3D Visualization of the Initial Yersinia ruckeri Infection Route in Rainbow Trout (Oncorhynchus mykiss) by Optical Projection Tomography

Abstract

Despite the fact that enteric redmouth disease (ERM) in farmed rainbow trout is one of the most devastating disease problems, little is known about the initial route of infection and pathogenicity of the aetiological agent, Yersinia ruckeri. In order to determine the initially infected organs, optical projection tomography (OPT), a novel three-dimensional (3D) bio-imaging technique, was applied. OPT not only enables the visualization of Y. ruckeri on mucosal surfaces but also the 3D spatial distribution in whole organs, without sectioning. Rainbow trout were infected by bath challenge exposure to 1×108 CFU/ml of Y. ruckeri O1 for 1 hour. Three fish were sampled for OPT and immunohistochemistry (IHC) 1, 10 and 30 minutes, 1, 3, 6, 12 and 24 hours, as well as 2, 3, 7 and 21 days after the start of the infection period. Y. ruckeri was re-isolated from the blood of infected fish as early as 1 minute post infection. Both OPT and IHC analysis confirmed that the secondary gill lamellae were the only tissues infected at this early time point, indicating that Y. ruckeri initially infects gill epithelial cells. The experimentally induced infection caused septicemia, and Y. ruckeri was found in all examined organs 7 days post infection including the brain, which correlated with the peak in mortality. To the best of our knowledge this is the first description of Y. ruckeri infection in the brain, which is likely to cause encephalitis. This in part could explain the lethality of ERM in rainbow trout. Using OPT scanning it was possible to visualize the initial route of entry, as well as secondary infection routes along with the proliferation and spread of Y. ruckeri, ultimately causing significant mortality in the exposed rainbow trout. These results demonstrate that OPT is a state-of-the-art technique capable of visualizing pathogenesis at high resolution.

B cells and their role in the teleost gut

“…Its preferential mode of entry is through the gills, but it has also been described to infect the intestine through the mucosal tissue (Ohtani et al, 2014; Tobback et al, 2009, 2010). Despite these findings, few studies have described the immune response against ERM in fish GALT.…”

Comparison of Two Chemically-Induced Colitis-Models in Adult Zebrafish, Using Optical Projection Tomography and Novel Transcriptional Markers

“…cytokines, transcription factors, acute-phase proteins, Toll-like receptors. Additionally, we have visualized the presence of serotonin in intestinal cells in zebrafish using optical projection tomography, a bioimaging method based on the use of specific antibodies that only recently have been implemented in fish immunology studies [14] [15]. Serotonin (5-HT) is a ubiquitous and highly conserved neurotransmitter that plays a pivotal role in a variety of behaviors (e.g.…”

Experimental infection by Yersinia ruckeri O1 biotype 2 induces brain lesions and neurological signs in rainbow trout (Oncorhynchus mykiss)

“…Up until now, literature describing Y. ruckeri infection in the CNS in rainbow trout has followed infection with virulent serotype O1 biotype 1 (Ferguson, ; Ohtani et al., ; Roberts, ). It has been demonstrated that Y. ruckeri serotype O1 biotype 1 strain 293/2003 appeared in the CNS at 7 dpi in rainbow trout fry following waterborne challenge, when fish suffered from systemic infection (Ohtani et al., ).…”