A González-Contreras

Universidad Andrés Bello, CiudadSantiago, Santiago, Chile

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Publications (3)5.99 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We present here the first evidence of the presence of iron uptake mechanisms in Streptococcus phocae, a beta-hemolytic bacterium frequently involved in disease outbreaks in seals causing pneumonia or respiratory infection as well as warm water streptococcosis in Atlantic salmon (Salmo salar). Fifteen Atlantic salmon isolates and type strain were able to grow in the presence of the chelating agent 2,2-dypiridyl and produced siderophores using the universal Chrome Azurol S assay in solid and liquid media. Based on the biochemical homogeneity of the bacterium and the results of the siderophore production assays, two representatives of Atlantic salmon isolates and the seal type strain were examined. All of them were able to utilize apo-transferrin, transferrin hemin, hemoglobin, ferric ammonic citrate and ferric chloride as iron sources when added to iron-deficient media; although S. phocae possesses a stronger capacity for iron acquisition from hemoglobin than hemin. Whole cells of all S. phocae strains, grown under iron-supplemented or iron-restricted conditions were able to bind hemin, indicating the existence of constitutive binding components located at the S. phocae cell surface. In all strains, at least two iron-regulated membrane proteins increased when S. phocae was cultured in iron-restricted medium. Iron did not play a regulatory role in the synthesis of some proteolytic enzymes and hydrophobic properties, since these activities were similar when the strains were cultured in iron-rich or iron-restricted conditions.
    No preview · Article · Oct 2012 · Aquaculture
  • M Cortez-San Martin · A González-Contreras · R Avendaño-Herrera
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    ABSTRACT: Streptococcus phocae is a beta-haemolytic bacterium that causes systemic infections in Atlantic salmon, Salmo salar L., cultured in southern Chile and also in seals. In this study, the host-pathogen interaction between S. phocae and seven types of cell lines (fish and mammalian) was examined using an indirect fluorescent antibody and confocal microscopy (CM). Chinook salmon embryo (CHSE-214), epithelioma papulosum cyprini (EPC), salmon head kidney (SHK-1) and Atlantic salmon kidney were used as the fish cell lines, while human cervix epithelial adenocarcinoma (HeLa), African green monkey kidney fibroblast (Cos-7) and mouse leukaemic monocyte macrophage (Raw 264.7) were included as mammalian cell lines. Streptococcus phocae type strain ATCC 51973(T) and isolates LM-08-Sp and P23 were selected as representatives from the salmon and seal host, respectively. For the CM examination, monolayers seeded on round coverslips were studied at 2- and 20-h post-inoculation (pi). The results showed that there is no common infectivity pattern between the three S. phocae strains at 2-h pi and the cell lines tested, regardless of the source of isolation (seal or salmon). All S. phocae strains could internalize and were found inside the fish and mammalian cell cytoplasm after 20-h pi. Regardless of the cells studied (fish or mammal) and incubation (2 and 20 h), S. phocae was never observed inside the nuclei. Seal and salmon isolates showed the highest number of bacteria entering into the primate cell lines (HeLa and Cos-7) from 2-h pi, while ATCC 51973(T) was not found outside or inside the HeLa and Cos-7 cells.
    No preview · Article · Apr 2012 · Journal of Fish Diseases
  • Source
    A González-Contreras · B Magariños · M Godoy · R Irgang · A E Toranzo · R Avendaño-Herrera
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    ABSTRACT: Streptococcus phocae is an emerging pathogen for Chilean Atlantic salmon, Salmo salar, but the factors determining its virulence are not yet elucidated. In this work, cell surface-related properties such as hydrophobicity and haemagglutination, adhesion to mucus and cell lines, capsule detection, survival and biofilm formation in skin mucus and serum resistance of the isolates responsible for outbreaks in Atlantic salmon and seals were examined. Adhesion to hydrocarbons and the results of salt aggregation tests indicated most of the S. phocae were strongly hydrophobic. All isolates exhibited a similar ability to attach to the Chinook salmon embryo (CHSE) cells line, but were not able to enter CHSE cells. Haemagglutination was not detected. Our data clearly indicate that S. phocae can resist the killing activity of mucus and serum and proliferate in them, which could be associated with the presence of a capsular layer around the cells. Pathogenicity studies using seal and fish isolates demonstrated mortality or pathological signs in fish injected only with the Atlantic salmon isolate. No mortalities or histopathological alterations were observed in fish injected with extracellular products.
    Full-text · Article · Mar 2011 · Journal of Fish Diseases

Publication Stats

19 Citations
5.99 Total Impact Points

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  • 2011-2012
    • Universidad Andrés Bello
      • • Facultad de Ciencias Biológicas
      • • Department of Biology
      CiudadSantiago, Santiago, Chile