The antimicrobial activity of tilapia piscidin 4 (TP4) was determined in vitro against four bacterial strains, Aeromonas hydrophilla, Pseudomonas fluorescens, Streptococcus iniae and Vibrio anguillarum. Nile tilapia were infected with low and high doses of the tested pathogens; after 3, 6, 24 h and 7 days of the specific TP4 gene expression, tissue immunolocalization was also performed. Histopathological examination revealed septicaemia and necrosis of hemopoietic tissue for all of the tested bacteria. Immunolocalization showed abundance in S. iniae-infected fish tissues. Quantitative RT-PCR analysis revealed that high doses raised mRNA expression levels compared to low doses and expression levels increased in the infected fish, particularly after 24 h, indicating that TP4 exerts potent bactericidal activity against some fish pathogens and plays an essential role in fish immunity.

罗非鱼 piscidin 4 (TP4)对四种细菌菌株的体外抗菌活性进行了测定，这些菌株是嗜水气单胞菌、荧光假单胞菌、链球菌和鳗鱼。尼罗罗非鱼感染了低剂量和高剂量的测试病原体；特异TP4基因表达3、6、24小时和7天后，还进行了组织免疫定位。组织病理学检查显示所有受试细菌的造血组织均出现败血症和坏死。免疫定位显示S. iniae-受感染的鱼组织。定量 RT-PCR 分析显示，与低剂量相比，高剂量提高了 mRNA 表达水平，感染鱼的表达水平增加，尤其是在 24 小时后，表明 TP4 对某些鱼类病原体发挥强效杀菌活性，并在鱼类免疫中发挥重要作用.