Overcoming antibiotics of last resort: determining the role of compensatory mutations in promoting vancomycin resistance in Staphylococcus aureus

摘要 对大多数抗生素具有抗药性的病原体的增加对公共健康构成了重大威胁，并预示着 回到抗生素出现之前的时代。目前，有几种细菌只能用几种药物来治疗 “抗生素是最后的手段”。这些病原体中最普遍的一种是耐甲氧西林。 金黄色葡萄球菌(MRSA)，每年造成80,000例侵袭性感染， 相关的医疗保健成本为40亿美元。50多年来，耐甲氧西林金黄色葡萄球菌主要用万古霉素治疗， 然而，令人惊讶的是，报告的万古霉素耐药金黄色葡萄球菌(VRSA)病例很少。目前仍不清楚 为什么VRSA没有在患者之间传播，尽管有人怀疑这是因为VRSA的生长速度很慢 VRSA在万古霉素存在的情况下。在这里，我们假设VRSA将克服这种健康缺陷 通过在受控实验室的实验进化过程中获得补偿性突变 布景。这个项目的目标是找出这些适应性突变，这可能在未来使我们能够 对获得阻力采取先发制人的措施。此外，我们会调查 观察到的代偿突变稳定了抗性，因此适应良好的VRSA不太可能恢复到 耐甲氧西林金黄色葡萄球菌，即使万古霉素已不再用于临床。因此，本项目对目前的临床应用提出了挑战 抗生素耐药性出现后应对的范例，潜在地揭示了一种维持 抗生素的疗效是最后的手段。如果成功，我们将确定可能使VRSA传播的因素， 这可以对这些突变进行先发制人的筛查，并为控制实践的发展提供信息 在抗药性流行出现之前。此外，这个项目将开创一条新的调查路线 在目前具有抗生素耐药性的病原体中，在恢复敏感之前必须采取的步骤可以实现。 这些结果对于降低VRSA取代MRSA成为主要病原体的风险至关重要， 更广泛地说，对抗抗生素耐药性的上升是最后的手段。 2.

Abstract The rise of pathogens that are resistant to most antibiotics poses a major threat to public health and portends a return to the pre-antibiotic era. At present, there are several bacteria that can only be treated with a few "antibiotics of last resort". One of the most widespread of these pathogens is methicillin resistant Staphylococcus aureus (MRSA), which is responsible for 80,000 invasive infections per year and an associated health care cost of $4 billion. MRSA has been treated primarily with vancomycin for over 50 years, yet surprisingly few cases of vancomycin resistant S. aureus (VRSA) have been reported. It remains unclear why VRSA has not spread between patients, although it is suspected that this is due to the slow growth rate of VRSA in the presence of vancomycin. Here we hypothesize that VRSA will overcome this fitness deficit through the acquisition of compensatory mutations during experimental evolution in a controlled laboratory setting. The goal of this project is to pinpoint these adaptive mutations, which may in the future enable us to take preemptive measures against the acquisition of resistance. Furthermore, we will investigate whether the observed compensatory mutations stabilize resistance, such that well-adapted VRSA is unlikely to revert to MRSA even if vancomycin was no longer used in the clinic. Hence, this project challenges the current clinical paradigm of confronting antibiotic resistance after it arises, potentially revealing a new tactic for maintaining the efficacy of antibiotics of last resort. If successful, we will identify factors that may predispose VRSA to spread, which could enable preemptive screening for these mutations and inform the development of control practices before an epidemic of resistance emerges. Moreover, this project would pioneer a new line of inquiry into the steps that must occur before reversion to sensitivity can be achieved in currently antibiotic-resistant pathogens. These outcomes are crucial for mitigating the risk that VRSA supplants MRSA as a dominant pathogen and, more generally, countering the rise of resistance to antibiotics of last resort. 2