Submitted to: Aquaculture America Conference
Publication Type: Abstract only
Publication Acceptance Date: 10/7/2004
Publication Date: 1/17/2005
Citation: Panangala, V.S., Shoemaker, C.A., Klesius, P.H. 2005. Phenotypic and genotypic comparisons of edwardsiella ictaluri and edwardsiella tarda isolates from fish. Aquaculture America Conference. Interpretive Summary:
Technical Abstract: Edwardsiella ictaluri, primarily a catfish pathogen is the cause of enteric septicemia in catfish and E. tarda predominantly an enteric pathogen of marine and fresh water fish has a broader host range. Phenotypic characteristics (outer membrane protein profiles, antigenic determinants, and biochemical properties) were comparatively analyzed between inter and intra-species, among 18 E. ictaluri and 6 E. tarda fish isolates from 3 geographic locations. Additionally, PCR amplification and DNA sequences of the intergenic spacer regions (ISR) between the 16S-23S rRNAs of the same isolates were analyzed for putative species-specific genetic polymorphisms. On the basis of the phenotypic parameters evaluated, E. ictaluri and E. tarda isolates respectively exhibited a high degree of homogeneity. However, each of species possessed distinctive identities when intra-species comparisons were made. rDNA sequence alignment revealed that five of the E. ictaluri isolates each exhibited marked heterogeneity at four nucleotide positions in the ISR. The sequences of the remaining thirteen E. ictaluri isolates were relatively homogeneous. The sequences of the smaller ISR of the E. tarda isolates were 97% identical to the E. ictaluri sequences, while the larger ISR's were 96-98% identical. Among the E. tarda isolates, there was 97% identity. Thus, analyses of the sequence diversity in the PCR amplified 16S-23S intergenic spacer region presents a stable and reliable method for detection of inter and intra species heterogeneity among Edwardsiella isolates.