The Pathogenicity Comparison About Six Species Bacterial Pathogenes Of Aquacultural Fishes

In this paper, different biologic and immunologic technologies were used to study cross reactions between bacteria and different antisera and discover a new kind of method to differentiate the pathogenesis of bacteria diseases. Then the new method was put into practice to diagnose several cases and obtain good results.Vibrio harveyi, Vibrio alginolyticus, Vibrio anguillarum, Vibrio parahaemolyticus, Edwardsiella tarda and Pseudomonas fluorescens were cultured on medium corresponding to the bacteria respectively, then were used to immunize mouse to obtain polyclonal antisera. By use of the technologies of Immediate Agglutination, SDS-PAGE, Western-blot, IFAT and ELISA, the author did detailed research to analyse the cross reactions between pathogenesis and antisera above-mentioned, finding that the level of cross reactions was not the same between different bacteria and different antisera. This supplies a basis for us to differentiate bacteria.The results of agglutination showed that cross reactions existed generally. The level of cross reactions was high when a bacterium react with a antiserum obtained from a bacterium of the same genus as it, or the level was low. There was a high level of cross reactions among the Vibrio, meanwhile Pseudomonas fluorescens could hardly react with any Vibrio, and the cross reaction between Pseudomonas fluorescens and Edwardsiella tarda was in a low level.Through Western-blot the author calculated the molecular weight of specific protein belt with antigenicity when a bacterium had cross reaction with a antiserum. The results showed that different bacteria had different antigenic determinant,although sometimes the bacteria of the same genus had a high level of cross reactions,we still could tell the numbers and sites of the special protein belts. These protein belts can be used as important basis to determine bacterial pathogen. Because it could be quantified using the method of Western-blot to determine the species of bacteria, Western-blot is worthy of being researched deeply.The fluorescence intensity varies with the level of cross reaction, the level of cross reaction between six strains and six antisera was determined, showing no difference with Western-blot and agglutination.ELISA is a high-sensitivity immunoassay technology, it determines the positive or negative of a reaction by reading the OD(optical density) value. It's an objectivity technology which can tell the level of cross reaction accurately. From the result it could be found that the level of cross reaction between Vibrios was high, it was the same as before. So it could be said that the level of cross reaction among the bacteria of the same genus is high. And the bacteria of the same genus have the specificprotein belts with the same molecular weight. These protein belts can be used as important basis to determine bacterial pathogen.Four strains of bacteria were separated from turbots. These four strains were determined by using the methods above, showing that strain 1 was Edwardsiella, the other three strains were Vibrio. Then the conventinonal method such as drug-fast test was used to examine the strain 1 and obtained the same result.Immunoassay methods can operate easily and cost little time and money, it's feasible in practice.