NUMERICAL TAXONOMY OF AEROMONADACEAE AND VIBRIONACEAE ASSOCIATED WITHREARED FISH AND SURROUNDING FRESH AND BRACKISH-WATER

A numerical taxonomic study was performed on 51 isolates of gram-negat ive, oxidase-positive, rod-shaped, heterotrophic, facultative anaerobi c bacteria isolated from aquatic samples (fresh and brackish water, ee ls, turbot and rainbow trout). These bacteria were compared with 28 ty pe and references strains which included most of Aeromonas phenospecie s and DNA hybridization groups, as well as strains of some arginine-po sitive vibrios and Plesiomonas shigelloides. The strains were characte rized by 137 morphological, biochemical, physiological and nutritional tests, and data were examined by simple matching (s(SM)) and Jaccard (S-J) coefficients. Unweigthed pair group mathematical averaging clust er analysis (UPG-MA) resolved 17 groups of operational taxonomic units at S-SM values of greater than or equal to 86%. A total of 16 phena w ere defined. Larger phena were identified as Aeromonas jandaei and A. hydrophila. The species A. caviae, A. encheleia, A. allosaccharophila, A. salmonicida, A. sobria, A. veronii biovar veronii, A. media, Vibri o anguillarum, V. fumissii and Plesiomonas shigelloides were also repr esented. One phenon was identified as a member of the genus Aeromonas. Similar groupings were obtained at S-J values of greater than or equa l to 79%. Virulence trials showed that most of the strains included in phena identified as A. jandaei, A. hydrophila and V. fumissii were pa thogenic for eels (sample mean LD(50) of 6.5 to 7.6 (log(10))), wherea s other aquatic isolates as well as reference strains from clinical or igin were avirulent for fish.