Submitted to: American Society of Microbiologists Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 4/20/2005
Publication Date: 6/5/2005
Citation: Panangala, V.S., Vansanten, V.L., Shoemaker, C.A., Mcnulty, S.T., Arias, C.R., Klesius, P.H. 2005. Intra-and interspecific phenotypic and genotypic comparison of fish-pathogenic edwardsiella ictaluri and edwardsiella tarda. American Society of Microbiologists Abstracts.
Technical Abstract: Background: Edwardsiella ictaluri and E. tarda are associated with enterohemorrhagic disease in fish. To determine whether Edwardsiella originating from disparate environments show adaptive pleiotropic alterations that are reflected as appreciable phenotypic differences, phenotypic and genetic characteristics of 18 E. ictaluri and 9 E. tarda isolates from outbreaks of fish disease in several geographic locations were examined. Methods: Isolates were compared by: numerical analysis of sodium dodecyl sulfate-polyacrylamide gel electrophoresed, bacterial whole cell protein profiles; immunoblotting with polyclonal goat anti-E.ictaluri and E.tarda antiserum; analysis of the fatty acid methyl ester (FAME) profiles; and nucleotide sequence analysis of 16S-23S rRNA intergenic spacer regions (ISRs). Results: On the basis of total protein profiles, E. ictaluri displayed a lower intraspecific variability than E. tarda. E. ictaluri isolates clusterd together at '70% similarity. Total protein profiles of E. tarda isolates revealed a higher degree of diversity, with as low as 30% similarity and were comprised of two main clusters. One cluster was more similar to E. ictaluri (50% similarity) than to other E. tarda isolates (30% similarity). Immunoblotting showed the major antigenic proteins of E. ictaluri (~12, 18, 30, 37 and 70 kDa) were similar in all isolates. In contrast, antigenic proteins varied in size among E. tarda isolates. Thirteen FAMEs detected in both species belonged to categories of saturated, unsaturated and cyclopropane fatty acids. The E. ictaluri FAME profiles differed from those of E. tarda quantitatively; but no qualitative differences were apparent. The nucleotide sequences of both ISR1 and ISR2 of all E. ictaluri isolates were identical. Those of E. tarda isolates differed up to 3% from each other and 3-4% from E. ictaluri ISRs. Conclusions: Our findings suggest that E. ictaluri displays a clonal bacterial population structure wherein essential phenotypic traits are maintained, possibly for a selective advantage, whereas the closely related E. tarda is genetically and phenotypically more polymorphic.