一株污水源多重耐药大肠杆菌的耐药性检测及全基因组测序分析

Drug resistance detection and whole genome sequencing of a multi-drug resistant Escherichia coli strain from sewage

摘要:

【背景】水体环境分布广、流动性强，是耐药菌和耐药基因传播的主要媒介。【目的】了解北方污水厂大肠杆菌携带的耐药基因及可移动遗传元件情况。【方法】从北方污水厂筛选出一株多重耐药大肠杆菌，通过药敏试验进行耐药性检验，采用96孔板法测定菌株的最小抑菌浓度，利用酶标仪探究亚抑菌浓度抗生素对菌株生长的影响，并对菌株进行全基因组测序，对其携带的耐药基因及可移动遗传元件进行预测。【结果】大肠杆菌WEC对四环素、环丙沙星、诺氟沙星和红霉素具有耐药性，亚抑菌浓度的四环素、环丙沙星和诺氟沙星能够延缓或抑制菌株的生长。WEC菌株的基因组中包含一条大小为4 782 114 bp的环状染色体和2个大小分别为60 306 bp (pWEC-1)和92 065 bp (pWEC-2)的环状质粒。菌株共携带129个耐药基因，其中128个位于染色体上，在染色体上预测到原噬菌体、基因岛及插入序列的存在，部分可移动遗传元件携带有耐药基因。质粒pWEC-1中无耐药基因，pWEC-2含有1个耐药基因，在质粒基因组中预测到原噬菌体和插入序列。【结论】污水源大肠杆菌WEC是一株多重耐药菌株，其基因组中携带耐药基因和多种可移动遗传元件，具有发生耐药性转移的潜力。

Abstract:

[Background] The water environment with wide distribution and high mobility is the main medium for the spread of drug resistant bacteria and genes. [Objective] To understand the drug resistance genes and mobile genetic elements carried by Escherichia coli from a sewage plant in northern China. [Methods] A multi-drug resistant strain of E. coli was isolated from the sewage plant. The antimicrobial susceptibility test was carried out. The 96-well plate method was employed to determine the minimum inhibitory concentrations of antibiotics against this strain. The effects of antibiotics at sub-inhibitory concentrations on the growth of the strain were explored by a microplate reader. The whole genome sequencing was carried out to predict the resistance genes and mobile genetic elements carried by the strain. [Results] E. coli WEC was resistant to tetracycline, ciprofloxacin, norfloxacin, and erythromycin. Sub-inhibitory concentrations of tetracycline, ciprofloxacin, and norfloxacin stagnated or inhibited the growth of strains. The genome of WEC was composed of a circular chromosome of 4 782 114 bp and two circular plasmids of 60 306 bp (pWEC-1) and 92 065 bp (pWEC-2), respectively. The strain carried 129 drug resistance genes, of which 128 were located on the chromosome. Prophages, gene islands, and insertion sequences was predicted to be present on the chromosome, and some mobile genetic elements carried drug resistance genes. There was no drug resistance gene in plasmid pWEC-1, and pWEC-2 carried one drug resistance gene. Prophages and insertion sequences were predicted to be present in the plasmid genome. [Conclusion] E. coli WEC from sewage is a multi-drug resistant strain. Carrying drug resistance genes and a variety of mobile genetic elements, the strain has the potential of drug resistance transfer.