Lloyd Sonja J, LaPatra Scott E, Snekvik Kevin R, St-Hilaire Sophie, Cain Kenneth D, Call Douglas R
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington 99164-7040, USA.
Dis Aquat Organ. 2008 Nov 20;82(2):111-8. doi: 10.3354/dao01969.
Strawberry disease (SD) in the USA is a skin disorder of unknown etiology that occurs in rainbow trout Oncorhynchus mykiss and is characterized by bright red inflammatory lesions. To identify a candidate bacterial agent responsible for SD, we constructed 16S rDNA libraries from 7 SD lesion samples and 2 apparently healthy skin samples from SD-affected fish. A 16S rDNA sequence highly similar to members of the order Rickettsiales was present in 3 lesion libraries at 1%, 32% and 54% prevalence, but this sequence was not found in either healthy tissue library. Based on phylogenetic analysis, this Rickettsia-like organism (RLO) sequence is most closely related to 16S rDNA sequences of bacteria that may form a novel lineage within the Rickettsiales. We used nested PCR assays to screen 25 SD-affected fish for RLO or Flavobacterium psychrophilum DNA. Sixteen lesion samples were positive for the RLO sequence and 4 of the matched healthy samples were positive resulting in a significant association between SD lesions and presence of RLO DNA. While F. psychrophilum is reportedly associated with 'cold water strawberry disease' in the UK, we found no significant association between SD lesions and the presence of F. psychrophilum DNA. The statistical association between SD lesions and presence of RLO DNA is not proof of etiology, but these data suggest that RLO may play a role in SD in southern Idaho, USA.
美国的草莓病（SD）是一种病因不明的皮肤疾病，发生在虹鳟鱼（Oncorhynchus mykiss）身上，其特征为鲜红色炎症性损伤。为了确定导致SD的候选细菌病原体，我们从7个SD损伤样本以及2个来自受SD影响鱼类的看似健康的皮肤样本构建了16S rDNA文库。在3个损伤文库中，存在一种与立克次氏体目成员高度相似的16S rDNA序列，其出现频率分别为1%、32%和54%，但在任何一个健康组织文库中均未发现该序列。基于系统发育分析，这种类立克次氏体生物（RLO）序列与可能在立克次氏体目内形成一个新谱系的细菌的16S rDNA序列关系最为密切。我们使用巢式PCR检测法对25条受SD影响的鱼进行RLO或嗜冷黄杆菌DNA筛查。16个损伤样本的RLO序列呈阳性，4个匹配的健康样本呈阳性，这表明SD损伤与RLO DNA的存在之间存在显著关联。虽然据报道嗜冷黄杆菌与英国的“冷水草莓病”有关，但我们发现SD损伤与嗜冷黄杆菌DNA的存在之间没有显著关联。SD损伤与RLO DNA存在之间的统计学关联并不能证明其病因，但这些数据表明RLO可能在美国爱达荷州南部的SD中起作用。
