Landscape of genes in hospital wastewater breaking through the defense line of last-resort antibiotics

Lin Zhu; Xin-Yi Shuai; Ze-Jun Lin; Yu-Jie Sun; Zhen-Chao Zhou; Ling-Xuan Meng; Yong-Guan Zhu; Hong Chen

doi:10.1016/j.watres.2021.117907

Landscape of genes in hospital wastewater breaking through the defense line of last-resort antibiotics

Water Res. 2022 Feb 1:209:117907. doi: 10.1016/j.watres.2021.117907. Epub 2021 Nov 28.

Authors

Lin Zhu¹, Xin-Yi Shuai¹, Ze-Jun Lin¹, Yu-Jie Sun¹, Zhen-Chao Zhou¹, Ling-Xuan Meng¹, Yong-Guan Zhu², Hong Chen³

Affiliations

¹ Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, PR. China.
² Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, PR. China; State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR. China.
³ Department of Environmental Engineering, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, PR. China. Electronic address: chen_hong@zju.edu.cn.

PMID: 34864622
DOI: 10.1016/j.watres.2021.117907

Abstract

Hospital wastewater contains abundant antibiotics, antibiotic resistance genes (ARGs), and pathogens. Last-resort antibiotic resistance genes (LARGs) include the New Delhi metallo-β-lactamase gene bla_NDM, mobile colistin resistance gene mcr and tigecycline resistance gene tet(X) which confers resistance to carbapenems, colistin and tigecycline. The presence and significance of LARGs in hospital wastewater treatment systems (HWTS) have not yet been systematically explored. Here, LARG variants were shown to be prevalent both influents and effluents of HWTS. A total of 989 Enterobacteriaceae isolates that confer resistance to last-resort antibiotics were collected from effluents and multiple genetic contexts of LARGs were analyzed. LARGs-carrying plasmids were confirmed to show high multidrug phenotypes and transferability. We also discovered the co-occurrence of plasmids harboring bla_NDM-1 and mcr-1 in single Escherichia coli, as well as E. coli HM016 containing two unique mcr-1-carrying plasmids. This result might accelerate co-dissemination of LARGs under environmental selection pressure. Different core genetic arrangements in these strains suggest several evolutionary pathways in HWTS. The resistance functions of LARGs were confirmed in vitro and in vivo by mass spectrometry. This study provides novel insights into the diversity, genetic context and function of critical ARGs in HWTS. The results raise the concern that LARGs may further spread into the environment, thus, more stringent discharge standards and regulations for hospital wastewater are urgently needed.

Keywords: Antibiotic resistance genes; Genetic context; Hospital wastewater treatment systems; Mass spectrometry.