To investigate the activity of a novel thiopeptide antibiotic nocathiacin against clinically isolated Gram-positive bacteria comparing with those commonly used antibiotics. Methods: MIC (Minimal Inhibitory Concentration) was determined by a two - fold agar dilution method. MBC (Minimal Bactericidal Concentration) was determined by a micro-broth dilution method. ED50 was determined by an infection-protection method. Results: Nocathiacin showed strong activities against MRSA and PRSP. MIC50 against MRSA, MSSA, MRSE, MSSE, PRSP/PISP, Streptococcus pyogenes, Enterococcus were 0.016, 0.016, 0.0625, 0.03125, 0.008, 0.008, 0.016 mg·L-1, respectively. Its MIC50 was 1/32~1/128 of vancomycin, 1/4~1/256 of moxifloxacin and 1/32~1/256 of linezolid, respectively. After intravenous injection, nocathiacin showed lower ED50 and stronger protective effect on infected mice than vancomycin or linezolid. Conclu-sions: Thiopeptide antibiotic nocathiacin has high antibacterial activities, which is obviously superior to vancomycin, linezolid and moxifloxacin, and there is no cross drug-resistance between them.%目的：研究新型硫肽类抗生素诺卡沙星对临床常见革兰阳性致病菌的抗菌活性，探讨其抗菌机制，并与临床常用抗生素进行比较。方法：采用琼脂二倍稀释法测定最低抑菌浓度（Minimal Inhibition Concentration，MIC），采用微量肉汤二倍稀释法测定最低杀菌浓度（Minimal Bactericidal Concentration，MBC），采用小鼠体内抗菌保护实验测定体内抗菌活性。结果：诺卡沙星对甲氧西林耐药的葡萄球菌、青霉素耐药的肺炎球菌均显示较强的抗菌活性，对金黄色葡萄球菌MRSA、MSSA，表皮葡萄球菌MRSE、MSSE的MIC50值分别为0.016、0.016、0.0625、0.03125 mg· L-1，对肺炎球菌（PRSP/PISP）、化脓性链球菌、肠球菌的MIC50值为0.008、0.008、0.016 mg·L-1，其MIC50值为万古霉素的1/32~1/128，为莫西沙星的1/4~1/256，为利奈唑胺的1/32~1/256。注射用诺卡沙星经静脉给药后，对金黄色葡萄球菌感染小鼠均呈现体内保护作用，其ED50值明显低于对照药万古霉素和利奈唑胺，体内抗菌保护作用优于对照药。结论：诺卡沙星具有高效抗菌作用，明显优于万古霉素、利奈唑胺及莫西沙星，且与它们之间无交叉耐药现象。
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