水产养殖尾水中抗生素抗性基因的去除及磺胺类耐药细菌研究

Removal of antibiotic resistance genes and sulfonamides resistant bacteria in aquaculture tail water

水产养殖环境中抗生素的大量使用促进了抗生素耐药细菌(antibiotic resistant bacteria,ARB)和抗生素抗性基因(antibiotic resistance genes,ARGs)的出现及传播.利用荧光定量PCR分析了浙江省某水产养殖尾水集中处理系统中8种ARGs的分布特征.结果表明,出水中ARGs的绝对丰度降低了0.91个数量级.磺胺类抗性基因(sul1、sul2)在所检测的抗性基因中占主导地位,且绝对丰度在出水中依然维持较高水平(4.94×10^(9)、1.79×10^(9)copies·L^(-1)).16S r RNA基因高通量测序结果显示变形菌门、蓝藻门、拟杆菌门、厚壁菌门和放线菌门是优势菌门,变形菌门和绿弯菌门与sul1、sul2和sul3呈显著相关.筛选出一株对磺胺类抗生素具有耐药性的弗氏柠檬酸杆菌,该菌株为条件致病菌,全基因组测序结果显示该菌株共携带了17个ARGs,其中sul1、sul2、tet A、bla;等ARGs均位于1个Inc FIB质粒上,质粒图谱揭示了磺胺类抗性基因的基因环境.

The extensive use of antibiotics in aquaculture has promoted the emergence and dissemination of antibiotic resistant bacteria(ARB)and antibiotic resistance genes(ARGs).Herein,we investigated the distribution of 8 ARGs in a tail water centralized treatment system in Zhejiang province by quantitative polymerase chain reaction(q PCR).The results showed that the absolute abundance of ARGs decreased by 0.91 orders of magnitude in the effluent.Sulfonamides resistance genes(sul1,sul2)were dominant among all the detected ARGs and their absolute abundance remained a high level in the effluent(4.94×10^(9),1.79×10^(9)copies·L^(-1)).Based on 16S r RNA gene sequencing results,Proteobacteria,Cyanobacteria,Bacteroidetes,Firmicutes and Actinobacteria were the dominant phyla.Proteobacteria and Chloroflexi had a significant correlation with sulfonamides resistance genes(sul1,sul2,sul3).One Citrobacter freundii strain conferring resistance to sulfonamides was isolated,which was an opportunistic pathogen.The whole plasmid genome showed that this strain carried 17 ARGs,among which sul1,sul2,tet A,bla;were located on an Inc FIB plasmid.The plasmid profile demonstrated the genetic environment of sulfonamides resistance genes.