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耐药性的病原体的增加对公共卫生构成了重大威胁，并预示着 回到抗生素时代。目前，有几种细菌只能用少数几种来治疗 “抗生素的最后手段”。这些病原体中最广泛的一种是耐甲氧西林的 金黄色葡萄球菌（MRSA），每年造成80，000例侵入性感染， 相关的医疗费用为40亿美元。MRSA主要用万古霉素治疗超过50年， 但令人惊讶的是，万古霉素耐药的S.金黄色葡萄球菌（VRSA）。目前还不清楚 为什么VRSA没有在患者之间传播，尽管人们怀疑这是由于VRSA的生长速度缓慢， 万古霉素存在下的VRSA。在这里，我们假设，VRSA将克服这种健身赤字 通过在受控实验室的实验进化过程中获得补偿突变， 设置.该项目的目标是精确定位这些适应性突变，这可能在未来使我们能够 采取先发制人的措施，防止获得抵抗。此外，我们将调查 观察到的补偿性突变稳定了抗性，使得适应良好的VRSA不太可能恢复到 MRSA，即使万古霉素不再在临床上使用。因此，该项目挑战了目前的临床 在抗生素耐药性出现后对抗它的范例，可能揭示了一种维持抗生素耐药性的新策略。 抗生素作为最后手段的有效性。如果成功，我们将确定可能导致VRSA传播的因素， 这可以使这些突变的先发制人的筛选，并告知控制实践的发展 在抗药性蔓延之前此外，该项目还将开辟一条新的调查路线， 在目前的耐药病原体中，在恢复敏感性之前必须发生的步骤可以实现。 这些结果对于减轻VRSA取代MRSA作为主要病原体的风险至关重要， 更广泛地说，是为了对抗对最后手段抗生素耐药性的上升。 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