Poey María Eloísa, de Los Santos Eliana, Aznarez Diego, García-Laviña César X, Laviña Magela
Sección Fisiología & Genética Bacterianas, Facultad de Ciencias, Montevideo, Uruguay.
Sección Bioquímica, Facultad de Ciencias, Montevideo, Uruguay.
Front Microbiol. 2024 Jun 12;15:1395953. doi: 10.3389/fmicb.2024.1395953. eCollection 2024.
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 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 () and trimethoprim (). Two structures were particularly interesting because they represented a highly cohesive arrangements ensuring cotrimoxazole resistance. They both carried a single gene cassette, or , integrated in two different points of a conserved cluster , 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.
复方新诺明是磺胺甲恶唑和甲氧苄啶的联合制剂，是多种传染病尤其是尿路感染的首选治疗药物之一。复方新诺明的两种成分都是合成抗菌药物，它们的组合大约在半个世纪前被引入医学治疗领域。在革兰氏阴性菌中，对复方新诺明的耐药性很普遍，这是基于从辅助基因组中获得赋予对其每种抗菌成分耐药性的基因。基于先前对一组耐复方新诺明的尿路致病性菌株中磺胺甲恶唑耐药基因型的了解，这项工作聚焦于确定这些相同菌株对甲氧苄啶耐药的遗传基础。所采用的分子技术包括特定扩增子的聚合酶链反应（PCR）和桑格测序、接合实验以及转移质粒的二代测序（NGS）。确定了赋予甲氧苄啶耐药表型的移动遗传元件，包括整合子、转座子和单基因盒。因此，菌株表现出多种联合抵抗两种抗生素的方式，这意味着赋予对磺胺甲恶唑（ ）和甲氧苄啶（ ）耐药性的基因之间存在不同程度的遗传连锁。有两种结构特别有趣，因为它们代表了一种高度紧密的排列方式，确保了对复方新诺明的耐药性。它们都携带一个单基因盒， 或 ，整合在一个保守簇 的两个不同位点上，该保守簇位于可转移质粒上。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朝着由移动遗传元件携带的越来越紧凑的基因排列方式进化，这些移动遗传元件在基因组中移动它们，并且还在细菌之间水平转移它们。
