Streptococcus parauberis is a pathogenic gram-positive bacterium that causes streptococcosis infection in fish. Since S. parauberis is becoming resistant to multiple antibiotics, the development of alternatives, such as antimicrobial peptides, has gained great attention. Octominin, derived from the defense protein of Octopus minor, showed a significant antimicrobial activity against multidrug resistance S. parauberis, with a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of 50 and 100 μg/mL, respectively. Furthermore, time-kill kinetics, agar diffusion, and bacterial viability assays confirmed the concentration-dependent antibacterial activity of Octominin against S. parauberis. Field emission scanning electron microscopy analysis showed morphological and ultra-structural changes in S. parauberis upon Octominin treatment. Moreover, Octominin treatment demonstrated changes in membrane permeability, induced reactive oxygen species (ROS), and its binding ability to genomic DNA, suggesting its strong bactericidal activity with multiple modes of action. We confirmed the inhibition of biofilm formation and the eradication of existing biofilms in a concentration-dependent manner. Additionally, Octominin on S. parauberis at transcriptional level exhibited downregulation of membrane formation (pgsA and cds1), DNA repairing (recF), biofilm formation (pgaB and epsF) genes, while upregulation of ROS detoxification (sodA) and DNA protecting (ahpF) related genes. An in vivo study confirmed a significantly (P < 0.05) higher relative percentage survival in Octominin-treated larval zebrafish exposed to S. parauberis (93.3%) compared to the control group (20.0%). Collectively, our results confirm that Octominin could be a potential antibacterial and anti-biofilm agent against S. parauberis.

副链球菌是致病的革兰氏阳性细菌，可引起鱼类链球菌感染。由于伞形链球菌对多种抗生素具有抗药性，因此诸如抗菌肽之类的替代品的开发引起了极大的关注。来源于小章鱼防御蛋白的八丁胺具有显着的抗多药链霉菌抗微生物活性，其最低抑菌浓度（MIC）和最低杀菌浓度（MBC）分别为50和100μg/ mL。此外，时间杀灭动力学，琼脂扩散和细菌生存力测定证实了Octominin对副链球菌的浓度依赖性抗菌活性。。场发射扫描电子显微镜分析表明形态和超结构变化S. parauberis时Octominin治疗。此外，Octominin处理显示出膜通透性，诱导的活性氧（ROS）及其与基因组DNA的结合能力的变化，表明其具有多种作用方式的强杀菌活性。我们证实了对生物膜形成的抑制和以浓度依赖的方式消除了现有的生物膜。此外，S上的Octominin 。在转录水平上的伞形虫表现出下调的膜形成（pgsA和cds1），DNA修复（recF），生物膜形成（pgaB和epsF）基因，同时上调ROS解毒（sodA）和DNA保护（ahpF）相关基因。的体内研究证实一个显著（P <0.05）相对较高百分比在暴露于Octominin处理的幼虫存活的斑马鱼S. parauberis（93.3％）相比于对照组（20.0％）。总体而言，我们的研究结果证实，Octominin可能是针对伞形旁链球菌的潜在抗菌和抗生物膜剂。