Isolation of Vibrio alginolyticus from seawater aquaria

The seawater bacterium Vibrio alginolyticus was detected in 5 of 20 water samples from seawater aquaria (from 3 of 5 units) and also from the surface of diseased stony corals. A total of 45 isolates were differentiated biochemically, of which 13 isolates (29%) proved to be V. alginolyticus. All those strains produced the virulence factors caseinase and lipase, 11 strains amylase and gelatinase. 7 strains showed lecithinase activity and 2 strains produced hemolysins. All examined strains showed a marked toxicity to vero cells proven by the MTT-bioassay, but no toxicity to plant cells with the saline alga Asteromonas gracilis as model. The isolates were mostly resistant to beta-lactam antibiotics, macrolides and lincomycin. However, they proved to be susceptible to aminoglycoside- and polypeptide-antibiotics as well as to tetracyclines, chloramphenicol, florfenicol, enrofloxacin and sulfamethoxazol-trimethoprim. The possible participation of this bacterium in the bleaching and dying of stony corals is mentioned as well as its role as human pathogen.