We evaluated the chronic impact of oxytetracycline (OTC) on performance and antibiotic resistance development during the mesophilic anaerobic digestion (AD) of antibiotic-containing biomass. Mesophilic AD was conducted in a completely stirred tank reactor by constantly feeding municipal excess sludge spiked with increasing concentrations of OTC (0–1000 mg L⁻¹) under a solid retention time of 20 days over a period of 265 days. Results showed that methane generation of mesophilic AD was inhibited when the OTC concentration in digested sludge was increased to around 18,000 mg kg⁻¹ (OTC dose, 1000 mg L⁻¹), due to the inhibition of fermenting and acidogenic bacteria. Metagenomic sequencing and high-throughput quantitative PCR analysis demonstrated that tetracycline resistance genes were the most dominant type (38.47–43.76%) in the resistome, with tetG, tetX, tetM, tetR, tetQ, tetO, and tetL as the dominant resistant subtypes throughout the whole experimental period. The relative abundance of these tet genes increased from 2.10 × 10⁻¹ before spiking OTC (OTC concentration in digested sludge, 8.97 mg kg⁻¹) to 2.83 × 10⁻¹ (p < 0.05) after spiking OTC at a dose of 40 mg L⁻¹ (OTC concentration in digested sludge, 528.52 mg kg⁻¹). Furthermore, mobile genetic elements, including integrons, transposons, and plasmids, were also enriched with the increase in OTC dose. Based on partial canonical correspondence analysis, the contributions of horizontal (mobile element alteration) and vertical (bacterial community shift) gene transfer to antibiotic resistome variation were 29.35% and 21.51%, respectively. Thus, considering the inhibition of hydrolytic acidification and enrichment of antibiotic resistome, mesophilic AD is not suggested to directly treat the biomass containing OTC concentration higher than 200 mg L⁻¹.

我们评估了土霉素对含有抗生素的生物质进行中温厌氧消化（AD）期间对性能和抗生素耐药性发展的长期影响。在完全搅拌的釜式反应器中，通过在265天的时间内将固体过量的OTC（0-1000 mg L ^-1）浓度不断增加的市政污泥不断进料，进行了中温AD处理。结果表明，当消化的污泥中的OTC浓度增加到大约18,000 mg kg ^-1（OTC剂量，1000 mg L ^-1时），抑制了嗜温性AD的甲烷生成。），由于抑制了发酵菌和产酸菌。宏基因组测序和高通量表明，四环素抗性基因在resistome的最主要类型（38.47-43.76％），用定量PCR分析tetG，tetX，tetM，tetR的，tetQ，tetO启动，并tetL的作为主导耐亚型整个整个实验阶段。这些tet基因的相对丰度从加标OTC（消化污泥中的OTC浓度，8.97 mg kg ^-1）之前的2.10×10 ^-1增加到2.83×10 ^-1（p 在以40 mg L ^-1的剂量加标OTC后（<0.05）（消化污泥中的OTC浓度为528.52 mg kg ^-1）。此外，随着OTC剂量的增加，包括整合素，转座子和质粒在内的可移动遗传元件也变得更加丰富。基于部分典型对应分析，水平（移动元素改变）和垂直（细菌群落转移）基因转移对抗生素抵抗组变异的贡献分别为29.35％和21.51％。因此，考虑到水解酸化的抑制和抗生素抗药性的富集，不建议使用嗜温性AD直接处理含有高于200 mg L ^-1的OTC浓度的生物质。