Nisin is a promising therapeutic candidate because of its potent activity against Gram-positive bacteria. The present study aimed to describe the in vitro and in vivo antibacterial effects of nisin against Streptococcus suis, an important zoonotic pathogen. The minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) of nisin against different S. suis strains ranged from 0.12 to 4.0 μg/mL and from 0.25 to 8.0 μg/mL, respectively. Time-killing curve assays illustrated that nisin killed 100% of tested virulent S. suis strains within 4 h when used at 2× MIC, which indicates the rapid bactericidal activity of nisin against the bacteria. Transmission and scanning electron microscopy revealed that nisin destroyed S. suis cell membrane integrity and affected its cellular ultrastructure, including a significantly wrinkled surface, intracellular content leakage, and cell lysis. In addition, nisin inhibited biofilm formation by S. suis in a concentration-dependent manner and exhibited strong degrading activities against preformed biofilms. More importantly, nisin displayed antimicrobial activity against S. suis infection in vivo. Upon treatment with 5.0–10 mg/kg nisin solution, the survival rates of mice challenged with a lethal dose of virulent S. suis virulent ranged 87.5–100%. Nisin significantly decreased bacterial proliferation and translocation in the mouse spleen, brain, and blood. These results indicate that nisin has potential as a novel antimicrobial agent for the clinical treatment and prevention of infection caused by S. suis in animals.

Nisin 是一种很有前途的治疗候选药物，因为它对革兰氏阳性菌具有很强的活性。本研究旨在描述乳链菌肽对猪链球菌（一种重要的人畜共患病原体）的体外和体内抗菌作用。乳酸链球菌肽对不同猪链球菌菌株的最低抑菌浓度 (MIC) 和最低杀菌浓度 (MBC) 分别为0.12 至 4.0 μg/mL 和 0.25 至 8.0 μg/mL。时间杀灭曲线分析表明，当以 2 倍 MIC 使用时，乳酸链球菌肽在 4 小时内可杀死 100% 的测试毒力猪链球菌菌株，这表明乳酸链球菌肽对细菌的快速杀菌活性。透射和扫描电子显微镜显示乳链菌肽破坏了猪链球菌细胞膜完整性并影响其细胞超微结构，包括明显起皱的表面、细胞内内容物泄漏和细胞裂解。此外，乳链菌肽以浓度依赖的方式抑制猪链球菌的生物膜形成，并对预先形成的生物膜表现出强烈的降解活性。更重要的是，乳链菌肽在体内显示出对猪链球菌感染的抗菌活性。用 5.0–10 mg/kg 乳酸链球菌肽溶液处理后，用致死剂量的毒力猪链球菌攻击的小鼠的存活率毒性范围为 87.5-100%。Nisin 显着降低了小鼠脾脏、大脑和血液中的细菌增殖和易位。这些结果表明，乳酸链球菌肽具有作为一种新型抗菌剂的潜力，可用于临床治疗和预防由猪链球菌引起的动物感染。