BIOCHEMICAL-PROPERTIES AND DRUG-RESISTANCE OF AEROMONAS-SALMONICIDA IN FINLAND

The biochemical properties of 105 Aeromonas salmonicida (AS) strains w ere examined in order to find criteria for distinguishing between 'typ icals' and 'atypicals' and for further subdividing the 'atypicals'. On e hundred of the strains had been isolated from fish at 35 fish farms and 5 from wild fish between 1986 and 1991. The fishes involved were a s follows: lamprey, whitefish, rainbow trout, salmon, sea trout, brown trout, arctic char, lake trout, grayling, dace and roach. Typical (AS subsp. salmonicida) and atypical AS strains could be differentiated u sing 10 biochemical tests: production of acid from saccharose, salicin , alpha-methyl-D-glucoside, L-arabinose and arbutin, production of gas from glucose and maltose, hydrolysis of aesculin, haemolysis, and hyd rolysis of Tween 80. Biochemically, the atypical isolates could not be classified as any of the proposed subspecies and could not be clearly subdivided. All of the AS strains were sensitive to oxolinic acid, tr imethoprim-sulpha, chloramphenicol and nitrofurantoin. Oxytetracycline -resistant typical strains were isolated from 9 of the farms.