Isolation of Bacteriophage Against Yersinia ruckeri and Determination of Host Range

Enteric red mouth disease caused by Yersinia ruckeri is one of the bacterial diseases that cause significant economic losses in fish. Antibiotics are used in the treatment of bacterial fish diseases. However, the rise in antibiotic resistance in recent years has necessitated the development of alternative therapies. Bacteriophage therapy is gaining importance as a promising alternative to antibiotics in the treatment of antibioticresistant bacterial infections. The aim of this study was to isolate and characterize bacteriophages against local Yersinia ruckeri isolates obtained from rainbow trout farms in Türkiye, and to determine the host range of the isolated phage using the spot assay method. In this study, enrichment and double-layer agar methods were used to isolate bacteriophage from municipal wastewater. One bacteriophage was isolated from municipal wastewater. The isolated phage was named YP4M based on the host species and strain. The lytic activity of phage YP4M was determined by spot assay against 18 Y. ruckeri isolates, as well as Lactococcus garvieae ATCC 49156, Aeromonas hydrophila ATCC 7966 and Vibrio anguillarum ATCC 43305. YP4M exhibited lytic activity against bacteria numbered 3, 4, 8, 9, 13, 14, 15, and 17 from the 18 Y. ruckeri isolates, but did not exhibit lytic activity against Lactococcus garvieae ATCC 49156, Aeromonas hydrophila ATCC 7966 and Vibrio anguillarum ATCC 43305 strains. It is believed that the characterization of phages and the preparation of phage cocktails will significantly contribute to the control of yersiniosis, an important disease in aquaculture.