Bacteriophage‐based cocktail modulates selected immunological parameters and post‐challenge survival of rainbow trout (Oncorhynchus mykiss)

Recently, a rapid increase in the resistance of pathogenic bacteria to antibiotics and chemotherapeutics admitted for use in aquaculture has been observed. This happens especially often in intensive breeding. The use of drugs in closed circuits is problematic because it can damage biological filters. Therefore, in recent years, there has been a growing interest in natural methods of combating pathogens. These include bacteriophages. The aim of the study was to determine the safety of the new BAFADOR^® bacteriophage‐based preparation, its effect on selected immunological parameters and the effectiveness of prophylactic and therapeutic use after experimental infections with pathogenic bacteria Aeromonas hydrophila and Pseudomonas fluorescens. The use of BAFADOR^® increased the activity of lysozyme, total protein level and immunoglobulin level. The level of ceruloplasmin in the rainbow trout serum remained unchanged regardless of the route of administration of the preparation. Potential killing activity and metabolic activity of spleen phagocytes and proliferation of pronephros lymphocytes were higher compared to the control group. Both therapeutic and prophylactic application of the preparation after mixed experimental infection of A. hydrophila and P. fluorescens limited the mortality of rainbow trout.