鲍曼不动杆菌多粘菌素耐药新机制研究

Acinetobacter baumannii is one of the important healthcare-associated infectious pathogens, and its infection of multidrug resistance is widely popular. Colistin is considered to the last resort to treat infection of multidrug resistance A. baumannii. However, the rate of isolates resistant to colistin in A. baumannii is increasing year by year. Existing mechanisms are insufficient to explain the colistin resistance phenomenon in clinical strains, suggests the presence of new colistin resistant mechanisms. We have previously got colistin resistant strains of A. baumannii ATCC17978 by in vitro selection, and found that colistin resistance was possibly mediated by four new genes using whole genome sequencing and comparative genomics approach. Function of target gene will be validated by homologous knockout replacement technology and the distribution of new resistance gene will be identified. Sequencing analysis between A. baumannii and its mutant strain is performed to find related expressed genes of colistin resistance and explicit their regulation by application transcriptome and i-traq sequencing technology. The epidemic outbreak of colistin resistant strain in A. baumannii is further evaluated by determining fitness cost. This study will systematically illuminate colistin resistance mechanism and provide the basis to prevent clinical colistin resistant isolates in A. baumannii.

鲍曼不动杆菌是院内感染重要病原菌之一，其多重耐药菌感染广泛流行。多粘菌素被认为是目前治疗多重耐药鲍曼不动杆菌感染的最后防线。近年来，对多粘菌素耐药的鲍曼不动杆菌的分离率逐年上升，现有的多粘菌素耐药机制不足以解释临床菌株对多粘菌素的耐药现象，提示存在多粘菌素耐药新机制。课题组前期已通过体外选择获得鲍曼不动杆菌ATCC17978多粘菌素耐药株，应用全基因组测序及比较基因组学方法发现4个极可能介导鲍曼不动杆菌多粘菌素耐药的新基因。本课题拟采用同源敲除置换技术，对新基因功能进行验证，并在临床耐药菌株中确认新耐药基因的分布；应用转录组及i-traq测序对原始菌株及耐药株进行测序分析，明确新耐药基因的表达调控；同时评估携带耐药新基因菌株的适应性代价，明确其介导的多粘菌素耐药株感染爆发流行的可能性。本研究将揭示鲍曼不动杆菌多粘菌素耐药新机制，为多粘菌素耐药鲍曼不动杆菌的防治提供基础。

多粘菌素被认为是目前治疗多重耐药鲍曼不动杆菌感染的最后防线，近年来对多粘菌素耐药的鲍曼不动杆菌的分离率逐年上升，现有的多粘菌素耐药机制不足以解释临床菌株对多粘菌素的耐药现象，提示存在多粘菌素耐药新机制。课题组前期发现4个极可能介导鲍曼不动杆菌多粘菌素耐药的基因，通过突变体构建验证这四个基因对鲍曼不动杆菌多粘菌素敏感性的影响，证实了单独四个基因的突变并未能显著改变多粘菌素的敏感性；利用基因组学、突变体构建等方法揭示了鲍曼不动杆菌外膜合成相关基因与多粘菌素敏感性的联系，阐明了鲍曼不动杆菌gnaA基因通过影响外膜的生物合成而改变了多粘菌素的敏感性；最后结合噬菌体研究，发现能够逃逸噬菌体感染的突变菌株对多粘菌素更为敏感，这为鲍曼不动杆菌多粘菌素耐药研究开拓了新的研究思路。我们的研究为多重耐药鲍曼不动杆菌多粘菌素的治疗及相关耐药机制提供了丰富的实验基础。