Submitted to: Aquaculture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 31, 2005
Publication Date: April 1, 2006
Citation: Panangala, V.S., Shoemaker, C.A., Mcnulty, S.T., Arias, C.R., Klesius, P.H., 2006. Intra- and Interspecific phenotypic characteristics of fish-pathogenic Edwardsiella ictaluri and Edwardsiella tarda. Aquaculture Research, 37: 49-60. Interpretive Summary: From both an epidemiological perspective, as well as the variability in virulence among isolates of Edwardsiella ictaluri and E. tarda evidenced from previous experimental studies, we were prompted to determine whether Edwardsiella isolated from disparate outbreaks of disease in fish exhibit uniquely distinguishable phenotypic characteristics. In the present study we used three phenotypic criteria, namely electrophoretic protein profiles, distribution of antigenic epitopes and the cellular fatty acid methyl ester composition to examine E. ictaluri and E. tarda isolates obtained from different outbreaks of fish disease, originating in several geographic locations. When the two species (E. ictaluri and E. tarda) were compared, there was a considerable degree of relatedness with each other. The study showed that E. ictaluri displays a more clonal population structure compared to the less monomorphic E. tarda.
Technical Abstract: Intra- and interspecific characteristics of fish-pathogenic Edwardsiella ictaluri and E. tarda were determined by numerical analysis of gel electrophoresed protein profiles, fatty acid methyl esters (FAME) and by immunoblotting. The 18 E. ictaluri isolates revealed a high degree of homogeneity (70% similarity or higher) in their protein profiles and 95% similarity in their FAME, while the 9 E. tarda isolates revealed 30% similarity in their protein profiles and 95 % similarity in their FAME. Immunoblots probed for antigenic epitopes with goat antiserum produced against E. ictaluri and E. tarda respectively, revealed that E. ictaluri were more homogeneous compared to the E. tarda isolates. Overall, there was a considerable degree of relatedness between the two species. Our findings suggest that phenotypically E. ictaluri represents a clonal bacterial population structure compared to the less monomorphic E. tarda.