摘要
      厌氧消化是处理和回收畜禽粪便的常用方法，厌氧消化物的农业应用是将抗生素抗性基因（ARGs）从畜禽粪便传播到土壤的重要途径。恩诺沙星是一种临床上重要的氟喹诺酮类抗生素，在畜禽粪便中残留浓度高，氟喹诺酮耐药基因的传播对公众健康构成巨大风险。与其他抗生素相比，恩诺沙星在厌氧消化系统中相对耐用。然而，它对厌氧消化过程中ARGs持续存在的影响及其机制尚不清楚。在本研究中，我们研究了0、4和8mg/L恩诺沙星对牛粪消化过程中五种质粒介导的氟喹诺酮ARGs和五种临床上重要的非氟喹诺酮类ARGs的丰度、持久性和转移风险的影响。评估整合子和微生物群落对恩诺沙星的反应，以揭示潜在的机制。所有10种检测到的ARGs在厌氧消化中都具有高度持久性，其中7种ARGs消化后增加了8.2倍以上。网络分析表明，ARGs的潜在宿主是厌氧消化过程中的关键功能类群，这可以解释ARGs具有高持久性。残留的恩诺沙星在整个消化过程中显著增加了aac（6′）-ib-cr、sul1、intI1和intI2的丰度，但对其他ARGs没有影响，表明其在促进质粒介导的aac（6′）-ib-cr的水平基因转移中的作用。恩诺沙星对微生物群落的影响在消化结束时消失，但恩诺沙星处理和对照之间的ARG谱仍然不同，这表明恩诺沙星诱导的ARG具有很高的持久性。我们的研究结果表明，ARGs在厌氧消化系统中具有很高的持久性，并强调了畜禽粪便中残留的恩诺沙星在增加氟喹诺酮抗性基因传播风险中的作用。
Abstract
Anaerobic digestion is a common approach to dispose and recycle livestock manures, and the agricultural application of anaerobic digestives represents an important pathway of spreading antibiotic resistance genes (ARGs) from livestock manures to soils. Enrofloxacin is a clinically important fluoroquinolone antibiotic with high residual concentrations in livestock manure, and propagation of fluoroquinolone resistance genes poses a huge risk to public health. Compared with other antibiotics, enrofloxacin is relatively durable in anaerobic digestion system. However, its effect on the persistence of ARGs during anaerobic digestion and its mechanism are not clear. In this study, we investigated effects of 0, 4, and 8 mg/L enrofloxacin on the abundance, persistence, and transferring risk of five plasmid-mediated fluroquinolone ARGs and five typic clinically important non-fluoroquinolone ARGs during cattle manure digestion. The responses of integrons and microbial communities to enrofloxacin were assessed to uncover the underlying mechanisms. All the ten detected ARGs were highly persistent in anaerobic digestion, among them seven ARGs increased over 8.2 times after digestion. Network analysis revealed that the potential hosts of ARGs were critical functional taxa during anaerobic digestion, which can explain the high persistence of ARGs. Residual enrofloxacin significantly increased the abundance of aac(6′)-ib-cr, sul1, intI1, and intI2 throughout the digestion, but had no impact on the other ARGs, demonstrating its role in facilitating horizontal gene transfer of the plasmid-mediated aac(6′)-ib-cr. The influence of enrofloxacin on microbial communities disappeared at the end of digestion, but the ARG profiles remained distinctive between the enrofloxacin treatments and the control, suggesting the high persistence of enrofloxacin induced ARGs. Our results suggested the high persistence of ARGs in anaerobic digestion system, and highlighted the role of residual enrofloxacin in livestock manure in increasing dissemination risk of fluroquinolone resistance genes.

https://www.sciencedirect.com/science/article/abs/pii/S0301479722024379