Phenotypic and genotypic identification of Aeromonas species from aquatic environment

A total of 50 strains of Aeromonas spp. were isolated from 50 water and fish samples, and identified biochemically and genetically. Biochemical characterization indicated that 20 out of 50 aeromonads were A. veronii, 19 were A. caviae, 9 were A. hydrophila and 2 were A. trota. Molecular identification of isolated aeromonads revealed restriction profile of four species i.e. A. sobria, A. media, A. allosaccharophila and A. schubertii in addition to A. veronii, A. caviae, A. hydrophila and A. trota in 16S rDNA RFLP. The 16S rDNA sequencing results for the 13 strains validated the results of PCR-RFLP analysis for Aeromonas identification. Most of the isolates identified by 16S rDNA RFLP were positive for virulence factors as revealed by phenotypic tests such as hemolysin production, casein hydrolysis, gelatinase activity, lipase activity, DNase activity, lecithinase production and siderophore production. Further, a variable number of Aeromonas spp. was positive for lipase and elastase genes indicating the presence of other genes responsible for these activities observed phenotypically. The present study highlights important incidence of motile Aeromonas spp. with virulence potential, from water and fish samples.