摘要
      诺氟沙星（NOR）是一种早期的第三代喹诺酮类抗生素，因其杀菌性能而被广泛应用于畜牧业和水产养殖业。NOR作为一种新出现的污染物，可能对鱼类产生毒性作用。本研究基于宏基因组测序评估了0（对照组）、100纳克/升（环境浓度）和1毫克/升NOR对幼年鲤鱼（鲤鱼）肠道微生物群的慢性毒性（6周）。宏基因组分析显示，变形菌门、拟杆菌门、梭杆菌门、厚壁菌门和放线菌门是鲤鱼肠道中的优势细菌。放线菌的相对丰度在对照组中最高。环境浓度NOR的α多样性显著低于对照组。主坐标分析（PCoA）表明，不同类群之间的细菌群落形成了明显的独立集群。NOR暴露会对鲤鱼的免疫功能和肠道微生物群中的一些物质代谢途径产生不利影响。此外，环境浓度的NOR在肠道微生物群中产生抗生素耐药性基因（ARGs），增强对药物的耐药性。总之，NOR的环境浓度可以改变肠道微生物群中ARG的组成、结构和丰度，从而影响鱼类的肠道健康。
Abstract
Norfloxacin (NOR) is an early third-generation quinolone antibiotic that has been widely used in animal husbandry and aquaculture because of its bactericidal properties. As an emerging contaminant, NOR may have toxic effects on fish. This study assessed the chronic toxicity (6 weeks) of 0 (control group), 100 ng/L (environmental concentration), and 1 mg/L NOR to the gut microbiota of juvenile common carp (Cyprinus carpio) based on metagenomic sequencing. Metagenomic analysis revealed that the Proteobacteria, Bacteroidetes, Fusobacteria, Firmicutes, and Actinobacteria were the dominant bacteria in the gut of common carp. The relative abundance of Actinobacteria was highest in the control group. The alpha diversity of the environmental concentration NOR was significantly lower than the control group. Principal coordinates analysis (PCoA) indicated that the bacterial community between the different groups formed clear separate clusters. NOR exposure adversely could affect immune function and some substance metabolic pathways in the gut microbiota of common carp. Furthermore, environmental concentrations of NOR produce antibiotic resistance genes (ARGs) in the gut microbiota, enhancing resistance to drugs. In conclusion, environmental concentrations of NOR could alter the composition, structure, and abundance of ARGs in the gut microbiota, thereby affecting the intestinal health of fish.

https://www.sciencedirect.com/science/article/abs/pii/S0045653523006562