Effect of Flavobacterium columnare inoculation, antibiotic treatments and resident bacteria on rainbow trout Oncorhynchus mykiss eyed egg survival and external membrane structure

Authors

  • M. E. Barnes,

    Corresponding author
    1. * South Dakota Department of Game, Fish and Parks, 19619 Trout Loop, Spearfish, SD 57783, U.S.A. and Department of Science, Black Hills State University, 1200 University, Spearfish, SD 57799, U.S.A.
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  • D. Bergmann,

    1. * South Dakota Department of Game, Fish and Parks, 19619 Trout Loop, Spearfish, SD 57783, U.S.A. and Department of Science, Black Hills State University, 1200 University, Spearfish, SD 57799, U.S.A.
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  • J. Jacobs,

    1. * South Dakota Department of Game, Fish and Parks, 19619 Trout Loop, Spearfish, SD 57783, U.S.A. and Department of Science, Black Hills State University, 1200 University, Spearfish, SD 57799, U.S.A.
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  • M. Gabel

    1. * South Dakota Department of Game, Fish and Parks, 19619 Trout Loop, Spearfish, SD 57783, U.S.A. and Department of Science, Black Hills State University, 1200 University, Spearfish, SD 57799, U.S.A.
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†Tel.: +1 605 642 6920; fax: +1 605 642 6921; email: mike.barnes@state.sd.us

Abstract

This study was conducted to evaluate the potential pathogenicity of the bacterium Flavobacterium columnare on rainbow trout Oncorhynchus mykiss eyed eggs. Survival to hatching was unaffected by the inclusion in the incubation water of either 300 colony-forming units (CFU) ml−1 or 3000 CFU ml−1 of F. columnare at either 10 or 12° C in either McConaughy or Shasta strain eyed eggs. Bacterial numbers, obtained via scanning electron microscopy or culture, and external membrane morphology were also not significantly different among eggs receiving different concentrations of F. columnare. Initial F. columnare burdens were significantly and positively correlated to the presence of biofilm on the egg external membrane, and biofilm was in turn significantly correlated with increased membrane degradation. The use of either streptomycin or tetracyclin antibiotics significantly reduced bacterial numbers on McConaughy strain eggs, and more eggs survived to hatch in those dishes treated with antibiotics.

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