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Haematological, biochemical and immunological biomarkers, antibacterial activity, and survival in Nile tilapia Oreochromis niloticus after treatment using antimicrobial peptide LL-37 against Streptococcus agalactiae
Aquaculture ( IF 4.5 ) Pub Date : 2021-02-01 , DOI: 10.1016/j.aquaculture.2020.736181
Elielma Lima de Sousa , Inácio Mateus Assane , Norival Alves Santos-Filho , Eduardo Maffud Cilli , Raphael Barbetta de Jesus , Fabiana Pilarski

Abstract Among the antimicrobial peptides (AMPs), which act as natural antibiotics in preventing the colonization of pathogens, LL-37 is noteworthy. It is a human cathelicidin characterized as a broad-spectrum antibiotic, with chemotactic and immunomodulatory properties. This study aimed to evaluate the antimicrobial activity and therapeutic effectiveness of peptide LL-37 against streptococcosis caused by Streptococcus agalactiae in Nile tilapia and to assess some of its potential adverse effects (in vivo haematological, biochemical, and immunological profiles) in the fish. After in vitro cytotoxicity studies of LL-37 against Nile tilapia red blood cells (RBCs) and antimicrobial susceptibility testing (minimum inhibitory concentration and minimum bactericidal concentration, MIC and MBC, respectively) against Aeromonas hydrophila and S. agalactiae, fish were divided into six experimental groups. G1 and G2 were challenged by intraperitoneal injection with S. agalactiae and received a single oral dose of LL-37 (15 mg/kg bw) and florfenicol (FFC) (15 mg/kg bw), respectively. G3 was challenged with S. agalactiae and received a single intraperitoneal dose of LL-37 (15 mg/kg bw). The other groups were controls for infection (G4) and antimicrobial administration (G5 and G6). LL-37 showed weak hemolytic activity against Nile tilapia RBCs (24.4% lysis at 625 μg/mL) and strong in vitro antimicrobial activity against S. agalactiae (MIC and MBC = 31.25 μg/mL). No significant effects were observed in the haematological, biochemical, and immunological profiles of fish medicated with LL-37 or FFC, compared to the control fish. Twenty days after the challenge, survival rates were 33.38% (G1), 38.51% (G2), 23.12% (G3), 25% (G4), and 100% (G5 and G6). Despite the strong in vitro antimicrobial activity, both antimicrobials were ineffective to control streptococcosis caused by S. agalactiae in Nile tilapia. These findings suggest that administration of LL-37 (15 mg/kg bw) is safe for Nile tilapia but not effective to control streptococcosis.

中文翻译:

使用抗无乳链球菌的抗菌肽 LL-37 处理尼罗罗非鱼 Oreochromis niloticus 后的血液学、生化和免疫学生物标志物、抗菌活性和存活率

摘要 在作为天然抗生素防止病原体定植的抗菌肽 (AMP) 中,LL-37 值得注意。它是一种人类导管素,其特征是广谱抗生素,具有趋化和免疫调节特性。本研究旨在评估肽 LL-37 对尼罗罗非鱼中由无乳链球菌引起的链球菌病的抗菌活性和治疗效果,并评估其对鱼的一些潜在不良影响(体内血液学、生化和免疫学特征)。在 LL-37 对尼罗罗非鱼红细胞 (RBC) 的体外细胞毒性研究和对嗜水气单胞菌和无乳链球菌的抗微生物药敏试验(分别为最低抑菌浓度和最低杀菌浓度,MIC 和 MBC)后,鱼被分成六个实验组。G1 和 G2 通过腹腔注射无乳链球菌进行攻击,并分别接受单次口服剂量的 LL-37(15 毫克/千克体重)和氟苯尼考(FFC)(15 毫克/千克体重)。G3 接受无乳链球菌攻击并接受单次腹膜内剂量的 LL-37(15 毫克/千克体重)。其他组是感染(G4)和抗菌素给药(G5和G6)的对照。LL-37 对尼罗罗非鱼 RBC 显示出微弱的溶血活性(625 μg/mL 时 24.4% 裂解)和对无乳链球菌的强体外抗菌活性(MIC 和 MBC = 31.25 μg/mL)。与对照鱼相比,在用 LL-37 或 FFC 治疗的鱼的血液学、生化和免疫学特征中没有观察到显着影响。攻击后 20 天,存活率为 33.38% (G1)、38.51% (G2)、23.12% (G3)、25% (G4) 和 100% (G5 和 G6)。尽管在体外具有很强的抗菌活性,但这两种抗菌剂都不能有效控制尼罗罗非鱼中由无乳链球菌引起的链球菌病。这些发现表明,给予 LL-37(15 毫克/千克体重)对尼罗罗非鱼是安全的,但对控制链球菌病无效。
更新日期:2021-02-01
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