BACKGROUND Francisella noatunensis subsp. orientalis (Fno) is the etiological agent of francisellosis in cultured warm water fish, such as tilapia. Antibiotics are administered to treat the disease but a better understanding of Fno infection biology will inform improved treatment and prevention measures. However, studies with native hosts are costly and considerable benefits would derive from access to a practical alternative host. Here, larvae of Galleria mellonella were assessed for suitability to study Fno virulence. RESULTS Larvae were killed by Fno in a dose-dependent manner but the insects could be rescued from lethal doses of bacteria by antibiotic therapy. Infection progression was assessed by histopathology (haematoxylin and eosin staining, Gram Twort and immunohistochemistry) and enumeration of bacteria recovered from the larval haemolymph on selective agar. Fno was phagocytosed and could survive intracellularly, which is consistent with observations in fish. Virulence of five Fno isolates showed strong agreement between G. mellonella and red Nile tilapia hosts. CONCLUSIONS This study shows that an alternative host, G. mellonella, can be applied to understand Fno infections, which will assist efforts to identify solutions to piscine francisellosis thus securing the livelihoods of tilapia farmers worldwide and ensuring the production of this important food source.

中文翻译：

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大蜡蛾幼虫是鱼类致病菌弗朗西斯菌（attis）noatunensis亚种的合适替代寄主。东方人。

背景弗朗西斯菌noatunensis亚种。Orientalis（Fno）是养殖温水鱼（例如罗非鱼）中龟头癣的病原体。可以使用抗生素治疗该疾病，但是对Fno感染生物学的更好了解将有助于改善治疗和预防措施。但是，使用本地宿主进行研究的成本很高，而获得实用的替代宿主将带来可观的收益。在这里，评估了拱廊的幼虫是否适合研究Fno毒力。结果Fno以剂量依赖的方式杀死幼虫，但可以通过抗生素治疗从致死剂量的细菌中拯救昆虫。通过组织病理学（苏木精和曙红染色，革兰氏Twort和免疫组织化学）和从选择性琼脂上幼虫血淋巴中回收的细菌计数。Fno被吞噬并可以在细胞内存活，这与在鱼类中观察到的一致。五个Fno分离株的毒力显示了G. mellonella和红色尼罗罗非鱼宿主之间的强烈一致性。结论该研究表明，可以将另一种寄主G. mellonella应用于了解Fno感染，这将有助于努力确定解决猪败血症的解决方案，从而确保全世界罗非鱼养殖者的生计并确保这种重要食物的生产。mellonella和红色尼罗罗非鱼寄主。结论该研究表明，可以将另一种寄主G. mellonella应用于了解Fno感染，这将有助于努力确定解决猪败血症的解决方案，从而确保全世界罗非鱼养殖者的生计并确保这种重要食物的生产。mellonella和红色尼罗罗非鱼寄主。结论这项研究表明，可以将另一种寄主G. mellonella应用于了解Fno感染，这将有助于努力确定解决猪败血症的解决方案，从而确保全世界罗非鱼养殖者的生计并确保这种重要食物的生产。