PDF(Pubmed)
Abstract：
Cotrimoxazole, the combined formulation of sulfamethoxazole and trimethoprim, is one of the treatments of choice for several infectious diseases, particularly urinary tract infections. Both components of cotrimoxazole are synthetic antimicrobial drugs, and their combination was introduced into medical therapeutics about half a century ago. In Gram-negative bacteria, resistance to cotrimoxazole is widespread, being based on the acquisition of genes from the auxiliary genome that confer resistance to each of its antibacterial components. Starting from previous knowledge on the genotype of resistance to sulfamethoxazole in a collection of cotrimoxazole resistant uropathogenic Escherichia coli strains, this work focused on the identification of the genetic bases of the trimethoprim resistance of these same strains. Molecular techniques employed included PCR and Sanger sequencing of specific amplicons, conjugation experiments and NGS sequencing of the transferred plasmids. Mobile genetic elements conferring the trimethoprim resistance phenotype were identified and included integrons, transposons and single gene cassettes. Therefore, strains exhibited several ways to jointly resist both antibiotics, implying different levels of genetic linkage between genes conferring resistance to sulfamethoxazole (sul) and trimethoprim (dfrA). Two structures were particularly interesting because they represented a highly cohesive arrangements ensuring cotrimoxazole resistance. They both carried a single gene cassette, dfrA14 or dfrA1, integrated in two different points of a conserved cluster sul2-strA-strB, carried on transferable plasmids. The results suggest that the pressure exerted by cotrimoxazole on bacteria of our environment is still promoting the evolution toward increasingly compact gene arrangements, carried by mobile genetic elements that move them in the genome and also transfer them horizontally among bacteria.
摘要：
复方新诺明,磺胺甲恶唑和甲氧苄啶的联合制剂，是几种传染病的首选治疗方法之一，尤其是尿路感染。复方新诺明的两种成分都是合成抗菌药物，他们的组合在大约半个世纪前被引入医学治疗学。在革兰氏阴性细菌中，对复方新诺明的耐药性很普遍，基于从辅助基因组中获得赋予其每个抗菌成分抗性的基因。从先前对一组耐复方新诺明的尿路致病性大肠杆菌菌株中对磺胺甲恶唑的抗性基因型的认识出发，这项工作的重点是鉴定这些相同菌株的甲氧苄啶抗性的遗传基础。采用的分子技术包括特定扩增子的PCR和Sanger测序，转移质粒的缀合实验和NGS测序。鉴定了赋予甲氧苄啶抗性表型的可移动遗传元件，并包括整合子，转座子和单基因盒。因此,菌株表现出几种联合抵抗两种抗生素的方法，暗示赋予对磺胺甲恶唑（sul）和甲氧苄啶（dfra）抗性的基因之间的遗传连锁水平不同。两个结构特别有趣，因为它们代表了确保耐复方新诺明的高度内聚排列。他们都携带了一个基因盒，dfrA14或dfrA1，集成在保守簇sul2-strA-strB的两个不同点中，进行可转移的质粒。结果表明，复方新诺明对我们环境中的细菌施加的压力仍在促进向日益紧密的基因排列进化，由可移动的遗传因子携带，这些遗传因子在基因组中移动，并在细菌之间水平转移。
