One of the major goals in aquaculture is to protect fish against infectious diseases as disease outbreaks could lead to economic losses if not controlled. Antimicrobial peptides (AMPs), a class of highly conserved peptides known to possess direct antimicrobial activities against invading pathogens, were evaluated for their ability to protect Channel Catfish Ictalurus punctatus and hybrid catfish (female Channel Catfish × male Blue Catfish I. furcatus) against infection caused by the fish pathogen Aeromonas hydrophila ML09-119. To identify effective peptides, the minimum inhibitory concentrations against bacterial pathogens Edwardsiella ictaluri S97-773, Edwardsiella piscicida E22-10, A. hydrophila ML09-119, Aeromonas veronii 03X03876, and Flavobacterium columnare GL-001 were determined in vitro. In general and overall, cathelicidins derived from alligator and sea snake exhibited more potent and rapid antimicrobial activities against the tested catfish pathogens as compared to cecropin and pleurocidin AMPs and ampicillin, the antibiotic control. When the peptides (2.5 µg of peptide/g of fish) were injected into fish and simultaneously challenged with A. hydrophila through immersion, increased survival rates in Channel Catfish and hybrid catfish were observed in both cathelicidin (alligator and sea snake) treatments as compared to other peptides and the infected control (P < 0.001) with alligator cathelicidin being the overall best treatment. Bacterial numbers in the kidney and liver of Channel Catfish and hybrid catfish also decreased (P < 0.05) for cathelicidin-injected groups at 24 and 48 h after challenge infection. These results show the potential of cathelicidin to protect catfish against bacterial infections and suggest that an approach overexpressing the peptide in transgenic fish, which is the long-term goal of this research program, may provide a method of decreasing bacterial disease problems in catfish as delivering the peptides via individual injection or feeding would not be economically feasible.

中文翻译：

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Cathelicidin 抗菌肽对 Ictalurid 鲶鱼细菌病原体的有效性

水产养殖的主要目标之一是保护鱼类免受传染病的侵害，因为如果不加以控制，疾病爆发可能会导致经济损失。抗菌肽 (AMP) 是一类高度保守的肽，已知对入侵的病原体具有直接抗菌活性，评估了它们保护沟鲶Ictalurus punctatus和杂交鲶鱼（雌性沟鲶×雄性蓝鲶I. furcatus）免受感染的能力由鱼类病原体嗜水气单胞菌ML09-119 引起。确定有效肽，对细菌病原体Edwardsiella ictaluri S97-773、Edwardsiella piscicida的最低抑制浓度E22-10，嗜水气单ML09-119，气单胞菌维罗纳03X03876和柱状黄杆菌GL-001在体外进行测定。总的来说，与天蚕素和截短链球菌素 AMPs 以及氨苄青霉素（抗生素对照）相比，来自鳄鱼和海蛇的导管素对测试的鲶鱼病原体表现出更有效和更快速的抗菌活性。当将肽（2.5 µg 肽/g 鱼）注射到鱼体内并同时通过浸泡攻击嗜水 A.对其他肽和受感染的对照（P < 0.001)，鳄鱼导管素是总体最佳处理。 在攻击感染后 24 和 48 小时，导管素注射组的鲶鱼和杂交鲶鱼肾脏和肝脏中的细菌数量也减少（P < 0.05）。这些结果显示了 cathelicidin 保护鲶鱼免受细菌感染的潜力，并表明在转基因鱼中过表达肽的方法，这是该研究计划的长期目标，可以提供一种减少鲶鱼细菌疾病问题的方法，因为通过单独注射或喂食的肽在经济上是不可行的。