Phenotypic and genotypic characterisation of Aeromonas isolates

In the present study 62 Aeromonas strains, isolated from different sources, were characterised by biochemical tests (Biolog system) and amplified 16S rDNA restriction analysis (ARDRA), previously proposed as a useful tool to identify Aeromonas species. Fifteen type strains and one reference strain were also analysed. The Biolog system ascribed most of the local isolates to A. media and A. veronii bv. sobria. Sixteen isolates were recorded as Aeromonas spp. ARDRA subdivided all analysed strains in 13 clusters. None of our isolates were attributed to A. sobria, A. schubertii, or to Aeromonas unnamed HG11 with both approaches. However, discrepancies were found between Biolog and 16S ARDRA species attribution of isolates. Moreover, total DNA restriction profile analysis on a selected group of isolates showed a low similarity among strains with identical ARDRA profiles. Therefore, sets of our data suggest that a single approach cannot be adequate for the identification of Aeromonas new isolates at the species rank and point out the need to apply a polyphasic approach, integrating phenotypic, phylogenetic (16S rDNA sequencing) and genomic (i.e. DNA/DNA hybridisation values) data, to define the taxonomic status of the genus Aeromonas.