State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing 100085, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing 100085, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
Environ Pollut. 2018 Jul;238:1017-1026. doi: 10.1016/j.envpol.2018.02.023. Epub 2018 Feb 13.
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) 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 (OTC dose, 1000 mg L), 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 before spiking OTC (OTC concentration in digested sludge, 8.97 mg kg) to 2.83 × 10 (p < 0.05) after spiking OTC at a dose of 40 mg L (OTC concentration in digested sludge, 528.52 mg kg). 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.
我们评估了在含有抗生素生物质的中温厌氧消化（AD）过程中，土霉素（OTC）对性能和抗生素耐药性发展的慢性影响。在 265 天的时间内，通过在 20 天的固体停留时间内不断向含有不断增加浓度的 OTC（0-1000mg/L）的城市剩余污泥中进料，在完全搅拌罐式反应器中进行中温 AD。结果表明，当消化污泥中的 OTC 浓度增加到约 18000mg/kg（OTC 剂量为 1000mg/L）时，中温 AD 的甲烷生成受到抑制，这是由于发酵和产酸细菌受到抑制。宏基因组测序和高通量定量 PCR 分析表明，在抗药性组中，四环素抗性基因是最主要的类型（38.47-43.76%），在整个实验期间，tetG、tetX、tetM、tetR、tetQ、tetO 和 tetL 是主要的抗性亚型。在添加 OTC 之前，这些 tet 基因的相对丰度为 2.10×10（消化污泥中的 OTC 浓度为 8.97mg/kg），在添加 40mg/L OTC 后增加到 2.83×10（p<0.05）（消化污泥中的 OTC 浓度为 528.52mg/kg）。此外，随着 OTC 剂量的增加，移动遗传元件，包括整合子、转座子和质粒，也得到了富集。基于部分典范对应分析，水平（移动元件改变）和垂直（细菌群落转移）基因转移对抗生素抗药性组变化的贡献分别为 29.35%和 21.51%。因此，考虑到水解酸化的抑制和抗生素抗药性组的富集，不建议中温 AD 直接处理含有 OTC 浓度高于 200mg/L 的生物质。
