Biochemical, serological and molecular properties of a group of 14 Vibrio ordalii strains isolated from cultured Atlantic salmon Salmo salar in Chile in recent years were studied. The characteristics of isolates were compared with the type strain V. ordalii ATCC 33509 T . The Chilean V. ordalii represented a biochemically homogenous group; however, some minor differences with the type strain were observed. The serological relationships among isolates, as well as the study of their antigenic determinant (LPS) revealed a strong reaction with antisera raised against Atlantic salmon strains and the antiserum raised against Listonella anguillarum serotype O2. However, LPS electrophoretic patterns were completely different from the V. ordalii type strain, regardless of the serum employed, suggesting the possibility that the Chilean strains constitute a new serological subgroup within this bacterial species. Genetic analyses by PFGE, RAPD, REP-PCR and ERIC-PCR demonstrated that all V. ordalii strains were genetically homogenous, displaying similar DNA patterns, regardless of the techniques used. Moreover, the analysis of DNA banding patterns generated by ERIC-PCR and REP-PCR also clearly separated the type strain from the Chilean strains. This is the first report of characterization of V. ordalii strains from the Southeastern Pacific area, the results of which should facilitate the development of vaccines for protecting cultured Atlantic salmon against vibriosis in this area. KEY WORDS: Vibrio ordalii · Fish vibriosis · Serotyping · Genotyping · Atlantic salmon Resale or republication not permitted without written consent of the publisherDis Aquat Org 79: [27][28][29][30][31][32][33][34][35] 2008 (Colquhoun et al. 2004) using conventional methods and miniaturized systems have demonstrated that Chilean V. ordalii isolates share the same biochemical properties present in the previous description of the species (Schiewe et al. 1981), with the exception of production of acid from trehalose and lack of acid production from mannitol. In addition, these Chilean strains could not be serotyped due to auto-agglutination of the isolates (Colquhoun et al. 2004).However, until now, no discriminative methods based on genetic techniques have been applied to this bacterium. Pulsed-field gel electrophoresis (PFGE) (Skov et al. 1995), randomly amplified polymorphic DNA (RAPD)-PCR, enterobacterial repetitive intergenic consensus sequence (ERIC)-PCR and repetitive extragenic palindromic (REP)-PCR have become accessible and sensitive methods for the intraspecific genetic variability in many pathogens (Williams et al. 1990, Versalovic et al. 1991, Bachellier et al. 1999. Therefore, the objective of this study was to describe in depth the biochemical and antigenic characteristics of the Vibrio ordalii strains isolated from disease outbreaks in Salmo salar in Chile, for future development and/or improvement of the vaccination program against vibriosis. In addition, PFGE and 3 PCR-based methods were employed to analyse the geneti...

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Streptococcus phocae is a beta-haemolytic bacterium frequently involved in disease outbreaks in seals causing pneumonia or respiratory infection. Since 1999, this pathogen has been isolated from diseased Atlantic salmon, Salmo salar, causing serious economic losses in the salmon industry in Chile. In this study, we used different molecular typing methods, such as pulsed-field gel electrophoresis (PFGE), randomly amplified polymorphic DNA (RAPD), enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR), repetitive extragenic palindromic PCR (REP-PCR) and restriction of 16S-23S rDNA intergenic spacer regions to evaluate the genetic diversity in S. phocae. Thirty-four strains isolated in different years were analysed. The S. phocae type strain ATCC 51973(T) was included for comparative purposes. The results demonstrated genetic homogeneity within the S. phocae strains isolated in Chile over several years, suggesting the existence of clonal relationships among S. phocae isolated from Atlantic salmon. The type strain ATCC 51973(T) presented a different genetic pattern with the PFGE, RAPD, ERIC-PCR and REP-PCR methods. However, the fingerprint patterns of two seal isolates were distinct from those of the type strain.

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