Metagenomic Analysis of Urban Wastewater Treatment Plant Effluents in Tokyo.

PURPOSE

Urban wastewater treatment plant (WWTP) effluents, even with proper treatment, may cause antimicrobial resistance (AMR) burden, with a high frequency of acquired antimicrobial resistance genes (ARGs). The dissemination of ARGs into the environment increases the risk of infectious diseases; however, there is little direct evidence regarding their epidemiological effects. This study aimed to assess effluents from urban WWTPs around the Tama River and Tokyo Bay using metagenomic analysis of (AMR) genes (ARGs) and heavy-metal resistance genes.

METHODS

Metagenomic DNA-seq analysis of water samples and resistome analysis were performed.

RESULTS

The most prevalent ARG was the sulfonamide resistance gene, , followed by the quaternary ammonium compound resistance gene, , suggesting that basic gene sets ( and ∆) in the class 1 integrons are the predominant ARGs. The aminoglycoside resistance genes, and , and macrolide resistance genes, (E) and (E), were the predominant ARGs against each antimicrobial. and were frequently detected, whereas the cluster was faintly detected. Non-metric multidimensional scaling plot analysis and canonical correspondence analysis results suggested that marked differences in ARGs could be involved in the seasonal differences; , and (C) increased markedly in summer, whereas (E) was more frequently detected in winter. Heavy-metal (Hg and Cu) resistance genes (HMRGs) were significantly detected in effluents from all WWTPs.

CONCLUSION

We characterized a baseline level of the environmental ARG/HMRG profile in the overall community, suggesting that environmental AMR surveillance, particularly in urban WWTPs, is a valuable first step in monitoring the AMR dissemination of bacteria from predominantly healthy individuals carrying notable ARG/Bs.