摘要
      基于发酵的抗生素生产产生了丰富的营养丰富的发酵残留物，具有很高的回收潜力，但高抗生素残留浓度限制了其用途（例如，在土地上用作有机肥料）。在本研究中，对用于处理红霉素发酵残留物（EFR）的工业规模水热设施进行了研究，并评估了处理后的EFR在土壤中长期施用促进环境抗生素耐药性发展的潜在风险。该处理有效地去除了细菌及其DNA，红霉素的去除率高达约98%。2018年至2020年，处理后的EFR被用作有机肥料，用于连续的田间施用，剂量范围为3750至15000 kg∙hm−2，导致土壤中红霉素的亚抑制水平（范围为0.83至76.00μg∙kg−1）。然后使用宏基因组鸟枪测序来表征土壤的抗生素抗性基因（ARGs）、移动遗传元件（MGEs）和细菌群落组成。土壤ARG丰度和多样性在施用EFR的第一年没有反应，但在施用的第二年和第三年逐渐发生变化。与对照组（CK；未施用）相比，大环内酯-林可酰胺-链脲菌素（MLS）和总ARGs的相对丰度的最高倍数变化分别为12.59倍和2.75倍。相关性分析和结构方程模型（SEM）显示，土壤MGE和分类组成显示出与ARG相似的时间趋势，并似乎有助于推动ARG增殖的增加。在应用EFR治疗的第三年，特定erm抗性基因（RNA甲基转移酶基因）的相对丰度显著增加。erm与MGEs的密切关联表明，水平基因转移在观察到的erm基因富集中起着关键作用。宏基因组装箱结果表明，携带mac基因的宿主的增殖是mac基因（外排泵基因）丰度增加的原因。这项研究表明，红霉素在土壤中的亚抑制水平随着时间的推移对土壤ARGs有累积影响，并强调了长期监测对评估经处理的工业废物改良土壤的风险的重要性。
Abstract
Fermentation-based antibiotic production results in abundant nutrient-rich fermentation residue with high potential for recycling, but the high antibiotic residual concentration restricts its usefulness (e.g., in land application as organic fertilizer). In this study, an industrial-scale hydrothermal facility for the treatment of erythromycin fermentation residue (EFR) was investigated, and the potential risk of the long-term soil application of treated EFR promoting environmental antibiotic resistance development was evaluated. The treatment effectively removed bacteria and their DNA, and an erythromycin removal ratio of up to approximately 98% was achieved. The treated EFR was utilized as organic fertilizer for consecutive field applications from 2018 to 2020, with dosages ranging from 3750 to 15 000 kg∙hm−2, resulting in sub-inhibitory levels of erythromycin (ranging from 0.83–76.00 μg∙kg−1) in soils. Metagenomic shotgun sequencing was then used to characterize the antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and bacterial community composition of the soils. The soil ARG abundance and diversity did not respond to the treated EFR application in the first year, but gradually changed in the second and third year of application. The highest fold change in relative abundance of macrolide–lincosamide–streptogramin (MLS) and total ARGs were 12.59 and 2.75 times, compared with the control (CK; without application), respectively. The soil MGEs and taxonomic composition showed similar temporal trends to those of the ARGs, and appeared to assist in driving increasing ARG proliferation, as revealed by correlation analysis and structural equation models (SEMs). The relative abundance of particular erm resistance genes (RNA methyltransferase genes) increased significantly in the third year of treated EFR application. The close association of erm with MGEs suggested that horizontal gene transfer played a critical role in the observed erm gene enrichment. Metagenomic binning results demonstrated that the proliferation of mac gene-carrying hosts was responsible for the increased abundance of mac genes (efflux pump genes). This study shows that sub-inhibitory levels of erythromycin in soils had a cumulative effect on soil ARGs over time and emphasizes the importance of long-term monitoring for assessing the risk of soil amendment with treated industrial waste.

https://www.sciencedirect.com/science/article/pii/S2095809922004271