Staphylococcus aureus is one of the most dreadful infectious agents, responsible for high mortality and morbidity in both humans and animals. The increased prevalence of multidrug-resistant (MDR) Staphylococcus aureus strains has limited the number of available treatment options, which calls for the development of alternative and effective modalities against MDR S. aureus. Endolysins are bacteriophage-derived antibacterials, which attack essential conserved elements of peptidoglycan that are vital for bacterial survival, making them promising alternatives or complements to existing antibiotics for tackling such infections. For developing endolysin lysin-methicillin-resistant-5 (LysMR-5) as an effective antimicrobial agent, we evaluated its physical and chemical characteristics, and its intrinsic antibacterial activity against staphylococcal strains, including methicillin-resistant Staphylococcus aureus (MRSA). In this study, we cloned, expressed, and purified LysMR-5 from S. aureus phage MR-5. In silico analysis revealed that LysMR-5 harbors two catalytic and one cell wall-binding domain. Biochemical characterization and LC-MS analysis showed that both catalytic domains were active and had no dependence on divalent ions for their action, Zn2+ exerted a negative effect. The optimal lytic activity of the endolysin was at 37 °C/pH 7.0 and in the presence of ≥ 300 mM concentration of NaCl. Circular dichroism (CD) demonstrated a loss in secondary structure with an increase in temperature confirming the thermosensitive nature of endolysin. Antibacterial assays revealed that LysMR-5 was active against diverse clinical isolates of staphylococci. It showed high lytic efficacy against S. aureus ATCC 43300, as an endolysin concentration as low as 15 µg/ml was sufficient to achieve maximum lytic activity within 30 min and it was further confirmed by scanning electron microscopy. Our results indicate that rapid and strong bactericidal activity of LysMR-5 makes it a valuable candidate for eradicating multidrug-resistant S. aureus.

中文翻译：

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对抗甲氧西林耐药的金黄色葡萄球菌的有效酶制剂。

金黄色葡萄球菌是最可怕的感染因子之一，对人类和动物都具有很高的死亡率和发病率。多药耐药（MDR）金黄色葡萄球菌菌株的流行增加限制了可用的治疗选择的数量，这要求开发针对MDR金黄色葡萄球菌的替代和有效方式。内溶素是细菌噬菌体产生的抗菌剂，它们攻击肽聚糖中对于细菌存活至关重要的必需保守元素，使它们成为解决此类感染的有希望的替代品或补充剂。为了开发抗溶血素的溶素耐甲氧西林5（LysMR-5）作为有效的抗菌剂，我们评估了其理化特性，及其对葡萄球菌菌株（包括耐甲氧西林的金黄色葡萄球菌（MRSA））的固有抗菌活性。在这项研究中，我们从金黄色葡萄球菌噬菌体MR-5中克隆，表达和纯化了LysMR-5。在计算机分析中，LysMR-5具有两个催化和一个细胞壁结合域。生化特征和LC-MS分析表明，两个催化域均具有活性，并且对二价离子的作用不依赖，Zn2 +发挥了负面作用。内溶素的最佳裂解活性是在37°C / pH 7.0和存在浓度≥300 mM的NaCl的情况下。圆二色性（CD）随温度升高显示二级结构损失，证实了溶血素的热敏性质。抗菌测定显示LysMR-5对多种葡萄球菌临床分离株具有活性。它显示出针对金黄色葡萄球菌ATCC 43300的高溶解效力，因为低至15 µg / ml的内溶素浓度足以在30分钟内达到最大溶解活性，并且通过扫描电子显微镜进一步证实。我们的结果表明，LysMR-5具有快速而强大的杀菌活性，使其成为消除具有多重耐药性的金黄色葡萄球菌的有价值的候选者。