Oz Tugce, Guvenek Aysegul, Yildiz Sadik, Karaboga Enes, Tamer Yusuf Talha, Mumcuyan Nirva, Ozan Vedat Burak, Senturk Gizem Hazal, Cokol Murat, Yeh Pamela, Toprak Erdal
Faculty of Engineering and Natural Sciences, Sabanci University, Istanbul, Turkey.
Department of Ecology and Evolutionary Biology, University of California, Los Angeles.
Mol Biol Evol. 2014 Sep;31(9):2387-401. doi: 10.1093/molbev/msu191. Epub 2014 Jun 24.
Revealing the genetic changes responsible for antibiotic resistance can be critical for developing novel antibiotic therapies. However, systematic studies correlating genotype to phenotype in the context of antibiotic resistance have been missing. In order to fill in this gap, we evolved 88 isogenic Escherichia coli populations against 22 antibiotics for 3 weeks. For every drug, two populations were evolved under strong selection and two populations were evolved under mild selection. By quantifying evolved populations' resistances against all 22 drugs, we constructed two separate cross-resistance networks for strongly and mildly selected populations. Subsequently, we sequenced representative colonies isolated from evolved populations for revealing the genetic basis for novel phenotypes. Bacterial populations that evolved resistance against antibiotics under strong selection acquired high levels of cross-resistance against several antibiotics, whereas other bacterial populations evolved under milder selection acquired relatively weaker cross-resistance. In addition, we found that strongly selected strains against aminoglycosides became more susceptible to five other drug classes compared with their wild-type ancestor as a result of a point mutation on TrkH, an ion transporter protein. Our findings suggest that selection strength is an important parameter contributing to the complexity of antibiotic resistance problem and use of high doses of antibiotics to clear infections has the potential to promote increase of cross-resistance in clinics.
揭示导致抗生素耐药性的基因变化对于开发新型抗生素疗法至关重要。然而，在抗生素耐药性背景下将基因型与表型相关联的系统性研究一直缺失。为了填补这一空白，我们让88个同基因大肠杆菌群体针对22种抗生素进化了3周。对于每种药物，两个群体在强选择下进化，两个群体在弱选择下进化。通过量化进化群体对所有22种药物的耐药性，我们为强选择和弱选择群体构建了两个独立的交叉耐药网络。随后，我们对从进化群体中分离出的代表性菌落进行测序，以揭示新表型的遗传基础。在强选择下对抗生素产生耐药性的细菌群体对几种抗生素获得了高水平的交叉耐药性，而在较弱选择下进化的其他细菌群体获得的交叉耐药性相对较弱。此外，我们发现，由于离子转运蛋白TrkH上的一个点突变，与野生型祖先相比，在强选择下对氨基糖苷类产生耐药性的菌株对其他五类药物变得更敏感。我们的研究结果表明，选择强度是导致抗生素耐药性问题复杂性的一个重要参数，在临床上使用高剂量抗生素清除感染有可能促进交叉耐药性的增加。
