AEROMONAS-SALMONICIDA SUBSP SALMONICIDA - CORRELATION OF PROTEIN-PATTERNS, ANTIBIOTIC-RESISTANCE, EXOPROTEASE ACTIVITY, HEMOLYSIS AND PATHOLOGICAL LESIONS PRODUCED IN-VIVO

A collection of 130 strains of the bacterial fish pathogen Aeromonas s almonicida subsp. salmonicida isolated from diseased salmonids in Denm ark, Norway, North America and Scotland has been characterized with re gard to protein patterns, antibiotic resistance and exoprotease activi ty. Whole cell and outer membrane protein profiling could distinguish three different profiles in A. salmonicida. Eight outer membrane prote ins were demonstrated (49, 40, 38, 37, 33, 31, 30 and 29 kDa). One pro tein profile was deficient in a 38 kDa outer membrane protein and inst ead contained an outer membrane protein of 37 kDa which was not detect able among the other protein profiles. Strains with the 37 kDa outer m embrane protein showed multiple low-level antibiotic resistance toward s cephalothin, penicillin, chloramphenicol, tetracycline and quinolone s. In addition, these strains were exoprotease deficient. Strains with the 37 kDa protein were unable to degrade cattle and trout serum prot eins and displayed a delayed degradation of casein. Haemolysis on catt le blood agar plates was similarly delayed. In vivo examination of ext racellular products from a normal protein profile strain and one with the 37 kDa outer membrane protein demonstrated major differences in pa thological effects in rainbow trout. The strain possessing the 37 kDa outer membrane protein produced almost no pathological effects while t he normal protein profile strain produced typical furuncles.