Genetic studies to re-affiliate Edwardsiella tarda fish isolates to Edwardsiella piscicida and Edwardsiella anguillarum species

The incorporation of these species into the genus makes necessary a revision of the taxonomic position of the isolates previously identified as E. tarda. Using AFLP technique, MLSA studies and in silico DNA-DNA hybridization, 46 of 49 E. tarda isolates were re-assigned as E. piscicida and 2 as E. anguillarum, whereas it was confirmed previous classification of the Edwardsiella types and reference strains used. The study of the taxonomic resolution of the genes 16S rRNA, adk, atpD, dnaJ, glnA, hsp60, tuf as well as the possible combinations among housekeeping genes, showed that the gene dnaJ was the more resolutive. In conclusion, the use of molecular techniques is necessary to accurately identify Edwardsiella isolates, especially when differentiating new species from E. tarda.