摘要

       保留在废弃活性污泥 (WAS) 中的克拉霉素不可避免地会进入厌氧消化系统。到目前为止，克拉霉素在连续运行的 WAS 厌氧消化系统中的复杂影响和归宿尚不清楚。本研究设置了两个半连续长期反应器，研究克拉霉素对 WAS 厌氧消化过程中沼气产量和抗生素抗性基因 (ARGs) 的影响，并进行批量试验以探索潜在的代谢机制。实验结果表明，较低浓度的克拉霉素（即 0.1 和 1.0 毫克/升）不影响沼气产量，而当克拉霉素的浓度进一步增加到 10 毫克/升时，沼气产量下降。相应地，长期接触克拉霉素会降低 WAS 厌氧消化中功能性细菌（即厌氧菌科和微滴虫）的相对丰度。 ARGs 的研究表明，属于靶位点修饰的甲基化作用对厌氧微生物在抗生素抗性的表达中起着关键作用，而 ermF 占主导地位的 ARGs 表现出最显着的增殖。相比之下，外排泵的作用减弱，两个检测到的外排基因显着减少。在 WAS 厌氧消化过程中，克拉霉素可部分降解为抗菌活性较低的代谢物，包括夹竹桃霉素和 5-O-desosaminyl-6-O-methylerythronolide 以及其他无抗菌活性的代谢物。

       Clarithromycin retained in waste activated sludge (WAS) inevitably enters the anaerobic digestion system. So far, the complex impacts and fate of clarithromycin in continuous operated WAS anaerobic digestion system are still unclear. In this study, two semi-continuous long-term reactors were set up to investigate the effect of clarithromycin on biogas production and antibiotic resistance genes (ARGs) during WAS anaerobic digestion, and a batch test was carried out to explore the potential metabolic mechanism. Experimental results showed that clarithromycin at lower concentrations (i.e., 0.1 and 1.0 mg/L) did not affect biogas production, whereas the decrease in biogas production was observed when the concentration of clarithromycin was further increased to 10 mg/L. Correspondingly, the relative abundance of functional bacteria in WAS anaerobic digestion (i.e., Anaerolineaceae and Microtrichales) was reduced with long-term clarithromycin exposure. The investigation of ARGs suggested that the effect of methylation belonging to the target site modification played a critical role for the anaerobic microorganisms in the expression of antibiotic resistance, and ermF, played dominated ARGs, presented the most remarkable proliferation. In comparison, the role of efflux pump was weakened with a significant decrease of two detected efflux genes. During WAS anaerobic digestion, clarithromycin could be partially degraded into metabolites with lower antimicrobial activity including oleandomycin and 5-O-desosaminyl-6-O-methylerythronolide and other metabolites without antimicrobial activity.

https://www.sciencedirect.com/science/article/abs/pii/S0013935121000864