1株携带质粒介导喹诺酮耐药基因qnrS1和qepA1的多耐药沙门菌的基因特点分析

Genotypic analysis of a MDR Salmonellastrain harbouring PMQR genes qnrS1 and qepA1

目的分析一株多重耐药沙门菌SM846的遗传背景,研究其对喹诺酮耐药的机制。方法测定SM846对14种药物的最小抑菌浓度(minimal inhibitoryconcentration,MIC)。用三代测序技术对菌株进行全基因组测序,根据耐药数据库注释SM846序列中的耐药基因。使用NCBI的BLAST工具搜索与耐药质粒相似的序列,并进行生物信息学分析。结果SM846对14种测试抗生素中的12种表现出耐药,包括喹诺酮类抗生素萘啶酸和环丙沙星。SM846包含1条染色体和1条质粒。染色体序列不含可导致耐药的基因和突变,质粒携带13个耐药基因,包括喹诺酮类耐药基因qepA1和qnrS1。qepA1和qnrS1位于质粒内部的可移动原件I类整合子上。13条相似质粒的分析表明中国分离的此型别的质粒耐药性强于美国和加拿大分离的。结论QnrS1和qepA1基因通过IS6和可移动元件整合到质粒的I类整合子上,说明SM846可能迫于抗生素压力通过获得耐药基因来快速适应环境。中国分离菌株的耐药性强,地区间的耐药情况差异,尤其是与不发达国家之间的差异提示我们应当继续监测各地区的耐药表现型,以制定本地的耐药控制策略。

To analyze the genetic background of a multi-drug-resistant Salmonella strain SM846 and investigate its mechanism of quinolone resistance.The whole genome of the strain was sequenced,and the resistance genes in the SM846 sequence were annotated according to the drug resistance database.NCBI BLAST tools were used to confirm the above results.SM846 showed resistance to 12 of the 14 tested antibiotics,including quinolone antibiotics nalidixic acid and ciprofloxacin.Gene or mutation that can lead to drug resistance was not found in Chromosone.While 13 resistance genes were carried in the plasmid,including quinolone resistance genes qepA1 and qnrS1.QepA1 and qnrS1 were located on the class I integron inside the plasmid.The analysis of 13 similar plasmids showed that the resistance of the plasmids isolated from China was stronger than that isolated from the United States and Canada.QnrS1 and qepA1 genes were integrated into class I integron of plasmid through IS6 and mobile elements,suggesting SM846 may adapt rapidly to the environment by acquiring resistance genes under the pressure of antibiotics.The differences of drug resistance among regions,especially between the developed countries and the undeveloped countries,suggested that we should continue to monitor drug resistance phenotypes to formulate local drug resistance control strategies.