Mapping the Role of AcrAB-TolC Efflux Pumps in the Evolution of Antibiotic Resistance Reveals Near-MIC Treatments Facilitate Resistance Acquisition.
Mapping the Role of AcrAB-TolC Efflux Pumps in the Evolution of Antibiotic Resistance Reveals Near-MIC Treatments Facilitate Resistance Acquisition.
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DOI：
10.1128/msphere.01056-20
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发表时间：
2020-12-16
期刊：
影响因子：
4.8
通讯作者：
Dunlop MJ
中科院分区：
文献类型：
--
作者：
Langevin AM;El Meouche I;Dunlop MJ
与抗生素耐药性上升作斗争是一项重大挑战。外排泵是产生耐药性的重要因素；它们存在于许多细胞类型中，可以输出许多种类的抗生素。抗生素耐药性已成为一个主要的公共卫生问题，因为细菌进化以逃避药物，导致反复感染和抗生素功效下降。系统的努力已经揭示了抗药性的机制。然而，在许多情况下，这些特定机制如何加速或减缓耐药性的演变仍不清楚。在此，我们系统研究了acrabb - tolc外排泵对抗生素耐药性演变的影响。我们绘制了种群增长率和耐药性随时间变化的图，作为抗生素浓度和亲本菌株遗传背景的函数。我们将野生型菌株与过表达AcrAB-TolC泵的菌株和缺乏功能泵的菌株进行了比较。在所有情况下，当用接近其各自亲本菌株MIC浓度的氯霉素处理培养物时，均出现耐药性。亲本菌株的遗传背景也影响抗性的获得。野生型菌株通过acrAB操纵子及其相关调节因子的突变在24小时内进化出耐药性。同时，过表达acrabb - tolc的菌株比野生型菌株产生抗性的速度慢；该菌株部分通过acrB和acrAB启动子的点突变获得抗性。令人惊讶的是，没有功能性AcrAB-TolC外排泵的菌株仍然获得阻力，这是通过上调冗余外排泵来实现的。总的来说，我们的研究结果表明，MIC以上的治疗条件对耐药性的演变构成了最大的风险，AcrAB-TolC外排泵影响了实现氯霉素耐药的途径。抗击抗生素耐药性的上升是一项重大挑战。外排泵是产生耐药性的重要因素；它们存在于许多细胞类型中，可以输出许多种类的抗生素。细胞可以调节泵的表达以维持较低的细胞内药物浓度。在这里，我们探讨了耐药性是如何根据抗生素浓度以及外排泵及其调节剂的存在而出现的。我们发现，接近抑制亲本菌株生长的抗生素浓度的治疗最有可能促进耐药性。虽然野生型、泵过表达型和泵敲除型菌株都能够进化出抗性，但它们在抗性进化的绝对水平、实现抗性的速度和所涉及的遗传途径方面存在差异。这些结果表明，特定的治疗方案可能对耐药性的演变尤其有问题，菌株背景可以影响如何实现耐药性。
Combatting the rise of antibiotic resistance is a significant challenge. Efflux pumps are an important contributor to drug resistance; they exist across many cell types and can export numerous classes of antibiotics. Antibiotic resistance has become a major public health concern as bacteria evolve to evade drugs, leading to recurring infections and a decrease in antibiotic efficacy. Systematic efforts have revealed mechanisms involved in resistance. Yet, in many cases, how these specific mechanisms accelerate or slow the evolution of resistance remains unclear. Here, we conducted a systematic study of the impact of the AcrAB-TolC efflux pump on the evolution of antibiotic resistance. We mapped how population growth rate and resistance change over time as a function of both the antibiotic concentration and the parent strain’s genetic background. We compared the wild-type strain to a strain overexpressing AcrAB-TolC pumps and a strain lacking functional pumps. In all cases, resistance emerged when cultures were treated with chloramphenicol concentrations near the MIC of their respective parent strain. The genetic background of the parent strain also influenced resistance acquisition. The wild-type strain evolved resistance within 24 h through mutations in the acrAB operon and its associated regulators. Meanwhile, the strain overexpressing AcrAB-TolC evolved resistance more slowly than the wild-type strain; this strain achieved resistance in part through point mutations in acrB and the acrAB promoter. Surprisingly, the strain without functional AcrAB-TolC efflux pumps still gained resistance, which it achieved through upregulation of redundant efflux pumps. Overall, our results suggest that treatment conditions just above the MIC pose the largest risk for the evolution of resistance and that AcrAB-TolC efflux pumps impact the pathway by which chloramphenicol resistance is achieved. IMPORTANCE Combatting the rise of antibiotic resistance is a significant challenge. Efflux pumps are an important contributor to drug resistance; they exist across many cell types and can export numerous classes of antibiotics. Cells can regulate pump expression to maintain low intracellular drug concentrations. Here, we explored how resistance emerged depending on the antibiotic concentration, as well as the presence of efflux pumps and their regulators. We found that treatments near antibiotic concentrations that inhibit the parent strain’s growth were most likely to promote resistance. While wild-type, pump overexpression, and pump knockout strains were all able to evolve resistance, they differed in the absolute level of resistance evolved, the speed at which they achieved resistance, and the genetic pathways involved. These results indicate that specific treatment regimens may be especially problematic for the evolution of resistance and that the strain background can influence how resistance is achieved.