Experimental infection of Flavobacterium psychrophilum in fins of Atlantic salmon Salmo salar revealed by scanning electron microscopy

Diseases of Aquatic Organisms

Alín Casado¹  Ricardo Enríquez¹  Juan Luis Martínez¹ 

关键词: Flavobacterium psychrophilum;    Scanning electron microscopy;    Salmonid;    Fin rays;    Pathogenesis;    Bacterial coldwater disease (BCWD);    Rainbow trout fry syndrome (RTFS);   

DOI  :  10.3354/dao059079

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: Infections caused by Flavobacterium psychrophilum include Œbacterial coldwater disease¹ (BCWD) and Œrainbow trout fry syndrome¹ (RTFS), which are severe diseases that can cause high mortality and significant losses in hatchery-rearedsalmonids worldwide. Usually, these conditions start with necrosis along the edge of the fins. As the infection progresses, both the fish surface and the internal organs can be involved. The aetiological agent produces a Ca-dependent protease that can beresponsible for some of the pathogenic responses, although the precise nature of the response remains to be elucidated. Atlantic salmon Salmo salar were experimentally infected by F. psychrophilum in order to investigate the bacterialinvasion in the fin tissues by scanning electron microscopy. The images showed numerous bacteria embedded in the mucous layer when this remained on the tegument. In other zones without mucus, it was observed that bacteria were present on the axis of finrays, but not on the epidermal surface. The material on these axes was largely eroded by tubular boreholes, and bacterial rods could be seen in these perforations. EDX (Energy Dispersive X-ray) microanalysis of the axis of the fin rays showed significantamounts of P and Ca, revealing the ossification of the ray axis. The protease activity could explain the formation of the tubular boreholes, allowing the bacteria the necessary Ca for the activation of the enzyme. The erosion pattern suggests that thegliding motility of F. psychrophilum could be involved in this burrowing ability.

【 授权许可】

Unknown