THE IMMUNOPROTECTION OF STENOTROPHOMONAS MALTOPHILIA LIPOPOLYSACCHARIDE IN CHANNEL CATFISH

Stenotrophomonas maltophilia is a vital pathogenic bacteria of a high-lethal infectious diseases affecting channel catfish (Ictalurus punctatus) in recent years. In order to evaluate the immune protective effect of Stenotrophomonas maltophilia lipopolysaccharide (LPS) on channel catfish, four hundred healthy channel catfish were chosen and divided into , , and groups randomly. Each group included Ⅰ Ⅱ Ⅲ Ⅳ two horizontal treatments which were treated with LPS, LPS plus polysaccharide of Ficus carica, whole cell inactivated vaccine and the saline source respectively by intraperitoneal injection. The initial immunization was carried out at the beginning and so was the booster immunization at the 28th day. During the trial period, the blood leukocyte bactericidal activity, complement C3 levels, IgM levels and agglutinating antibody titers were determined at intervals of 7 days. The challenge with live Stenotrophomonas maltophilia was carried out at the 49th day. The results showed that the agglutinating antibody titers in the sera of channel catfish treated with LPS and LPS plus adjuvant of polysaccharide of Ficus carica. And the leukocyte bactericidal activity, complement C3 levels, IgM levels and the relative percentage survival of the fish treated with LPS, LPS plus polysaccharide of Ficus carica were both significant after the initial immunization. After the booster immunization, to the channel catfish treated with LPS and LPS plus adjuvant of polysaccharide of Ficus carica, the agglutinating antibody titers in the sera of those were 1∶256 and 1∶512, the leukocyte bactericidal activity of those were 0.565 and 0.511, the complement C3 levels of those were 0.194 and 0.180mg/mL, the IgM levels of those were 1.415 and 1.464mg/mL respectively, and the relative percentage survival of those were 70.0% and 65%, respectively. Conclusion: the above index of the fish treated with LPS and LPS plus polysaccharide of Ficus carica were significant (PPFicus carica on the channel catfish was better than the whole cell inactivated vaccine.