Table 1_Evaluating the effects of hospital wastewater treatment on bacterial composition and antimicrobial resistome.docx

Hospital wastewater treatment systems (HWTS) are crucial in reducing the spread of antimicrobial resistance genes (ARGs) and antibiotic-resistant bacterial pathogens in hospital wastewater. This study aims to evaluate the impact of HWTS on the changes of bacterial composition and the relative abundance of ARGs. We collected wastewater samples from influent and effluent in a university hospital, and performed metagenomic sequencing. The results showed that HWTS altered the bacterial composition, with a decrease in the proportion of Gammaproteobacteria. However, phylogenetic analysis of metagenome-assembled genomes showed that Mycobacterium and Zoogloea from influent and effluent had a close relationship. A total of 140 non-redundant ARGs were identified based on open reading fragments analysis, with beta-lactam and aminoglycoside resistance genes being the most prevalent. The relative abundance of ARGs generally decreased after wastewater treatment (p < 0.0001), with 70.0% of genes that conferring resistance to “last-resort” antibiotics being undetectable in the effluent. However, the relative abundance of quaternary ammonium compounds resistance genes increased in the effluent. We identified that 66.4% of ARGs were located on plasmids, and 17.9% of ARGs were adjacent to mobile gene elements (MGEs), suggesting their potential for mobility. Subsequent analysis showed that ARGs originating from plasmids and adjacent to MGEs were negatively associated with their relative abundance reduction. In conclusion, this study provides a comprehensive evaluation of the impact of HWTS on composition of bacteria and the relative abundance of ARGs, highlighting the importance of effective wastewater treatment in combating the spread of antimicrobial resistance.

医院废水处理系统（Hospital Wastewater Treatment Systems，HWTS）是遏制医院废水中抗菌耐药基因（Antimicrobial Resistance Genes，ARGs）与抗生素耐药细菌病原体传播的关键设施。本研究旨在评估HWTS对细菌群落组成变化以及ARGs相对丰度的影响。我们从某大学医院的废水进水口与出水口采集样本，并开展宏基因组测序。结果显示，HWTS改变了细菌群落组成，γ-变形菌纲（Gammaproteobacteria）的占比有所下降。然而，对宏基因组组装基因组的系统发育分析表明，取自进水与出水的分枝杆菌属（Mycobacterium）和动胶菌属（Zoogloea）亲缘关系较近。基于开放阅读片段（Open Reading Fragments）分析，本研究共鉴定出140个非冗余ARGs，其中β-内酰胺类与氨基糖苷类耐药基因最为普遍。经废水处理后，ARGs的相对丰度整体呈下降趋势（p < 0.0001），70.0%的“最后一线”抗生素耐药基因在出水中未被检出。不过，季铵盐类化合物耐药基因的相对丰度在出水中有所上升。本研究发现，66.4%的ARGs位于质粒（Plasmid）上，17.9%的ARGs与移动基因元件（Mobile Gene Elements，MGEs）相邻，提示其存在潜在的移动性。后续分析表明，源自质粒且与移动基因元件相邻的ARGs，其相对丰度的下降程度呈负相关。综上，本研究全面评估了HWTS对细菌群落组成与ARGs相对丰度的影响，凸显了高效废水处理在对抗抗菌耐药性传播中的重要意义。