CHARACTERIZATION OF AEROMONAS-SALMONICIDA SUBSP SALMONICIDA - A COMPARATIVE-STUDY OF STRAINS OF DIFFERENT GEOGRAPHIC ORIGIN

A total of 130 strains of the fish pathogen Aeromonas salmonicida isol ated in Denmark, Norway, Scotland, Canada and the USA were examined. T he strains originated from farmed salmonid fish. The biochemical, phys iological and serological characteristics, antibiotic resistance patte rns and cell surface-related properties were compared. Aeromonas salmo nicida was found to be remarkably consistent in general cultural and b iochemical characteristics. It is noteworthy that the strains were pos itive in the fermentation of L-arabinose and were negative in the ferm entation of D-arabinose. All the strains were highly proteolytic. It w as observed, however, that 5% of the strains did not digest calf and t rout serum and the production of haemolysin and degradation of casein by the same strains were delayed compared with the other strains. Comm on to all of the rough strains were auto-aggregation and ability to bi nd the dyes Coomassie brilliant blue and Congo red and the majority of these strains were highly hydrophobic. The strains were tested for th eir susceptibility to 22 antibacterial agents. Antibiotic resistance p rofiles of Aer. salmonicida indicated that resistance to the quinolone s and oxytetracycline was increasing and that multi-resistant strains were found in several countries. The variation found in antibiograms c ould have potential as epidemiological markers in certain geographic a reas.