EFFICACY OF INTRAPERITONEAL AND IMMERSION VACCINATION AGAINST ENTEROCOCCUS SP, INFECTION IN TURBOT

In this study the effectiveness of a toxoid-enriched whole-cell bacter in (ET-2) in cultured turbot (Scophthalmus maximus) against Enterococc us sp. was evaluated by bath immersion and intraperitoneal (i.p.) inje ction. In addition, the influences of fish size as well as enrichment of the standard semimoist diet with the commercial preparation Trouvit ol plus(R), which contains beta-glucan from yeast, were also investiga ted. Regardless of fish size, type of diet, and bacterial dose employe d in the experimental challenges, our Enterococcus bacterin ET-2 prove d to be very effective when it was delivered by injection. The RPS (re lative percent of survival) values achieved by this route ranged from 89 to 100 (for 45-g turbot) and from 67 to 86 (for 150-g turbot), depe nding on the bacterial levels and time of experimental challenge. More over, this strong degree of protection lasted for at least 1 year. No circulating antibodies were detected in the vaccinated turbot. However , the injected bacterin, irrespective of the diet utilized, elicited a significant (P < 0.01) increase of the phagocytic activity in the spl een. Although the glucan alone also induced an enhancement of the non- specific defence mechanisms, this stimulation was not correlated with the protection of turbot against Enterococcus infection.