaluated configurations and operational conditions impacting ARG removal during anaerobic digestion (AD) of sewage sludge, 3) quantified intracellular, extracellular polymeric substance (EPS)-associated, and cell-free ARG fractions, and 4) performed a meta-analysis of 54 studies to resolve conflicting reports of process conditions’ role in ARG-based risk reduction. Surveillance qPCR results indicate reduced levels of ARG (including sul1, tetA, msrE, etc.) during 2021-early 2022 compared to subsequent years, suggesting significant perturbation of resistance profiles during the pandemic. ARG gene copies were not significantly correlated with SARS-CoV-2, though positive correlations were observed with mobile genetic elements (MGE). 16S rRNA sequencing results revealed potential association of ARGs with Bacteroidota and Firmicutes, among other phyla.

Sewage sludge treatment by AD revealed highest ARG removal was achieved under thermophilic, single-phase operation (75.80% vs. 45.78% in mesophilic), thermophilic–thermophilic two-phase systems (97.61±0.21%), with 45-min ultrasonic pretreatment (68.54±1.58%), and with addition of a storage tank (92.38±0.89%). Results of different ARGs fractions showed that intracellular ARGs decreased by 79.89±1.41% and roughly the same for EPS-associated ARGs, while cell-free ARGs increased. Finally, meta-analysis confirmed that contaminants did not increase ARG abundance (3% removal overall), substrate pre-treatment was more effective than additives (77.4 % vs. 0 %) removal, thermophilic AD was generally more effective than mesophilic and psychrophilic in reducing ARGs (73%) and MGEs (71–81.4%), and continuous feeding outperformed batch systems. Mono-digestion was more effective for ARG reduction (50%) than co-digestion (18%), and livestock waste was least effective for reducing ARGs (12.2%) and MGEs (6.8–9.5%). Digestion times of 31–40 days yielded better ARG reduction (68.6%), and, in continuous/semi-continuous systems, periods > 120 days enhanced removal.

Overall, these results provide a framework for combining surveillance and treatment for reducing AMR threats to the SDGs and could be used to enact real changes in developing solutions.

Biography:

Maggie Williams is an assistant professor in the Department of Civil and Environmental Engineering at Michigan State University. She was previously an assistant professor in the School of Engineering and Technology at Central Michigan University. She earned her Ph.D. in environmental engineering in 2017, her M.S. in environmental engineering in 2013, and her B.S. in civil engineering in 2010 at Michigan State University. Her Ph.D. research earned her the 1^st Place Fitch Beach award for most outstanding research in the College of Engineering.

Williams leads research on quantifying and harnessing the role of microorganisms in global sustainable development to protect human health, clean waste, and produce useful end products. Specifically, the Williams Lab focuses on 1) developing tools and assays relevant to surveillance of microbial functional genes and interactions in soil, water, and waste including antimicrobial resistant bacteria and mobile genetic elements, and viral and bacterial pathogens, 2) treating waste and removing of pathogens and emerging contaminants of concern in anaerobic biotechnologies and developing optimized process and operational conditions, and 3) integrating research, education, and community-engagement by developing experiential service-based learning courses and activities. Her work has led to 42 publications that have been cited over 1300 times. She recently was named to the Engaged Scholars Initiative Cohort with Campus Compact for community engagement.