摘要

铜绿假单胞菌在囊性纤维化（CF）慢性感染中的存活基于由特定基因的突变组成的遗传适应过程，其可以产生有利的表型开关并确保其在肺中的持续存在。其中，使调节剂MucA（藻酸盐生物合成），LasR（群体感应）和MexZ（多药物外排泵MexXY）失活的突变是最常观察到的，使失活DNA错配修复系统（MRS）的那些突变在P 。铜绿假单胞菌CF分离株，导致hypermutator表型，可能有助于这种适应性突变，凭借增加的突变率。在此，我们鉴定了从阿根廷CF患者获得的铜绿假单胞菌分离株中mucA，lasR，mexZ和MRS基因中发现的突变，并分析了mucA，lasR和mexZ诱变与MRS缺陷和抗生素抗性的潜在关联。因此，来自26名慢性感染的CF患者的38个分离物的表型性状，PFGE基因型模式，mucA，lasR，mexZ，mutS和mutL基因编码序列和抗生素抗性谱中的突变表征。最常见的突变基因是mexZ（79％），其次是mucA（63％）和lasR（39％），以及由于mutL中功能丧失突变而观察到的高变异高度发生率（42％） 60％），其次是mutS（40％）。有趣的是，突变谱对于每个基因都是特定的，这表明在慢性感染期间有几种机制负责突变。然而，在mucA，lasR和mexZ中hypermutability和诱变之间没有建立联系，表明MRS缺陷并不参与这些突变的获得。最后，尽管mucA，lasR和mexZ的灭活先前已经显示赋予对抗生素的抗性/耐受性，但只有MRS基因的突变可能与抗生素抗性增加有关。这些结果有助于揭示导致铜绿假单胞菌适应CF肺的突变动力学。

Survival of Pseudomonas aeruginosa in cystic fibrosis (CF) chronic infections is based on a genetic adaptation process consisting of mutations in specific genes, which can produce advantageous phenotypic switches and ensure its persistence in the lung. Among these, mutations inactivating the regulators MucA (alginate biosynthesis), LasR (quorum sensing) and MexZ (multidrug-efflux pump MexXY) are the most frequently observed, with those inactivating the DNA mismatch repair system (MRS) being also highly prevalent in P. aeruginosa CF isolates, leading to hypermutator phenotypes that could contribute to this adaptive mutagenesis by virtue of an increased mutation rate. Here, we characterized the mutations found in the mucA, lasR, mexZ and MRS genes in P. aeruginosa isolates obtained from Argentinean CF patients, and analyzed the potential association of mucA, lasR and mexZ mutagenesis with MRS-deficiency and antibiotic resistance. Thus, 38 isolates from 26 chronically infected CF patients were characterized for their phenotypic traits, PFGE genotypic patterns, mutations in the mucA, lasR, mexZ, mutS and mutL gene coding sequences and antibiotic resistance profiles. The most frequently mutated gene was mexZ (79%), followed by mucA (63%) and lasR (39%) as well as a high prevalence (42%) of hypermutators being observed due to loss-of-function mutations in mutL (60%) followed by mutS (40%). Interestingly, mutational spectra were particular to each gene, suggesting that several mechanisms are responsible for mutations during chronic infection. However, no link could be established between hypermutability and mutagenesis in mucA, lasR and mexZ, indicating that MRS-deficiency was not involved in the acquisition of these mutations. Finally, although inactivation of mucA, lasR and mexZ has been previously shown to confer resistance/tolerance to antibiotics, only mutations in MRS genes could be related to an antibiotic resistance increase. These results help to unravel the mutational dynamics that lead to the adaptation of P. aeruginosa to the CF lung.

https://www.ncbi.nlm.nih.gov/pubmed/20844762