Centro Nacional de Biotecnología, CSIC, 28049, Madrid, Spain.
Sci Rep. 2019 Mar 20;9(1):4917. doi: 10.1038/s41598-019-41308-9.
The emergence of antibiotic resistant Gram-negative bacteria has become a serious global health issue. In this study, we have employed the intrinsically resistant opportunistic pathogen Stenotrophomonas maltophilia as a model to study the mechanisms involved in the acquisition of mutation-driven resistance to antibiotics. To this aim, laboratory experimental evolution studies, followed by whole-genome sequencing, were performed in the presence of the third-generation cephalosporin ceftazidime. Using this approach, we determined that exposure to increasing concentrations of ceftazidime selects high-level resistance in S. maltophilia through a novel mechanism: amino acid substitutions in SmeH, the transporter protein of the SmeGH RND efflux pump. The recreation of these mutants in a wild-type background demonstrated that, in addition to ceftazidime, the existence of these substitutions provides bacteria with cross-resistance to other beta-lactam drugs. This acquired resistance does not impose relevant fitness costs when bacteria grow in the absence of antibiotics. Structural prediction of both amino acid residues points that the observed resistance phenotype could be driven by changes in substrate access and recognition.
抗生素耐药革兰氏阴性菌的出现已成为一个严重的全球健康问题。在本研究中，我们以固有耐药机会性病原体嗜麦芽寡养单胞菌为模型，研究了获得抗生素突变驱动耐药性的相关机制。为此，我们在第三代头孢菌素头孢他啶存在的情况下进行了实验室实验进化研究，并进行了全基因组测序。通过这种方法，我们确定了通过一种新的机制，即 SmeH 氨基酸取代，SmeGH RND 外排泵的转运蛋白，在暴露于越来越高浓度的头孢他啶的情况下选择高水平的嗜麦芽寡养单胞菌耐药性。在野生型背景下重现这些突变体表明，除了头孢他啶之外，这些取代的存在还使细菌对其他β-内酰胺类药物具有交叉耐药性。当细菌在没有抗生素的情况下生长时，这种获得的耐药性不会带来相关的适应性成本。对两个氨基酸残基的结构预测表明，观察到的耐药表型可能是由底物进入和识别的变化驱动的。
