Fitness of Escherichia coli mutants with reduced susceptibility to tigecycline.
Fitness of Escherichia coli mutants with reduced susceptibility to tigecycline.
复制标题
DOI：
10.1093/jac/dkv486
复制
发表时间：
2016-05
期刊：
影响因子：
--
通讯作者：
Andersson DI
中科院分区：
文献类型：
--
作者：
Linkevicius M;Anderssen JM;Sandegren L;Andersson DI
本研究的目的是确定在体外和体内暴露于不利条件后对替加环素敏感性降低的大肠杆菌突变体的适应性。对低pH值、胆盐、氧化应激和人血清的存活率进行了检测，以寻找对替加环素易感性降低的大肠杆菌突变体，其原因是单突变导致外排（marR、lon）增加或LPS （rfaC、rfaE、lpcA）受损。采用体外竞争法测定生长适宜性缺陷。采用小鼠感染模型评估竞争适能。对基因重建的双突变体和三突变体的mic、指数增长率和外排相关基因的表达水平进行了测量。与ERN突变体和WT相比，LPS突变体对胆盐的敏感性提高了48 - 85倍。体外竞争显示，ERN突变体的适应度降低了0.3%-13%，LPS突变体的适应度降低了24%。在体内生存实验中，LPS突变体在大腿感染模型中被WT菌株打败。构建的双ERN和LPS突变体在替加环素mic中表现出加性和协同性的增加。一般来说，对替加环素的敏感性降低导致体外和体内应激条件下的适应度下降，其中ERN突变体比LPS突变体更适合。当联合使用时，ERN突变引起替加环素MIC的协同增加。这些发现可以解释为什么大肠杆菌对替加环素的临床耐药主要与AcrAB外排系统的上调有关。
The objective of this study was to determine the fitness of Escherichia coli mutants with reduced susceptibility to tigecycline after exposure to adverse conditions in vitro and in vivo. Survival in response to low pH, bile salts, oxidative stress and human serum was examined for E. coli mutants with reduced susceptibility to tigecycline due to single mutations that caused increased efflux (marR, lon) or impaired LPS (rfaC, rfaE, lpcA). An in vitro competition assay was used to determine growth fitness defects. Competitive fitness was assessed using mouse infection models. MICs, exponential growth rates and expression levels of efflux-related genes were measured for genetically reconstructed double and triple mutants. The LPS mutants were 48–85-fold more susceptible to bile salts compared with the ERN mutants and the WT. As shown by in vitro competitions, the fitness reduction was 0.3%–13% for ERN mutants and ∼24% for LPS mutants. During in vivo survival experiments, LPS mutants were outcompeted by the WT strain in the thigh infection model. Constructed double ERN and LPS mutants showed additive and synergistic increases in tigecycline MICs. Generally, reduced susceptibility to tigecycline caused a decrease in fitness under stressful in vitro and in vivo conditions with ERN mutants being fitter than LPS mutants. When combined, ERN mutations caused a synergistic increase in the MIC of tigecycline. These findings could explain why clinical resistance to tigecycline in E. coli is mainly associated with up-regulation of the AcrAB efflux system.