肠球菌新型利奈唑胺耐药基因optrA传播机制研究

肠球菌是重要的院内感染病原菌，多重耐药尤其是万古霉素耐药菌株的出现和传播给临床抗感染带来很大挑战，利奈唑胺是治疗这类细菌感染的重要选择，因此其耐药问题备受关注。肠球菌对利奈唑胺耐药的主要原因包括23S rRNA基因和核糖体蛋白氨基酸突变以及携带cfr基因。本课题组最近发现一个新型利奈唑胺耐药基因optrA，该基因可定位于质粒或染色体上，然而其传播机制尚不清楚。本项目收集到46株optrA基因阳性的肠球菌，拟通过Southern杂交对optrA进行基因定位；通过接合和转化试验、质粒分型等研究optrA质粒特性；通过全质粒测序和全基因组测序获得optrA质粒序列及optrA基因侧翼序列；采用生物信息学技术研究optrA质粒结构特征、optrA基因所在遗传结构特点以及介导optrA基因转移的可移动元件，阐明optrA基因在肠球菌中的传播机制，为控制耐药基因的播散和延缓耐药性的发展提供科学依据。

Enterococci are important nosocomial pathogens causing a variety of infections. The emergence and rapid spread of multidrug resistant strains especially the vancomycin-resistant enterococci represent a particular challenge. Linezolid is an important alternative for treatment of infections caused by such strains, and linezolid resistance therefore becomes a critical issue. Mutations in 23S rRNA gene and ribosomal proteins and presence of cfr gene are the main mechanisms of linezolid resistance in enterococci. Recently, we identified a novel linezolid resistance gene optrA in enterococci. optrA gene can located either on plasmid or in chromosomal DNA, however, the transmission mechanism of optrA gene remains unclear. Forty-six optrA-positive enterococci were collected from multiple hospitals in the current study. The location of optrA gene will be determined by S1-nuclease digested PFGE and Southern blot hybridization. The characteristics of optrA-carrying plasmid will be investigated by conjugation and transformation experiments, and plasmid typing. The sequence of optrA-carrying plasmid and sequence surrounding optrA gene will be obtained by high-throughput whole-plasmid sequencing and whole-genome sequencing. The structure characteristics of optrA-carrying plasmids, genetic structure surrounding optrA gene, and mobile genetic elements involving the transfer of optrA gene will be analyzed by bioinformatics. This study aims to reveal the transmission mechanism of optrA gene in enterococci and provide the scientific basis for preventing the spread of resistance genes and delaying the development of resistance.