摘要

由于废水中大量的抗生素抗性细菌（ARB）和抗生素抗性基因（ARG），废水回用的不断增长的实践对进一步传播抗生素抗性构成了重大风险。厌氧膜生物反应器（AnMBR）是一种新兴的废水处理技术，与传统的好氧处理工艺相比，能够减少排放到接收环境中的总ARG和ARB负荷。尽管大小排阻可以有效保留ARB及其相关的细胞内ARG，但尚未检查AnMBR流出物中细胞外ARG的丰度和结局。这项研究阐明了抗生素负荷（氨苄青霉素，红霉素和磺胺甲恶唑）在五周时间内对AnMBR废水中细胞内和细胞外ARG的丰度的影响。靶向基因的定量显示，响应添加抗生素，细胞内ARG（iARGs）整体富集，而细胞外（exARGs）耗竭，这表明exARG吸收是AnMBR废水中水平基因转移的重要方式。 iARG和exARG丰度图的比较显示，与大质粒相比，小质粒上的exARG摄取存在潜在偏差。

重要性通过ARG的水平基因转移（HGT）促进了抗生素耐药性的传播。目前，共轭被认为是废水处理过程中的主要机制。但是，最近的研究发现大量的exARGs，这表明转化可能在传播中发挥更大的作用。尽管先前的研究对废水处理设施中的iARG和exARG进行了量化，但他们并未评估两种形式之间的时间变化。此外，在厌氧工艺中，iARG和exARG之间几乎没有任何研究可区分，而厌氧工艺被认为可替代好氧活性污泥工艺。这项研究专门调查AnMBR中针对抗生素压力的靶向iARG和exARG的数量，以量化细胞内和细胞外区室之间ARG的潜在交换。我们的发现表明，与大质粒相比，位于小质粒上的exARGs优先被细胞在抗生素压力下摄取，这意味着质粒群落之间存在异质HGT机制。

The growing practice of wastewater reuse poses a significant risk to further dissemination of antibiotic resistance due to the abundance of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) in wastewater effluents. Anaerobic membrane bioreactors (AnMBRs) are an emerging wastewater treatment technology capable of reducing the total ARGs and ARB load discharged to receiving environments compared to conventional aerobic treatment processes. While size exclusion is effective at retaining ARB and its associated intracellular ARGs, the abundance and fate of extracellular ARGs in an AnMBR effluent have not been examined. This study elucidates the effect of combined antibiotics loading (ampicillin, erythromycin, and sulfamethoxazole) on the abundance of intracellular and extracellular ARGs in an AnMBR effluent over a period of five weeks. Quantification of targeted genes revealed an overall enrichment of intracellular ARGs (iARGs) and depletion of extracellular (exARGs) in response to antibiotics addition, which suggests exARG uptake as a significant mode of horizontal gene transfer in AnMBR effluents. Comparison of the iARG and exARG abundance profiles showed a potential bias for exARG uptake located on small plasmids compared to large plasmids.

Importance Antibiotic resistance dissemination is facilitated through horizontal gene transfer (HGT) of ARGs. Currently, conjugation is considered to be the dominant mechanism during wastewater treatment. However, recent studies have detected high abundances of exARGs, implying that transformation may play a greater role in dissemination. While previous studies quantified iARGs and exARGs in wastewater treatment facilities, they did not evaluate temporal changes between the two forms. Further, almost no research has differentiated between iARGs and exARGs in anaerobic processes, which are being considered to replace aerobic activated sludge processes. This study specifically investigates the abundance of targeted iARGs and exARGs in AnMBRs in response to antibiotic pressure to quantify potential exchange of ARGs between intracellular and extracellular compartments. Our findings suggest that exARGs located on small plasmids are preferentially taken up by cells under antibiotic pressure compared to large plasmids, which implies heterogenous HGT mechanisms among the plasmid community.

https://www.biorxiv.org/content/10.1101/702076v1.abstract