Effect of wastewater treatment plant effluent on fates of antibiotic resistance genes in receiving rivers: a large-scale and metagenomics analysis

Abstract

Wastewater treatment plants (WWTPs) are major sources of antibiotic resistance genes (ARGs) in the aquatic environment, but their global-scale effects remain under-evaluated. In this study, a total of 391 metagenomic samples were collected from 35 WWTP effluent-receiving rivers across three continents: Asia, North America, and Europe. The effects of effluent discharge on the fates of ARGs were compared, and the driving factors were determined. Globally, the discharge of WWTP effluent increased the number of ARG subtypes downstream. However, at the regional level, WWTPs only increased the abundance of ARGs and risk index of downstream sites in North America, while reducing them in Europe and having no significant effect in Asia. Procrustes analysis and Mantel test indicated that the variation in microbial communities and MGEs significantly affected the constitutions of ARGs. Network analysis revealed important ARG hosts such as Catenibacterium, Monoglobus, and Prodigiosinella. Further co-localization analysis of ARGs and MGEs highlighted that class 1 integrons served as the primary MGEs promoting the dissemination of ARGs. Linear regression analysis indicated that NH₄⁺, PO₄³⁻, NO₃⁻, pH, and ORP were the important environmental factors influencing ARG profiles. Based on a partial least squares path model, we identified a driving pattern of water properties-microbiomes-MGEs-ARGs, with MGEs acting as the most critical driver. Overall, our results highlighted that the effect of WWTP effluent should be viewed dialectically, and precise source tracking should be incorporated into future governance strategies of antibiotic resistance.

Graphical abstract

Keywords

Antibiotic resistance genes (ARGs) / Wastewater treatment plant / Effluent-receiving river / Metagenomics / Driving mechanism

Highlight

	● WWTP effluent globally enhances the diversity of ARGs in the receiving rivers.
	● An increase in environmental ARG loads induced by effluent is only observed in NA.
	● Bacillota, Bacteroidota, and Pseudomonadota are the major ARG hosts.
	● Class 1 integrons are the vital MGEs transmitting ARGs.
	● Water properties influence ARGs via microbiomes and MGEs in a cascade.

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