Some factors affecting the potency of Yersinia ruckeri bacterins

Abstract

Several factors affecting the potency of Yersinia ruckeri bacterins were evaluated by vaccinating rainbow trout, Salmo gairdneri Richardson, with various bacterins using the immersion method and determining the level of protective immunity after a virulent challenge. The potency of bacterins prepared with tryptic soya broth at room temperature was not affected by growth at pH from 6-5 to 7-7 or by a culture age from 9 to 96 h. Chloroform and formalin inactivated (0 3%) bacterins gave comparable results and no enhancement of potency occurred by prior extraction of bacterial cells with either butanol or phenol. Cell lysis, as measured by reduced optical density, occurred when cells were held at pH9-8 for 60 to 120 min. Bacterins prepared from pH-lysed cells resulted in a significant increase in protective immunity. Bacterins prepared at pH 7-2 for 48 h, pH-Iysed and inactivated with 0 3 % formalin could be diluted up to 1:100 without loss of efficacy when applied to rainbow trout by a single 20 s immersion. However, with bacterin diluted 1:10 loss of potency occurred after 20 consecutive immersions (100 kg of fish) in the same bacterin at a rate of 0 5 kg/1 of diluted bacterin for each immersion. Factors affecting optimum duration of immunity are discussed.

Passive transfer of specific maternal immunity does not protect Atlantic salmon (Salmo salarL.) fry against yersiniosis

“…However, protection against furunculosis in fry from vaccinated mothers has also been reported in a salmonid species, the white-spotted char (Salvelinus leocomaenis), by Kawahara et al (1993). A possible explanation for this discrepancy might be that resistance against the bacterial infection yersiniosis requires relatively high levels of antibodies against the lipopolysaccharides (LPS), which are the protective antigens (Amend et al, 1983). Moreover, in addition to antibodies against LPS, contributions from other components of the immune system, in particular the phagocytic system, are probably necessary in order to inactivate Y. ruckeri.…”

Antigens ofEdwardsiella ictalurirecognised by serum antibodies from naturally infected channel catfish

“…Moreover, LPS molecules are important antigens in other fish diseases, and are the protective antigens in the Vibrio sp. and Yersinia ruckeri vaccines used in salmonids (Amend et al, 1983;Ellis, 1988). It is unknown if antibodies against the LPS of E. ictaluri are protective in naturally exposed fish.…”

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

“…From the virulence and antigenic data, it appears that the LPS structure is the dominant protective antigen in Y. ruckeri vaccines. Indeed, LPS was considered to be the dominant immunogenic molecule in formalin‐killed vaccine preparations for ERM (Amend et al. 1983).…”