The Infection Process of Yersinia ruckeri: Reviewing the Pieces of the Jigsaw Puzzle.

José A Guijarro,Desirée Cascales,Ana I García-Torrico,Jessica Méndez

doi:10.3389/fcimb.2018.00218

José A Guijarro, Desirée Cascales + Show 2 more

Open Access

https://doi.org/10.3389/fcimb.2018.00218

Copy DOI

Abstract

Finding the keys to understanding the infectious process of Yersinia ruckeri was not a priority for many years due to the prompt development of an effective biotype 1 vaccine which was used mainly in Europe and USA. However, the gradual emergence of outbreaks in vaccinated fish, which have been reported since 2003, has awakened interest in the mechanism of virulence in this pathogen. Thus, during the last two decades, a large number of studies have considerably enriched our knowledge of many aspects of the pathogen and its interaction with the host. By means of both conventional and a variety of novel strategies, such as cell GFP tagging, bioluminescence imaging and optical projection tomography, it has been possible to determine three putative Y. ruckeri infection routes, the main point of entry for the bacterium being the gill lamellae. Moreover, a wide range of potential virulence factors have been highlighted by specific gene mutagenesis strategies or genome-wide transposon/plasmid insertion-based screening approaches, such us in vivo expression technology (IVET) and signature tagged mutagenesis (STM). Finally, recent proteomic and whole genomic analyses have allowed many of the genes and systems that are potentially implicated in the organism's pathogenicity and its adaptation to the host environmental conditions to be elucidated. Altogether, these studies contribute to a better understanding of the infectious process of Y. ruckeri in fish, which is crucial for the development of more effective strategies for preventing or treating enteric redmouth disease (ERM).

Highlights

Yersinia ruckeri is able to infect different fish species such as carp, catfish, sturgeon, perch and burbot (Tobback et al, 2007; Kumar et al, 2015), it mainly affects salmonids
The most important pathway for the development of enteric red mouth disease (ERM) has still to be elucidated, but it seems clear that, the primary bacteremia is generated by the entry of the bacterium into the fish through the gills, the very significant presence of the bacterium in the intestine and the signs of the disease, strongly suggest that the digestive route must play a relevant role
A temperature below the optimal for bacterial growth and close to the one at which outbreaks occur seems to be important in the expression of some of the genes encoding virulence factors

Summary

Introduction

Yersinia ruckeri is able to infect different fish species such as carp, catfish, sturgeon, perch and burbot (Tobback et al, 2007; Kumar et al, 2015), it mainly affects salmonids. It was shown that production of the siderophore is upregulated during the infection of fish (Fernandez et al, 2004; Fernández et al, 2007a) and it is involved in virulence since 100-fold attenuation, in relation to the parental strain, was obtained when an isogenic mutant in rucC, a gene from the ruckerbactin cluster, was used in LD50 experiments (Fernandez et al, 2004).

Results

Conclusion