Biochemical and serological comparison of selected Vibrio spp. isolated from fish

• Main Author: Pipoppinyo, Somsak
• Other Authors: Winton, James R.
• Language: en_US
• Published: 2012
• Subjects: Vibrio; Fishes > Diseases
• Online Access: http://hdl.handle.net/1957/28831

Nine isolates of bacteria recovered from fish dying at marine facilities were collected from different geographic areas. The strains included: an isolate from chinook salmon (Oncorhynchus tshawytscha) reared in net pens in New Zealand, an isolate from chum salmon (Oncorhynchus keta) held at a laboratory in Oregon, USA., and seven strains recovered from tilapia (Oreochromis spilurus), silvery black porgy (Acanthopagrus cuvieri), and greasy grouper (Epinenhelus tauvina) cultured in Kuwait. All isolates were characterized by examination of morphological and biochemical properties and were confirmed to be members of the genus Vibrio. All isolates differed phenotypically from each other, from vibrios known to be pathogenic for fish, and from other named Vibrio species. Analysis of key phenotypic characteristics used to establish existing species suggested that the isolates tested were new Vibrio species. Four of the isolates (two from coldwater fish and two from warmwater fish) were selected for further study. This included determination of percent guanine plus cytosine (%G+C), comparison of growth characteristics, analysis of major 0 antigens and testing of pathogenicity. The four isolates examined had an absolute requirement for NaCl. Optimum growth temperatures varied among the isolates and were consistent with the temperature optima of the hosts from which the isolates were obtained. Serological analysis using slide agglutination, microtiter agglutination, and Ouchterlony double diffusion tests detected specific thermostable (0) antigens unique for each of the four isolates. A common minor antigen was observed between two of the other isolates from Kuwait. Experimental infections were produced in fingerling rainbow trout (Salmo gairdneri) using intraperitoneal injection of the four isolates. The pathogenicity of the two isolates from Kuwait was higher than that of the two salmonid isolates. The strains from Kuwait were used to challenge juvenile chinook salmon by waterborne exposure. The pathology produced by infection was characteristic Gram-negative hemorrhagic septicemia. === Graduation date: 1988