TY - JOUR

T1 - Interactions between Rainbow Trout Eyed Eggs and Flavobacterium spp. Using a Bath Challenge Model

T2 - Preliminary Evaluation of Bacteriophages as Pathogen Control Agents

AU - Donati, Valentina L.

AU - Dalsgaard, Inger

AU - Runtuvuori-Salmela, Anniina

AU - Kunttu, Heidi

AU - Jørgensen, Johanna

AU - Castillo, Daniel

AU - Sundberg, Lotta-Riina

AU - Middelboe, Mathias

AU - Madsen, Lone

PY - 2021

Y1 - 2021

N2 - The microbial community surrounding fish eyed eggs can harbor pathogenic bacteria. In this study we focused on rainbow trout (Oncorhynchus mykiss) eyed eggs and the potential of bacteriophages against the pathogenic bacteria Flavobacterium psychrophilum and F. columnare. An infection bath method was first established, and the effects of singular phages on fish eggs was assessed (survival of eyed eggs, interaction of phages with eyed eggs). Subsequently, bacteria-challenged eyed eggs were exposed to phages to evaluate their effects in controlling the bacterial population. Culture-based methods were used to enumerate the number of bacteria and/or phages associated with eyed eggs and in the surrounding environment. The results of the study showed that, with our infection model, it was possible to re-isolate F. psychrophilum associated with eyed eggs after the infection procedure, without affecting the survival of the eggs in the short term. However, this was not possible for F. columnare, as this bacterium grows at higher temperatures than the ones recommended for incubation of rainbow trout eyed eggs. Bacteriophages do not appear to negatively affect the survival of rainbow trout eyed eggs and they do not seem to strongly adhere to the surface of eyed eggs either. Finally, the results demonstrated a strong potential for short term (24 h) phage control of F. psychrophilum. However, further studies are needed to explore if phage control can be maintained for a longer period and to further elucidate the mechanisms of interactions between Flavobacteria and their phages in association with fish eggs.

AB - The microbial community surrounding fish eyed eggs can harbor pathogenic bacteria. In this study we focused on rainbow trout (Oncorhynchus mykiss) eyed eggs and the potential of bacteriophages against the pathogenic bacteria Flavobacterium psychrophilum and F. columnare. An infection bath method was first established, and the effects of singular phages on fish eggs was assessed (survival of eyed eggs, interaction of phages with eyed eggs). Subsequently, bacteria-challenged eyed eggs were exposed to phages to evaluate their effects in controlling the bacterial population. Culture-based methods were used to enumerate the number of bacteria and/or phages associated with eyed eggs and in the surrounding environment. The results of the study showed that, with our infection model, it was possible to re-isolate F. psychrophilum associated with eyed eggs after the infection procedure, without affecting the survival of the eggs in the short term. However, this was not possible for F. columnare, as this bacterium grows at higher temperatures than the ones recommended for incubation of rainbow trout eyed eggs. Bacteriophages do not appear to negatively affect the survival of rainbow trout eyed eggs and they do not seem to strongly adhere to the surface of eyed eggs either. Finally, the results demonstrated a strong potential for short term (24 h) phage control of F. psychrophilum. However, further studies are needed to explore if phage control can be maintained for a longer period and to further elucidate the mechanisms of interactions between Flavobacteria and their phages in association with fish eggs.

KW - Flavobacterium psychrophilum

KW - Flavobacterium columnare

KW - rainbow trout

KW - eyed eggs

KW - phage-mediated control

KW - bacteriophages

KW - ONCORHYNCHUS-MYKISS WALBAUM

KW - COLD-WATER DISEASE

KW - ATLANTIC SALMON

KW - CYTOPHAGA-PSYCHROPHILA

KW - COLUMNARE INFECTION

KW - GENETIC DIVERSITY

KW - IN-VIVO

KW - FISH

KW - VIRULENCE

KW - SURVIVAL

U2 - 10.3390/microorganisms9050971

DO - 10.3390/microorganisms9050971

M3 - Journal article

C2 - 33946270

VL - 9

JO - Microorganisms

JF - Microorganisms

SN - 2076-2607

IS - 5

M1 - 971

ER -