PDF(Pubmed)
Abstract：
Lysins (peptidoglycan hydrolases) are promising new protein-based antimicrobial candidates under development to address rising antibiotic resistance encountered among pathogenic bacteria. Exebacase is an antistaphylococcal lysin and the first member of the lysin class to have entered clinical trials in the United States. In this study, the bacteriolytic activity of exebacase was characterized with time-kill assays, turbidity reduction assays, and microscopy. Three methicillin-susceptible Staphylococcus aureus and three methicillin-resistant S. aureus isolates were tested in time-kill assays over a range of concentrations from 0.25 to 8 × MIC. Exebacase demonstrated a concentration-dependent killing and showed bactericidal activity (≥3 log10 kill achieved relative to the starting inoculum) within 3 h at 1 × MIC against all strains tested. Dose-dependent lysis by exebacase was, furthermore, observed in the turbidity reduction assay, wherein decreases in initial OD600 of 50% were observed within ~15 min at concentrations as low as 4 µg/mL. Membrane dissolution, loss of cytoplasmic material, and lysis were confirmed by video and electron microscopy. The demonstrated rapid bacteriolytic effect of exebacase is an important distinguishing feature of this novel modality. IMPORTANCE To guide the development of an investigational new antibacterial entity, microbiological data are required to evaluate the killing kinetics against target organism(s). Exebacase is a lysin (peptidoglycan hydrolase) that represents a novel antimicrobial modality based on degradation of the cell wall of Staphylococcus aureus. Killing by exebacase was determined in multiple assay formats including time-kill assays, wherein reductions of viability of ≥3 log10 colony-forming units/mL were observed within 3 h for multiple different isolates tested, consistent with very rapid bactericidal activity. Rapid reductions in optical density were likewise observed in exebacase-treated cultures, which were visually consistent with microscopic observations of rapid lysis. Overall, exebacase provides a novel antimicrobial modality against S. aureus, characterized by a rapid cidal and lytic activity.
摘要：
溶素（肽聚糖水解酶）是有希望开发的新的基于蛋白质的抗微生物候选物，以解决致病菌中遇到的不断上升的抗生素耐药性。Exebacase是一种抗葡萄球菌溶素，是第一个在美国进入临床试验的溶素类成员。在这项研究中,用时间杀灭测定法表征了外泌菌酶的溶菌活性，浊度降低测定，和显微镜。在时间杀伤试验中，测试了三种甲氧西林敏感的金黄色葡萄球菌和三种耐甲氧西林的金黄色葡萄球菌分离株，浓度范围为0.25至8×MIC。Exebacase表现出浓度依赖性的杀灭作用，并在3小时内以1×MIC对所有测试菌株显示出杀菌活性（相对于起始接种物达到≥3log10杀灭）。蛋白酶的剂量依赖性裂解是，此外，在浊度降低试验中观察到，其中在低至4μg/mL的浓度下，在约15分钟内观察到初始OD600降低50％。膜溶解,细胞质物质的损失，和裂解通过视频和电子显微镜证实。已证明的促杆菌酶的快速溶菌作用是这种新型方式的重要区别特征。重要性为了指导研究新型抗菌实体的开发，需要微生物数据来评估针对靶生物体的杀伤动力学。Exebacase是一种溶素（肽聚糖水解酶），它代表了一种基于金黄色葡萄球菌细胞壁降解的新型抗菌方式。在包括时间杀伤试验在内的多种试验形式中确定了由分解酶引起的杀伤,其中在3小时内观察到多个测试的不同分离株的活力降低≥3log10集落形成单位/mL，与非常快速的杀菌活性一致。光密度的快速降低也同样观察到了经过解构酶处理的培养物，这在视觉上与快速裂解的显微镜观察一致。总的来说,exebacase提供了一种针对金黄色葡萄球菌的新型抗菌方式，以快速杀菌和裂解活性为特征。
