In Vitro Evolution of Specific Phages Infecting the Fish Pathogen Flavobacterium psychrophilum

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  • Daniel Castillo
  • Alexander Ravndal Højsting
  • Andrea Roosvall
  • Giorgos Smyrlis
  • Johanna Jørgensen
  • Middelboe, Mathias

Background: Flavobacterium psychrophilum is the causative agent of the bacterial cold-water disease and rainbow trout fry syndrome. Owing to the issues associated with increasing use of antibiotics to control the diseases, phage therapy has been proposed as an alternative method to control Flavobacterium infection within the industry. Materials and Methods: We explored two simple and fast in vitro strategies for the isolation of evolved F. psychrophilum phages, using three well-characterized phages FpV4, FpV9, and FPSV-S20. Results: During in vitro serial transfer experiments, 12 evolved phages were selected 72-96 h after phage exposure in the first or second week. Phenotype analysis showed improvement of host range and efficiency of plating and adsorption constants. Comparative genomic analysis of the evolved phages identified 13 independent point mutations causing amino acid changes mostly in hypothetical proteins. Conclusions: These results confirmed the reliability and effectivity of two strategies to isolate evolved F. psychrophilum phages, which may be used to expand phage-host range and target phage-resistant pathogens in phage therapy applications against Flavobacterium infections.

Original languageEnglish
JournalPHAGE: Therapy, Applications, and Research
Issue number1
Pages (from-to)28-37
Number of pages10
Publication statusPublished - 2022

Bibliographical note

Publisher Copyright:
© 2022, Mary Ann Liebert, Inc., publishers 2022.

    Research areas

  • F. psychrophilum, phage evolution, phage mutations, phage-host range

ID: 322279227