Antigenic and cross-protection studies of biotype 1 and biotype 2 isolates of Yersinia ruckeri in rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract

Aims: The study investigated antigen characteristics of biotype (bt) 1 and bt 2 isolates of Yersinia ruckeri. Methods and Results: The cell surface characteristics of Y. ruckeri were compared for their antigenic characteristics using polyclonal antibodies that revealed that both biotypes had a homogenous whole‐cell protein antigenic profile. Notable differences in the antigenic properties were observed in the lipopolysaccharide profile of both biotypes. Two iron‐regulated outer membrane proteins (IROMP) of c. 90 and 100 kDa were shown to be major specific antigens. The results demonstrate for the first time differences in antigens between bt 1 and bt 2 isolates of serotype O1 isolates of Y. ruckeri. The protection induced in rainbow trout by a commercial monovalent, and bivalent inactivated vaccine was tested with the outcome that the ability of isolates to cause mortality in vaccinated fish varied with geographical location. In this context, vaccination studies suggested that the O antigen was the dominant immunogenic molecule involved in protection against the disease. Conclusions: The O antigen of Y. ruckeri was the dominant immunogenic molecule involved in the protection of rainbow trout against enteric redmouth disease. Significance and Impact of the Study: There are distinct phenotypic and antigenic differences in Y. ruckeri bt 1 and bt 2 with O antigen recognized as the dominant immunogenic molecule. The data have significance in explaining the lack of success of the earlier monovalent vaccine and demonstrate the effectiveness of the newer bivalent vaccine.

Yersinia ruckeri Isolates Recovered from Diseased Atlantic Salmon (Salmo salar) in Scotland Are More Diverse than Those from Rainbow Trout (Oncorhynchus mykiss) and Represent Distinct Subpopulations

“…However, it is also notable that Y. ruckeri strains isolated from Atlantic salmon in Australia and Chile are also members of biotype 1 and not biotype 2 (7,9). It has been postulated that vaccination may be providing the selective pressure that is driving the loss of flagellar motility in Y. ruckeri (20,42). If this is the case, it is surprising that biotype 2 has emerged in rainbow trout but not in Atlantic salmon because Atlantic salmon are generally vaccinated with the same serotype O1-based vaccines as those used for rainbow trout (9).…”

“…In this scheme, five O serotypes, O1, O2, O5, O6, and O7, are recognized by rapid slide agglutination assay using defined O antigens (14); the individual O serotypes correspond to discrete lipopolysaccharide (LPS) types as identified by SDS-PAGE and Western blotting (18). It is well established that serotype O1 strains of Y. ruckeri are responsible for the majority of disease outbreaks in rainbow trout worldwide (3,14,(19)(20)(21). However, yersiniosis of Atlantic salmon in Australia (7,8) and Chile (9) is associated with a serotype O1 subtype (O1b).…”

“…Since the first identification of biotype 2 isolates in the United Kingdom, nonmotile variants have been described elsewhere in Europe (16,17,(23)(24)(25), the United States (26), and Australia (7). Indeed, biotype 2 Y. ruckeri strains are causing increasing concern because they are responsible for disease in fish previously vaccinated against biotype 1 strains (17,20,23,26,27). A typing scheme based on the molecular mass variation of the major outer membrane proteins (OMPs) was developed to further differentiate between strains of Y. ruckeri (28).…”

Analysis of Yersinia ruckeri strains isolated from trout farms in northwest Germany

“…The disease was initially controlled by vaccines prepared with classical motile Y. ruckeri strains (Johnson & Amend 1983), but after appearance and spreading of non-motile variants, the vaccine failed to control infections in Europe (Austin et al 2003, Wheeler et al 2009) and the USA (Arias et al 2007). With the inclusion of both types of strains into the vaccine preparation, an enhancement of protection was achieved (Tinsley et al 2011), but despite the use of those bivalent vaccines, ERM outbreaks occurred in vaccinated Atlantic salmon in Chile (Bastardo et al 2011, Navas et al 2014 as well as in European rainbow trout stocks. In 4 trout farms from the present study, the stocks were vaccinated with a bivalent vaccine, and in 3 of these farms, ERM outbreaks caused by non-motile strains were observed during several sampling campaigns.…”

Improving disease prevention and treatment in controlled fish culture

“…About 13 fish species have been found to be susceptible to infection by Y. ruckeri, as are some mammals (muskrat, Ondatra zibethicus) and birds (European herring gull, Larus argentatus). Humans (Homo sapiens) are also susceptible to this infection (Pêkala 2010, Tinsley 2010, Sudheesh et al 2012 (Koziñska and Pêkala 2004, Bernad 2013, Koziñska et al 2013, Pêkala et al 2015a, Bernad et al 2016a.…”