Localized hypermutation drives the evolution of unstable colistin resistance in small populations of Pseudomonas aeruginosa
Localized hypermutation drives the evolution of unstable colistin resistance in small populations of Pseudomonas aeruginosa
复制标题
局部超突变驱动铜绿假单胞菌小群体中不稳定的粘菌素耐药性的进化
DOI：
--
复制
发表时间：
2021
期刊：
影响因子：
--
通讯作者：
R. MacLean
中科院分区：
文献类型：
--
作者：
N. Kapel;Julio Diaz Caballero;R. MacLean
粘菌素已成为治疗由抗生素耐药性革兰氏阴性病原体引起的感染的重要最后一道防线。在这里，我们研究了1,000个小种群（1004 CFU）的MDR铜绿假单胞菌菌株对高剂量粘菌素（2 mg/L）的反应。多粘菌素暴露导致细胞快速死亡，但由于异源抗性细胞的生长，一个亚组的群体最终恢复。基因组测序显示，异源耐药主要是由PmrAB双组分系统中的突变驱动的，其发生率（每细胞分裂102 ×10−5）是典型耐药突变率的103-104倍。至关重要的是，这种升高的突变率仅在pmrB中发现，表明超变性局限于该基因。PmrAB提供对参与宿主免疫的抗微生物肽的抗性，表明该病原体可能已经进化出高突变率作为适应以产生对感染期间分泌的宿主抗微生物肽具有抗性的突变体。有趣的是，我们在一些异耐药菌群体中没有发现突变，这表明铜绿假单胞菌细胞的一小部分由于表型可塑性而对粘菌素具有内在耐药性。
Colistin has emerged as an important last line of defence for the treatment of infections caused by antibiotic resistant Gram-negative pathogens. Here we investigate the responses of ≈1,000 small populations (≈104 CFU) of an MDR strain of P. aeruginosa to a high dose of colistin (2 mg/L). Colistin exposure resulted in rapid cell death, but a sub-set of populations eventually recovered due to the outgrowth of heteroresistant cells. Genome sequencing revealed that heteroresistance was primarily driven by mutations in the PmrAB two-component system that occurred at a rate (≈2×10−5 per cell division) that was 103-104 fold higher than typical resistance mutation rates. Crucially, this elevated mutation rate was only found in pmrB, demonstrating that hypermutability is localized to this gene. PmrAB provides resistance to antimicrobial peptides that are involved in host immunity, suggesting that this pathogen may have evolved a high mutation rate as an adaption to generate mutants that are resistant to host antimicrobial peptides that are secreted during infection. Interestingly, we found no mutations in some heteroresister populations, suggesting that a small sub-set of P. aeruginosa cells are intrinsically resistant to colistin as a result of phenotypic plasticity.