Abstract：
Piscine francisellosis is one of the most important bacterial diseases affecting various fish species worldwide. Francisella orientalis, F. noatunensis, and F. salimarina (F. marina) have been reported as etiological agents of disease in fish. A Francisella sp. was isolated from several diseased red drum Sciaenops ocellatus experiencing morbidity in Florida, USA, in 2008. In this study, molecular and phenotypic characterization of the recovered isolate was conducted. Phenotypically, the isolate showed a biochemical reaction profile distinct from that of F. orientalis and F. salimarina. Although the 16S rRNA sequence of this isolate shared 99.61% identity to the type strain of F. philomiragia O#319LT, whole genome analysis (average nucleotide identity <95%; digital DNA-DNA hybridization <70%) and a multilocus sequence analysis of 8 concatenated housekeeping genes in comparison with other Francisella spp. indicated that this isolate was a novel Francisella species, more closely related to F. orientalis. Immersion, intracoelomic injection, and co-habitation challenges using a Nile tilapia Oreochromis niloticus fingerling model of infection were done to investigate virulence in a piscine model. Variably pigmented granulomas and pigmented macrophage aggregates were observed in the kidneys and spleens of the challenged fish, but no mortality was recorded during the 15 d challenge period, suggesting that this novel Francisella sp. might be an opportunistic pathogen of fish. Based on the phenotypic and genotypic differences from other Francisella spp. observed in this study, we propose the name Francisella sciaenopsi sp. nov. for this novel isolate.
摘要：
Piscinefrancissellosis病是影响全球各种鱼类的最重要的细菌疾病之一。东方弗朗西拉，F.诺顿，和F.salimarina(F.码头）已被报道为鱼类疾病的病原体。Francisellasp.从佛罗里达州几个患病的红鼓Sciaenopsocellatus中分离出来，美国,2008年。在这项研究中,对回收的分离物进行了分子和表型表征。表型，该分离物显示出与东方F.和salimarina不同的生化反应谱。尽管该分离株的16SrRNA序列与嗜血杆菌O#319LT型菌株具有99.61%的同一性，与其他Francisellaspp相比，全基因组分析（平均核苷酸同一性<95％；数字DNA-DNA杂交<70％）和8个串联管家基因的多位点序列分析。表明该分离株是一种新颖的Francisella物种，与东方F.更密切相关。Immersion,体内注射，使用尼罗罗非鱼罗非鱼鱼种感染模型进行了同居攻击，以研究猪模型中的毒力。在受攻击的鱼的肾脏和脾脏中观察到不同的色素肉芽肿和色素巨噬细胞聚集体，但是在15d的攻击期间没有记录到死亡率，这表明这部小说Francisellasp。可能是鱼类的机会病原体。基于与其他Francisellaspp的表型和基因型差异。在这项研究中观察到，我们提议叫Francisellasciaenopsisp。11月。对于这个新颖的孤立。
