Genetic characterization of compensatory evolution in strains carrying rpoB Ser531Leu, the rifampicin resistance mutation most frequently found in clinical isolates
Genetic characterization of compensatory evolution in strains carrying rpoB Ser531Leu, the rifampicin resistance mutation most frequently found in clinical isolates
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DOI：
10.1093/jac/dkt224
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发表时间：
2013-11-01
影响因子：
5.2
通讯作者：
Hughes, Diarmaid
中科院分区：
文献类型：
--
作者：
Brandis, Gerrit;Hughes, Diarmaid
目的：结核分枝杆菌对利福平耐药性的演变是结核病有效治疗的主要威胁。关于利福平耐药性的最初出现已经知道很多，但这些耐药菌株的进一步进化只是最近才受到调查。尽管rpoB的许多不同突变可引起耐药，但在临床M.具有rpoB S531L的临床分离株经常在RNA聚合酶亚基基因中携带额外的突变，并且已经推测这些是适应性补偿突变，改善了主要耐药突变的适应性成本。我们测试了这一假设，使用沙门氏菌作为一个模式organis.Methods：我们创建了沙门氏菌的rpoB S531L突变，然后演变成独立的谱系与突变体的选择增加相对健身。与推定的补偿突变相关的相对健身后，在同基因strains.Results遗传重建测定：在编码RNA聚合酶的不同亚基的基因：rpoA，rpoB和rpoC的补偿突变。基因重建表明，这些次级突变中的每一个都降低了rpoB S531L耐药突变的适应度cost.Conclusions：在沙门氏菌中发现的补偿突变簇在类似的位置发现的额外的突变在M。结核病分离株。这些新的数据有力地支持了这样的观点，即在利福平耐药的M.结核病（rpoB S531L）确实是适应性补偿突变。
Objectives: The evolution of rifampicin resistance in Mycobacterium tuberculosis is a major threat to effective tuberculosis therapy. Much is known about the initial emergence of rifampicin resistance, but the further evolution of these resistant strains has only lately been subject to investigation. Although resistance can be caused by many different mutations in rpoB, among clinical M. tuberculosis isolates the mutation rpoB S531L is overwhelmingly the most frequently found. Clinical isolates with rpoB S531L frequently carry additional mutations in genes for RNA polymerase subunits, and it has been speculated that these are fitness-compensatory mutations, ameliorating the fitness cost of the primary resistance mutation. We tested this hypothesis using Salmonella as a model organism.Methods: We created the rpoB S531L mutation in Salmonella and then evolved independent lineages with selection for mutants with increased relative fitness. Relative fitness associated with putative compensatory mutations was measured after genetic reconstruction in isogenic strains.Results: Compensatory mutations were identified in genes coding for different subunits of RNA polymerase: rpoA, rpoB and rpoC. Genetic reconstructions demonstrated that each of these secondary mutations reduced the fitness cost of the rpoB S531L resistance mutation.Conclusions: The compensatory mutations identified in Salmonella cluster in similar locations to the additional mutations found in M. tuberculosis isolates. These new data strongly support the idea that many of the previously identified rpoA, rpoB and rpoC mutations in rifampicin-resistant M. tuberculosis (rpoB S531L) are indeed fitness-compensatory mutations.